mhead
NAXJA Forum User
- Location
- Encinitas, CA
Hi All,
Have a 1992 XJ 4.0 with auto tranny. I've a lot of weight on this vehicle and wanted more HP to move it all.
Purchased a stroked 4.0 from http://www.titanengines.com/. Engine is bored 0.030 over and has a different crank bring it up to 4.6 liter according to Titan. Paid about $2100 for the engine plus shipping, core. Titan assured me that engine would not run extra hot and would run on mid-grade fuel, 89 octane here in CA. I was told the only mod I would need is to purchase 24 pound injectors, which I did. They built engine almostly immediately and in a week or so I had it. Installed without major problems.
Started engine. No big clunks! But it seemed to heat up really quickly and run much hotter than expected. Temperature indicator showing near the red while traveling 45 MPH on level ground at about 60 deg F air temperature. Ok, I guessed the engine was just really tight.
Drove 800 miles out to Tucson from San Diego and back. Engine ran really hot but by driving carefully I managed not to loose any coolant. Drove 800 miles to Mammoth. Very cold weather and didn't notice any heat problems except at one point where the Jeep was pulling really hard into a head wind.
On the above trips there were a couple of points where the engine started missing due to heat, but no coolant loss. Stopping for a moment allowed engine to cool and return to normal operation. Noticed significant ping on 89 and also 91 octane gas ate 2500 rpm. Mostly drive at 2000 rpm - 65 MPH.
Idle now rough. Compression test shows
#1 - 195 PSI
#2 - 205 PSI
#3 - 200 PSI
#4 - 195 PSI
#5 - 105 PSI
#6 - 155 PSI
Air pressure into cylinders causes loud hissing at intake manifold on #5 and very noticable hissing at intake from #6.
Head removed. Detonation balls of aluminum within cyl #6. Piston not too badly eroded. Intake valve on #5 cyl stem bent. Crack in head below #4 exhaust valve on #3 cylinder side.
Ok, engine has run hot and been damaged. The way I see it there are two problems: compression and heat.
Compression: 200 PSI cranking pressure seems really high for an engine supposed to run on 89 octane. This is a possible explanation for pinging. Don't know about heat. Does anyone know what compression pressures to expect from a stroked 4.0?
Heat, pinging: Possible explanations: lean air/fuel, advanced timing. To my knowledge the ignition timing is not adjustable, being set by the CPS at rear of motor. Correct?
If so this leaves lean air/fuel. The 24 pound injectors should allow computer to provide sufficient fuel. Oxygen sensor is not terribly old. Installed new factory fuel pump some months prior to engine swap and observed correct fuel pressure at that time. Anyone know anything about air/fuel adjustments for stroked 4.0? I've purchased a Auto Meter air/fuel sensor + gauge and intend to install this so I'll have an idea of mixture. But that's another thread....
So the head of my new stroker is wrecked and, because of the high compression numbers, perhaps the engine is not correctly built. I'll keep posting to this thread but I'm kinda discouraged right now.
Have a 1992 XJ 4.0 with auto tranny. I've a lot of weight on this vehicle and wanted more HP to move it all.
Purchased a stroked 4.0 from http://www.titanengines.com/. Engine is bored 0.030 over and has a different crank bring it up to 4.6 liter according to Titan. Paid about $2100 for the engine plus shipping, core. Titan assured me that engine would not run extra hot and would run on mid-grade fuel, 89 octane here in CA. I was told the only mod I would need is to purchase 24 pound injectors, which I did. They built engine almostly immediately and in a week or so I had it. Installed without major problems.
Started engine. No big clunks! But it seemed to heat up really quickly and run much hotter than expected. Temperature indicator showing near the red while traveling 45 MPH on level ground at about 60 deg F air temperature. Ok, I guessed the engine was just really tight.
Drove 800 miles out to Tucson from San Diego and back. Engine ran really hot but by driving carefully I managed not to loose any coolant. Drove 800 miles to Mammoth. Very cold weather and didn't notice any heat problems except at one point where the Jeep was pulling really hard into a head wind.
On the above trips there were a couple of points where the engine started missing due to heat, but no coolant loss. Stopping for a moment allowed engine to cool and return to normal operation. Noticed significant ping on 89 and also 91 octane gas ate 2500 rpm. Mostly drive at 2000 rpm - 65 MPH.
Idle now rough. Compression test shows
#1 - 195 PSI
#2 - 205 PSI
#3 - 200 PSI
#4 - 195 PSI
#5 - 105 PSI
#6 - 155 PSI
Air pressure into cylinders causes loud hissing at intake manifold on #5 and very noticable hissing at intake from #6.
Head removed. Detonation balls of aluminum within cyl #6. Piston not too badly eroded. Intake valve on #5 cyl stem bent. Crack in head below #4 exhaust valve on #3 cylinder side.
Ok, engine has run hot and been damaged. The way I see it there are two problems: compression and heat.
Compression: 200 PSI cranking pressure seems really high for an engine supposed to run on 89 octane. This is a possible explanation for pinging. Don't know about heat. Does anyone know what compression pressures to expect from a stroked 4.0?
Heat, pinging: Possible explanations: lean air/fuel, advanced timing. To my knowledge the ignition timing is not adjustable, being set by the CPS at rear of motor. Correct?
If so this leaves lean air/fuel. The 24 pound injectors should allow computer to provide sufficient fuel. Oxygen sensor is not terribly old. Installed new factory fuel pump some months prior to engine swap and observed correct fuel pressure at that time. Anyone know anything about air/fuel adjustments for stroked 4.0? I've purchased a Auto Meter air/fuel sensor + gauge and intend to install this so I'll have an idea of mixture. But that's another thread....
So the head of my new stroker is wrecked and, because of the high compression numbers, perhaps the engine is not correctly built. I'll keep posting to this thread but I'm kinda discouraged right now.
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