Thread: why no compression

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i have a 427 bored 60 with speed pro L2308AF pistons. heads are merlin 119 cc alm. cam specs are 255/260 @ 50 688 lift lobe sep 107 degreed at 103. compression is susposed to be 11.53 to 1 but checking it with the gauge it only has 140-148 psi on all cyl. whats the problem?

i have a 400 sbc with 9.8 to 1 pistons & 64 cc heads & it has 170 psi

would changing the degree of the cam make much difference or would i have to change to a different cam to raise it much.the engine is in a drag car and just doent seem like enough comp

Are you holding the throttle wide open when checking compression?

I was just playin' around on my DynoSim with a motor very close to yours and there's no way I could make UNDER 700 hp and 645 ft/lbs with it. I used a Comp solid roller 11-700-9, advanced it 5 degrees so that the IC is 103, EC is 113, LSA is 108, timing events are 41/67/81/35 with 0.680"/0.680" lift. 0.050" duration is 251/260. So, very close to what you have. 1050 on a Victor Jr, stepped tube race headers. 11.5:1 SCR. Merlin heads. 705hp @6500, 645 ft/lbs torque @5000. Peak volumetric efficiency 106.8% @5500. Peak BMEP 221.6 @5000. So, something ain't right. Could be me.

it called bent valves? or bad valve job bad???. lash set wrong holding off the valve seat???? i would have to look that piston up i know them by dome not numbers but i doing two 427 now both with old trw piston about the same as speed pro for valve notch .the one 427 with a 246/254 @050 621/621 on lsa108 with them small lsa will not fit in a bbc with trw or speed pros pistons they need to be cut . less some ones has cut them . the running lash may save you but ? for PV room ??? never had that kind of luck i have had to cut the pistons .your running a 2.300 intake or 2.250 intake valve in the merlin heads ? over the years i have had to cut for PV room and with your cam you would or they change up the valve cuts in the pistons . thats why i do not used them much .hard to beat a SRP . but i understand the used what you have thats why i have to fly cut some 427 pistons today

havent checked valve job but brand new heads valve lash is right and piston dome is .585 & dont appear to have ener been cut down