25+mpg 4.0l ohv build

[gaz]

Eric:

I covered all the bases to have the donor be reliable; timing chain, water pump, oil pump, push rods. I am getting ready to inspect the lifters as a new set is not currently in the budget. I was concidering slipping in SOHC Pistons with new rings but the looming PCM choice has me twisted.

I thought that I would just grab a 94 non-EGR comp/harness and be done with it. Turns out where I live that's rarity in the yard.

So I brought this issue to the boards, the responses I received were all over and didn't help me make a decision. The one that stuck out in my head was to use a 98 setup to capitalize on the newer tech for better performance.

Adding to this, since I can't manually advance the timing I am left with either a piggyback power module on a 90-94 or tuning on the Dyno for the newer systems.

I was able to get away with a lot on the old 87 computers, more than I needed but I don't know how much these new systems will permit.

The only OB² I have messed with, I only did a cold air, cat-back and hot ignition. It worked very well but I am less certain about this

So my delima is, I would like to do this once and have it run well; I am willing to CHiP it or tune to get the timing it will need.

Initially it didn't seem reasonable to consider using a newer computer/harness but now I wonder if it would work better?

 

[Eric_Pickens40]

GAZ:
Installing a later model harness with OBD2 capability would make tuning much easier and allow you to optimize your fuel use through RPM range.

In my opinion, having balanced rods, high compression pistons and a new set of lifters, pushrods and rockers, plus port matching the intake and exhaust would improve your fuel economy a great deal. Especially after tuning it with the newer harness.

If you can’t get your hands on a newer harness I’d suggest all the previous mods plus a moderate cam and a chip.
-Eric

 

[gaz]

Eric:

Thank you for your input. I am also now considering the use of the older PCM's, 90, 91, 92 + 93. Since I may just be using a plug on power chip, these can also benefit from them.

I have conceded that the BEST choice is a 98+ 4.0L ohv system, I wish that I knew how much better but in the end, my choice will almost certainly be dictated by the parts available in the yards. All the parts will come from the same donor except the dash piece choice.

 

[Eric_Pickens40]

GAZ:
I’m happy to help, if you have any further questions feel free to ask. Goodluck on your build, keep me in the loop if possible!
-Eric

 

[gaz]

Today I received the Hypertech Stage 1 Power Module, new in the box; what are the odds of that, RIGHT???

Though I will need to hold off on the bottom end, my Porter finnally has time to do the intakes/heads, so that will finally get done.

 

[gaz]

It took me a while to figure out that the flat top Pistons to use in the 4.0 are sourced from the SOHC 4.0. What I read was to use second generation SOHC Pistons. Which year are second gen SOHC's.

Without knowing for certain, it looks like the 07 Pistons will fit the bill. I would like to know why the 98 SOHC are not desirable.

Next thing I want to get strait is what year engines used the lighter connecting rods? I see that there are 4 different rods, are the 3rd and 4th versions the lighter sets; because of the much smaller balance pads or what?

 

[Eric_Pickens40]

It took me a while to figure out that the flat top Pistons to use in the 4.0 are sourced from the SOHC 4.0. What I read was to use second generation SOHC Pistons. Which year are second gen SOHC's.

Without knowing for certain, it looks like the 07 Pistons will fit the bill. I would like to know why the 98 SOHC are not desirable.

Next thing I want to get strait is what year engines used the lighter connecting rods? I see that there are 4 different rods, are the 3rd and 4th versions the lighters sets; because of the much smaller balance pads or what?

I believe so, never a bad idea to weigh all the rotating parts (pistons, wrist pins, rods and rod caps) helps to rev up the motor quicker and increases balance which is very important. Going with high compression I think it would be beneficial to stud your heads and maybe use an MLS head gasket, these types of head gaskets have a thin ring of aluminum around the bore which crush and provide extra strength.

