Found my compression problem

[Strikeking10]

A while ago I swapped a new TVS on my Cobra, I only got about 500 miles before doing a compression test to find I was low in two cylinders. Ford told me it was the rings... well turns out the rings are in great shape it was the Exhaust valves not quite closing all the way which is what caused the compression to be low, im not sure if being tuned at only 15* of timing caused this or not but it looks like I will be needing some new valves, the builder is thinking about 1mm oversized on the exhaust because of the way the valve seats look now and stock size on the intake since they look great, they would prefer not to have to do new seats.

I want to get new ones all around but not sure what brand or if I can order the intake and exhaust separate, I can only seem to find complete sets that are 1mm over. Anyone have any insight as to what brand or who to get them from?

 

[R.D.P.]

Sorry to hear. Definitely strange that you ran into problems so quick. Can't help you on sourcing the valves, but would love to see some pics. You should definitely do new\upgraded guides if you weren't already planning on it. If the engines is coming out you could also do head studs while it's apart.

 

[cj428mach]

Which head is it?

You might want to consider the head cooling mod, or the revised 05 cylinder head so this doesn't happen again. The 05 head is only still available for the drivers side.

 

[blood]

What was the compression like onthe two low cylinders? All mine were 170-180, lowest was cyl 1 at 165. But I have noticed gas in my oil recently and fear it could be a ring, do you know what theyre charging you to do all this work to your car? maybe give me an idea. That's unfortunate that this has happened to you, I wonder why the TVS could have caused it? My tuner put 22* of timing on my 17# boost 2.2 kb, now I am regretting taking it there.

 

[MG0h3]

What was the compression like onthe two low cylinders? All mine were 170-180, lowest was cyl 1 at 165. But I have noticed gas in my oil recently and fear it could be a ring, do you know what theyre charging you to do all this work to your car? maybe give me an idea. That's unfortunate that this has happened to you, I wonder why the TVS could have caused it? My tuner put 22* of timing on my 17# boost 2.2 kb, now I am regretting taking it there.

Damn! You on 93? My tuner must be conservative. IIRC, my peak is 19 and it drops to 17 @ peak torque. Im on 15psi/91 octane

 

[R.D.P.]

What was the compression like onthe two low cylinders? All mine were 170-180, lowest was cyl 1 at 165. But I have noticed gas in my oil recently and fear it could be a ring, do you know what theyre charging you to do all this work to your car? maybe give me an idea. That's unfortunate that this has happened to you, I wonder why the TVS could have caused it? My tuner put 22* of timing on my 17# boost 2.2 kb, now I am regretting taking it there.

22* is typically only considered safe on e85 or at least race gas mix.

 

[Strikeking10]

Sorry to hear. Definitely strange that you ran into problems so quick. Can't help you on sourcing the valves, but would love to see some pics. You should definitely do new\upgraded guides if you weren't already planning on it. If the engines is coming out you could also do head studs while it's apart.

I already have some bronze valve guides waiting to go in and every ARP bolt/stud I can get is going back in also lol

Which head is it?

You might want to consider the head cooling mod, or the revised 05 cylinder head so this doesn't happen again. The 05 head is only still available for the drivers side.

It was on all 16 of the exhaust valves, my car had the revised head and I already did the head cooling mod when I installed the TVS. The theory is that it was the low timing wasnt closing the exhaust valves quite all the way and it allowed it to blow by the valves when the combustion happened

What was the compression like onthe two low cylinders? All mine were 170-180, lowest was cyl 1 at 165. But I have noticed gas in my oil recently and fear it could be a ring, do you know what theyre charging you to do all this work to your car? maybe give me an idea. That's unfortunate that this has happened to you, I wonder why the TVS could have caused it? My tuner put 22* of timing on my 17# boost 2.2 kb, now I am regretting taking it there.

The two low ones were in 5 and 6 with 135 and 145, we havent talked about money yet though, We dont think it was the TVS itself the theory is that being tuned at only 15* timing caused it but its just a theory, they werent the ones who tuned my car.

Damn! You on 93? My tuner must be conservative. IIRC, my peak is 19 and it drops to 17 @ peak torque. Im on 15psi/91 octane

Im on 92 here in Oregon

 

[blood]

22* is typically only considered safe on e85 or at least race gas mix.

^^^ This, I am having to pay 600 more $ to retune the car correctly. Cause the guy I took it too to work on it a week ago said it would have never left there with more than 18*, and so did half of the SVTP gentlemen. SO now I am out 550$. And I think he tuned it to run too rich. Hint dont go to PSI

 

[Blueline]

The theory is that it was the low timing wasnt closing the exhaust valves quite all the way and it allowed it to blow by the valves when the combustion happened

:shrug::dw: