2.5 245 hp carb motor stock psi on heads

[action20]

I bought a used powerhead from a local drag racer ad he sid it was a 245hp block.

It has compression in the heads of around 125 psi ????

Did the 245 hp come with higher compression heads ???

I was thnking about bumping the compression on the heads but i like the way it idles and i would like some longevity out of the motor.

What is a safe PSI ??

Maybe i should leave it alone ?

any help would be apperciate3d.

[Liqui-Fly]

But 260's are supposed to run around 135. I don't think the carb version is any different.

David

[action20]

Ok,

thanks

[shortBUS]

The 125 psi could be a function of many different things.

-- the first 2.5's came with 42cc heads, they had an update to bring the cc's down to 38cc
-- the first 2.5's came with soft rings that were later replaced with titanium nitrate rings
--you could have a soft gauge
--you could have worn rings

I would do a leakdown on the motor, and see.

145psi is safe, as long as you have GOOD gas, 91 oct plus, with no oxy or booze added.

[MTCM]

If all cylinders are 125 psi, that's one good sign...............

How's the Leakdown?

[action20]

That is really good info thank you.

I know the rings were replaced last year before it was sold to me i will call the guy who sold it to me and ask him if it was an early 2.5 or a late 2.5 and i will ask him what type of rings he used.

Thanks

Scott

[shortBUS]

could also be that the new rings have not yet seated. The new rings will be the good nitrated.

[OLD BOB]

My 93 model 260 never had more than 125 with even with fresh rings. I never knew that the later models were different until I started reading this board.

[Jay Smith]

Most ALL 2.5 Nic motors are between 125 lbs and 140 ish. It has alot to do with the way its done , oil in bores , altitude, ambeant temperatures , battery condition , throttle openings, etc.... To many variables to make an educated dession on rebuilds Buy a leak down tester from Balzy and take the wonder out of ring and bore condition.

my opinion,

[Greg Moss]

Or you could buy my heads that are fresh JSRE cut to 34cc and have 145lbs of compression. :D How's that for salesmanship?:D

[WaterBoy]

Head gasket thickness will have an affect also. I have a 96 260 just reringed with comp of 121 on all six holes, but the head gaskets are as thick or thicker than a penny.

Waterboy