4.2 to 4.0 head/MPI is underway!

[Sasquach]

The swap only brings you up to a little over 9 to 1 compression. I just run regular unleaded and it doesn't ping at all. Just make sure you set your ignition timing so that it's advanced as far as it can go without pinging. It's really that simple. I've put a lot of miles on mine and haven't had to do anything other than change the oil every three thousand miles. It still runs as good as the day I bolted it together, and I never have to worry about maintaining highway speeds into the wind on long uphills. The greatly increased gas mileage is also a huge bonus!

Good Luck!

If you go MPI the distributor timming is computer controlled.

 

[DirtyB]

Be sure and get a 4.0 head that was made before 1999!

I've seen some arguments that the design of the intake manifold after 1999 was better (some call it the horseshoe design). From JP Magazine (for whatever that's worth)

While a free-flow intake manifold can deliver more power, it's only going to allow as much air to flow as the cylinder head and camshaft will call for. Upping the intake runner volume too much will cause the intake charge to lose velocity, killing low- and mid-speed power and torque. On a '98-earlier engine running a stock camshaft and unported cylinder head, it's wasted effort.
Claimed Gains: 5-30hp
Actual Gains: 5hp loss

Whatever donor vehicle I find, I'll post a pic. I don't have the cash for a before and after dyno test, but I can give you my "font de cullotte (seat of the pants)" evaluation.

I'm not a power hungry nut. I just want my rig to start and run without having to pump it at the stop signs for the first 15 minutes. I'm in LA and they aren't really picky about emissions testing on older vehicles. Besides, I'm sure my mods are drastically improving emissions by increasing my gas mileage. Thanks for all of the feedback and advice.

 

[ThisGuyUKnow]

I've seen some arguments that the design of the intake manifold after 1999 was better (some call it the horseshoe design). From JP Magazine (for whatever that's worth)

While a free-flow intake manifold can deliver more power, it's only going to allow as much air to flow as the cylinder head and camshaft will call for. Upping the intake runner volume too much will cause the intake charge to lose velocity, killing low- and mid-speed power and torque. On a '98-earlier engine running a stock camshaft and unported cylinder head, it's wasted effort.
Claimed Gains: 5-30hp
Actual Gains: 5hp loss

Whatever donor vehicle I find, I'll post a pic. I don't have the cash for a before and after dyno test, but I can give you my "font de cullotte (seat of the pants)" evaluation.

I'm not a power hungry nut. I just want my rig to start and run without having to pump it at the stop signs for the first 15 minutes. I'm in LA and they aren't really picky about emissions testing on older vehicles. Besides, I'm sure my mods are drastically improving emissions by increasing my gas mileage. Thanks for all of the feedback and advice.

I installed a horshoe style intake on mine. Its aesthetically more pleasing but seemed to run about the same as my obd1 intake