73 replies to this topic

[vvillium3]

hello all,

Well I am at the cross roads at deciding whether I should build my own cylinder head from scatch or not, and I need a couple of your guys advise.
The reason why I am even considering this, is because a co-worker(fellow cnc toolpather) and I have always wanted to build our own upper half of a motor from scratch(minus block). But have never really just done it. Well now, I just bought a spare motor for my 95' bmw m3, and now we have some numbers to work from, and time to do it. Plus, our boss bought a true 5-axis cnc with programming about 6 months ago, and gave us the go ahead to do some of our private jobs on the weekends. This is going to make it real easy to cut all of the ports and cc all in one set-up...
In thinking about this, here is where I run into two main problems, and this is where I need your guys insight...

1. Oviously this is going to be made from billit aluminum, but my question is what kind. I have taken metaluragy classes and do know some ins and out of aluminum, but not so much about best material selection or heat treatments. I do know which has higher tensil strengths and better characteristics, but I was looking for actual experience out there to tell me which is the best type and heat treatment to use...
Does anyone out there know the right material selection and heat treatment????

In the mold shop that I work in, its all steel work. So the process generally goes like this for important cavity shapes that need to be extremely accurate:
a. rough material, leave about .02 inches stock (generally h-13)
b. heat treatment (~46-48 rockwell C)
c. finish to size
d. stress relieved
e. polish
f. finished product

I don't know if this is any similar to aluminum. But I do know that as the material is removed, the metal is going to warp, alot. Especially after head treatment. Also, what is the best type of heat treatment to use, and can you stress relieve it????

2. Which valve angles to use??? I could always use the same angles as the original head, but I am changing the combustion chamber design quite drastically due to larger valves and a larger bore.
The reason why I am not using the original angles, is because they are quite wide, and I am looking for a flatter more efficient cc design. Also, I haven't decided if I am going to use a angled quench area or not yet. It depends really on how much cc area I need. That will be decide soon though after I do some numbers with deck height and amount of lift with the decided valve angles...

All right, well I am just throwing this all out for you. I know some of you are going to disagree with the whole idea. Which is good, because I want some different ideas or ways to go. But I just want to do something one off, and a little different then just going with oversized valves and a port+polish job. Plus it would be damn cool to say, "hey, I built that head in that car." Its nice to see what you can do every now and then. And hell, if I fail, at least I failed trying....

thanks,
Jason

[Canuck]

FWIW - H-D aftermarket "billet" heads are 6061-T6, though they only look after one cylinder each so distortion over length isn't as much as an issue with them.

[Stian1979]

I actualy plan to build a complete engine so I have done some researtch. I think you should go to the scrapyard and find some aluminium engine blocks and melt down to a cylinder head.
This way you get the right alloy. You find mutch information on http://www.backyardmetalcasting.com/ If you look under the links you actualy find some goys making aftermarket aluminium engines for old austin harlys. You find information about making your own low cost furnace and how to melt it into shapes by using molds and how to make molds. Look into it and tell me what you think.

[Powersteer]

With billet maybe the oil galleries would be a bit difficult. You can go external I guess. How did they build cylinder heads during the 60's and 70's?

[vvillium3]

I have the oil passages figured out. One of the last things to design in the whole process after the ports, plugs, cc, and valves are all positioned. We have a gun drill here at work that can drill an extremely straight and to size hole to about 4 ft. long....

[vvillium3]

and also, I have a ton of 6061-t6 laying around from a previous project. But I wonder if melting it down is going to change the heat treatment??? I really don't know. I have looked down in the library at school with no sucess, so I am kind of stuck now.....

[McGuire]

Originally posted by vvillium3
and also, I have a ton of 6061-t6 laying around from a previous project. But I wonder if melting it down is going to change the heat treatment??? I really don't know. I have looked down in the library at school with no sucess, so I am kind of stuck now.....

When you melt and recast 6061-T6, it becomes plain old 6061 whatever...lawn furniture, pots and pans more or less. 6061 is the alloy, while Tx refers to the treatment. Check out the catalogs and websites of the metals suppliers; plenty of good starting info on alloys and treatments. Another decent basic primer is the metals section of Carroll Smith's Engineer to Win. Academic metallurgists may take issue with some of the explanations, but the practical info is solid.

