21 replies to this topic

[fredeuce]

I posted this previously on the Repco Brabham V8 thread however it perhaps is deserving of a separate thread.

On another forum a thread has developed about the 303 ci Pontiac engine. The link below takes one to an article about the development of this engine. Interestingly, there is a Jack Brabham connection with the project. The cylinder heads appear to be styled on the early 620 style Repco V8 heads but there is no mention of Repco. Jack's book "The Jack Brabham Story" makes no mention of this project.

One of the posters has asked me to post some pictures he has of an existing head. These are also posted below.

Is anyone able to add to or clafify this story?

http://www.wallacera...y-engine-1.html

[Ray Bell]

What an incredible story...

I never heard of that before at all. Well, you wouldn't expect to unless you were talking to the un-talkative Jack or Phil Irving or someone else at Repco... and as it was undoubtedly a hush-hush deal, little would be said anyway.

[johnny yuma]

Perhaps the sub-400bhp figure is reflective of honesty.Nowadays dyno operators seem to find formulae to give customers the power results they want !
Allan Moffat's 302 Trans-Am which swept all before it in Australia developed less than 400bhp,but it was revved hard and I don't remember it failing often,if at all.Moffat ran long distance races with low diff ratios--it takes race engines to do this not hotted-up factory motors which may show more bhp on a dyno then fail at the track regularly.

This was the daddy of undersquare--4.12 inch bore,2.84 inch stroke !

[Bruce302]

I have read several articles regarding the Pontiac 303, and from what I can gather it was modelled, in principle, after the Tunnel Port Ford T/A engine.
The Pontiac wasn't as good as it should have been, the ports were really way too big, and there were inherent oiling problems. There was insufficient development time, and the client base was likewise extremely small.

I can dig up more on the 303 if you wish, but as far as Repco being involved, I haven't seen that ever mentioned. But in the auto world, it would fit in the general time line that there may have been some knowlege of the style of port.

Bruce

[fredeuce]

Perhaps the sub-400bhp figure is reflective of honesty.Nowadays dyno operators seem to find formulae to give customers the power results they want !
Allan Moffat's 302 Trans-Am which swept all before it in Australia developed less than 400bhp,but it was revved hard and I don't remember it failing often,if at all.Moffat ran long distance races with low diff ratios--it takes race engines to do this not hotted-up factory motors which may show more bhp on a dyno then fail at the track regularly.

This was the daddy of undersquare--4.12 inch bore,2.84 inch stroke !

My memory of the Moffat Boss 302 is that it was dynoed , in final form, at some 484 bhp. I will need to research that.

Edited by fredeuce, 29 May 2009 - 07:55.

[Bruce302]

Ok, I have now had a quick read of the article. The impression I get is that it was a Repco-Brabham project as opposed to the one built and used, though briefly, in the T/A series cars.

An interesting line is: "Pontiac engineers were much too involved in a 303 variant to further develop the performance potential of the Brabham/Pontiac".

The only other pic I have seen of a Pontiac engine that looks like the Brabham, was a 421 ohc, and I believe that only one was made.

480 ish hp for the Moffatt engine would be very good, and in the right ball park. Most other reported T/A 302 engines were said to be circa 440 hp. But Moffatt had more time and rule freedom.

Bruce.

[McGuire]

Though it was found in a closet and restored 25 years ago, far as I know the one complete engine known to exist is still at GMI, which is now Kettering University. You could try contacting the school. May be on display in a lobby or serving as a classroom prop or fancy doorstop. Or maybe it went back in a closet.

I don't know this but from what I gathered over the years, the SCCA Trans Am application was a GM cover story. With Lucas FI, overhead cams, etc, it would be very difficult to legalize. Pontiac would have to do a type homologation and produce some number of them for sale -- unlikely. I believe the project's real purpose was directing money to reward favors, and also to learn what there was to the Repco Olds, doing it with a current production engine family rather than the BOP V8.

In the years leading up to this Pontiac had been doing a lot of work with SOHC engines with the OHC six production engine, along with various prototype V8s designed along the same lines. A few of those V8s still exist as well. Mac McKellar, who was Pontiac's key engine guy in the '60s, brought one to the Meadowbrook concours several years ago. A 421 CID version if I recall.

