solex cams with 914/6 pistons

MaRu · 03-03-2014, 01:11 AM

Hello everyone,

do you know if the piston used in the 110 hp engines like 914/6 have enough valve to piston clearance with early solex cams?

many thanks, Malte

roblav · roblav's Garage

Why would you want to do that? You will lose effective compression because of the valve overlap.

T77911S · 03-03-2014, 03:47 AM

effective compression is determined by when the intake closes, not overlap.
the later it closes, the less time it has to build compression.

Flieger · Flieger's Garage

And you gain top end power at the expense of low end when you close the intake valve late. So I wouldn't call it a "why would you do that" moment.

MaRu · 03-03-2014, 06:52 AM

Thanks for your answers! I have a 1965 engine without piston and cylinders and I have 914/6 piston and cylinders. So for me the best solution would be to match these parts. but I am afraid that there is not enough clearance because of to little valve pockets in the pistons. Do the original 130hp pistons for solex cams have these pockets?

1QuickS · 03-03-2014, 08:07 AM

PM sent

T77911S · 03-03-2014, 08:10 AM

do a pre-assymbly check. put it together and there is some stuff kinda like paydough that you can put in there to check clearance.

you might look for 2.0E pistons or maybe something a little bigger.
roblav's point is with a low compression piston and a cam with a late closing time can be a not so fun car. i dont know for sure with that engine.

get bruce andersons book, he talks about upgrades for various motors.

i think the pistons you have may be the same as the 2.0T motor.

chris_seven · 03-03-2014, 08:10 AM

The 914/6 is a 901/37 and has valve sizes at 42/38 which is the same as the early 911S.

The compression as much lower than the S so the piston crown is likely to be lower and there will probably be enough clearance.

The 901/01 piston has pockets but for smaller valves although the lift of the cams is higher than the T style cam fitted to the 914 -6.

The best pistons to run would be a 1968S which has enough of a cut out and plenty of clearance and gives decent compression.

Woessner keeps them in stock in a forged 4032-T6 and for a reasonable price.

Are the cylinders Cast Iron?

larrym · larrym's Garage

as all above say - bad idea - i ran solexes on a 2.7 8.5 CR motor - no torque below 3000 rpm - get "E" cams and forget the Solex

- read Bruce Andersen's book

Flieger · Flieger's Garage

Quote:

Originally Posted by larrym

as all above say - bad idea - i ran solexes on a 2.7 8.5 CR motor - no torque below 3000 rpm - get "E" cams and forget the Solex

- read Bruce Andersen's book

The easier (and more fun) solution is to keep it above 3000rpm.

MaRu · 03-04-2014, 12:56 PM

OK, thank you guys. I understand it is a bad idea!

Roger 911 · Roger 911's Garage

Quote:

Originally Posted by MaRu

OK, thank you guys. I understand it is a bad idea!

It really depends on how you plan to drive it. If its mainly in stop and go traffic, low speed stuff, then yes, it might be a bad idea. On the other hand, if you plan to open it up a lot, like at the track, it could be a great idea...if there is sufficient valve clearance.

FWIW, I swapped E cams into my 2.4T motor, with 7.5:1 pistons. Yes, it was a bit lethargic below 3K, but above 4K it was awesome. I was primarily using the car for DEs at the time, so this is exactly what I wanted. I should add that I originally installed Solex cams (at the urging of the geniuses at Motormeister). Got them installed and then checked the piston to valve clearance. No dice! Took them back out and put Es in (which is what I wanted in the first place!) and everything was fine.

Good luck!

Roger