While it is extremely ambitious, your project is not totally nuts. It can be done... and if you do accomplish it, by the time you are done you will have learned a lot. One recommendation: separate the job into multiple components: make the head in two main pieces, upper and lower, a cylinder head and a cam carrier, both retained by the same head bolts. Also separate timing case and cover, cam cover(s) etc. That way you can begin with the simpler parts, gathering experience and skill, and if you screw up at some point you don't have to start all over from scratch. If you take each part or function and examine it separately, you will see how some pieces can be done as castings, some as billet, some as plain old plate.

The other "benefit" of this approach (if you see it as such) is your engine will end up with a very classic or traditional look. That's because this is exactly how all those olde time engines were built...their resources were limited just like yours. Study Bugatti, Miller, Offy, etc to see how they were put together.

Also: memorize the parts catalogs and know what is available so you can use as many off-the-shelf components (valves, springs, seats, guides, cam blanks etc) as possible. You might want to simply pick another cylinder head design you like and copy and adapt it, borrowing all the components. It's been done... in fact that is essentially what many of the DOHC conversions etc. of yesteryear were, once you dig around in them. Very seldom is stuff built entirely from scratch... that's just too much time, money and trouble. Prototyping -- which is what this is, basically -- is a true skill and a disappearing art.

[J. Edlund]

When it comes to valve angles you could take a look at some typical values in F1; for example 25 and 6 degrees (compound angle).

One difficulty with heads are the internal cooling passages, that is if you are going to run the engine for more than just a few seconds. Otherwise it's common practise to machine the ports using a five axis CNC machine.

Also, I can recommend you to take a look at this:
http://www.atomracing.se/6M.html

[Halfwitt]

If I were you, I'd stick to non-compound valve angles. Extra complexity / time / cost for perhaps marginal benefits. As you are guessing ports / valve sizes / angles etc your initial guess with non-compound angles will likely be every bit as good in practice as a compound angle head.

The advice about head and cam carrier seems sensible.

Melting aluminium is going to turn it from good metal into nastiness, and you will. You will likely introduce impurities / dissolve gas etc and get a poor quality casting. Then you would need to heat treat it anyway. Casting heads is an art, and you might end up disappointed. A billet head will be heavy, but material quality and component integrity won't be in doubt.

Rudimentary cooling passages might be possible by machining, and splitting the head horizontally into three slices (bottom, middle and cam carrier) would allow you to machine in a proper water cooling circuit.

Most of what Mr. McGuire advises seems like good advice.

Good luck.

[vvillium3]

thanks guys for the great info....
After a little thought, I am still going to stick with a billit piece, and use the most parts I can off of my exsisting cylinder head. But I am still undecided on the material of the head. I checked out the W-9 motor and they used AA5026 aluminum which not head treatable, but more stable of a material as far as warpage. So that kinds of throws me off.
So I think I am going to stick with the standard 6061. Then after roughing out, I will send it out to be heat treated, then finish to size, and then finally stress relieved. Unforchunalty though, it is an inline 6 so I can't wait to see how much the aluminum is going to cost. Especially now with high aluminum prices.....
I like the idea of dividing the head into different parts. Definaly use that idea. The only thing that worries me about that idea though, is leakage. Any ideas how to avoid coolant passage leaks between two different blocks without using gaskets. So that tighter tolerances can be obtained???
Also, I am not going to make a new block. That would be much to difficult for my first try. I am going to put in oversized liners in an existing block though, and make a shorter stroked crank for much higher revs. What type of liner material would you all recomend??? Stick with cheaper nodular iron or go with a higher strength steel???
Finally, Is the 25 deg angle of the valves the measure off of the vertical, or is that the included angle of both of the valves??? And if it is the included angle, is it biased or is it symmetrical????
Once again guys, thats for the suggestions. You have defianatly helped me make up some ideas that have been in my head for a little while.

thanks,
Jason

[McGuire]

Originally posted by Halfwitt
Most of what Mr. McGuire advises seems like good advice.

