nitro/headz

Hi guys , i got an OS CVR and i got a Nova Race Pro Head for that engine.
So, i swapthe heads with the shims off my stock head.
The temp drop alot with the swap, i pass from 220f to 135-140f, the same day, same temp, same tuning....
Ifeel i got less top speed but plenty of torque...

I want to know if anyone ever install this Nova head on a OS 18 CVR ?

What is the clearance needed between the TDC of the piston and the lowest part of the combustion chamber (head)

Any advices will be greatly appreciated...

Ben

secretsg

I just used the stock shimming with the nova head. The nova fits a little differently but I don't think the clearance is any dfferent.

nitro/headz

But when you check the specsof the head, it supposed to raise a llittle bit the compression...

I got all the measuring instruments to check it (clearance) thn i only need to no what is the minimum clearance required and if this have any incidences with the % of nitro u use....

Secrettsg, how is your top speed ?

D.DJ

I would check the the height of the part that goes into the sleeve, if it does do that, using a vernier and compare the difference in depth. If the Nova head sits inside the sleeve more than the original, add enough shims to make it the same. If it sits less than the original, take enough shims out to make it the same, but dont have no shims in there otherwise you could create a leak/improper seal.

nitro/headz

:O but there is 2 shims.... i will measure it in the next days...

secretsg

I never did use this engine in an onroad. It was the engine for the original Tamiya TNX.

Just checked it again and nova is is 1.73mm, os head is 1.85mm. The 2 shims were .9 and .18mm. THey are different after all.

nitro/headz

So, the Nova sit .12 mm higher than the stock OS. It lower the comp if you put the two shims with the nova head. So we can remove the .09 mm shim and let the .18...

D.DJ

if it does sit higher, just remove that .9mm shim, and let it stay there, its a tiny amount of lost compression, that would also explain the cooler running temps, but performance must also have been affected slightly.

Anthoop

Measuring how far the head extends into the bore will only tell you how many shims to add/remove to adjust the squish band correctly. It will not ensure you are running the same compression ratio as the concave shape of the head may not have the same dimensions.
The manufacturers of the head did not supply any information regarding shimming?

nitro/headz

Yeah D.Dj i lost a bit of top end performance...

Anthoop, you're right too, the combustion chamber comes into play with the compression ratio...

I will try to speak to a Nova guy...
I keep you informed !

PrjctStrtFrce

My Feedback: (10)

Dropping the temperature too low will decrease the life of the motor. It needs to get to operating temperatures to run properly and efficiently, and 140's is exactly operating temperature.

.02