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What Heads OHV 4.0?

gaz

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Kirby,

If I were using a 98 spec engine in a 91-94 chasis, there is no question which components I would use; they are the same that I recommend.

Using 94 spec pistons with 94 spec heads is the simplest option, as it will require no tuning.

A) Since pistons must be changed to accomplish this, using 01 SOHC 4.0L flat top pistons with the 94 spec head is a much better solution as your engine will benefit from the extra point of compression. You will then also have the benefits of fresh pistons/rings for higher engine reliability.

B) The only other factor is the exhaust manifold. If you are using 98, then I would definitely get 98 heads, and leave the pistons alone. If you will be using headers, then I would get 98 spec heads and have them flow bench port/polished to you intakes and headers. Neither the 94 or 97 spec exhaust manifold will be optimum with 98 heads.

Here are the 2 choices I completely advice against:
1) 94 pistons/ 97 or 98 heads (compression raised more than 1 point and unknown CLEARANCE)
2) 98 pistons/ 97 or 94 heads (reduced compression and performance).

Buying anything from Morana would be a WASTE of money. New or refurbished 94 spec heads with 94 pistons is your #1 simplest build for your computer.

He does sell some items that are worth consideration but his prices are out of this world. The reduced weight piston rods he sells are a great move but they are just the light weight stock set that Ford offered. If you want more info on them, I have it all. They are worth using just not for the Morana cost.

**IF YOU FIND THAT YOU MUST CHANGE** the pistons, then the use of the SOHC 4.0L flat tops (+3%) with 94 heads, Ford's 4.0L light weight piston rods and a complete bottom end balance (+10%) will transform your engine into what Ford should have delivered.

I do not know your expected annual distance driving but the 13% (conservative) improvement in fuel economy will eventually pay for the expense.
 
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Kirby N.

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@gaz Thank you! That helps a bunch. Morana is not worth it.

Unfortunately, I do have brand new motorcraft 98 style pistons already installed in the block. So my only option to keep those 1998 pistons would be: 1998 head and a 1998 exhaust manifold (or headers or whatever). Would the head work with the intake? This would also require a tune- Do you know anyone who would do a tune?

I like the idea of doing 2001 pistons and a 1994 spec head (maybe skip the rods and bottom end balance due to cost/ I already have the parts) but this will require a tune also, I assume? Which I am still stuck with the need for a tuner and dont know how to accomplish that.

now I am leaning toward throwing away the pistons and using 94 pistons and a 94 head for simplicity as you say.
 
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bobbywalter

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I have seen too many mix match 4.0 that came with warranty. Reman in crate with mismatched weight rods...which in some cases resulted in chasing what was perceived as a miss.



94 down is what I would suggest with you setup..but you already have a short block..

Be easier to run all 98 for tune. And easier to find a tuner


Good luck tuning OBD1.
 

gaz

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Kirby,

Since you have new 98 pistons, I would use those with 98 heads. If you use all 98 spec your 91 computer should be happy; though the 98 spec engine used different pistons and heads the end compression ratio is the same as the 91's, the original engine.

If you decide to use the SOHC 4.0L flat tops with 94 heads, you will not need to tune it; those computers can only be flashed not tuned. I would only use premium and enjoy the increased compression.
 
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Kirby N.

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Kirby,

If I were using a 98 spec engine in a 91-94 chasis, there is no question which components I would use; they are the same that I recommend.

Using 94 spec pistons with 94 spec heads is the simplest option, as it will require no tuning.

A) Since pistons must be changed to accomplish this, using 01 SOHC 4.0L flat top pistons with the 94 spec head is a much better solution as your engine will benefit from the extra point of compression. You will then also have the benefits of fresh pistons/rings for higher engine reliability.

B) The only other factor is the exhaust manifold. If you are using 98, then I would definitely get 98 heads, and leave the pistons alone. If you will be using headers, then I would get 98 spec heads and have them flow bench port/polished to you intakes and headers. Neither the 94 or 97 spec exhaust manifold will be optimum with 98 heads.