Well I have done it once or twice. What was the part you didn't you like?

[McGuire]

Originally posted by vvillium3
I like the idea of dividing the head into different parts. Definaly use that idea. The only thing that worries me about that idea though, is leakage. Any ideas how to avoid coolant passage leaks between two different blocks without using gaskets. So that tighter tolerances can be obtained???
Also, I am not going to make a new block. That would be much to difficult for my first try. I am going to put in oversized liners in an existing block though, and make a shorter stroked crank for much higher revs. What type of liner material would you all recomend??? Stick with cheaper nodular iron or go with a higher strength steel???
Finally, Is the 25 deg angle of the valves the measure off of the vertical, or is that the included angle of both of the valves??? And if it is the included angle, is it biased or is it symmetrical????
Once again guys, thats for the suggestions. You have defianatly helped me make up some ideas that have been in my head for a little while.

thanks,
Jason

If the surfaces are true, anaerobic gasket maker (Permatex makes it) will provide a perfectly reliable seal.

An "included valve angle" of 25 degrees typically indicates that the valves are 24 degrees from each other, and each is 12.5 degrees from vertical. I would never employ compound angles (as in current F1 engines) for a project like this as it requires skewing the valvetrain and other hassles that just aren't worth it.

[JwS]

As far as the material, I would suggest you do some online reasearch and look for specifications for cast alloys for cylinder heads. I think you will find some information if you look around a bit. I think that 6061 or similar alloys are going to cause you serious headaches by warping around during machining and afterwards when you start to heat cycle it also, based on my experience it will probably keep shifting around for a while before all the stresses in the material get worked out. Correctly cast alloys will have very little internal stress and will not move much (if at all) when machined and heat cycled.
You may be able to find an appropriate material in billet because similar materials are used to make aluminum molds (for temporary plastic molding) where dimensional stability is required. The other viable option may be to have a mold made up and have a foundry sand cast the correct alloy. If you are not making internal passages the molding design is pretty easy.
As far as water passages, you could machine or mold them into the outside of the head and put covers on to form the jacket, that is the way they used to do it in the 23's-30's and I think it would work fine.
JwS

[vvillium3]

Jws,

I will ask here at the shop what kind of material they use for the blow-molds that they make. I would imagine the material they use are similar to what you are talking about...

Jason

[JwS]

A few minutes of internet search identified 356 as the alloy typically used for engine components, both production and specials. There are probably places online that will cast it for you if you want.

JwS

[vvillium3]

Jws,

Thanks again for the great info... You have been a great help. Now I have to decide on a valve angle, and work from there out. Any other suggestions on this??? I definaly will not use a compound angled valve train. 2d is good enough for me.
Just to let you guys in a little more. The motor is going to be overly square at 90mmx75mm. Hopefully with a beefer/lighter bottom end, It should have about a 9000 redline with a 1.9:1 conrod/stroke ratio. This with variable valve timing shouldn't be too much of a top end motor with absolutly no bottom end at all...

thanks,
Jason

[Halfwitt]

A good solution for sealing is to machine o-ring grooves, either to suit o-rings (funnily enough) or rubber cord. Choose Viton rubber if you are sealing against fuel (a good policy is to use it everywhere).

The valves are probably biased to having the inlets steeper than the exhausts. For instance in an engine with a 25 degree included angle, the inlet might be one or two degrees steeper than the exhaust, i.e. inlet 12, exhaust 13 or inlet 11.5, exh 13.5

Typical F1 included valve angles (discounting compound) are probably around 20 degrees now.

For casting alloys, A356 and A357 seem popular in racing and if you're machining from solid and not intending to weld anything to your heads, 2000 series alloys are probably a good choice, with 2618 probably being the best among these (expensive, it's used for high performance forged pistons). 2014, and 2024 are both good enough though.

[hydra]

Run of the mill production engines use castings made of 319 and 356 aluminum. Use 354 or 357 if you want the highest, hardness and fatigue strength, although there are relatively few places that will cast them for you, and you won't see that much of a difference unless you design the casting to be on the bleeding edge. Also I'm not too big on the billet head idea, its like using a sledgehammer to crack a nut.

