5.0 Ho 302 To 347 Stroker Rebuilt (jeep) - Seems Like I've Lost Power

bwall

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Jul 13, 2017
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I picked up a rebuilt 89 or 92 highway patrol 5.0 HO 302 to a 347 stroker with about 500 miles on it. It's a beast and sits in a 87 wrangler. I've put maybe 600-800 miles on the jeep it since i bought it. I know this may not be the best home for a jeep post, but it carries the 5.0 badge and I can't get enough of it. I'm ready to try to run dual exhaust and give it a real good sound. The downfall to this, is the jeep runs an old F100 (listed as NP435) 4 speed manual transmission. The engine is loud and strong, but the 4 speed has a crawl gear in first and at about 65 mph is running about 2900 rpms. The jeep is wound up at hwy speeds and feels like it would love to run a lower rpm, but its a 4 speed... no more gears left. I would love to switch out the transmission, but not sure were to go with that at this point. The jeep was really built for rock crawling, but I couldn't pass it up. I bought it for the engine, and can't get enough of it in the jeep.


Now my worry...


I was headed to the shop the other day to get a transfer case seal replaced and a rear differential looked at for a leak. One the way there I came around to an entrance ramp from one highway exit to another highway entrance on about a 270 degree circular exit ramp (if that makes since..) head on west hwy exiting to a heading south hwy 30 mph exit. I came around the corner to a busy 3 lane exits entrance combo and a cop had a guy pulled over on the southbound exit. Of course the police car was halfway out in the entrance exit lanes. I was doing about 30-35 and dropped the jeep from 4th to 3rd to power into traffic and get around the cop and the car he had pulled over. I had cars exiting around and in front of me and the police car and its stop and cars on my tail entering with me. When I dropped the 5.0 in 3rd I had a very odd hard drop of power and then jerk, the jeep then seemed to come back and find itself. I could see this if I was doing 55 or 60 or more, but I was maybe doing 40 tops (lifted jeep on 33's). I thought of crap what was that...... I pulled it out of 3rd and put it back into 4th after getting into traffic and got on down the road


I took the jeep onto the shop and dropped it off for the seals to be looked at. I had a transfer case seal replaced along with a rear pinion seal replaced. When i got the jeep out of the shop it feels like its lost some of its power and torque. It even sounds a little different. Our temperatures here have been mild 70-mid 80s so far this year until around the day I took it to the shop. Now we are pushing 95-100 with heat index over 100.


I'm worried I may have pushed the engine to hard entering traffic during an engine break in period. I also don't like dropping the thing off at the shop while there may be a break in period and its a 347 stroker in a jeep! After fixes the cars always go on a test drive. I've had the thing in the shop with minor look overs and repairs to alignment, brakes and the above mentioned seals.


Is it possible I may have caused an issue with the engine during the shift transition. Can warmer temperatures make it run a little lighter? It just feels like I don't have the same power and engine muscle sound. I haven't been pushing it much past 3K rpms tops 4K-4200 (not sure I've even got it that high except entering the hwy on the above mentioned detail). Can things slow down/loosen up as the engine breaks in? I probably have somewhere around 1200-1500 miles on it now since it was rebuilt. I have a few other cars running 300-390 hp or so, so I'm used to this type of horsepower, but the jeep seems like its having issues since I drove it into the shop that day, experienced that power drop/jerk and then got it back.


Thanks for reading all that and any responses!
 
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bwall

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I may need to provide some pictures. Most of the stuff goes to the shop for work. My knowledge at the mechanic/repair level is pretty low. I'm trying to get better at doing some things myself but I can sure turn a short job into a long job or a long job and a tow! I can try to post some engine pics.
 

bwall

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Jul 13, 2017
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I understand that sentence. Haven't done one personally before, but I can buy a kit and give it a run! I have an OBD II reader, but I think I need a OBD I for this engine.

I checked Harbor Freight but the compression kits have bad reviews. Do you recommend any brand or type of compression kit?

I looked in the engine bay for the EMS, but not sure if its there or under the dash.

Oddly the oil seemed low and it was just changed about 600 miles ago. It should be running Shell Rotella 15-40W. The coolant overflow bin was pretty low too. I filled those and will keep a way better eye on them. It doesn't seem to be leaking either of those fluids. My transfer case and pinion seal seem to be good to go so far. The floor is all clean.

I can't answer the fuel and spark questions at this point and not sure about 4 speed and t5.
 
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The conversion harnesses try to mimic the Fox body harness and retain most of the same component locations. Therefore....

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/