1972 Replacement LS6

[SuperNovaSS]

I'm wondering isf anyone here has ever seen something like this before.

I bought a late 71 LS6 engine yesterday. It has the CRR suffix on the pad and sounds like it is totally original except the intake and carb. It even still has the 1111437 distributor. The strange part is the engine has a 3964291 head on one side and a 3994026 head on the other.

I have seen later 69 engines with a 840 head on one side and a 291 on the other. Since they are essentially the same head it does not cause any problems.

The difference on this engine is a 3964291 head is a closed combustion chamber design and I believe the 3994026 is an open chamber. I will not have the engine until the end of the month so I can't open it up and inspect it until then. It is just driving me crazy thinking of how this happened and how the engine can possibly run OK.

Any ideas?

Happy New Year,

Jason

[Fast67VelleN2O]

Whats the date spread on the heads?

[SuperNovaSS]

I believe they were pretty close. I bought the engine over the phone and I will not have it in my hands until the end of January.

Jason

[396L35]

Yes they made them and I know someone on here that has one...

[SuperNovaSS]

Mark,

Are you saying you know another member who has an engine with a 291 head on one side and a 026 head on the other?

Thanks,

Jason

[Lynn]

Jason,

Never saw this on a big block. Have seen a 69 Chevy 300 horse 350 with one 041 head and one 186 head. Pretty sure it came that way from the factory.

[Chevy454]

I was told of a late Camaro L72 getting a 291 on one side and an 840 on the other...I ran across that info while researching a set of 840 heads cast the last week before the 291s started.

[SuperNovaSS]

The 840 on one side and 291 on the other is fairly common. The issue I see with the 72 LS6 is it has a closed chamber head on one side and an open chamber on the other.


Jason

[396L35]

Not to worry Jason, just think that one side of your motor will pull more horsepower then the other...

[markjohnson]

I'd be worried about launching and the car pulling to the side with the most compression since one head is open chambered and the other head is closed chamber.

[SuperNovaSS]

OK, for those interested I got the engine home today and popped the heads off. Sure enough, a open chamber head on one side and a closed chamber on the other. The heads are pretty closely dated for a marine engine and it may have been a factory goof. I'm not sure. Funny thing is, the boat was supposed to run well.

Jason

http://i179.photobucket.com/albums/w301/super-novass/71LS6017Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6018Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6019Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6020Small.jpg

[SuperNovaSS]

http://i179.photobucket.com/albums/w301/super-novass/71LS6021Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6022Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6023Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6024Small.jpg

[SuperNovaSS]

http://i179.photobucket.com/albums/w301/super-novass/71LS6025Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6026Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6027Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6028Small.jpg

http://i179.photobucket.com/albums/w301/super-novass/71LS6029Small.jpg

[69SSZL1]

I would think the difference in compression would cause a vibration or off-balance?
What letter is stamped on the rockers?
What cam is in it?

[SuperNovaSS]

I have not checked the cam. The rockers are "H".


Jason

[69SSZL1]

I would have thought they would be "L" or "M" long slot. "H" is the ZL-1 and L-88 extra long slot. Good Rockers. I wonder if it has the 3863143 cam or the 3904362 cam.

[SuperNovaSS]

If I tear it down far enough to see in cam numbers I will let you know.


Jason