advice on ratio rockers

tayloredvw Seriously Crusin Dubber

165 posts · joined May 2006 · 12 Apr 2011, 9:45 pm

#835449

Hey guys, I have a 1915 im replacing the heads on. The crank, rods, flywheel have all been balanced when put together but with the standard un-counterweighted crank.

I have a c-35 cam in it now and the new heads are mofoco 050 with 42inlets and 37 exhausts.

I have either 40 or 48idf carbs to run it. And my question is would 1.4:1 ratio rockers work alright and would 48 idf's be to big?

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 · 12 Apr 2011, 10:17 pm

#835460

The C35 is not for 1.4:1 ratio rockers.
Have a look here
http://www.vwparts.net/mm5/merchant.mvc?Screen=CTGY&Store_Code=VWP&Category_Code=scatcam

I'd only run it with 1.1:1 (stock) rockers, but I'm generally conservative in this area.

As for the 48's, choke them down and they will work ok. Really depends on what you want, rev it's ring off or day to day driveability.

Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

tayloredvw Seriously Crusin Dubber

165 posts · joined May 2006 · 14 Apr 2011, 9:06 am

#835665

Thanks matt, do the rockers enhance the lift of the cam?

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 · 14 Apr 2011, 11:11 am

#835676

Std rockers are 1.1:1 ratio, so by increasing the ratio of the rocker (lever) it increases lift at the valve, but the down side is the acceleration rate is also increased and this is where problems occur. Performance cams are already designed to reach some max limits and going beyond these usually causes damage to the valvetrain

Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

vwo60 Veteran Volks Folk

2,036 posts · joined Feb 2007 · 15 Apr 2011, 4:08 pm

#835869

I would run the 40 IDF'S as you have a standard crank, to quote the standard, "Hot to hot rod VW engine's" consenses is that a standard crank is good for 5000RPM, if you have to rev it to make power you will pound out the centre main bearing over this RPM, i think the C35 that i had earlier in the piece stops making usable power at about 5500RPM, if you run to larger set of carbs you will not have the bottom end which will make it drivable for every day use, the book is still in print and is available, old but still revelent

tayloredvw Seriously Crusin Dubber

165 posts · joined May 2006 · 16 Apr 2011, 10:40 am

#835987

Thanks Matt, you might have just saved me killing my new heads.