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Is it possible to put the heads and cams from a 3.0 164 S on a GTV6 2.5 engine? If so other than the benefits of the Scams would there be any other benefits/improvements? Terry
 

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Interesting thaught. Not having seen 3.0 heads, I dont know the sure answer, but I dont think it is possible. more informed people on here will know.

I would have thaught the diameter of the combustion chamber on the 3 litre heads would be an issue. there would be no benefit over a well prepped set of 2.5 stage 2-3 heads with oversized valves, and 164s cams anyway.
 

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Richard Jemison
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3.0 heads on 2.5

It can be done, but heres the issues:
1- The oiling sleeve that is partially pressed into the block is different on early 2.5 motors, and the later 2.5 and all 3.0 motors.
2- The differences in combustion volumn and and valve sizes are very different. Yes it can be mounted on a 2.5 block, but:
3- You will have about 6.5 C.R. so assuming you cut about .080 (2mm) off of the head and get back to close to stock compression, you have another pair of issues.
one, that the valves are bigger than the reliefs in the pistons. (This will be an issue if deck iscut or not.)
Then there is valve timing issues caused by deck drop. Adjustable Sprockets solve that. But

Why would you want to to start with.
The 2.5 heads will fit on a 3.0 and breath very adequately when prepared correctly. (you do know that intake ports & exhaust ports are the same size don`t you?)
Correct bowl shaping and tapered cut seats, will have them breathing as good as 3.0 heads.. Even larger valves are unnecessary when seat position is done correctly. The larger valves are just a larger lip for intake charge to get around.
The only problem is compression hits 11.3 with non shaved heads. No problem for the racers! ;)
 

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No its not a bolt on issue..The valves will hit the top of the sleeves when opening.The headgasket is very marginal and will blow out,irrespective of using 2.5 or 3.0 l One will blow top,the other below.
 

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Right. You have to realize that the 3L heads are for 93mm bore and the 2.5 is 88mm. You'll never get a proper seal, as the "Fire-rings" have to sit on top of the sleeve and seal to the edge of the combustion chamber...

The "S" cams were really developed for the 3L. Put those in your 2.5 and you'll lose considerable static compression at lower rpm's (read: power & torque) Yes, you will pick up some nominal power at higher RPM. So, unless you are racing this car, I would recommend against it - really.

If you have access to a whole "S" engine, that would be a better way to go. Swap the whole thing. Naturally, you'll have to swap over several components to get it to fit. Basically the 164 engine swap procedures.

If the 164 "S" donor is "tired", you might consider just swapping the pistons, sleeves, and cams instead. You'll end up with 11:1 or 11.5:1 compression. This would be the 2.8 conversion (but with "S" pistons!) which has been done before. You'd have to have the block bored to accept the larger sleeves, but I have never seen any specific info on what has to be done to the 2.5 heads to mate with the 3.0 liners...
 
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