4.0L head vs 4.0LHO Head

Hello,

:helpme: So I did a thorough search before posting this thread. I could not find the answer so I decided to start this thread. I have read on some internet sites some upgrades that you can do on a 4.0L to get more horsepower etc short of stroking it. I don't have enough funds to fully stroke the engine so I wanted to find out if what I read was true before starting a project. I have a 1987 Cherokee with a 4.0L engine. I am going to be rebuilding the engine over the off season coming up here in CA, starting after Winterfest in JAN. I read that you can replace a 4.0L head with a 4.0LHO head. To gain a little more horse power due to the larger intake and exhaust valves and the shape of the heads compression chamber. I have not yet sought out a 4.0LHO head to look so I visually have not seen what it looks like. Is any of this true?

There are differences, notably in the intake ports which mean using the HO intake. Or you could just keep an eye out for a good HO engine on craigslist.

Well, I have read that the Renix era--97-90--4.0 head is considered a performance upgrade on the 258 ci sixes.

Depending on what kind of performance you are looking for different things will provide different returns at various cost levels.

If you want torque--more bottom end--the biggest bang for the buck is lower gearing, like grabbing a pair of 4.10 axles from a 4 cylinder XJ and stuffing them in.

If you want more throttle response then a free flowing CAT-back exhaust would be what you are looking for.

Again, what is it you want--Jeep Speed or rock crawling.

As you are rebuilding the engine you could put in a cam for more torque, then a larger throttle body and header would be justified.

An issue you will face is the elimination of the EGR if you swap heads and use the newer style (HO) intake/exh manifolds. In CA, that's a big No-No and you won't pass emissions testing.

If you go the free flow CAT route, you'll need to make sure it's a CA approved one which is pretty expensive.

The HO head just isn't that big a deal. Match port your Renix head to the intake and exhaust manifolds, get a 60mm throttle body from www.strokedjeep.com, and a set of injectors from www.painjection.com, eliminate the crushed zone of the headpipe and be done with it. Emission police won't have a clue and you'll have a great running Jeep. Ask me how I know.

cruiser54 said:

Ask me how I know.

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OK, How?

Because I've done it. The HO might have a little bit of an advantage in the upper end of the RPM range due to the better header and the port design than the Renix, but the response and torque of the Renix with the above mods will easily run with an HO without the trouble of swapping the head.

I have performed the mods to my personal Jeeps, one Renix, one Renix with HO head match ported.

Quote:
Originally Posted by cruiser54
Ask me how I know.

OK, How?

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L (about 1/3 of an lol)

I think he was just giving you the gears, although the number of times I've seen that expression I'm suprised I don't see that response more often.

The swap itself is not the problem. Passing inspection is. In CA, they will input your VIN and get a detailed list of things to test. One is specifically the EGR. If it's gone, blocked off or obviously tampered with, you fail. Or course, if it just doesn't work, you fail anyway. Doesn't matter if it passes the sniffer. They even pressure test the evap system (and charge extra for it) if it's prior to 1996.

My earlier comment was directed at using the HO manifolds in conjunction with the HO heads.

Saudade said:

The swap itself is not the problem. Passing inspection is. In CA, they will input your VIN and get a detailed list of things to test. One is specifically the EGR. If it's gone, blocked off or obviously tampered with, you fail. Or course, if it just doesn't work, you fail anyway. Doesn't matter if it passes the sniffer. They even pressure test the evap system (and charge extra for it) if it's prior to 1996.

My earlier comment was directed at using the HO manifolds in conjunction with the HO heads.

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Since it is Kalifornia, that's why I suggested what I did. You can keep the Renix manifold and EGR but add some performance without getting busted.

I would recommend sticking with bolt on goodies. TB, intake, headers, exhaust, pretty much what ever you can legally do in your state. I doubt that swapping heads would be worth it/legal anyways.

CherBear said:

I would recommend sticking with bolt on goodies. TB, intake, headers, exhaust, pretty much what ever you can legally do in your state. I doubt that swapping heads would be worth it/legal anyways.

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Upgraded injectors, even skip the header if you want to. As important in the exhaust system is removing the "crush" in the downpipe. Check it out sometime, right below the exhaust manifold flange. I had a custom one made that swoops back and clears the front driveshaft for $50. If you have a 3' lift or more, you can route it where it was.