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Wedge TR8 guys...Rover 4.0 heads on a 3.5L?

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C

Cheapsnake

Jedi Trainee
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OK, just scored a set of 4.0 heads on ebay that I "assumed" (yeah, I know) would work on my 3.5. Physically, I think they'll fit, but my main concern, now that I've had a chance to think about it, even if they do fit is that they'll lower my CR if the combustion chambers are larger than the stock 3.5's. On an engine with an already low CR, I don't want to lower it anymore. I looked all over for combustion chamber volumes so I could calculate CR's but couldn't find anything.

I know some of you guys have upgraded to the larger displacement Rovers so any thoughts on this would be greatly appreciated. Thanks.

Tom
 
Hey, Tom -

Got this from a list I'm on:

28cc is the smaller type.

3.5 & 3.9 heads (14 bolt) have 36cc. They all came with the thin tin gasket.

3.9, 4.2, 4.0 & 4.6 (all 10 bolt) that originally used the composite gasket all had 28cc heads

The Olds 3.5 head also had 28cc, but is hard to find.

Basically, Rover skimmed the heads to reduce the volume to accommodate the composite gaskets.

Mickey
 
If you bolt the 4.0 heads onto a 3.5, your copmpression will rise to 9.35 from the 8.13 you have now. Don't be alarmed that they have less head bolts. Those weren't needed anyway. Rover did away with them when they redesigned the heads for the 4.0. Seems that if you over torqued the old style heads at the lower bolts, the head was then prone to warping. Do away with the bolts- problem solved.
 
Alright, that'll make make me sleep better. 9.35 CR is just about where I want to be.

Now I have a confession to make. This engine is going into a Porsche 914. I'm still keeping my TR8, but I needed a winter project and the Rover V8 and 914 seemed like a natural. I've had my TR8 for going on 5 years now and am constantly impressed with the engine's flexibility and resilience. I overheated and seized it and it still has the original compression. Of course, now I'm going to have to start looking for a set of 4.0 heads for the TR8. Oh darn! :banana:

Thanks guys.

Tom
 
Will do td. I started a build thread on 914world.com if anybody's interested. Great bunch of guys over there, just like BCF, cept they wear a different badge on their hoods.

It's going to be awhile before I actually get to the fun stuff like dropping the engine in. 914's are plagued with lots of rust issues and that's where I'm at right now. Master plan calls for 200hp, GT flared fenders, 911 suspension, upgraded brakes, body stiffening kit and whatever else before time/money/energy runs out. In the meantime, I've got my TR8 to make bad days go away.

Tom
 
one of my friends has a 914 with a 350 in it sitting in his back yard. It's a nice clean modification; I don't know how they fit it all together. He says its the fastest street car he has ever been in. I wonder if the owner can even register it in California?
 
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