635Csi intake manifold

[grave77]

I saw a full manifold unit of the old 635Csi car, I have heared before that they allow more air in as they are wider than the new M30 engine.

any more information from you mates ?!

[Bill R.]

are bigger to allow more flow since it has bigger intake valves as well in the newer motor.

I saw a full manifold unit of the old 635Csi car, I have heared before that they allow more air in as they are wider than the new M30 engine.

any more information from you mates ?!

[grave77]

so 635i intake monifold and valve is smaller?! ..does that apply the old 745i manifold too?

[DaCan23]

For the most part, the 3.5L M30 was the same for all 635s. From 1978-81 did have a slightly larger bore 93.4 vs 92 for all other years and from 82-86 it had a 10-1 compression w/ DME II. The only real difference was the DME, L-Jet 1978-79, DME I 1980-81. From 1987 on it was DME III with a 9.2-1 compression, which is the same for the E34 89-91 right?

[632 Regal]

bigger intake passages result in lower torque at lower rpms and for the most part will posibly de-tune the whole intake system and make your car slower.

I saw a full manifold unit of the old 635Csi car, I have heared before that they allow more air in as they are wider than the new M30 engine.

any more information from you mates ?!

[grave77]

well I think the 9.2:1 is the old M30 compression. E34 M30 has something like 12:1 I think .... maybe some guys will correct me.

[grave77]

I never knew that Jeff, but why then many people try to enhance the flow from the passages ( Intakes, air filters, bigger throttle butterfly ..etc ) and after all it gets slower takeoff?! I thought this would make the engine gain better compression

[Interceptor]

I never knew that Jeff, but why then many people try to enhance the flow from the passages ( Intakes, air filters, bigger throttle butterfly ..etc ) and after all it gets slower takeoff?! I thought this would make the engine gain better compression

You cannot change the compression ratio by simply replacing your intake manifold. Unless you turbo/supercharge your car, you won't gain much by tampering with the intake manifold - and as Jeff said, you'll end up with a detuned car that will be slower.

[grave77]

so that ends up the intakes issue.

Does a camshaft change the compression ratio? for example stage II camshaft. also do I need new rockers and springs or will the OEM work with it?

[632 Regal]

k....what a cam does is change the dynamic compression at a different time compared to the stock cam...not static compression. You could in theory change to a larger lift cam with the same timing and get higher static compression at a slightly higher RPM range. If you went with a larger lift cam with more duration it would make more power at a higher RPM but you will sacrifice lower RPM power. This kind of discussion could go on forever. What you want to do is the most important aspect than just sticking in a bigger bumpstick. Usually if you go with a higher lift and duration cam it will tend to run better at higher ropms, so if thats whats going to happen the rest of the package will have to be tuned for that modification such as higher compression, larger valves, free flowing exhaust, stronger valve springs that wont bottom out from higher lift etc etc etc.... At that point you can concider the larger intake manifold.

so that ends up the intakes issue.

Does a camshaft change the compression ratio? for example stage II camshaft. also do I need new rockers and springs or will the OEM work with it?