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4.0L Performance mods???


BIIHawg

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I'm gonna be rebuilding a 1991 4.0L OHV to throw in the old B2. Any suggestions (other than the Morana stroker kit) to help build some horsepower and torque. Flat top pistons?, performance cams?, chips?, or anything else anyone has done od heard of/seen and where I might be able to purchase such items. Any help would be much appreciated?

Oh, and cone filter, hedders and electirc fan are already checked off the list.

Thanks
 


bandit

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james duff had chips for them dont know if they still carry them
 

mxracer652

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If you're going to rebuild it anyway , have the stock crank (2.123" journal, I believe) offset ground down to a 2" rod journal, picking up somewhere around .100" stroke. This costs no more than turning the crank, which you were going to have to do anyway.

Buy a set of off the shelf 5.7" SBC rods with a 2" big end, a quality forged Scat set will run you about $160 (cheaper than you can buy reman stock junk). A call to Wiseco for a custom 1.4xx" c/h piston (should be around $500). And you have one very light rotating assembly, that is more reliable, and less expensive than a stock rebuild.

You now have a 4.18L stroker kit for less than $1000 including bearings and gaskets. The machine work is a wash because you were going to have to do that anyway.
 

MAKG

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You forgot the custom cam grind.

'Cause changing the stroke like that is going to change the cam you need in order to make anywhere near the full 5% effect you're looking for. Of course, you'll never feel 5% with an ass dyno, so you really have no idea.

And weakening the crank doesn't seem like a very good idea for an effect that can't be felt.

This is a SYSTEM and by shotgunning modifications, you are not going to do much (if any) good. You CAN make it worse.
 

Monzilla

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Those pistons are a 4.000" bore 1.425" pin height. They are used with a 350sbc block, 400sbc crank (3.750" stroke) and 5.7 rods to make a 377 stroker. Or the .030" overbore makes the common 383 stroker. Find some chevy guys with blown up engines. Collect 6 rods. Then 6 pistons. Then machine work. Then let me know if it works.
 

Bird

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Those pistons are a 4.000" bore 1.425" pin height. They are used with a 350sbc block, 400sbc crank (3.750" stroke) and 5.7 rods to make a 377 stroker. Or the .030" overbore makes the common 383 stroker. Find some chevy guys with blown up engines. Collect 6 rods. Then 6 pistons. Then machine work. Then let me know if it works.

And when you overbore the 4.0 block to accept those pistons and start pressurizing your cooling system, then you will realize it's not worth it - would have to have custom pistoms made specifically for the bore of our engines for it to be marginally 'feasible'.

I prefer 'artificial' displacement.....aka: forced induction.

Bird
 

mxracer652

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And weakening the crank doesn't seem like a very good idea for an effect that can't be felt.
Your previous cam points are valid, but for less money and better pieces, why not take the free cubes? Shit, I'm running 10psi on my SOHC with the stock cams, it's not ideal, but it does make more power. I would have 2 ground, but no blanks are made, and I'm not using reduced base circle garbage. I agree it is not optimal, but I hardly would accept it running worse.

There's nothing to be scared of with a 2" journal, the radius is the key. Look at all the cast crank 347s & SBCs out there living above 6500. A measly 180 hp (at best) below 6000 isn't going to do anything.

Monzilla,
I'd be hesitant to go to 4.000" bore, that's .050 over, and I don't think the walls would sonic that far. I don't know if it can be decked down to that c/h, trust me, I've thought of the OTS SBC rebuild stuff before.
 

Monzilla

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Most publications say not to overbore small block fords past .030". Ive had 351W done to .060" with 11:1 pistons. As long as its a naturally aspirated engine, not forced induction or additive like NOS or nitropropane, I dont see any forseen problems.

Live on the edge. Try something new. Henry Ford didnt create this corporation by saying, "It might have to thin of metal. I think we should be safe and not do it."

Never know til ya try.
 

Bird

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Most publications say not to overbore small block fords past .030". Ive had 351W done to .060" with 11:1 pistons. As long as its a naturally aspirated engine, not forced induction or additive like NOS or nitropropane, I dont see any forseen problems.

Live on the edge. Try something new. Henry Ford didnt create this corporation by saying, "It might have to thin of metal. I think we should be safe and not do it."

Never know til ya try.
Guess what - it's been tried before............... Ever hear of a guy called Sven Pruitt? He's played that game before and has repeatedly stated that even .40 over on the 4.0 has caused porosity problems and ring sealing inadequacies due to cylinder wall flex at rpm. Now, get some custom pistoms made up ($$$$) that will fit the stock/.020 over bore, then you'd be OK.

Bird
 

mxracer652

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What if that N/A engine is 8300 down the straight or through the traps?

All I am saying is that if you're going to bore a block, you should get it sonic checked so that you know it doesn't suffer from a shift and that it has an acceptable amount of wall thickness left. If it sonics OK to go .050, then by all means, have at it, but I'd rather KNOW it will live than hope.

I've blown up way too many engines to guess anymore, LOL!
 

Monzilla

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Then what about filling the block? Cures cylinder wall flex and porosity problems with exhaust gasses and coolant.

And I have heard of Pruitt. Once again. Just because one person tried and failed we should all give up.
 

brickhousen

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whatever you do dont do a rebuild with .090 over pistons from northern automotive ive been there done that and let me tell ya it dont give you any noticible power and it will overheat all the time i found out the hard way lol!
 

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