valve size question

[bo]

hi all,


i was wondering about valves on a type 1. Sometimes i have to realte vws to v8 because that is the first kind of motor i learned about. anyway, on aour v8 rail we use a bigger exhaust valve than intake valve . can this be applied to vws because it seems like a good way to get all the exhaust out before the net stroke.please help.




                                                                                thanks, bo

[Darren DVKK- K-Roc]

Hi, because of the extremely high pressures and temperatures of the exhaust during it's blow down phase you should only require an exhaust valve that is about 72-76% as big as the intake.

[Bad Bug Two]

…on our v8 rail we use a bigger exhaust valve than intake valve…

I doubt that!  You might want to double check with who ever built the heads to find out for sure.  I would bet that maybe they increased the exhaust size and left the intake stock sized or possibly increased the exhaust more than they increased the intake?  Depending upon what type of heads are on the V-8, if stock castings, it would take a lot of work to move the guides and decrease the intake size to make room for exhausts bigger than the intakes.  If aftermarket heads, then it would be easier to do, but again not practical… in my opinion.

… can this be applied to vws because it seems like a good way to get all the exhaust out before the net stroke….

Depending upon the application, you may want to increase the exhaust, but you would still want to do some intake work too.  The closest to the same size I’ve ever run was a 40mm intake and 37.5 exhaust.  But I’ve also run as much of a spread on sizes as a 50mm intake and 38.5mm exhaust!

Keep asking questions.  If I recall correctly from previous posts, you are very young and still have a lot to learn.  The more ideas that you bounce around, the better chance that you will be able to formulate your own opinion, based on some of other peoples experiences.

 

[bo]

thanks guys

yes i am still young and learning. thanks for not doggin on me like some others do because a not so smart question. for the record they are aftermarket heads on the v8 but we upsized the exhaust and didnt fool with the intake side

thanks, bo

[Mag00]

Some Formula one teams used a larger exhaust to intake....But that's not your typical V8 ,now, is it?

[bo]

nope, but i thought they were v 12's. and this isnt a stock motor by any strech it is pushing 700 hp