As for valve angles, the objective is to minimize surface to volume ratio. Assuming a 1.2 B/S (90/75) and a 12:1 compression ratio the ideal valve angle would be around 22-24 degrees. With an 11:1 compression ratio you can go up to 30 degrees, which may allow you some more latitude with valve sizes... The stock M3 engine is a pretty "square" design, which probably explains its large valve included angle, same goes for a lot of Honda engines with their 45 degree included angles

Just out of curiousity, why are you destroking the engine? The only reason I would ever de-stroke a stock (production) engine would be to meet some class limit in racing, otherwise its a lose-lose situation, you've got nothing to gain except another 500-1000 rpm, at the expense of increased frictional losses, less overall reliability, more valvetrain issues, and poorer combustion

[rhm]

Can you take lots of photos and upload them to Flickr (or similar) please? I'd love to see this project take shape.

[vvillium3]

well I am not too big on the billit idea myself. But at this point I have no experience with casting myself. So the only reliable way to get this done is from billit.
Also, how stable is the 2000 series alloys??? I would love to use a cast block of 356, but I don't think I can find a place that distributes it...

[JwS]

Well, glad to be of some help.
There are some issues besides the mechanical ones when it comes to alloy selection, some alloys may be more affected by coolant etc. For instance, Saab had alot of trouble with cracking of cylinder heads at one point, they changed the alloy used and pretty much eliminated the cracking problem, but they later discovered the heads were being eaten up by corrosion from the coolant.
There is a good arguement to try to stick to proven material, even if another material seems similar and is more available or whatever.
JwS

[vvillium3]

as far as destroking the motor. The idea behind that, is to get a better rod/stroke ratio(strock conrod/stroke ratio is ~1.5:1), allowing for higher revs and lower piston speeds. I was trying to stay with another crank shaft that would fit my block. For instance, the cranks from both the 325(75mm stroke, ~1.9:1 conrod/stroke) and 328( 80mmstroke, ~1.7:1) bmw motor fit my block. All three of them are not forged so no loss in that department. I do realize the natural balance of the I6 allows for a longer stroke with less vibration. But what would I be really giving up with a shorter stroke besides low end torque, and lower valve lift (which could be off set with larger valves)??? Are there other things that I should be considering???? How does a shorter stroke translate into poorer combustion and reliability???

thanks,
Jason

[Greg Locock]

"higher revs and lower piston speeds"

If this engine is for your own use then that is the wrong solution. When you need a powerful IC engine you go for displacement not speed. The most powerful IC engine in the world has a 300 rpm redline.

" I do realize the natural balance of the I6 allows for a longer stroke with less vibration."

No it doesn't, on realistic sized engines. A shorter crank is high speed's friend. An I6 has a crank almost as long as that of a V11.

[Ray Bell]

It might interest you to know that back in the late 1970s Comalco developed an alloy which had the purpose of providing a cylinder head material that could be used without valve seat inserts...

It was used in John McCormack's McLaren M23 Leyland, with the Australian version of the BOP/Rover V8 (taller block) stretched to 5-litres.

Phil Irving had a lot to do with the head design...

[vvillium3]

Greg Locock,

Please by all means lead me in the right direction. In no way am I saying I am a engine design expert while I post here, but I do belive you time here is better spent helping all of us. Instead of pointing out what I am doing wrong.
The stock motor design is 86mm(bore)x85.8mm(stroke) with a 135mm connecting rod. People have tried stroking these motor to 3.5 litres, but a common complaint is reliability issues.
The most stock that the motor can be bored to is 87.5mm, but 90mm can be achieved through the use of wet sleeves. Do you recommend staying with the stock crank with the lower rod/stroke ratio and boring the motor to 90mm??? If this design were used, what valve angles and sizes would you recommend??? I would like the compression ratio to be at 11:1. So that I can still use pump gas.
The reason why I thought to go to either the 75mm or 81mm crank is because a lot of production performance cars are using a overly square engine design. I thought there were some advantages to be had there.
Please, let me know what you all think would be the best way to go. Once again, I am no engine expert. I just want to make my own cylinder head, and make the most power wise that I can...

