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1992 / 1999 4.0 Head swap


bpsinned

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Hey guys, I was wondering if anyone knew if it was possible to use a set of 90tm heads from a 1992 4.0 on a 1999 4.0 block?
Long story short, 1999 gave way, got a donor 1992 and ordered after market heads,had 988 double springs installed for 422 cam before I realized the difference in a whole lot of things,sensors, mounting brackets ect..ect. Head gasket part #is the same, but Ive read some conflicting things about swapping.
Any input would be greatly appreciated.
 


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gaz

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Welcome bpsinned,

As long as your 99 is a 4.0L OHV and not a 4.0L OHC, then the only issue I know you need to consider is that 90tm 4.0 ohv heads on a 98tm 4.0L ohv block will have a significant drop in compression ratio. This is due to the much larger combustion chamber on 90-94tm heads.

You could compensate for the loss by using either 90-94 pistons which have a much small dish or the use of 01+ 4.0L OHC flat top pistons which will actually raise the stock compression ratio a full point with 90tm heads.
 

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Thanks for the response gaz, at least there's hope now. The 99 is a X vin OHV . As for the 01+ SOHC flat top pistons, would you know if they are a direct fit, or does any other alterations need to br done?
I would certainly rather the bump in compression if they are as simple as just swapping for the earlier type. Im going to be buying a set regardless.
 

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bp,

They are direct fit but make sure you know wether your block is still at standard bore or if it's been rebored.

When I received my 4.OL ohv, it had already been rebuilt once and the bore was @ +0.50mm, my cylinders are shiney but with no ridge/lip, I discussed it with my machinist buddy, he unformed me that with shiney cylinder walls and no lip, just replacing the pistons "could" work very well. I replaced the stock +0.50mm 94 4.0L ohv pistons with +0.50mm, 01 SOHC 4.0L flat top pistons. Dropped in like they were getting paid.
 

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Thanks for your help, block is heading to the machine shop to check cylinders for appropriate action before purchasing new flat top pistons. Cracked ring destroyed #3 cylinder on original block, hoping the different heads and piston set will bump up the previous setup.
 

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Great thread guys, I'm getting ready to having a replacement 4.0L OHV engine built.
I just received the Comps CAM 49-422-8 & plan on using the 98TM heads (will have them ported)

I'll trying to find a 98 4.0 OHV block from the junkyard (probably) & have it rebuilt
I already run premium gas & would like to raise the compression to get some extra power, so are 90-94 dished or flat top pistons the way to go? I know the 4.0 SOHC has 9.7:1 & the 4.0 OHV has 9:1. I'd like to get above 9..7:1 to get the most HP I can without a lot of additional changes.

I already have shorty headers, & a BBK throttle body with cold air induction & custom exhaust.

I plan on have the exhaust ports ported larger in the 98TM's from 1.40 to at least 1.70, the heads & upper/lower intake port matched, 3 angle valve job, & dual beehive springs. Any advice/recommendations ?
 
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Hey Rhodes, I got some great info from gaz on issues that I was uncertain on. I'm working a 99 block which is a 97tm with 90tm heads. Pistons are 2001 hypereutectic flat tops 1.441 height . Block/pistons going. 20 over. Beehives are only single spring... I'm using 988's which are doubles and recommended with my 422 comp cam. Push rods are from Smith Bros. and are 5.550,stocks don't work with that cam. I'm in the process of reworking a 92 aluminum upper intake (like it better than composite). Crank and rods are from the 99. Also plan on bumping the injectors to 24#, not sure if really help things... maybe the idle @ least.
 

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RhodesCD,

Since you chose 98tm ohv heads my advice is that you use 2.9L headers and have the ports matched to them. Ford cut the 94 and 95tm exhaust ports perfect for 2.9L headers but the inlets to the exhaust manifolds they used were oversized to try and trick/beat emissions; this ruined the exhaust velocity as will a set of 4.0L headers.