 

[Blmpkn]

I havnt seen it mentioned yet in the thread, so I'll bring it up. Unless your work is going to increase compression enough to require use of 91 or 93 (whatever "super" is in your area) your unlikely to see a meaningful increase in anything.

That said... I'm wondering if the increase in efficiency with the high compression would even outweigh the increase in cost of the higher octane gasoline.

Where I am, super Is usually 50¢ more than regular (93 octane has become the standard here)

I don't think it's reasonable to expect a bump in compression to increase mpgs to scale with the added cost of fuel. I don't think it would even be close.

If you ARE increasing compression by enough points to require the fancy gas, it's unlikely the ecu or your programmer would be able to adjust parameters enough for the motor to run properly, much less likely that even if it would.. It would be at its most efficient.

Your firmly into dyno tune territory if your to meet your goal. Interested in your results, good luck!

 

[gaz]

Blmpkn:

Where I reside the difference in cost from the 87 regular no-lead to 93 premium is $0.22-0.26; this less than a 10% increase in cost from the 87 octane and using it I see an approximate 10% improvement in fuel economy. Hence I always use premium.

The heads will be milled 0.03" which will yield under 2 points of compression and will effectively retard my ignition timing 5°; so I will be advancing the cam 1 tooth to (+9°) settle with 4° cam advance @ approximately 11:1 compression. Each point of compression increase yields between 4-8 hp, so let's call that +12hp (+7%).

The next 0.7 point of compression, with a final right around 11.5:1, +/- from the SOHC 4.0L flat top Pistons set. Though Marano Racing suggests this is good for an extra 25 hp, I believe 6 hp is a reasonable expectation. In the end, 6 for the flat tops and 12 for the head mill gets me a conservative 9% more efficient powerplant.

The 94 PCM's are the same style as the one in my 87 Ranger, which has no problem running the 2.9L @ 11.5:1 compression ratio.


ERIC:

These (see pic) are the goal, they are referred to as the ribbed version (UPDATE; stamped FbOC A). Shaving 240g (well over a ¼ lb) off the rotational weight will also increase efficiency.

I will look into the MLS head gasket, I hadn't heard of them.

 

[Eric_Pickens40]

Yes, shave the weight and even up the rotating parts. That will absolutely help the efficiency.
As far as the 11.5:1 compression ratio running premium gas, I really do think you’ll increase mpg’s. The motor won’t need so much fuel to get it down the road and with the gear ratio to tire size you have I’m almost certain you’ll have enough torque to move your rig much more efficiently than stock.

 

[gaz]

My bust...

Milling the head on this will not retard the cam, that is on OHC engines . May have to run with the cam timed to zero and hope the CHiP can give the timing it needs.

 

[Blmpkn]

I imagine a 11.5:1 4.0 would sound pretty wild at the very least, certainly better than the farm equipment sound they make stock lol.

 

[gaz]

Blmpkn:

Your RIGHT, they get poppy; anyone that hears it can tell something is up.

I met with my Machinist today, he felt that using the flat tops for the bulk of the compression would be the soundest plan in the long run. I am onboard with him so the the head will not get milled to the max just resurface. Now I am counting on the bulk of future compression bump from the 4.0 SOHC piston, even more.

I can't buy my Flat Top SOHC 4.0L pistons yet, so I am focused on identying the most suitable set. So far I have been able to identify 2 for sure maybe a 3rd; the difference is the compression height (CH).

Though the ohv 4.0L has a CH of 1.45", so far I have found 4.0 SOHC's set that have CH's of 1.425" and 1.435" with a third style simply listed as "RAISED TOP". I have contacted the manufacturer to learn what they mean by raised height and what the CH of the piston is.

The article I read about using the SOHC 4.0 pistons to raise compression suggested 2nd Generation SOHC pistons, I still have not determined which are second Gen's.

 

[bobbywalter]

dude. you are hard core.



all day.....3.7... 5 to 700 bux.. 6r80.......5 to 700 bux.





all day.















low miles.....1000 bux....

 

[bobbywalter]

all day.