Jeep Strokers

Hi,

I just finished my stroker build and install.

I fired it up and smooth as can be. Run for 5 or 6 minutes. Oil pressure at 3 bars and when I apply throttle it comes up to around 4 or so. Thought I had burped the coolant fairly well but must have had a bit of a bubble. Got up to 110 and I turned it off. Found there was some air and topped coolant. Crank was slow... I got a bit concerned but after that all good.

Ran for another 20 minutes varying the throttle from 1000 - 2000 burped the coolant a bit more as well. Everything seems great.

Drove it to work about 5 km. All good. Oil pressure good and Temps at 90c

Changed the oil and filter
Oil is kinda darker than I figured. But clean. Coolant looks good.

I go for a drive on the highway for the first time. At about 3 km it starts knocking. I turn around and drive back to work , knocking is getting worse. Park it at work. Fire it back up and pull each plug wire. Knocking is consistent on all. I pull the valve cover and everything ĺooks good.

Drain the oil and it looks OK.

Any advice where to go from here?

It seemed to have decent power and the engine is smooth. Just the terrible knocking what follows the rpm. I will post a video of the knock on YouTube and try to link it.

Have you checked the torque converter bolts?

Not yet. I will pull the cover and check them today though

No cracks or loose bolts on the flexplate

A good amount of glittery oil in the filter found in the filter. Ripping it back out....

I had the same knock a few minutes after start-up on my new stroker build. Mine turned out to be 2 stuck valves. When I pulled the valve cover, it was obvious as the rockers were loose on the stuck valves. I had to get the machine shop to replace the two valves and recheck the other valves as they had them too tight. Now, I'm at 5000 miles and it's running well. I do not recommend Walker Machine Shop in Raleigh NC. Good luck with yours. Hopefully, you won't have to pull the block.

Doug

I had the same knock a few minutes after start-up on my new stroker build. Mine turned out to be 2 stuck valves. When I pulled the valve cover, it was obvious as the rockers were loose on the stuck valves. I had to get the machine shop to replace the two valves and recheck the other valves as they had them too tight. Now, I'm at 5000 miles and it's running well. I do not recommend Walker Machine Shop in Raleigh NC. Good luck with yours. Hopefully, you won't have to pull the block.

Doug

#1 piston is scarred up pretty badly and the cylinders wall is marked up. I think that should hone out. All the damage is on the side with the cam. It seems like it was the top ring that caused the damage although I can't figure out why. Ring gap was .015 on all the rings at installation. The wrist pin is also fairly tight on the damaged piston. It didn't go in like that. Maybe heat deformed?

The mains and rod bearings all look good. So the issue must be with a cam bearing.

So I send the block back out and the machine shop recut all the cylinders .001" over the .030 . I reassembled with new gaskets and rings but reused bearings and lifters as the looked fine. When I set the dizzy in I had some issues with alignment though . One tooth either side but not at the hole. Pulled the timing cover and tried to re set the chain. Everything seemed right but re aligned the sprocket marks with a straight edge. Put everything back together and installed.

Now to start time. It still doesn't want to find the right spot on the dizzy. I put the pin in the cam sensor to lock it to the dizzy housing and rotate it into place. It's either too far advanced or retarded. Too far advanced and the rotor sits at almost 6 o'clock and the engine fires but then immediately stops. Way far advanced . But if I set it one tooth back it runs.. starts a bit wierd bu runs nice and throws a 1391 code. Cause the cam sensor is off.


Any help would be appreciated.

1. 015" is way too tight top ring gap, then it got hot 110*c, and seized the top ring. Top ring gap for a street gas engine of 3.95 bore are about .026" street and .032" towing, given that this is bored and stroked and are known for overheating at .060" I would go with a gas normally asspirated towing ring gap factor of .0080, (3.95 x .0080 = .0316") or about DOUBLE your gap.
2. Pretty sure the shop only honed the cylinders .001" to clean them up for the new rings. But unless you open that ring gap it will happen again. The reason it scuffed the pistons on the cam side is that is the thrust side of the cylinder.
3. I assume this is a different cam, which means different cam/oil pump/dizzy drive gear relationship from stock (possibly due to machining tolerances)
4. Since most engines have ballpark 10* advance at idle. I set the balancer at 10* BTDC and drop the dizzy in until it is right AT #1 plug terminal. Works on EVERY motor.
5. If you are still having issues with it being between 2 dizzy terminal posts on the dizzy, try removing the dizzy gear and putting it back on after rotating 180*, it may have been removed at some point and put on the other way. There are 13 teeth on a dizzy gear and 2 ways to put the gear on. One side the roll pin lines up with a tooth and the other side lines up with a valley between 2 teeth. I have pics of the roll pin and gear teeth relationship if needed.

And ALWAYS double check the CRANK Position Sensor connection and function.

Thanks for the response TR1Hemi. Great info !! I just read it 2 days too late

I had replaced the cam with a new comp cam that Russ put in a package for me. I read a bit on the dizzy gear being on backwards and tried to turn it 180 degrees to match the teeth but on both my dizzys the hole was slightly offset and the roll pin wouldn't allow for it. I ended up grinding an ear off and as I had read on some posts here and set it where it needed to be. It fired up instantly.

Now onto the bad part. After a 10 km drive it started knocking again. It sounds like the #1 again.

I am going to borescope the cylinders today minimum and maybe pull it this weekend and check how bad the damage is.

I had not heard of setting the ring gap that high.

This time I filed the gap more. 0.018 IIRC but the jeep 4.0 book I was following had a way tighter tolerance .010- .024 and some of the mechanics I talked to here after the first failure told me the rule of thumb in their books was 0.004 per inch of bore.

Obviously I have done something wrong twice and I can't think of anything else so that has to be it. Just wish I had heard it before firing it up.

Thanks ! I've been so frustrated trying to figure out what I had done wrong twice. at least I know now