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Discussion Starter · #1 ·
Hey guys, I just dropped a reman 351W EFI into my 90 Bronco...old one had 160k on it. When we swapped it in we put all new parts in i,e: distributor, cap, rotor, plugs, wires, cleaned all the parts. Since the manifolds were cracked I went with JBA headers and I put the stock air box with a K&N back in. I've been told that a new motor takes about 5k miles to start to feel broke in and up on power. Right now I've got 1200 miles and it feels like a dog. Where before it could hold it's own in OD, you need to kick down to 3rd and this is just to hold speed. I know the heat and AC use here in Vegas will take its toll, but this seems way too much. We also put a new torque converter in it and the tranny and trans case have about 16k miles on them. The guys who helped me drop this engine in is fairly stumped as to why the engine feels like its plugged. He recommended checking the catalytic converter and the ignition timing advance. It runs real well, just feels like no power. I put the FIPK back on it and that seemed to help, but it's still not pulling in OD on the highway. I am getting really frustrated that I put this much time and money into it and it runs down on power. Any ideas, suggestions or advice would be so great. I'm at the end of my rope here...I'm getting tempted to sell it cause I'm tired of pouring money into it. Thanks for your help.

~Mike
 

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mine is very similar to what you describe, though i have 141k on original block. i checked my vacuum and it's 6" Hg at all rpms with very little needle movement during revving. i think this means i have a wicked vac leak somewhere, probably the vac lines that are missing in several places. check your vac with a gauge and see if it's about right, plus you can diagnose a clogged cat with this method too. it's possible that you just forgot to hook up something like the brake booster that's just sucking in air like a mofo
here's a page that will help you out, but you need to get a mityvac or some other vac gauge to use it.
http://www.users.bigpond.com/ergoff/vac1.htm
 

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I had the same problem with my swap, and I forgot to hook up the PVC in the back of the motor on the pass. side and a broken vac line didn't help either. I replaced all my lines with silicone hose not that hard sh!t and my power is cool
. If that's not it I'd check the timing. 10 degrees BTC is factory.
 

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I feel your pain.My rebuilt 302 is a dog also.I'm to the point of pulling the front cover to see if the cam was installed retarded or checking valve lift at the rockers to see if the cam has a bad lobe.The first thing I would do is a compression check.You can check your plugs for signs of problems.Check your fuel pressure at idle and under throttle.Replace the fuel filter if you haven't done so already.I would also put #1 at TDC.Stick a dowel or pencil in the sparkplug hole and verify that at TDC the balancer mark is at 0.I have seen a balancer spin it's inner rubber piece and the timing marks be off.Also check or replace the ignition coil to make sure you have good spark.I have also seen people put the torque converter in a bind or not have it engaged completely when installing an engine.Good luck and let me know if you find anything.

Billy
 
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Discussion Starter · #5 ·
Haven't checked the fuel pressure yet. The coil is the MSD TFI unit. Gonna check for a vacuum leak. The engine just seems like it builds up a head of steam, but can't use it. It'll rev to 3k at about 25mph and shift with a firm push, and then its a dog in 2nd...almost like a flat spot. The distributor is new and we timed it to 10*BDTC, but I'll double check it. The balancer and fuel filter is brand new so it should be ok. Keep the ideas coming...I really appreciate the help!
~Mike
 
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Discussion Starter · #6 ·
When you set the dist to 10* BTDC did you disconnect the wire to the dist from the computer (I know this wire is called something else I just can't remember). On my 86 you had to disconnect this wire before you could set the initial timing. Also, are you sure when you put the new torque converter in that you got it all the way in you should have felt two good bumps as it went in. Hope this helps and Good Luck,
 
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Discussion Starter · #7 ·
Well, I feel a little dumb, but relieved. When I double checked the timing with the PIP disconnected it was at 0*BTDC. I reset it to 10*BTDC and double checked everything including the advance and it runs SO MUCH BETTER. Idles smooth(almost can't feel it) and has power on demand now. It will finally accelerate in OD on the freeway(albeit slowly, but it does)!! I think it's finally back to where it should be on power. I'll keep an eye on it and let you guys know. I'm hoping it might even pep up a bit more after a few thousand miles (only 1200 so far). Thanks again for all your help!!
~Mike
 
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