thanks,
Jason

[Stian1979]

If you increase the diameter and decrease the stroke the engine will have less time to combust the fuel. I think maybe you that making a new cylinder head will give your engine a performance lift if you get it all right because you can customise it to the new cylinder diameter with biger valves placed to fitt the new cylinder. If you are going to do annything to your stroke you should defently not make it shorter.
A good reason for making the stroke shorter is that the biger area of the pistion the more power. So if you are limited to lets say 3litres you want to make as big piston surface as posible and replace the lost stroke by more rpm, but this cost you lost low end torque and more pit stops at the local gas station.

[McGuire]

Nothing wrong with billet, especially with automated multiaxis machine equipment. If you know what you are doing you can go straight from art to part. That is how CNC has revolutionized the prototype business. There is not much sense or economy in building a set of patterns and cores to cast one or two pieces. The time, cost and trouble will be equal to the billet part, and then you still have the casting to do.

For maximum performance per dollar or unit of effort expended, destroking is not the way. It really only makes sense in racing classes regulated by displacement. Everywhere else, there is no replacement for displacement.

[McGuire]

Originally posted by Greg Locock
[BAn I6 has a crank almost as long as that of a V11. [/B]

Exactly. Or a W19 for that matter.

[Joe Bosworth]

A356 was being used by Coventry Climax and others as far back as the 1950's.

I used it in the 1960's with no problems.

I used again for a production run of Karting engines in the 1990's with absolutely no problemswith either cranckcases or heads.


Can recommend without reservation.

Regards

Joe B

[hydra]

Vvillium,
you're not the one who has to have experience in casting. Just draw the heads up in CAD (which you're going to have to do anyway if you're going to make them out of billet) and any half-decent casting or SLA/rapid-prototyping place will take care of the rest. Also 356 is probably the most readily-available cast Aluminum alloy.

Another thing, its almost never a good idea to give up stroke to improve the rod/stroke ratio in a production engine. Like I said, the only reason you would want to destroke the engine would be to fit a displacement limit in some racing class, otherwise its a lose-lose situation. By all means go with the 90mm bore, but stick with the 86mm stroke. The M3 engine (most BMW engines in general actually) is one of the best engines in the world, and if BMW think a 1.5 rod/stroke is fine to 8000rpm, then it probably is...

Come to think of it, have you really sat down and examined just why you want to do this in the first place? I'm sure you can get at least a 10-20% improvement in flow from the existing heads (by suitably enlarging the ports and valves) without having to go through all this effort and expense. Add to that a custom intake manifold and headers and you should be set. The way I see it, the main (sole perhaps?) advantage of making your own head would be the cool/wow factor you mentioned...

Ray,
If I were to guess, the head alloy you speak of is probably some form of hypereutectic high-silicon Aluminum alloy. Several racing engines have been made like this over the years, which brings up another interesting point. What do you guys think of thermally-sprayed valve seats? i.e. a thin coating of beryllium-bronze or stellite or whatever on an aluminum surface?

McGuire,
I was under the impression that casting could be done for pretty cheap, even for a one-off.
Besides, how would you machine the water passages and internal cavities with a billet head?

[Powersteer]

You can increase the rod ratio by getting one of those high pin pistons.

[Greg Locock]

A one off casting will cost about double what a one-off billet head will, basically because you'll have twice as much machining to do - once for the pattern, once for the machined casting.

The probability of success is lower as well.

However, if you wanted to go into any sort of production the casting will obviously pay for itself quickly.

