building up a 4.0 ohv short block

[Mackhedq]

The truck is 1994 with a 4.0. Rebuilt the trans on it at 200k miles and the motor is probably next. Here's my list for a slightly better motor.
94 Ohv short block
Com cams 49-422-8
95Tm heads
Bbk 66mm throttle body
Melling high volume oil pump
Valve cover support tails
Crane springs #99858, 99835 or comp cams 988-16
Possibly make my own headers or pacesetter #70-1385
Plan is to find a decent lower mile 94 motor. Use 95-97 heads to bump the compression up to 10:1. Cam for the slight power and that nice idle. If my truck doesn't like the motor like that I'd use Jet tuning for my od1

Anything else anyone would add to the list?

 

[Eddo Rogue]

sounds awesome, interested in this project. post pics!

They say lack of flow is the 4.0 biggest culprit. maybe do a good port & polish of the heads and intake.

 

[RonD]

Do a little reading on exhaust manifolds and how they work to get extra power, scavenged power

The MYTH of back pressure comes from people not understanding how properly designed exhaust manifold can lower pressure and SUCK OUT exhaust, leaving more power on the crank

Stock 4.0l exhaust manifolds add mid-rpm power
Most 3rd party change it to lower RPM power, "off the line power"
Racing headers change it to high RPM power


Any compression ratio(CR) above about 9.4:1 means you won't be able to run 87 octane(regular) gas, so just a heads up, as CR goes up octane must also go up to avoid pinging/knocking
Most car makers add a knock sensor to their higher CR engines so computer can adjust spark timing to match octane, there is a loss of power of course but no engine damage, and customer can run 87 octane with no issues

The 4.0l OHV never had knock sensor since it was 9.0:1
The 4.0l SOHC did, it was 9.7:1

As far as I know there is no way to add Knock sensor software to 1994 and earlier EEC-IV computers
The 1995 - 2000 EEC-V could have different "tunes" for running 87 or 93 octane

 

[Mackhedq]

sounds awesome, interested in this project. post pics!

They say lack of flow is the 4.0 biggest culprit. maybe do a good port & polish of the heads and intake.

From my reading and research the 95-97 TM heads are the better of both worlds. They have the "big valves" from the 94 and earlier but have a smaller chamber since those year trucks had different pistons.

Do a little reading on exhaust manifolds and how they work to get extra power, scavenged power

The MYTH of back pressure comes from people not understanding how properly designed exhaust manifold can lower pressure and SUCK OUT exhaust, leaving more power on the crank

Stock 4.0l exhaust manifolds add mid-rpm power
Most 3rd party change it to lower RPM power, "off the line power"
Racing headers change it to high RPM power


Any compression ratio(CR) above about 9.4:1 means you won't be able to run 87 octane(regular) gas, so just a heads up, as CR goes up octane must also go up to avoid pinging/knocking
Most car makers add a knock sensor to their higher CR engines so computer can adjust spark timing to match octane, there is a loss of power of course but no engine damage, and customer can run 87 octane with no issues

The 4.0l OHV never had knock sensor since it was 9.0:1
The 4.0l SOHC did, it was 9.7:1

As far as I know there is no way to add Knock sensor software to 1994 and earlier EEC-IV computers
The 1995 - 2000 EEC-V could have different "tunes" for running 87 or 93 octane

I'm not super worried about exhaust set up really. That will be more of a fun project for me to try if I make my own. For gas yeah it will be a 91 only truck when this is done. I know there's not much tuning for a stock OBD1. An upside though is piggyback engine management is pretty well fleshed out on this old computer.

 

[Eddo Rogue]

From my reading and research the 95-97 TM heads are the better of both worlds. They have the "big valves" from the 94 and earlier but have a smaller chamber since those year trucks had different pistons.





I'm not super worried about exhaust set up really. That will be more of a fun project for me to try if I make my own. For gas yeah it will be a 91 only truck when this is done. I know there's not much tuning for a stock OBD1. An upside though is piggyback engine management is pretty well fleshed out on this old computer.

I made my own exhaust, it was a fun lil project.

 

[Mackhedq]

I made my own exhaust, it was a fun lil project.

Do you remember size tube, thickness, etc of the material you used?

 

[Eddo Rogue]

Do you remember size tube, thickness, etc of the material you used?

Yes. I planned to use my old flange, but found a new one online, it was either ebay or rock auto. I also got a new set of flange bolts and the metal gasket thing. while I was at it. Then I bought a few pre made pieces, and a cheapo muffler.

I used 2.5" tube, not sure of thickness, I think 18 or 20 gauge. Regular exhaust tubing. I even found some lengths and hangers at my local autozone. In the end I used a few 18" lengths of straight tubing, and a few 90s and 45s, and 2 hangers.

I fitted and tacked everything together under truck, then carefully brought it out and onto a bench for welding. I think it could use another hanger, which I will eventually add, but it sounds and works great!

Oh I must disclose did the one piece driveshaft swap, eliminating the support bearing crossmember, and the bends required to plumb around it. I ran a straight length in its place, and got everything tucked up much better than stock, but too close so as not to cook the truck.