Budget Rovan 27.5 cylinder/engine upgrade

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quentrm250

LSF Plus Member
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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.
 
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Nice right up. Now you,ve done it though you,ve given away our secret!!!;)
The f270 top end on a rovan/km CC is def a winning combination for those of us running lean(money wise).:cup-1:

Now we just need some vids of these badboys in action
 
I swapped my pipe from the thor to the dragon pipe. A heavily modded f270 on a Km 30.5 bottom end. I couldn,t even believe the difference. It has turned it into an uncontrollable monster.Im running stock gears and an 8k clutch,with tarmac busters. On pavement the bottom end is so ridiculous it just peels the tires and doughnuts all over the place. I managed a few high speed passes by very gently getting it going and then giving it WOT. The acceleration is ballistic. I,m hoping 19/55 gears and a 6k clutch will make it a little more driveable.
 
I told ya. LOL. I couldn't believe the difference when I took mine from stock to this. The gears helped but definitely did not kill the low rpm power on mine. Checked ur plug? Keep an eye on ur plug for small white spots. Had to tune mine twice as it broke in. The thing runs so hard I tried to keep it a hair rich to be safe.
Can you imagine how good it would run if you leaned it way out?!?!
 
Every once in a while during my run I stop the car and richen the lsn slowly until it affects the idle speed and then very slowly lean it again just until I hear the idle speed go back to where it was. just my way of making sure the needles are staying put. So for so good. Plug is good. Running like a champ. Its hard to imagine anyone spending 500.00 on a modified motor.;)
 
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