[Bob Riebe]

I have read several articles regarding the Pontiac 303, and from what I can gather it was modelled, in principle, after the Tunnel Port Ford T/A engine.
The Pontiac wasn't as good as it should have been, the ports were really way too big, and there were inherent oiling problems. There was insufficient development time, and the client base was likewise extremely small.

I can dig up more on the 303 if you wish, but as far as Repco being involved, I haven't seen that ever mentioned. But in the auto world, it would fit in the general time line that there may have been some knowlege of the style of port.

Bruce

The main problem with the Pontiac 303, as reported, was that the SCCA refused to allow the special low-deck 303 block.
The were used with some success in the NASCAR Grand-Am. pony car series.

Magazines of the era regularly reported the Boss 302s as having apprx. 480 hp with the two Holley Dominator carbs.
The AMC engine was reported as being similar but the stud-girdle necessary was disallowed and so they raced with more like 400 hp.

The next year, 1970 Ford Boss engines were said to have apprx. 460 hp on a single carb.

[Bruce302]

In thinking about this Brabham/Pontiac, it would never be legal in the SCCA Trans Am, unless they put it into production, and I think 1000 units were the required number to be 'sold'.
It may have been possible that it could be dipping a toe in the water of the then rising FA/5000 series, but that was pretty well sewn up by the small block Chevrolet.

Perhaps it was just a joint excercise.

Bruce.

[Lola5000]

The Boss 302's put out a lot more then 400hp in 1970.
Today on Webbers a Boss 302 in historic NC would have about 530hp and 430 ibs of torque.
Any good 302 will put out 500hp in NC form.

[Lee Nicolle]

In thinking about this Brabham/Pontiac, it would never be legal in the SCCA Trans Am, unless they put it into production, and I think 1000 units were the required number to be 'sold'.
It may have been possible that it could be dipping a toe in the water of the then rising FA/5000 series, but that was pretty well sewn up by the small block Chevrolet.

Perhaps it was just a joint excercise.

Bruce.

I agree, it would never have happened. All of those engines were modified road engines, homolgation specials to be sure but that engine would have been totally unsuitable for road use. It may have been able to be homolgated as a base for F5000/F.A though, I dont know the exact rules there. A little short stroke screamer would probably be good to cart around 600k of openwheeler but not so good to cart around 1200+k of Pontiac!
The Boss 302, Z28 engines are not very nice road car engines but defenitly more suitable for a high RPM sedan race engine.
Moffats engines were reputedly in the vicinity of 500 hp and he supposedly normally only used 7500 rpm, turn that another 1000 like they did in the states and you will get 500+ and ofcourse a good Z28 race engine made 500 or so.
Reputedly they are making well over 500 in GpN these days on Boss's, though modern oils and components make this far easier and I bet they are using at least 8000rpm.

[Ray Bell]

I'm pretty sure the F5000 rules specifically excluded overhead camshafts...

It's interesting to ponder why they did this. I'm doubtful that the short stroke of this unit would have made a very good Trans-Am engine at all, though on a very fast circuit it could have been okay.

[Bob Riebe]

I'm pretty sure the F5000 rules specifically excluded overhead camshafts...

It's interesting to ponder why they did this. I'm doubtful that the short stroke of this unit would have made a very good Trans-Am engine at all, though on a very fast circuit it could have been okay.

On the Boss engines in the Trans-Am some of the Ford people complainws how poorly they ran below four thousand rpm, Ford told them "then gear them so they don't drop below four thousand rpm!"

[Lola5000]

I've had 2 Mustang race cars , 1967/8 302 coupe and a Boss302,yep secret was to drop a low diff ratio in 'em and let em rev.Just look at John Mann his 289 would just be reving and reving.
The secret to the Boss 302 was to fill in the ports,way to big,but adding metal was illegal thus reading the rule book one would put tongues in the ports,till they banned that,thus I sold my car and never raced again.

[Ray Bell]

Jack Brabham brought a Boss-engined Mustang into Australia, Barry Sharp tried it and found it useless on our local circuits...

They gave up on that and built a 351.

