ok i bought a 1981 ford f100 with what was told had a 302 and not to after i got it home looked and it had a 4.2 255 i believe thats the right liter but anyways its tore apart now waitin to be rebuilt but i wanted to know if i could bore it out to a 302 with i think is like 32 thousands of an inch is what i would have to do and just put stock 302 pistons in it cause as far as i know everything else is the same as far as cam crank

 

Bore is 3.68, you'll never get to 4". You have to go 320 thousanths, not 32. (.320 fs. .032)

Google search this engine and you will find the best way here is to send it to the scrappy and find a 302 or 351w if you want more beef.

The heads and valves are too small, intakes don't interchange, and there is really no aftermarket as it was produced in low numbers and universally hated.

If you have a small boat in need of an anchor, you may find a use for it.

OTHERWISE just rebuild it stock and drive it.

 

well than looks like its back to stock it really dont matter its goin in a ranger either way it be more then a 4 banger in there now but thanks for the help ill build it back stock andfound a new 302 to swap later

 

Well, depending on what is in the Ranger now, you may, at stock specs, be going down in HP....it was rated 115 or 122, depending on application.

Full of good news, ain't I.....

 

i got the 2.5 in it right now and i dont believe its makeing much power i dont know the specs on it i know its just aint enough to turn the mud tires i got a already got a 4.10 gears i just want the who v8 thing and ill look at the spec for the 255 and see what they are and if there aint much differents then ill leave it stock and find a real 302

 

In what condition is the 255? Could you just rering it and go, and then get a replacement engine at your leisure?

The 260 had a 3.800 bore, you could maybe bore the 255 to that just for fun, although a .120" overbore might not work out well (but hey, what's to lose?).

A friend put a 302 top end (heads and intake) on his 255 but wasn't particularly impressed with it.

I vote for running the 255, for a while anyway, just to be different. Get some long tube headers and dual exhaust for it, which will be retained if and when you replace the engine with a 302.

One other thing, I believe the 255s are all 28 oz in balanced, same as early 289/302/5.0 engines, whereas 1982 or so up 302/5.0 engines use a different unbalance of 50 oz in.

 

the 255 looks great had stock everything inside the only reason to why i took it apart was cause it was buring alot of oil and i dont know about ya bout i rebuilt the 2.5 in my ranger for the same reason. the the way i look at it is its cheaper then a new one and ill know its good cause i did it but ok the 255 burned oil cause i believe the oil rings where lined up well no all 8 where lined up and i know that had most of the problem but im takeing it to the meching shop today to get him to look at it and see what he thinks more then likely going to get it claend up and just rering it

 

Post your location in your personal details, if you're under 100 miles I'll buy your 255 off you and you can buy a 302 somewhere. $4 gas is not over, Obama's out to save the world from carbon and if the Arabs don't raise the price the government will raise the gas tax. 255's breathe well at the low speeds I drive, it's an economical torquey little v8 to run in front of a 3.56 rear end. There's an option for you, put in a lower rear end and compensate with a m5r2 or zf5 overdrive manual or an AOD auto trans. I'm in Louisville.

 

im in fl north part but already got the motor on the way so im just gonna stick with the 255 seems to be a good motor for what im doing but thanks for the offer but im gonna keep it

 

Biggest horsepower sucker on the 255 v8 was the tiny catalytic converter installed in the y-pipe at the back of the engine. You can put a bigger cat back in tailpipe somwhere and get rid of the little cat restrictor. Got to have a welder, muffler shops won't mess with this. I made up custom duals by cutting the ends off the Y-pipe and welding drops on. Second biggest low end torque sucker was all the vacuum hoses, mine came with 60 hoses and all tees and temp sensors etc. were broken and sucking air. I have two vacuum accessories, now, pcv (crankcase ventilator) that is shut off cold by a temperature sensor, and distributor vacuum advance, shut off cold by a temperature sensor for good emmisions. The variable venturi 2 bbl carburator is a loser, it will be jetted too rich for modern rfg gas and too complicated to work 30 years. Factory Rebuilds 2bbl will also be jetted too rich, I believe the EPA requires the shops to tune them for the old type gas they haven't made since 1990. The holes in the 255 2 bbl manifold are tiny, get a 4bbl manifold and a 450 cfm 4 bbl carb and put in smallest jets, I'm using 51 jet. reJet carburator until motor doesn't miss (rich enough) and plugs stay light tan (not too rich). You can tell too rich by hot catalytic converter temperature too.

 

The 255 uses unique intake ports and a valley cover, so how does the 4V intake deal with this? I assume that a specific 255 4V intake doesn't exist.
You can get Holley jets smaller than 51. I used 48s in a 370 cfm on my old 260. The speed shop I bought them at was pretty surprised they actually had them in stock!

 

Scare up a set of 260/early 289 heads with the 53cc chambers and 1.67 intakes and they'll bolt right on and allow you to use a four barrel intake.
The valve sizes and combustion chambers are the same size as the 255's
heads. Be sure to do some light porting and put some headers on.

 

"Scare up a set of 260/early 289 heads with the 53cc chambers and 1.67 intakes and they'll bolt right on and allow you to use a four barrel intake."

Those old 260s have a warm spot in my heart, and I'm quite familiar with the 260 engines. I had one with a stock 289-4V intake and small Holley carb and it seemed to go pretty well.

Actually the 1964 260 has the 289 size valves and ports, I think, while the 1962-3 has smaller ones.
Of course it's not exactly easy finding this old junk quick so this could be rather moot.

 

Sure the valves will clear in this small-bore engine?

 

Yes, the valves will clear. Think about it, they all use the same head gaskets and the chamber volume is the same as is the valve sizes. And the valve guide spacing did not change.