Sluggish Acceleration
- Thread starter Duner
- Start date
OP
The engine was rebuilt so I’d imagine those all should be newer, but I don’t want to assume.
The belt looks like it’s in good shape too, but the fact that from TDC in exhaust to compression goes from no leak to complete leak makes me think it’s a timing issue and maybe something jumped a tooth
OP
OP
@macleanflood
Update:
I wasn’t able to grab the valve but I did do some more testing to compare cylinder leak down results.
All cylinders valves, exhaust and intake, leaked during exhaust stroke TDC. No cylinder valve leakage occurred at compression stroke TDC.
Update:
I wasn’t able to grab the valve but I did do some more testing to compare cylinder leak down results.
All cylinders valves, exhaust and intake, leaked during exhaust stroke TDC. No cylinder valve leakage occurred at compression stroke TDC.
OP
Update:
I discovered something called “valve overlap”. This occurs as the piston nears TDC as the strokes transition from exhaust to intake. This is consistent with my results as all cylinders leaked from exhaust and intake valves during this transition.
None of my valves leaked during compression stroke TDC. At most I saw 7-10% pressure loss, which is well within spec especially with a cold engine.
I discovered something called “valve overlap”. This occurs as the piston nears TDC as the strokes transition from exhaust to intake. This is consistent with my results as all cylinders leaked from exhaust and intake valves during this transition.
None of my valves leaked during compression stroke TDC. At most I saw 7-10% pressure loss, which is well within spec especially with a cold engine.
OP
Update:
Removed head and intake/exhaust valves for cylinder 3. Im gonna assume the intake valves are disgusting. Should I be concerned with the carbon up the stems of the valves?
Valve seats also look a bit gunked.
Removed head and intake/exhaust valves for cylinder 3. Im gonna assume the intake valves are disgusting. Should I be concerned with the carbon up the stems of the valves?
Valve seats also look a bit gunked.
BDub7473
New Member
OP
Still had 20% leak on cylinder 4 after lapping the valves, new head gasket, and getting the head machined. No leakage from the valves but a lot was coming from the crank case up through the oil drain holes in the head.
Pulled the cylinder and the wear looks suspicious. Both sides or the piston/ cylinder wall.
Pulled the cylinder and the wear looks suspicious. Both sides or the piston/ cylinder wall.
OP
I’d have to get the hardware for this. I’ll look into it. I’m in deep on this thing
OP
Decided to measure the bore diameter on all cylinders and the ring gap on cyl 4 rings, I think all bores are out of spec.
Manual specs say bore diameter should be 3.4446-3.4452 but all mine are 3.45132-3.45148, that’s roughly 0.006-0.007 out of spec.. so they definitely aren’t oversized.
Top ring Gap:
Spec: 0.0098-0.020
Measured: 0.018
2nd Ring Gap:
Spec: 0.009-0.018
Measured: 0.014
Those bore diameters have me confused.
Manual specs say bore diameter should be 3.4446-3.4452 but all mine are 3.45132-3.45148, that’s roughly 0.006-0.007 out of spec.. so they definitely aren’t oversized.
Top ring Gap:
Spec: 0.0098-0.020
Measured: 0.018
2nd Ring Gap:
Spec: 0.009-0.018
Measured: 0.014
Those bore diameters have me confused.
OP
Just found on the top surface of the piston “0.50” which would mean 0.50mm oversized or 0.019685”, so basically 20 thou over.
The other marking said “87.97 SF0.03”, which I think means the piston diameter +/- 0.03mm
So you're 6 to 7 thou over spec, you have 2 thou larger pistons? I don't see the mm on there...so I'm assuming 5 thou over which liberally would get you in spec.
You could throw new rings on. You could just try number 4. You could do a quick hone and replace the pistons. You're there anyways so at least rod bearings.
Or find a machine shop to bore it out, order a $2000 stroker kit and send it. Maybe you'll have better luck with machine shops in your area.
Or maybe it's time to shop around for something used or a short or long block.
Clearly seems like you've got the time and enough know how to make some good decisions. I don't know what's in your budget... time or money wise.
Wish I was closer to upstate NY and could help.
-Mac
You could throw new rings on. You could just try number 4. You could do a quick hone and replace the pistons. You're there anyways so at least rod bearings.
Or find a machine shop to bore it out, order a $2000 stroker kit and send it. Maybe you'll have better luck with machine shops in your area.
Or maybe it's time to shop around for something used or a short or long block.
Clearly seems like you've got the time and enough know how to make some good decisions. I don't know what's in your budget... time or money wise.
Wish I was closer to upstate NY and could help.
-Mac
OP
Is it worth stroking a 2.4L? I saw someone selling a stroked 4.0 for 3k.
There might be a decent amount of 2.4 short/long blocks around from PT cruisers, but they would need configuration since they are installed sideways. 2.4 is underpowered and has way less support, which is why I’m not opposed to looking into an upgraded swap.
My dad does also have a 2.4 in his 06, so I’m not opposed to donating it to him.
OP
Manifesting me swapping in a 4.0 haha. I’d just be nervous about getting someone to weld the new mounts.
Did find a frame for $1700 that is ready for new mounts and has been completely sandblasted and repainted, looks damn nice.
When I totalled my TJ last summer the replacement frame was a 2.4. I cut off the 2.4 brackets and my 4.0 brackets on my bent frame and welded them on.
If you've ever looked at the welds on our frames a kid could do better.
Metal is thin enough...you can also preheat with a propane or butane torch for more penetration.
I bought my frame and tub for $1300 in Oregon. I'll bet you could get a hot shot trucker to deliver something to you for $1000 or less.
-Mac
If you've ever looked at the welds on our frames a kid could do better.
Metal is thin enough...you can also preheat with a propane or butane torch for more penetration.
I bought my frame and tub for $1300 in Oregon. I'll bet you could get a hot shot trucker to deliver something to you for $1000 or less.
-Mac
OP
Ive definitely seen the booger welds on some spots on my frame, I guess I’m not the only one with them haha.
I’ll keep my eyes open for a good donor or maybe replace rings if it makes sense.
I’ve seen so many clean vehicles when I’ve been to Portland for Nike cross country nationals a few times, I’m jealous.