advice needed

Should I spend $600-$900 rebuilding the f head in the 56 cj5. It only has 20000 mi on it but the PO took the head off and left it off so exhast valve seats need reground. The cylinders look great no ridge at top But while the shop has it they can hone them. Or should I just look for a different engine that will give me better proformance for everyday use. and if so what engine should I look for that I can keep the rest of power train. I'm not building a monster I just want this to be dependable more than authentic.

 

If the rest of the engine is in good shape, I'd have them go through the head and do a quick hone and re-ring job. Nothing wrong with the F-head engine, as long as you're not trying to cruise the highways at high speed. Gas isn't getting any cheaper, either.

 

I'm not a big fan of the F-head, but IMO it's very hard to do an engine swap for the amount of money it takes to refurbish the original engine. Plus, there are always a lot of little things to do to make any engine work in place of the original. These can add up, in both time and money. The main problem with the F-head is the weightower ratio is very high compared to modern cars, and you may find driving it tedious on the highway. It can be a very durable engine if you don't push it too hard - because of the very long stroke, if you try to run it too fast, the rod bearings may not hold up.

I assume you want to keep the original transmission; if so, there are plenty of engines that will bolt up to the transmission using the GM adapter. It consists of a long input shaft and an aluminum bellhousing-to-transmission adapter. Just about any GM engine will bolt up to the T-90 using this adapter with the engine's original bellhousing. These adapters are avilable here (occasionally), on ebay or on Willystech quite often.

There are plenty of modern four-cylinder engines that could replace the F4, including the 153 Chevy (from Novas or mail Jeeps), the 151 GM/Pontiac (S10s and Cavaliers?), and the 150 AMC (from XJs, MJs, YJs and TJs). The 2L or 2.3L Pinto engine is an option, and has its own adapter. The Jeep/Buick V6s have lots of fans here; the buick V6 fits into the CJ engine compartment very well, and makes more power than any of the above 4 cylinders. All of the above will use the GM adapter, except for the Pinto.

 

If you live near and have to traverse hills every time you use the jeep skip rebuilding a 4 cyl. That was my problem. In NY no one has the patience to sit behind a downshifting jeep doing 28mph in a 45 zone going up a mile long hill. It's gotten more congested here and there is no time that there was no traffic and besides I want to go when I want to go. The 225 V6 weighs approx 90 lbs less and has 2 x the HP and torque and, w/ some minor changes, it drops in. Forget 60 or 65MPH w/ either unless you get an overdrive and do a 11" drum brake conversion. Just my 2 cents

 

not a bad deal, since I spent $1200 in parts alone last winter to overhaul the :v6: . could always: regear to 4.27, add an Overdrive or get larger tires to increase speed.

 

Look for a good used F head?

 

As said earlier, if speed isn't an issue, then rebuild it. And have hardened exhaust seats put in while you're at it. I had mine done for about $1200. This included going .020 over, new pistons, new crank bearings, head rebuild, hardened seats, new timing set, etc. I was looking to keep it stock though.....

 

Regearing will help the F4 to go faster in the flatlands, but doesn't change the weightower ratio. I'd estimate the net HP of the F4 is about 50, and the aerodynamics of a CJ are terrible - thus making an excellent hill detector, as Bill points out. Compare the AMC 150 at 120 net hp, and the Buick/Jeep 225 at 160 net hp ... you can see it's easy to at least double the net hp using a modern 4-cyl or V6 engine.

Another possibility is the Chevy V6, which came in a lot of cars and trucks and is widely available. It uses the GM adapter too. The Buick V6 has the advantage of the distributor in front, so it fits the engine compartment a little better, but the Chevy is also a good choice.