RV8 - Crank case Ventilation.

[garrycol]

The 3.5 RV8 has the inlet for crankcase ventilation at the right hand rear of the block - basically a hole from the outside to the inner crankcase - this takes filtered air from the air intake into the crankase and them out the outlet at the top of each rocker cover into a large intake at the base of each carburetor.

I have installed a 4.6 in my vehicle but retained 3.5 carbs and manifold and the 4.6 takes in air from the left rocker near the throttle body (Thor) and out into the intake manifold via the right hand rocker. If I use this basic system with the t means unmetered air goes straight into the engine so bypassing the fuel metering system (carbs).

Ideally I would like to make the system the same as the 3.5 with a hole at the rear of the block.

Given there are subtle differences between the 3.5/9 blocks and the 4.0/6 blocks I need to know if I can just drill a hole in the rear of the 4.6 block in the same spot as the 3.5 block.

Does anyone know for sure if this is possible - after comments from people who know rather than guessing.

Thanks

Garry

[garrycol]

Hmm so no one knows

[GDCobra]

I wanted to reply but it would only be an educated guess based on my experience rather than knowing so I got put off.

[garrycol]

I wanted to reply but it would only be an educated guess based on my experience rather than knowing so I got put off.

Yes my educated guess is that they are the same - BUT if wrong the drill hole goes through a water jacket or something else. Hence yes I want responses from people who actually know on this occasion but thanks for you consideration.

I do have a 4.6 bare block that has a slipped liner so I suppose I could experiment with it if a knowing response is not forthcoming but we will see

Garry

[GDCobra]

I wanted to reply but it would only be an educated guess based on my experience rather than knowing so I got put off.

Yes my educated guess is that they are the same - BUT if wrong the drill hole goes through a water jacket or something else. Hence yes I want responses from people who actually know on this occasion but thanks for you consideration.

I do have a 4.6 bare block that has a slipped liner so I suppose I could experiment with it if a knowing response is not forthcoming but we will see

Garry

What I was going to say is that the later cars, certainly when fuel injection replaced the carb's, had extraction from one rocker cover and inlet on the other via a slim pipe with a filter on top, the pipework also has specific sized orifices (orifi?) which control airflow as this enters the inlet air post MAF
hence unmetered.
Presumably the EFi system takes this 'controlled' airflow into account in its mapping.

My original 3.5 engine had the hole in the rear of the block and an outlet on each rocker cover, don't know where the pipework went on the original SU carb's as I never used them, but on my Edelbrock and Holley carb's these went to the aircleaner hence not unmetered.

Why can't you employ a similar arrangement to the later engines (which a 4.6 will be) surely this makes more sense than drilling into the block?

[paul c]

I drilled my 4.6 and vented it to the air cleaner thru a filter as per the original 3.5. The hole is just thru the rear web below the inlet manifold the same as the 3.5 block, it goes into the valley. The rocker covers are both plumbed to the carb ports via flame traps.

[garrycol]

Hi Paul, that is great to hear. I thought that would be the case but wanted to hear from someone that has done it.

Thanks - much appreciated.

Garry