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How much power did you lose with cracked heads on your 4.0 ohv?

JeffAllen

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Hey guys I have a 2000 4x4 ranger with a tired 4.0 ohv with 235k miles. It has never had much power since I got it at 215k miles but it's completely GUTLESS pulling any kind of a load..I can barely get 55-60mph pulling my bass boat on a flat road in 4th gear which is far from normal.

What I found is I have cracks on #1,4 and 6 cylinders between the valves on the heads so I have to replace the heads. My question is everyone who has had this happen to your 4.0s after you replaced the heads and got it back to running how much better did the truck run? I'm wondering how much power this motor was losing with 3 of the 6 cylinders having cracked heads.Surely when I replace them and everything goes back together it will gain a very noticeable amount of power back.I'm also going with a pair of headers and thinking of ditching the stock fan and clutch for an electric fan.
 


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Well, given you were probably running on 3 cylinders. You should expect a 50% power increase. :icon_rofl:

And you may wanna re-think the headers. Most headers are tuned for higher RPM horsepower so you will actually loose some low end torque which isn't good if your going to be towing a boat.
 

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Jeff,

If you were running on 3 cylinders, you should expect 100% power increase. I'm pretty sure that a set of JBA headers will improve your low end torque. I think they even lower the rpm that MAXimum torque is produced.

Good call on going to an electric fan. Also consider an engine oil cooler. It adds a quart or so to your total fluid and will help keep things cool. It has been my experience that the water pump bearings become accustomed to the fan/clutch load. Upon removal, a new water pump will save you some strive.

You may also want to consider a set of hardened rockers and adjustable push rods. These engines make decent torque but if the preload on the lifters isn't correct (and I mean Spot-on) performance will suffer. The valve train relies on proper lifter preload to maintain efficient valve operation.

With 235k on the iron, perhaps a new timing set and oil pump would be a prudent consideration.
 

JeffAllen

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Jeff,

If you were running on 3 cylinders, you should expect 100% power increase. I'm pretty sure that a set of JBA headers will improve your low end torque. I think they even lower the rpm that MAXimum torque is produced.

Good call on going to an electric fan. Also consider an engine oil cooler. It adds a quart or so to your total fluid and will help keep things cool. It has been my experience that the water pump bearings become accustomed to the fan/clutch load. Upon removal, a new water pump will save you some strive.

You may also want to consider a set of hardened rockers and adjustable push rods. These engines make decent torque but if the preload on the lifters isn't correct (and I mean Spot-on) performance will suffer. The valve train relies on proper lifter preload to maintain efficient valve operation.

With 235k on the iron, perhaps a new timing set and oil pump would be a prudent consideration.


The truck doesn't miss it's running on 6 cylinders but I believe it lost a lot of its compression on those cylinders because it has so little power pulling a load or pulling a hill. I'd like to put a 422 cam in it but at 235k I just can't justify it. I did order a new set of rockers and pushrods for it but they aren't hardened. I have seen where people talk about hardened rockers and pushrods but I haven't been able to find anywhere you can actually buy them or I would have. I'm difinitely gonna install a new H20 pump getting this deep into it. Been thinking about going with a set of new injectors off of flea bay since they are cheap.
 

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You're much better off removing and cleaning your old injectors than buying chinese injectors off ebay. I'd trust a OEM Ford injector with 250,000 miles over a brand new Ebay injector any day.
 

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You're much better off removing and cleaning your old injectors than buying chinese injectors off ebay. I'd trust a OEM Ford injector with 250,000 miles over a brand new Ebay injector any day.

If they were Chinese junk I would never buy them..I looked at some awhile back that said they were factory ford injectors that were just cleaned and flow tested and you send them in your injectors.
 

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I put a set of headers on the 2003 when I had it. I ran it on the dyno before and after. It actually lost measurable torque up to about 3500 rpm where it came back up to factory level. The butt dyno told me that there was a nice increase in torque at around 3500 rpm so the headers "felt" like an improvement, but the real dyno told the truth. I know that's on the sohc, but based on that I would not put headers on the 4.0.

I had a 1997 B4000 that developed cracks in both heads, just on #2 and #5. It was completely gutless at that point - down at least 30% in power. It quickly progressed to the point where it "burned" as much coolant as gas.
 

gaz

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Jeff,

Delta Camshaft of Tacoma Wa is the only company I know that is working with these rockers. What they offer is a service, you ship them your set of rockers, they clean/prep them and install the hardened inserts. They charge $120 (ish) plus return shipping.
 

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Jeff,

Delta Camshaft of Tacoma Wa is the only company I know that is working with these rockers. What they offer is a service, you ship them your set of rockers, they clean/prep them and install the hardened inserts. They charge $120 (ish) plus return shipping.

Wish I would have known this before I bought new ones..smh Oh well these new ones should last another 200k miles without being hardened..
 

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I hope you're going to rebuild the bottom end and not just stick new heads on a high mile short block.
 

JeffAllen

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I hope you're going to rebuild the bottom end and not just stick new heads on a high mile short block.

Why would I pull a motor that doesn't smoke,use a drop of oil, all cylinders and pistons look perfect to rebuild the bottom end? All it needs is new heads,gaskets and im gonna replace the waterpump,rockers and pushrods while I'm at it...
 

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It's already partially disassembled and the rings and bearings have 235,000 miles on them. If the increased compression from the new heads and better valve sealing stresses the old rings and it burns oil you'll have to do it all over again to redo the short block. I would always rather do a complete job once than have to do a job over. If you don't rebuild it I wish you luck, that would bite me every time.
 

JeffAllen

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Nope I'm not rebuilding the whole motor just what's needed..It has good oil pressure, don't burn or leak a drop of oil, and ran fine just low on pulling power so I'm gonna fix what's broke and let it eat..
 
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55trucker

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I'm in complete agreement with Walt

tightening up the top end & doing nothing at all to the bottom end on a 235,000 mile engine is asking for trouble.
How do you know if the oil pressure is near what's called for? the oil pressure *gauge* isn't a gauge at all, it's just an off/on switch, the switch closes at 5lbs. pressure & the needle responds.

The bottom end bearings are sure to be opened up, the oil pump on the tired side, at the very least pull off the pan, remove both a main bearing cap & rod cap & do whats required to properly plastigauge them to see what the clearances are.
 

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Normally, I'd agree with you guys about a total rebuild at that mileage, but when I rebuilt my 4.0 SOHC, the bottom end was actually in great shape at 265k. The crank was perfect. Very little wear on the rod or main bearings and the cylinders were all round and round and within spec. Had it not been for the two holes that were rust pitted, I might have just done the heads myself...

Nah, I'd have still done a full rebuild.
 

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