[Stian1979]

http://backyardmetalcasting.com

cheap if you chose to do it yourself.
The forum is helpfull

[JwS]

Potentially cheaper, but your chances of success in the backyard are reduced. All kinds of casting problems could crop up.
I have had some castings done, I think that as long as you are not looking to cast in many details, you might do well to get a basic shape cast. On the other hand if cast billet is readily available in an appropriate size, it may work out better for any number of reasons.
JwS

[vvillium3]

you must realize too, is that I have the US version. So even though its the same bore and stroke as the euro motor, the us motor is completely different. euro motor has a longer connecting rod, and also the head design is completely different. It has lower valve angles, larger intake valves, much smaller intake and exhaust ports(high velocity ports), and dual vanos. So alot of gains are there to be had by making another head. Also at this point, considering using the dual vanos istead of the single off a e46 motor...
With the us version, people are having a hard time putting 270hp to the ground, where with the euro version without headers or any other tuning improvements can almost do that stock. I would love to buy a euro motor and put it in, but it would break me. Its almost around 9grand to do that swap...
I am starting to look around for 356 cast billits. No sucess thus far. Does anyone know where I can get one????

jason

[Fat Boy]

Can we step back for a moment?

What is your goal? Is the goal to make 270 or 300 HP at the wheels or is your goal to make a new cylinder head regardless of what power it eventually makes for you?

If the HP is your end goal, then the ways of getting there are massively more simple than casting your own cylinder head. I would say cheif among them would be to hang out on Ebay for a month until the Euro engine that you're interested in comes across.

The other option is to take the head that you have and put in bigger valves, cut the head and raise compression, and do some port work. Do some real design work and have a cam ground to match your specifications, and then select the proper valvetrain components to match. Then do real testing to determine things like cam timing. That right there is a reasonable enough project to keep most people busy. I would bet that the possibilities of success on the HP end of things is massively improved over building your own head.

If your goal is to learn to cast and to attempt to make something that might run on your car, then by all means, build your own head. But be prepared to spend more money and time for less power.

[Stian1979]

I don't think it would be dificult to find a german scrapdealer trough a european based BMW club that can ship you a cylinder head from a car that has had a acident on the highway.

If you want to build yourself annyway, I'm trying to download msc adams and analysis cfx for simulating components and airflow with bittorrent, but I will not recomend this unless you have a license.

[hydra]

Vvillium,
If its a Euro M3 engine you're looking for I might be able to help out. I've got a friend who's got a couple, PM me offlist if you're interested...

[GeorgeTheCar]

Congratulations to FatBoy!

Getting to define the purpose of the mission is key.

On the other hand if you are just doing it for the experiece it doesn't much matter.
On the other hand you could go and find people with real projects and volunteer to do their work, you would learn as much but contribute to a larger effort and get to learn some of whatthey are doing as well.

Good luck choosing!

[dominick]

Originally posted by vvillium3
I just bought a spare motor for my 95' bmw m3, and now we have some numbers to work from, and time to do it. Plus, our boss bought a true 5-axis cnc with programming about 6 months ago, and gave us the go ahead to do some of our private jobs on the weekends.

-do you have insurance?
-that cnc machine is not gonna run away...

[vvillium3]

well I have stood back and considered what I am really accomplishing here. I have done a couple of valve jobs as well as port+polish jobs. Now I want to take it a step further, and just go ahead and try to build the entire thing. I realize that the first design is going to loose horsepower, but to me it worth it. If the motor runs well and reliably, then thats and A in my book.
No, power is not my first concern here, although it may seem that way from post. But its more about being able to get another experience under my belt. I am not completely confident yet to do work on other people stuff. But if I get this head up and running, I might consider doing work for other people. Right now, if I trash something its out of my own wallet...

"-do you have insurance?
-that cnc machine is not gonna run away..."

dominick, what do you mean???



"As for valve angles, the objective is to minimize surface to volume ratio. Assuming a 1.2 B/S (90/75) and a 12:1 compression ratio the ideal valve angle would be around 22-24 degrees. With an 11:1 compression ratio you can go up to 30 degrees, which may allow you some more latitude with valve sizes... The stock M3 engine is a pretty "square" design, which probably explains its large valve included angle, same goes for a lot of Honda engines with their 45 degree included angles"

hydra, what are the basic equations that you have seem to figure out here. Just the cc surface area/cylinder volume??? I understand the fact with increased valve angle the surface area is going to increase, but what effect does this have on cylinder displacement???

thanks,
Jason

[shaun979]

All else equal, increased chamber volume from increased valve angle doesn't affect displacement, only compression ratio.

