81 F100

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Feb 19, 2003 | 07:30 PM

rusty_nail2

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81 F100

I have a 81 F100 sitting in the yard and thinking of fixing it up
it has a dead 300 I6 and 3spd column shifter. anybody tell me what engines will fit and with what transmission.

Feb 19, 2003 | 07:51 PM

Chuck 6083

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From: Where they take the census by counting the appliances on the front porch and multiplying by five

81 F100

Welcome to FTE rust nail2!

I think a 302 or a 351w should bolt up where the I-6 was. If you can get one of these cheap then that may be the way to go. It's not a bad swap from what I've read, just kind of involved.

If you're looking for towing, hauling, and just plain pick-up truck normal useage, then you've already got Ford's best engine. Fix it and save all the parts huntin'.

My .02

Welcome again. Glad to have you aboard!

Chuck

Feb 19, 2003 | 10:29 PM

xuare

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From: SW Maryland

81 F100

Depends on what you mean by "fit". The 302/351 needs a different set of mounts on the frame or crossmember, but several people on this forum have done it in their trucks. The transmission will need either an adapter plate for the bolt pattern of the 302/351 or you will need the tranny off of a 302/351. There may be other issues (I have not personally gone through the exersize, just read others tales). I think you could put a 460 in if you go through the same exercise, though it may (?) need those hot fuel electric tank pumps to keep extra gas coming to the thristy engine. The radiator would have to be changed out also to accomidate the bigger engine, may need heftier front springs for the heavier engines, etc.

I personally have a 351w, but those who talk about their 300 I6 speak fondly of it. If you want a daily driver that dependable and easy on the gas, the I-6 sounds like a very nice engine based on their accounts.

Feb 20, 2003 | 09:47 AM

cdd5599

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From: tx

81 F100

ok here is the deal,

You do need new frame mounts (302 and 351w same-which bolt on ) from junkyard or donar truck. 300 I6, 302, 351w all use the same bell housing so it will bolt right to existing transmisson. They all use different flex plates or flywheels (auto, or Manual) do to the counter weight balance. You will aslo need a bigger radiatior (if you have just the 2 core six cycl radiator). I recomend 4core. Starter will work on all three engines. You will need differnt kickdown linkage for automatic. You will also need different accelerator cabel. Your truck is a 81 which makes wiring awesome. As long as you have the duraspark 2 iginition system you just have to have the distributor from 8cyc and plug in . If you have a factory tack you need to cut #12 pin that plugs in to dash gauges and ground (do this for all v8's).
It is well worth the swap to 351w. I went from 6cyc 4brl headers to a upgraded 351w with 3.50 rearend and I love the new power.

Chuck D.

Feb 20, 2003 | 09:57 AM

cdd5599

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From: tx

81 F100

I just noticed you said you have a 3spd. I feel these transmissions are junk. They are two high geared if you want any larger size of tire on your truck. I would upgrade to a 4spd or auto. If you put in a 4spd all you have to do is find a 4spd for 80's . Cut a hole for 4spd tranny shifter hole in floor is in right spot. Or unscrew hump and get the fourspeed hump form donar truck. Then your crossmember is allready reay for a four speed. You just have to unbolt it and flip it around. So your mount holes are in the right spot. You will also need the pig tail from the 4spd and cut and spice into existing harness (two wires allready colored same (you got to love ford's universal upgrades.)
If you want to put in a auto i can give you tips on c6's.

Chuck D.