- Messages
- 66
- Location
- Endicott, NE
After doing a lot of experimenting I believe I have come up with a nice engine upgrade for the Rovan 27.5 and on a budget. My car is used almost exclusively on dirt oval but I have tested on pavement too. During testing I changed to 55/19 gear ratio. The car also has the 6000 rpm clutch.
Changing out the top end kit for a CY-F270 kit (cylinder and piston and using the stock gasket) decreases the squish by about half (from approx. 1mm to .5mm) which raises the compression which equals more power.
Note: Assembling the top end without the gasket the piston will actually hit the top of the cylinder and with minimal pressure you can turn the crankshaft 360 degrees.
I have been running premium 91 at 28:1 with full synthetic oil and proper tuning. The plug burns a nice brown color. I have not seen any signs of pre-detonation. When comparing cylinders the F270 seems to have a slight amount of factory porting done to it so not only are you getting higher compression but the intake and exhaust flow better too.
I have tested mainly on dirt oval and some pavement with 3 different exhaust systems. Stock square muffler, Rovan rear exit tuned pipe (similar to Dom) part#rv85037, and Rovan rear mount tuned pipe (SS style) part#rv85050.
Stock square muffler: There was a definite performance increase and after testing I will actually use this on dirt oval on a dry and dusty track to tame down the motor.
SS Style: This will be intermediate pipe that I will use on dirt oval when the track has some grip in it and some dry spots and works good on a track that has lots of good traction too. This pipe would be my choice on pavement on a very technical track with lots of short straightaways and lots of corners.
Dom Style: This pipe on dirt means you better have a lot of good traction or it's going to be a handful to control if you have a heavy trigger finger. This pipe rips through the low and midrange rpm's extremely fast! This pipe would definitely be my choice on pavement with longer straightaways.
With the 6k clutch and steeper gears it still pulls real hard from a dead stop and I gained topend speed.
Total cost of doing the pipe and the top end kit is between $80 and $120 depending on which pipe.
If someone else does the head upgrade I would really like to hear your thought's.
Changing out the top end kit for a CY-F270 kit (cylinder and piston and using the stock gasket) decreases the squish by about half (from approx. 1mm to .5mm) which raises the compression which equals more power.
Note: Assembling the top end without the gasket the piston will actually hit the top of the cylinder and with minimal pressure you can turn the crankshaft 360 degrees.
I have been running premium 91 at 28:1 with full synthetic oil and proper tuning. The plug burns a nice brown color. I have not seen any signs of pre-detonation. When comparing cylinders the F270 seems to have a slight amount of factory porting done to it so not only are you getting higher compression but the intake and exhaust flow better too.
I have tested mainly on dirt oval and some pavement with 3 different exhaust systems. Stock square muffler, Rovan rear exit tuned pipe (similar to Dom) part#rv85037, and Rovan rear mount tuned pipe (SS style) part#rv85050.
Stock square muffler: There was a definite performance increase and after testing I will actually use this on dirt oval on a dry and dusty track to tame down the motor.
SS Style: This will be intermediate pipe that I will use on dirt oval when the track has some grip in it and some dry spots and works good on a track that has lots of good traction too. This pipe would be my choice on pavement on a very technical track with lots of short straightaways and lots of corners.
Dom Style: This pipe on dirt means you better have a lot of good traction or it's going to be a handful to control if you have a heavy trigger finger. This pipe rips through the low and midrange rpm's extremely fast! This pipe would definitely be my choice on pavement with longer straightaways.
With the 6k clutch and steeper gears it still pulls real hard from a dead stop and I gained topend speed.
Total cost of doing the pipe and the top end kit is between $80 and $120 depending on which pipe.
If someone else does the head upgrade I would really like to hear your thought's.
Last edited: