US V8 and Japanese cylinder heads

[100SRV]

Hi,
I am pretty sure that I read an article, maybe in Octane magazine, regarding an American V8 which was fitted with some Japanese cylinder heads (possibly 16 valve) these had a beneficial effect on the engine but the idea was rejected by the Americans. I think this was in the 1970's.

I am fairly sure that I haven't imagined this but can recall so little of the detail that the few web searches I've made have borne no useful results so I turn to the wealth of experience that is the PH Engines & Drivetrain area...please put me out of my misery!

What are the facts behind my vague recollections?

[Steve_D]

100SRV said:

.....What are the facts behind my vague recollections?

Senior moment?

Steve

[V10Mike]

Are you sure you are not thinking of the Moser DOHC heads from around 1970?

Original article Here: http://www.harveycrane.com/images/hotrod_0871.pdf

[chuntington101]

Could the the Chevy LT5?.... THink Yamaha did some work on it.

[100SRV]

Thanks for the replies Chuntington and V10 Mike...the Moser article is interesting but not "it", I'll have a look at the LT5 though. Thinking further on the problem it may have been related to the CARB smog laws which were passed in the early '70's. Bill Boddy or LJK Setright would be the folks to ask...

[HairbearTE]

There have been numerous 4 valve per cylinder conversions attempted on V8s over the years. Some even made production in small volumes in the aftermarket, including a conversion for the big block chevy engine! The fact they it never really caught on was more down to the fact that it was almost always much cheaper to get the same or more horsepower by different methods. A few years ago someone noticed that the bore spacings on the 2.2 Lotus twincam engine and the Rover V8 engine were very similar and tried to adapt a pair of the Lotus heads to that engine. I'm not sure how far along they got with it.

[anonymous-user]

HairbearTE said:

2.2 Lotus twincam engine and the Rover V8

That doesn't sound like a match made in reliability heaven.......... ;-)

[Pumaracing]

100SRV said:

Thanks for the replies Chuntington and V10 Mike...the Moser article is interesting but not "it", I'll have a look at the LT5 though. Thinking further on the problem it may have been related to the CARB smog laws which were passed in the early '70's. Bill Boddy or LJK Setright would be the folks to ask...

You'd need some sort of portal to the hereafter seeing as both of them are dead but it's worth a try.

[rev-erend]

Lotus did 4 valve heads on one of the Corvette's... cant recall what the ending / model was.

[HairbearTE]

It was the LT5 engine in the early 90s ZR1.

[rev-erend]

HairbearTE said:

It was the LT5 engine in the early 90s ZR1.

Yes..



For model year 1990, Chevrolet released the Corvette ZR-1 with the radical overhead cam LT5 engine, which shared only the 4.4 inch bore spacing with any previous LT engine. The LT5 was engineered by a team headed by Mercury Marine Project Engineer Terry D. Stinson.[2] It was an all-aluminum 5.7 L (349 cu in) small-block V8, but was thoroughly different from any of the other Chevrolet 350 engines. The bore and stroke were both different at 3.9 by 3.66 in (99 by 93 mm) instead of the usual 4 by 3.48 in (102 by 88 mm) and it featured Lotus-designed 32-valve DOHC heads. It was hand built by specialty engine builder, Mercury Marine in Stillwater, OK. This engine produced 375 horsepower (280 kW) and 370 lb·ft (502 N·m) for the 1990-1992 Corvette ZR-1 and jumped to 405 horsepower (302 kW) and 385 lb·ft (522 N·m) for 1993 to its final year in 1995, thanks to cam timing changes and improvements to the engine porting. 1993 also added 4-bolt main bearing caps and an exhaust gas recirculation system. The engine was used only in Corvettes.[3] The LT5 was very expensive, and after six years of production, GM canceled the ZR-1 option. A total of 6939 were produced.[4] The LT5 however wasn't an evolutionary dead end. Despite being discontinued, a new class of premium V8s for Cadillac and eventually Oldsmobile, the dual overhead cam V8 Northstar and its derivatives, drew heavily from the LT5's design and lessons learned from its production.[5]

The LT5 was available on the following vehicles:

1990-1995 Chevrolet Corvette C4 ZR-1 equipped with 6-speed manual transmission (Production: 6,939)