max compression?

[hh03bullet]

whats the max compression for a 2.5 on 91-93 pup gas at 32:1

[rev.ronnie]

135#, play it safe.

34cc heads should do the trick. If you are at a higher altitude, you can bump it up a little from there though.

[hh03bullet]

thanks Rev, ive got 125 across the board in a 260 wanting to bup it up some

[rev.ronnie]

Mine is 135-138 with the 34cc heads. It runs excellent. I only run non-oxy, but I don't think I'd have a problem with E-10, I'd just richen up the ACU a little if it needed it.

I have heard of guys running more compression on pump gas, but 135 seems to be common. Why run it on the ragged edge when the benifet is really negligible.

[Jay Smith]

I target 140-145 lbs cranking at sea level with max timing at 25* we do hundreds of 260's heads a year this way with no issues..Stockers will yield 130 ish and the addition of 15 lbs compression is VERY noticeable on the bottom and mid range..

Jay

[chad202]

That's a trick question. lol

[WATERWINGS]

[QUOTE=rev.ronnie;2336218]
I have heard of guys running more compression on pump gas, QUOTE]

I ran 170+ on pump gas for a short while.... A new set of rings and the old 150 psi kept climbing till it hit 170-175.... I swapped heads back down to around 130-135 psi....

Didn't seem to cause any trouble...and the motor builder said keep running it like that.....but I didn't have the nads for that....

[chad202]

Yep waterwing, been running that compression for several years. No additives other than quickleen every other tank. All I have around here is 10% ethanol so I run that too.

[hh03bullet]

thanks guys for all the input, i picked up a couple of diffrent sets of heads and some gaskets gonna see what happens here shortly.

[WATERWINGS]

I would still shoot for 145 - 150 psi

[hh03bullet]

got one set of heads on it now that make 140 across the bord, liking that much better! thanks guys!

[sxpilot]

Of all the things I did to my engines, the biggest difference I noticed was changing the heads from 38cc to 35cc on my Talon, went from 135/137 to now 148/150, still blending fuel to get 93/94. I could notice the bottom and mid seemed more responsive, also noticed temps run a bit hotter, but still 140 at WOT w/OAT at 107F+, ran 2 tanks/80 gallons and took a look inside for piece of mind. They look real nice, did the quick clean as well as enviro-tech the 3rd time running them, these 2.5's will bump start in gear, idle at 650 in gear, and with a full bag of fuel, 2x people+, it will scream to 8500 with 30's

I have Happy Engine's for the time being, considering another 280 and switching the power heads, so I can make it more of a pleasure boat with stereo ext..

[STVBOY]

I have 26cc heads with the exhaust chest cut and I run 93 octane with no problems. Compression is around 170psi!

[eli]

35 cc heads timing at 23 ,1/2 oz lead per gallon pump 91 runs good