Matt's (mis)adventures with a cammed 3400

[3400-95-Modified]

Might have shorted out the ignition system and fried half a coil if your ground strap was touching a plug.

[stewartfn18]

check the piston rings, excessive blowby could cause a bad afr causing excessive carbon build up.

[95SleeperAcheiva]

how was the fuel pressure? Is computer good? I ask because I've seen comps fail and ground 1-2 injectors that then get stuck open, dumping fuel. Engine still runs, poorly and very rich, but it runs sometimes with a miss.

[mfuller]

Fuel pressure was fine, and the PCM's good too.
Looks like bad rings on both #5 and #6. Headgaskets were fine. A huge buildup of carbon in the combustion chambers for both cylinders. Drained the oil (which had only 300 miles on it), and it was so black (likely from the fuel blowing right by the rings into the crankcase) you'd think it had been in the car for 15,000 miles.
Thankfully, cylinder walls look okay, so putting in new rings and bolting it back together. We'll see......

[sprucegagt]

I suggest that you mic. those cylinders and check ring gap before reassembly.

[stewartfn18]

Fuel pressure was fine, and the PCM's good too.
Looks like bad rings on both #5 and #6. Headgaskets were fine. A huge buildup of carbon in the combustion chambers for both cylinders. Drained the oil (which had only 300 miles on it), and it was so black (likely from the fuel blowing right by the rings into the crankcase) you'd think it had been in the car for 15,000 miles.
Thankfully, cylinder walls look okay, so putting in new rings and bolting it back together. We'll see......

did you even check to see what i suggested. i guarentee that what it was. theres no other reason that new piston rings would be bad and get blowby like that. youre lucky that you didnt score the cylinder walls either.

[mfuller]

Figured I'd post an update on this.
Mark pulled the motor, and re-ringed 5 and 6. The end gaps were a touch off, but not by any stretch that you would think.
Long story short, we still have no compression on 5 or 6. We're double-checking pushrod lengths now; my new theory is that the valves are not closing, so the cylinder can't hold pressure. Perhaps the lifters are frozen up....or Ben also suggested that because of the proximity of the 5 and 6 lifters to the oil pump, that they are becoming overly-pumped up an behaving like solid lifters.....I don't know. Hoping it's something stupid like pushrds or lifters and not my mega-dollar heads or a bad cam grind.

[SappySE107]

the oil/lifter deal was if the pushrods are on the long side, which i had a problem with in the beginning because I was using the 1-1.5 turns that the old thread pitch for the non rollers used. This gave more preload than I wanted and caused 1 customer to have a problem on number 6. I am surprised its 5 and 6 if its the pushrods, as it should be the rest at that point as well.

[sprucegagt]

the oil/lifter deal was if the pushrods are on the long side, which i had a problem with in the beginning because I was using the 1-1.5 turns that the old thread pitch for the non rollers used. This gave more preload than I wanted and caused 1 customer to have a problem on number 6. I am surprised its 5 and 6 if its the pushrods, as it should be the rest at that point as well.

How much preload should you use with 3500 heads and block?

[mfuller]

Well....I'm kinda discouraged.
All the pushrods measured what they should be, and the lifters are fine also.
So, Mark performed a leakdown test on the bad cylinders today. Removed the rocker arms so that the valves would all be closed.
The #6 cylinder wouldn't hold any pressure - Mark could hear the compressed air rushing back into the intake manifold. DOH!
I'm going to have the machine shopthat did the shortblock work check the heads to see what happened. Anyone want to wager what it is? Bad seats? Bent valve stems?

[3400-95-Modified]

I'm gonna be nice and say bad seat or poor valve job... Bent stems is mean to wish on anyone.. LOL

too bad you didnt listen to me before Just busting ya.

[mfuller]

Okay, here's the latest from the machine shop:
Poor valve job, slightly bent exhaust valves, and one broken retainer/keeper.
Installed height of the valves is wrong, and the pushrods might still be too long.
Thankfully, no evidence of piston-to-valve contact.
We'll see if the heads can be saved.

[SappySE107]

I found out 3 days ago that the Comp keepers are bad. They varied over .040" on install height (retainers are fine) and some would have the stem below the retainer. For the reason, I no longer sell them. I am certain this is the problem with your heads. The valve job seems strange though, as they are serdi cut and all are the same. If it was bad, you would have a problem with all the cylinders. The valves however are SI, and I no longer use/sell those either. They are not good as they come from SI, and I have to cut them concentric. I need to talk to Mark for details but I am guessing they saw the width of the cut as being different around the valve and called it poor. There is nothing that can be done about that, but they are concentric, which is the important part.

I don't know how the valves bent. I will replace them with 3500 valves however so there won't be any more issues there. Pushrods are good, or you wouldn't have been able to drive it home (which should never have been done). I was initially told it ran fine minus exhaust leaks. Now I am told it never ran fine plus exhaust leaks.

I will talk to Mark in the morning.

[3400-95-Modified]

eek, that blows, but at least it all sounds fixable for a reasonable amount.

[mfuller]

I was initially told it ran fine minus exhaust leaks. Now I am told it never ran fine plus exhaust leaks.

I will talk to Mark in the morning.

Thanks for your reply Ben. I sent you a PM on the other stuff.
I suppose I am to blame for being too anxious and driving it home when Mark and I both knew it wasn't right. We both initially thought that it was because of massive exhaust leaks from POS TOG headers. I'm sure you can appreciate that a leaky exhaust can mask other problems and make diagnosis difficult. When a new set of S&S headers were installed and the condition did not improve, we started looking elsewhere.