1987 Ford LTD Flat Tappet Cam Idle

1930 FORD LTD
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PHORDMAN
  • MEMBER
  • 2 POSTS
1987 Ford LTD with a roller cam 302. I installed a rebuilt 302 from an '85 flat tappet Merc Grand Marquis into a '87 Ford LTD equipped with a 302 roller engine. The computer is not at all happy with the cam change. I have to run 20 degrees idle advance in order to get reasonable smoothness at idle. Is it possible to reprogram the computer to accept the older engine. Could a computer from an '85 model be installed in the '87? Would the early computer fit the '87 wiring harness?

Thanks for your help
Dec 22, 2006 at 1:50 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
if you installed the whole engine that is your problem. If you put the 87 fuel and distributor stuff and hooked up everything then it should be ok. Bu tby now you probably don't have the car..
Sep 14, 2009 at 1:49 PM

Suggested Repair

Use the 1987 fuel-system and distributor components with the installed engine rather than the complete older engine setup. The rough idle is attributed to installing the whole flat-tappet engine without the original roller-engine fuel and ignition parts.

Conversation Summary

The owner installed a rebuilt 1985 flat-tappet 302 from a Mercury Grand Marquis into a 1987 Ford LTD that originally had a roller-cam 302. The computer runs poorly, requiring about 20 degrees of idle advance for reasonable smoothness, and the owner asked about reprogramming it or installing an 1985 computer. The expert said installing the whole older engine is the problem and that using the 1987 fuel and distributor equipment should allow it to run acceptably.

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