To be clear bpsinned is using 90tm heads in a 97 4.0L; he can safely add 94, 4.0L OHV pistons and run very near stock compresion. He can use 4.0L SOHC flat tops and raise the compression a whole point because he is using the big dish 90th heads.

With 97TM HEADS you can use 97 ohv pistons and mill the heads 0.030" and realise a full compression point. I have been told that a 97 EEC will run 95 or 97 4.0L ohv pistons no problem but that it will not get along with 94 shallow dome pistons and using SOHC 4.0L pistons is definitely not recommended for that EEC.

Neither of you need more than #19 injectors; they are supposed to be plenty through 250hp.

bpsinned,

If you haven't bought your cam or springs yet, I can help you save some money. My custom reground cam only cost $200 including shipping both directions from Oregon Cam Grinders of Vancouver Wa (they offer both Comp Cam profiles). My springs are a double set used in Ford V8's which worked out perfect for the new lift needs, the set was only $80. I have the part number if you are interested. I also have the cam specs that I'm using, though they are specific to the flow characteristics of my engine and used with an automatic.

I strongly urge you both to consider having your stock T/B bored, though not the cheapest procedure, that extra 3hp across the RPM band is a solid gain!!!

Also, since you are both stepping into higher compression power, don't skimp where money is best spent; spend the extra couple dollars and get the ARP piston rod bolts. If you are adding headers, Stage 8 offers great locking header bolts; there is nothing better than torquing header bolts once, FOREVER ☕☕☕

FYI; the heads need a little work but of the 4 pieces that lower intake manifold came back the lightest. Just like with it's sibling the 2.9L, the lower intake manifold required the most material removed.
 
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bpsinned

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Once again gaz I appreciate your input.Unfortunately Ive made the purchase on the cam and springs already, had I posted sooner I would have certainly taken you up on the offer. As of this morning the machine shop is beginning prep on my block and was able to get the pistons over night from a close source. I have been blown away by numerous variants, and combinations of this engine. Had I known when I started I might have opted for a 5.0 swap...lol. Never the less , Im neck deep now, and cant wait to start bolting things up, and getting a tune on this thing.
 

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Just wondering, with the rebuild of a 98 OHV 4.0, raising compression to 10:1, the comps cam 422, 98TM heads exhaust port ported, triple angle valve job, upper & lower intake ported, BBK throttle body, shorty headers, cold, air induction, approximately what kind of HP would be expected?
 

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I would imagine with a good tune somewhere just north of 200. I have a very similar setup going on and I'm going to be using the sct x4 tuner, working w/ 5 Star tuners to squeeze the most out in one of my tunes. The other 2 will be a economy, and a tow tune that I can flash to the pcm. I have a local tuner that can Dino and tweak it for me. The x4 will store up to 10 tunes.
 

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I was very much hoping getting at least 75 more HP, putting me at 235 HP. And had thought that I wouldn't need a tuner since I don"t need bigger injectors & didn't plan on changing the MAF meter
 

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RhodesCD,

quality headers +20 hp
correct cam +20 hp
one full compression point +4 hp
t/b +3 hp across RPM band

If you really want more, get the heads and intake manifold flow bench port/polished, that can be worth another +20 hp.

If your engine isn't yet assembled, you can polish the crank and balance the whole bottom end; that will improve your overall efficiency by an additional 10%, that will also get you to your mark.
 
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bpsinned

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Rhoades I'm going with a 65mm MAF from a SOHC engine, and a 66mm throttle body from BBK. Where exactly are you pulling intake air from, a seal box, or a filter located in the engine compartment?
 

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I already have the bbk throttle body in place with araide cold air induction but air box removed leaving an open cone filter. I've been thinking about a MAF meter from a 1999 sohc but don't know how much bigger it might be compared to my 98 MAF on my ohv, or how much difference it might make? And i believe i`d have to get a programer if i made that MAF change
 


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