low compression in all cylinders help!

[fallingup693]

I'm having an issue with compression in all 8 cylinders.

Here are my mods:
-5.0 stroker
-custom ground cam (stage 3+?)
-pulleys (boosting 14#'s)
-all applicable fuel mods
-intake/tb/full exhaust
-BAP
-ported eaton
-heat exchanger
-some other not important mods

I took it to a dyno and I wasn't making the power I should have been.
476whp 475wtq
tuner said it should be a bit more (around 520ish?)
figured out my ported eaton is ported wrong or just not ported at all(because of boost drop-off). Have yet to pull the blower off to check.

So we decided to do a compression check and all 8 cylinders were at 90-100.
Borescoped the cylinders and didn't find any oil residue so i don't think its in the rings. Plugs look clean. I think it might be because the previous owner didn't install aftermarket springs with the cams? Or maybe the cam itself is just plain too big? Any thoughts on this?

Thanks,
Steve

 

[Blueline]

I would pull the valve covers and check cam timing

 

[cozmo2806]

Whats the compression ratio of the engine? Large cams will decrease cylinder pressure.

 

[moot09]

I would pull the valve covers and check cam timing

+1

How much power were you previously making? If it's always made around that power cam timing could be the culprit if they weren't properly timed when installed.

 

[fallingup693]

Ok, so i looked into the intake elbow of the supercharger and found it wasn't ported. I took the passenger valve cover off and found I have stock cams
(YL7E 6A270)....which leads me to believe that I probably don't have a stroker motor like the seller of the car said he had......sooooo you are probably correct about the timing. I'll have to find some time to re-do the timing..... With that being said.... Do my numbers sound right?

 

[earico]

So when you did the check all the cylinders were within 10 psi of each other. Sounds like you have a stock motor and a bad compression gauge. Sounds like the motor is fine. 476 on a nonported blower is good.

Or maybe the gauge wasn't threading in far enough.

 

[mach1033]

Ok, so i looked into the intake elbow of the supercharger and found it wasn't ported. I took the passenger valve cover off and found I have stock cams
(YL7E 6A270)....which leads me to believe that I probably don't have a stroker motor like the seller of the car said he had......sooooo you are probably correct about the timing. I'll have to find some time to re-do the timing..... With that being said.... Do my numbers sound right?

No the numbers are not right because you were lead to believe that you had a 5.0 stroker motor with custom cams and ported blower. That alone would piss me the Fck off!!!!!!!

 

[20SVT03]

:nonono:That really really sucks to hear. Sorry about the bad luck but yeah I'm really doubting that is a 5.0 stroker myself.

 

[fallingup693]

So when you did the check all the cylinders were within 10 psi of each other. Sounds like you have a stock motor and a bad compression gauge. Sounds like the motor is fine. 476 on a nonported blower is good.

Or maybe the gauge wasn't threading in far enough.

Yea, we were thinking that the guage was bad too.... so we switched to the backup guage and it read the same. We'll see after this weekend whether or not the timing is good. I hope that's the problem cause I'm tired of dealing with this car already.

Mach1033 - Yea but shouldn't compression on a stock block be around 150? Cam timing might be retarded to produce less compression?

20SVT03 - Yea, I am pretty pissed. But there's no point in starting anything over it. For what I paid for the car, even if it doesn't have all the goodies he said it did, I still got a hell of a good deal.

 

[mach1033]

Yea, we were thinking that the guage was bad too.... so we switched to the backup guage and it read the same. We'll see after this weekend whether or not the timing is good. I hope that's the problem cause I'm tired of dealing with this car already.

Mach1033 - Yea but shouldn't compression on a stock block be around 150? Cam timing might be retarded to produce less compression?

20SVT03 - Yea, I am pretty pissed. But there's no point in starting anything over it. For what I paid for the car, even if it doesn't have all the goodies he said it did, I still got a hell of a good deal.

i was speaking of the HP numbers not the compression numbers. That is another story. You can also do a leak down test and see if the compression goes up by throwing a splash of oil down the cylinder.

 

[fallingup693]

i was speaking of the HP numbers not the compression numbers. That is another story. You can also do a leak down test and see if the compression goes up by throwing a splash of oil down the cylinder.

oops, my bad mach. that was meant for earico.... but thanks for the tip. I'll do that when I redo my timing.

 

[fallingup693]

Anybody know any good cam degreeing write-ups? I can't find any DOHC motor write-ups..

 

[03mustang92]

Anybody know any good cam degreeing write-ups? I can't find any DOHC motor write-ups..

there was one on modular fords, ill look for it

 

[03mustang92]

or why not just line everything @ "0" or "straight up"?

 

[Quick Strike]

Anybody know any good cam degreeing write-ups? I can't find any DOHC motor write-ups..

Here - Right from Comp.

 

[ugotbit03]

Here - Right from Comp.

To add to that-

Camshaft degreeing, why and how

Tech: Comp Cams & Lash Adjuster Preload

Whipple 2.3L + 10.7:1 Compression

03Steve and nasvt are some of the few that don't keep good info a secret.