=====

Hydra, I always thought the primary reason for shallow valve angles was for bring air in on an angle as close to cylinder axis as possible, to aid flow. Not for surface area to volume ratio? As I understand it reasons we don't go all the way to 0 degree is because of a mix charge motion, valve area, and packaging considerations. Someone please correct me if I'm wrong, or if possible share more accurate or better reasons why there are no 0 degree valve angles in current race engines whether 2 or 4 valve.

[vvillium3]

sorry I didn't type correctly. I meant, what affects does cc surface area have when correlated to cylinder displacement...

jason

[Nathan]

If I may ask an off the side question.

What would the cost and time frame be *roughly* to get a couple of prototype aluminum engines block and heads casted? What is a typical required production run?

Thank you!

[Powersteer]

I admire your desire to carry out this project and think you should finish it. Whatever the results should be a learning curve for you to improve on. The accomplisment is to be able to complete a four stroke cylinder head for six cylinders. You never know what will come next.

By the way, I think there should be balance between how much squish area you choose and surface area. Generally a combustion chamber should have as little surface area given its compression ratio but with modern day swirl and combustion ideas this has changed the design. The piston should also cater this. Surf around this FORUM for some F1 combustion chamber design pictures.

[vvillium3]

thanks powersteer,

what ratio should there between surface area and squish??? This is all going to be design on unigraphix, so figuring out final surface area shouldn't be a problem. I have inquired on here about f1 cc's, with good results. I have a couple of very good, and detailed pictures to go from...
Just to refresh, the compression ratio will be about 11:1, bore and stroke at 90x85.8, and 35mm intake and 30.5 exhaust valves. I haven't gotten as far as actually design the whole package, so the production process is quite a time away. But any suggestions on the cc design, angled squish, surface area, and valve angles are welcome???

thanks,
jason

[Halfwitt]

What rpm do you aim to run?

I'd seen that when you were planning 75mm stroke, you were going for 9000rpm.

9000rpm and 85.8mm stroke is a bit ambitious (very high piston speed). Also what speed do you aim to make peak power? Perhaps 8000 peak speed with 7500 peak power speed would be sensible enough though?

I've seen a full race engine run with a bit bigger bore than you plan, at 10500rpm with a ~1.7:1 conrod/stroke ratio, but these were using proper forged steel racing rods, forged pistons etc.

[Greg Locock]

Nathan, that depends very much on the complexity of the parts. If they are simple sand castings with one or two cores (and I think that would be a reasonable way to do a head), you'd be in and out of the foundry in a day. Best bet is to go and talk to your local light metal foundry. You'd need to chat to them first to get advice about designing the patterns. Make them from any old thing - wood and body filler and a donor head might be the way to go - but you need to include draft angles and allow for metal expansion. If you go to a pattern maker expect a big bill, I'd guess $5000 for a head.

Cost would be something like $200 plus time for the guy to make the sand moulds and inserts, at a guess. An alternative is to get the sand moulds made in one place and then drive round to your local BIG foundry, and slip someone 20 bucks to pour metal in to them.

The more you talk to the foundry, the more you'll learn.

[Powersteer]

SQH = SQUISH What would I do without my coreldraw.



The Honda RC51 V-Twin cylinder head. Notice the exhaust cam/valve side is smaller or lower than the intake. I think you should apply this to your design. Shorter (meaning lighter) valves and a lighter construction.

[Nathan]

Nathan, that depends very much on the complexity of the parts. If they are simple sand castings with one or two cores (and I think that would be a reasonable way to do a head), you'd be in and out of the foundry in a day. Best bet is to go and talk to your local light metal foundry. You'd need to chat to them first to get advice about designing the patterns. Make them from any old thing - wood and body filler and a donor head might be the way to go - but you need to include draft angles and allow for metal expansion. If you go to a pattern maker expect a big bill, I'd guess $5000 for a head.

Cost would be something like $200 plus time for the guy to make the sand moulds and inserts, at a guess. An alternative is to get the sand moulds made in one place and then drive round to your local BIG foundry, and slip someone 20 bucks to pour metal in to them.

The more you talk to the foundry, the more you'll learn.

Thank you very much Greg!