Here are the 2 choices I completely advice against:
1) 94 pistons/ 97 or 98 heads (compression raised more than 1 point and unknown CLEARANCE)
2) 98 pistons/ 97 or 94 heads (reduced compression and performance).

Buying anything from Morana would be a WASTE of money. New or refurbished 94 spec heads with 94 pistons is your #1 simplest build for your computer.

He does sell some items that are worth consideration but his prices are out of this world. The reduced weight piston rods he sells are a great move but they are just the light weight stock set that Ford offered. If you want more info on them, I have it all. They are worth using just not for the Morana cost.

**IF YOU FIND THAT YOU MUST CHANGE** the pistons, then the use of the SOHC 4.0L flat tops (+3%) with 94 heads, Ford's 4.0L light weight piston rods and a complete bottom end balance (+10%) will transform your engine into what Ford should have delivered.

I do not know your expected annual distance driving but the 13% (conservative) improvement in fuel economy will eventually pay for the expense.
Sorry to beat a dead horse- but I had 95TM heads recommended from a few others on another forum due to them working with my current exhaust. You say reduced compression and performance- do you have any idea of the numbers on that? I also found some OEM new 95TM heads- so I am strongly considering that. Thank you in advance for all the information!
 

gaz

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@Kirby N. ,
If you chose 95 spec heads, the use either:
• 98 spec pistons, no tune or change in performance.
• 95-97 spec pistons, no tune or change in performance.

In summary, using either 95-97 or 98+ spec OHV pistons will result in stock compression ratio/performance and require no tuning with 95 spec heads and your 91 ECM .)
 

Kirby N.

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Excellent. Thank you! I am going to spend some money now!
 

Kirby N.

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A little update. Perhaps @gaz can offer some advice.

I purchased 95tm heads. Got the engine out, started to build the new engine. Noticed my eBay NOS 95tm heads are actually 93tm heads. Argh.

Called the seller and he has gotten them mixed up and had a bunch of pallets- with a few 95tm heads- the rest are 93 and he is sold out of 95tm heads.

So I have some NOS 93TM heads. They are brand new, nice and shiny. trying to figure out what to do.

My 98 block has 98 spec pistons installed that are .75mm overbored. I can't find any 94 spec pistons that are oem .75mm overbored.

Considering the 01 SOHC pistons maybe, with the 93tm head. Can I get away with running this with no tune and my obd1? Will I need to change rods and cam if I do this? IDK if I can find 01 pistons, but it might be a better chance.
 

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I just ran across this on Explorer Forum... apparently there is a lot of misinformation out there about 4.0 heads. I was told that 93TM heads were not usable on a stock 90-92 engine (apparently not true.)

I'm not quite sure what to suggest in regards to your situation. My buddy built a 4.0 using a '91 block, I think 93TM heads, stock cam and some other engine mods that increased the compression just a bit. Really nothing out of the ordinary but it needed a tune to run right - he had a '94 Explorer ECM. I would just expect to need a tune and be pleasantly surprised if you don't.

HeadInfo.jpg
 

Eddo Rogue

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I think you 1994 heads.
 

Eddo Rogue

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Kirby N.

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I really want 95TM heads. Just can't find them.

today, I am considering keeping the 93 heads, pulling a set of 95 heads from the junkyard and having the 93 valve components installed in the 95 heads after they have been machined and checked for cracks.
 

gaz

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Here is a reasonable solution to achieve normal stock compression ratio with your stock 98 spec short block using these stock 93 spec heads.

-have the 93 spec heads milled 0.035", this will raise the compression just over 1 full point, while the piston/head combo had lowered it approximately 1 whole point (the machinist will need to make an adjustment to the lower intake manifold also. If they do not agree with this point, don't mention it or did not know it...GO SOMEWHERE ELSE).

- 9.0:1 - 1.0 = 8.0:1, due to 93 heads on 98 short block
- 8.0:1 + 1.0 = 9.0:1, due to milling the heads 0.035"...back to STOCK RATIO achieved 🎁

Milling the heads 0.035" should cost $120-$200, depending on the machine shop rates.

This will work with your 91 accessories, intakes/exhaust manifolds and ECM, without tuning.
 

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