4.0 ohv build questions | Ford Explorer Forums - Serious Explorations

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4.0 ohv build questions

My build starts in two weeks and there a few questions I need to find answers to and a few details to nail down.

1) With SI Valves (0.020 oversize), (988-12) comp cam springs, and comp cam retainers (1730-12), What locks do I need? Part numbers please.

2) Would it be beneficial to run the older style Alabama head (90TM) with flat top pistons (3155HC-5MM on summit) vs oem spec dished piston with Alabama 98TM heads? Important tidbit, the block will be decked to whatever it can be cut down to, still researching that one. Trying to get to around 10:1/10.5:1 compression

3) Using the older style heads, what is the limit on porting and polishing the intake and exhaust runners? With the newer style heads, what should the final finish be on the intake runner? I had heard/read smooth, but not polished. Anyone care to confirm or deny?

4) Running the above setup with the 422 cam, do ARP rod bolts and main studs warrant the cost? This setup will never be FI or sprayed.

5) What is the preferred 24lb injector? Part #? Do the 24lbs from a mustang work?

.....What transmission is going to back this up?


The 5r55e thats behind it now, until it blows, then probably a t5.

your not getting much for answers here, so I'll take a stab at this.

If your porting and polishing, might as well go with the 98TM heads. There's more meat on the exhaust to be removed. You might want to use SI valves.
I have read that the intake runners should not be mirror smooth also.

I think you can get the compression up higher with the 422 cam. I think you need to (As Planned) to run an automatic as you need the vacuum.

Im not sure what the best way to get compression would be. Any of the methods you describe would work.

Also, I dont think you need the ARP rods and studs.

As for the 24lb injectors, wouldn't a tune be an absolute requirement after installing?

1-stock locks work fine
2-98tm head with stock 90-94 dished pistons will give you about 10:1. Every 3cc removed from the heads will give you 0.5:1increase.90+ gas or good tune is a must
3-stock 19lb will work fine if you never go fi
4-with fuel injection you can go all most mirror
5-stock head bolts will be fine
there is a ton you can take out the heads.there is even more in the lower and upper intake that can be taken out.go crazy with the p+p that is where most power will be gained and if your getting a tune i would go 11:1.don't forget longer pushrods are needed also and i suggest a mellings high flow pump.as well as bbk ,headers,under drive pullies and efan.