Have you done a compression check on ALL cylinders? Also, have you removed the spark plugs and looked at condition?



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If everything was put back together correctly, ping, knock and loss of power are symptoms of a clogged catalytic converter.

If you had an exhaust leak before the repair, with the exhaust leak now fixed, all of that air is now being forced to go where it should and if the Cat is clogged you could now have an exhaust restriction at the converter instead of an exhaust leak at the manifold.

My Story:
https://www.ford-trucks.com/forums/14...converter.html

Hope it helps...

 

Thanks for the replys. I will be doing a compression check today and checking for a clogged Cat.

 

If those check out its carbon buildup on the pistons... I would bet my paycheck. Don't think these things get carbon buildup?

https://www.ford-trucks.com/forums/1...-or-die-6.html

Look at the first two cylinders in that picture. I believe they are 1,2. Or the two furthest to the right in the pictures.

Granted this engine had a bunch of miles on it, and who knows what gas was ran through it... But clearly you can see what looks like ash/dirt buildup on the cylinders in question towards the exhaust side of the cylinder walls. I had the same pinging/detonation and it drove me NUTS. It was obviously caused by all the carbon on top of the pistons.

I would also recommend against using any type of cleaner in your intake system/fuel system as that carbon just gets moved from your intake to the top of your pistons.

I should have taken better pictures of the engine after it was rebuilt. Basically the pistons do not come anywhere near the top of the deck of the block on these engines. This allows carbon to settle/accumulate on the pistons and not get blown out the exhaust ports if you use fuel/intake cleaners.

I could go into theory of why I believe intake/fuel cleaners for these particular engines are bad, but it would be too much to read and bore everyone.

Basically, dont use any engine vac hocus pocus on these engines.

I do highly recommend chevron with techron gas. It's all I use in my vehicles.

BTW, this is the worst example of carbon buildup I have ever seen in any of the vehicles I have rebuilt in my life...

 

I ran a compression check today and found the left bank (readings between 190-195) was consistently 15% lower than right (220-225). Plugs on the banks with the low readings are a much darker tan/brown. I couldn't measure exhaust pressure but it doesn't feel restricted. As for carbon, I wasn't having an issue before the heads were off and I didn't see anything like the pics in the link with them off.

 

Which head was replaced? Right or left?

Either the compression is different because the timing chain is one tooth off, or the cam may be different.

I'm starting to wonder if the heads and pistons went through a change around the timeframe of your truck... but I thought all "PI" heads for the V10 were the same compression chamber volume.

 

You are 100% sure its pinging/detonation?

Add some VP100 to your tank of gas on your next fill up. (you can get it at a performance auto shop) and see if the noise goes away. If you still have the issue, that would lead more towards coil packs/spark. With that high of octane even if it was bad timing, I would imagine the octane boost would hide the timing issue.

If your timing is off, it could explain the misfiring. What year is your truck again? Could be that you have the crappy plastic tensioners for your timing chain and one could have failed causing the chain to jump a tooth?

 

Thanks again for the feedback. Right side (higher compression) is the new head. I had the same thought about the cam and also resurfaced head because of the exhaust sound change but have been assured by the supplier (ATK) all should be good and meet min OEM specs.

I did add octane booster and it appeared to help but I also wasn't towing for that tankful. I still think performance lagged. I think it's probably time to pull the valve and timing chain covers to eliminate mis timing.

2003 F250 6.8L V10 4x4
Outback 25' Camper

 

Wanted to follow-up on fix. I pulled timing cover off and found I was one tooth off on the right bank. I haven't pulled the camper yet but power is noticeably better. Thanks for the input.

 

That's great news!! Glad you got it sorted out. I'm a huge fan of the V10.



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