[275 GTB-4]

I've had 2 Mustang race cars , 1967/8 302 coupe and a Boss302,yep secret was to drop a low diff ratio in 'em and let em rev.Just look at John Mann his 289 would just be reving and reving.
The secret to the Boss 302 was to fill in the ports,way to big,but adding metal was illegal thus reading the rule book one would put tongues in the ports,till they banned that,thus I sold my car and never raced again.

Couldn't you have worked some standard heads Rob

Edited by 275 GTB-4, 31 May 2009 - 06:29.

[Lola5000]

to hard sold it and enjoyed my road cars.plus I could store more rubbish in the Boxer 512 then in the mustang.Thank you for the DVD on the Escort rally cars.

[275 GTB-4]

to hard sold it and enjoyed my road cars.plus I could store more rubbish in the Boxer 512 then in the mustang.Thank you for the DVD on the Escort rally cars.

Trailers are where you put your rubbish! ....glad you enjoyed it.

[Lola5000]

The Boss was hoot to drive on the Goodyears,then they banned them,the only tyre that had the correct period look.
Never again will i go near another race track or put up with the people whom TRY to run historics in Australia.
"Pass the port please"

[lotcor]

Hi All, with regards to the Repco Pontiac engine I replied to the last post on the Repco Brabham engines thread and have only
picked up on this one.

It turns out the above head is mine
I have since found out what it is and some of the history of it.
As far as I can tell Repco started looking into the Trans Am arena and built some of these engines based on a 303 pontiac block. One of which is in the Wallace racing article. What happened to the rest (I believe 1or2) is up for grabs. My head is number 4 which came off an engine that expired and along with lots of other parts may have been stored (and eventually binned) at Repco Research where I was apprenticed in the late 70's. With the help of a few other ex Repco employees we have uncovered some documentation for this engine (drawing set). They were designated RPO-XXXX numbers (RPO being Repco Pontiac). It was built in late '68 early '69 but not many people know about it now (or then for that matter) . It is a 'Repco Brabham' going by drawing title blocks so it could be added to any register if one ever exists.

Thanks Fredeuce for your input.

[lotcor]

I just read this in another thread, re the las paragraph.
If this is true then the head would be off the other of the 2 engines. Don H told me also that they only made 2 engines.
Mystery solved I guess.

Yep. If you read between the lines of the 1968 HOT ROD story the backward three-valve proved inferior to a standard layout... and they surely knew that before they built it. But here is a perfect example of how GM used to do things, and how all OEs still do it to some extent. What are the pros and cons of two divergent approaches? Let's build them both and find out the whole story. And while there are some attractive aspects (chamber layout, intake valve and spark plug position, exhaust valve temps) you can't get around the fact that intake valve area needs to be around 125% (pick a number in that neighborhood) of exhaust valve area.

At least one of the two-valve SOHC V8s escaped into the world and survives. Mac MacKellar (the Pontiac engineer in the above story, long since retired) has one installed in a 63/64 Pontiac B-body and has driven it around to local car shows. I last saw it maybe five years ago in the parking lot at the Meadowbrook Hall Concours. He would be getting on in years -- hope he is doing well.

There was another SOHC Pontiac V8 at about the same time that article was written that was totally unrelated to this program. Pontiac contracted Repco to build a two-valve SOHC V8 on the short deck 303 block, supposedly for use in the Trans Am series. Sort of a shot in the dark slash feasability study, or most likely an excuse to throw some money in a particular direction. And maybe to find out just what Repco had in the Olds, if it was really any good. Basically the two-valve Repco Olds layout adapted to a Pontiac block, there was one known example... which ended up in a store room at the General Motors Insitute, now Kettering University. In the '80s some students and instructors restored it but couldn't make it run. I am sure it is still around somewhere too, but I don't know where.

[lotcor]

I just read this in another thread, re the las paragraph.
If this is true then the head would be off the other of the 2 engines. Don H told me also that they only made 2 engines.
Mystery solved I guess.

A lttle bit more,
2 more unfinished heads have turned up.
I believe the engine that I have came from one that expired on the dyno as a result of the block having core shift on one of the bores
that wasnt't picked up. They made another block and that engine is the one in the US. A figure of 450hp was talked about on the dyno here,
not in this artilcle though.
http://www.wallacera...y-engine-1.html

Edited by lotcor, 02 August 2012 - 03:57.