8 replies to this topic

[Bob Riebe]

http://www.enginelab...iron-sbc-block/

 

Some thing interesting

 

http://www.enginelab...rom-show-floor/

 

http://www.enginelab...-mecum-auction/

[Lee Nicolle]

That 'new' Dart Block seems to have what I consider a large fault for a race engine. The OEM Chev has a seies of drain holes inthe valley which has been replaced with a big slit like some Fords and Holden V8s.

For a roadcar having the oil drain back over the camshaft and eventually the crank is fine, BUT not good in a high RPM race engine. The more oil bouncing off the crank is a real problem.

What many including me have done over the decades is drill the holes a bit larger and then press tube into them about 1/2 above the valley floor. You breathe the crankcase pressure and the top end oil only comes back in the drains front and rear. Less aerated oil that you are trying to scavenge.

 

On the other subject of W Chevs here is a rare engine and car.

Both pics did not get the details, the reg no is TRI348,,, and it is, a 348 Tripower manual Chev. A very rare beast. I should have stooped a bit more to get the carbs under the filter

[Magoo]

http://www.motortren...c-6-2l-lt5-v-8/

[Bob Riebe]

Ack, ack a dak, that thing has three too many camshafts and 16 to many valves.

If it comes to pass I hope it goes the way of the other four cam engine.

 

As a yout I thought OHC multi-valves was as tits as things get but in my old age, for the street they are just extra expense with little real gain.

Edited by Bob Riebe, 26 December 2016 - 23:19.

[desmo]

Cams and valves are marketing gold though.

[Canuck]

Perhaps separation of intake and exhaust cams provides a broader power band that can't be achieved when you're trying to go variable valve time with a single, unified camshaft. Try and stuff that mess into the V and going OHC makes all kinds of sense. Going with a 4-cam 2-valve engine would still piss off the cam-in-block purists, and leave the technophiles thinking WTF GM - a lose/lose scenario from a marketing standpoint even if it's a better engineering solution.

[Lee Nicolle]

That is the only point that makes sense.

VCT can be an advantage,, but driven by chains is seldom effective as chains S t r e t c h !! And move the cam timing anyway.

For simplicity and practicality the simple pushrod is small and generally very powerfull.

Look at Ford, the modular lump and now the Coyote and still are no more effective than a Windsor with decent heads. And that is a tiny little thing in comparison to the more modern engines. 

GM have a simple tyhing now, putting more bulk into the front of the car makes no real sense.

I have been for a ride in the Lotus Vette and was underwhelmed. As is the owner who bought it from photos. Car is excellent and it should appreciate nicely. But he gets hosed by Vortex late model Vettes yet alone LS ones.

[Greg Locock]

Yeah, the LT5 wasn't exactly a stellar example of achievement in terms of specific power or torque. I was not involved in any of the interesting stuff, did a little bit of vibration/balancing work on it. It would be interesting to know why but I don't suppose that story will ever come out. I did hear that the subsequent Corvette engine, designed in the USA, was viewed as a death march, as they quite simply HAD to beat the Poms. Which they did.So perhaps it was all a devious plot by GM management to get the American engineers off their butts (they did the same with Opel). Knowing how GM operated at the time, I might guess they laid down a spec and insisted that Lotus stuck to it, but their own guys would have known how to get the rules changed for a better overall outcome. 

[Almag]

Yeah, the LT5 wasn't exactly a stellar example of achievement in terms of specific power or torque. I was not involved in any of the interesting stuff, did a little bit of vibration/balancing work on it. It would be interesting to know why but I don't suppose that story will ever come out. I did hear that the subsequent Corvette engine, designed in the USA, was viewed as a death march, as they quite simply HAD to beat the Poms. Which they did.So perhaps it was all a devious plot by GM management to get the American engineers off their butts (they did the same with Opel). Knowing how GM operated at the time, I might guess they laid down a spec and insisted that Lotus stuck to it, but their own guys would have known how to get the rules changed for a better overall outcome. 

Sounds about right. As I remember it, in the early stages of the LT5, Tony Rudd of Lotus told GM that 400 hp was doable. Then GM found out that Tony's plans were around a wider bore spacing than the traditional smallblock 4.4-inch centers. GM insisted on 4.4-inch spacing.

 

Tony found this arbitrary and foolish since it in turn limited valve size, for no reason other than blind tradition. In the end of course, GM was the boss and so 4.4-inches won out. They compromised on 385 hp for the initial variant of the engine. Later this was upped to 405 hp, and a stillborn 2nd gen LT5 was in the wings that promised 450-475 hp to trump the Viper.

 

The LT5 suffered in part from 'not invented here' syndrome and died an unfortunate and early death. It definitely lit a fire under the GM smallblock engineers for all of the engines that followed it, though.