CC size differences between renix and HO head?

[stroked'73]

Are the combustion chamber sizes the same between the renix and HO head? I was told they were different but it doesn't sound right.
I'm putting a 95 head on a renix motor - is there anything I need to do to match these up or is it a simple swap? All water passages the same, etc?
Also, the 95 uses the longer nose heat range 12 spark plugs, the renix the shorter heat range 9 ones. Should I stay with the long ones and use the cooler range?

[Muad'Dib]

CC size should be the same... however do be aware that the intake ports are higher on the head compared to your RENIX head. I think people have gotten the renix intake and exhaust manifold's to work on the 7120 head... but with some work.

If it were me i would use the intake and exhaust manifolds from that year range (91 -95 for 7120) and use them. However you will have to buy or make a TPS adapter for the RENIX tps to work on the newer Throttle Body. You will also need the TV and Accelerator cables from the same rear range.

[stroked'73]

Thanks! I was wondering about the exhaust - I have the newer manifold but was hoping to use the old one so as not to have to rework my exhaust routing. Good to know in advance.
The tps is no biggie since my motor is carb'd.
Thanks!

[cherokee]

Actually, the Jeep engines book lists the renix(89) combustion chamber as between 64 and 67ccs and the HO(99) chamber as between 52 and 58 ccs.

[Muad'Dib]

Actually, the Jeep engines book lists the renix(89) combustion chamber as between 64 and 67ccs and the HO(99) chamber as between 52 and 58 ccs.

Thats interesting ... the first time i have heard of that.

[stroked'73]

Would that mean they started in 99? My head is a 95.

[cherokee]

Those are just the two years listed for specs in the book, 89 and 99. I'm guessing (and could be way wrong too) that all HO heads have a similar combustion chamber volume even though there are a few different HO heads.

Renix ran from 87 to 90 (91?), then HO with some changes along the way up until the end in 06.

[stroked'73]

I should look into this further then - do some measuring of my own. If it's true about all HO heads, that would throw my already high CR thru the roof!
However, my thought is unless the piston-to-deck height changed, there should be a bump up in factory CR from the renix to the HO engines, right? Unless HO pistons have more factory dish then renix ones? If that was the case - which would make the most sense, then renix stroker owners could cheat and use stock pistons from an HO motor instead of buying expensive pistons or paying to dish them out.
Just brainstorming here.......

[Cheromaniac]

Actually, the Jeep engines book lists the renix(89) combustion chamber as between 64 and 67ccs and the HO(99) chamber as between 52 and 58 ccs.

It's the 4.2 heads that have a 64-67cc chamber. All 4.0 heads have a 55-58cc chamber.

[cherokee]

Actually, the Jeep engines book lists the renix(89) combustion chamber as between 64 and 67ccs and the HO(99) chamber as between 52 and 58 ccs.

It's the 4.2 heads that have a 64-67cc chamber. All 4.0 heads have a 55-58cc chamber.

So it's a misprint then?

[Cheromaniac]

So it's a misprint then?

Yes.