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4.0 Head on a 232

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FSJunkie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Feb/16/2019 at 4:18am
I've often wondered how the performance of a 4.0 head swapped 232 or 258 compares to an intact 4.0.

I've driven 232's and I've driven 258's. I really can't tell you which one feels more powerful or in what way. I know the 258 is rated higher and I can see it in the horsepower and torque curves, but they feel identical while driving. 232's feel a little smoother though. I think the longer stroke on the 258 shows itself as increased vibration, friction, and wear. That means the 232 is technically the superior design.

I don't think the 232 or 258 block with a 4.0 head could ever beat an intact 4.0 for power. The 4.0 has the shortest stroke of them all other than the 199, and that means less friction. It has the largest bore of them all and that more than makes up for the shorter stroke in torque output.

4.0's are noisy though. I think it's the tubular header with it's thin walls letting noise through and their poorly muffled throttle body. They just don't have the refined smoothness and quiet of the old sixes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 232jav3sp Quote  Post ReplyReply Direct Link To This Post Posted: Feb/16/2019 at 11:16am
biggest issue with the former head is having to plug off the casting ports on the driver side. That way there is no coolant leakage. easily done. Many on here have done it and have run it with no issues. Really have to ask yourself ,is it worth the effort to swap to the 4.0 head and exhaust system when a 232, or even 258, head will give you everything that you need?

It sounds like your engine is stock, so there is a lot of room for improvement. Deck the head to keep compression in the 8.5-9:1 range (or more of you wish) as replacement head gaskets are much thicker than stock. Run a cam that will give a dynamic compression of 7.5:1-8:1 and a 4v carb and you'll be really surprised at how spirited it will be. 

Using the dynamic compression ratio calculator from Wallace racing, and the intake valve closing of the Lunati 703 cam (38*), you would have a dynamic c/r of 7.91 IF you have 8.5:1 static. Granted there are a couple of other camshaft factors the calculator doesn't account for, but, it gets you a good idea.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/17/2019 at 7:54am
If the head needs work I'd replace it with a 4.0L head. Since you mention porting and polishing, I'd just put a stock 4.0L head on it instead. The ports are smaller but better shaped and flow much better than the 232 will even with a pro port and polish job. Just clean up the pocket on the 4.0L head and be done with it. You will likely have more time and money in the 232 head porting and polishing and still not have the flow of a stock 4.0L head. You will need to measure for for pushrods. See http://theamcforum.com/forum/4-0-ho-port-flow-velocity-map_topic2477.html. I wouldn't do any radical porting on the 4.0L head as he did unless you're building an all out race engine. Just smooth the rough edges in the pockets and maybe gasket match, that's it. Really depends on what you have to pay for a 4.0L head. You're not going to get a big boost from either porting a 232 or using a 4.0L head. Along with the better cam you will get a noticeable boost, but the head alone will only add 3-5 hp -- hardly noticeable. Many sites claim 20-25 hp -- but that's coupled with other mods (or just bad guesses). With the other mods you're talking about I think you'll get a 25-35 hp boost and a noticeable amount of torque though.

That said, there is little difference between your options. The 4V carb will be a bit more economical AND provide better power when needed. If the small carb is hard to find I just posted about a modification to a 600 Holley that turns it into about a 450 cfm carb. 600s are usually easy to fins used, at least here in the US. If you're buying new I think I'd get Carter 400, but if you like Holleys better (maybe some experience tuning them, or have mates who can) either is good. I ran a 390 on a 258 for a while. It could have used a little more, but delivered plenty power and was economical as long as you kept your foot off the go pedal! Was in a Jeep j-10, four speed manual, 2.73 gears... really needed a little more gear instead of more carb, Renix 4.0L head, Offy DP intake, stock cam.

An Isky 256 Supercam is mild, you might want the 256/262 Hydraulic or the 262 Supercam. The 256/262 looks good, but a low axle ratio is recommended. You can get by with less than the 3.55-4.10 Isky recommends (mainly because it's a good towing cam), but I wouldn't go below a 3.08. If you have a 3.15 or 3.31 that would be enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mjt084 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/19/2019 at 1:39am
Thanks for the replies guys.

I'm leaning towards option 3 without the port and polish. I was under the impression that the gains would be much more.

Interesting watch RE: the Holley 600/450, down here in Australia 390's seem a rarity and expensive as do most small 4bbl carbs. Every second 70s & 80s Falcon or Holden (GM) V8 has a 600cfm Holley 4bbl on it and they come up all the time at swap meets and online for not many $$$. Would be keen to see a more in depth instructional video of how he made the modifications.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/19/2019 at 6:32am
Once you start adding a better cam and intake/exhaust manifolds to the equation, the 4.0L head adds a lot more. It breathes better, but adding just the head without other items that support that better breathing doesn't add much. 3-5 hp for each manifold, 10-12 for carb (assuming 400-500 cfm 4V or 2V), 5-7 for 2.25" exhaust and turbo muffler, 20-25 hp for the cam, then you're talking about more like 10-15 for the head. All that is at high rpm -- around 4500-5000 though. Should probably have said 10-12 for the head alone since you have to use a header or the 4.0L exhaust manifold. 

So that's 6-10 for manifolds, 10-12 carb, 5-7 exhaust, 20-25 cam, 10-15 for the head -- 51-69 hp added. So let's estimate 50-70 hp.

The carb mods aren't that hard once you understand a Holley. Take one of the throttle blades out and make a plug that will press in under the blade. You could make a block-off gasket and even leave the throttle blade in. Then use a fuel resistant epoxy (or something else) to block off/plug all the fuel passages for the blocked off barrel. I haven't looked hard at this, but it's easy enough to find Holley info.
Frank Swygert
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