more power from 4.0

spacers are junk, they just move the throttle body and essentially shorten the throttle cable. You can get the same general effect by gluing a block of wood to your right shoe.

Cat-back, headers, a bored-out throttlebody, electric fan rather than motor driven, that's about it before you realy have to start opening the ol wallet. Then it's multispark ignition, porting, stroking, and or blower/supercharger. As they say at Hesco, "Speed costs money, how fast do you want to go?" :)

These trucks came from the factory with a VERY restrictive exhaust. Mostly the muffler and tailpipe. Some of them even had a 1.875 inch tailpipe, which choked the engine at anything above 3,000rpm. I installed a replacement muffler that used a 2.250 inch outlet and a tailpipe from an older model which was also 2.250 inch. You would not believe what it did for my 3,000 to 5,000rpm power.

The NAPA part number for the "Turbo Muffler" I used is 17748 and the tailpipe is 44171. You may need a short piece of straight pipe to go between the muffler and the convertor, and you will need new clamps to attach the tailpipe.

A caution, anything less restrictive than a "turbo muffler" type will give you an annoying exhaust sound like some kid driving his ricer with a fart pipe.

Bruce

DougW: Side question: Did you have to do anything special to your 4.0L after supercharging it?

A friend installed a supercharger and is having issues with knock/ping, but only in 3rd gear under full throttle(?). (Sorry, don't know the brand at the moment.)

TIA

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Your talking about the muffler being sensitive someone put a little muffler on this thing (like on on a car) it has the 2.25 outlet and inlets but the stock one is like huge compared to the one on the truck now.

I installed a boost-a-pump that increases the fuel pressure to 70 psi and a pressure regulator on the fuel rail that's stonger than stock.

If it wasn't there before then suspect dirty fuel filter or clogged injectors. Also poor spark will cause problems. If all else is fine have him try one range cooler on the plugs. And don't use platinum or splitfire as they cary too much heat and can cause detination problems.

If it was always there then he needs to retard the timing a bit and increase fuel flow with either larger injectors or a higher pressure pump/regulator. Some systems use a seperate injector.

Thanks, I'll pass the info along.

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Forgot to add one thing.

If the engine has excessive carbon builup that will cause pinging. Usually the plugs will show how bad things are.

The cheap way is to use whipped cream cans.

Yeah and stick a rubber hose into the throttle body, hold the can upright and spray it!

..urp..

He asks what boost-a-pump you used, and if you'd recommend it. TIA

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Thats crazy! I wonder how he rigged the electrical wiring?

Website is in my .sig

It's a Kenne-Bell unit that has an adjustable output and a fixed >2psi kickoff switch. It splices into the fuel pump line and increases the voltage. Stock pumps can handle the increase. You still need a higher pressure regulator to make it all work, or the excess will simply flow back into the tank.

I agree with Bruce, the exhaust system needs work. If you know a good pipebender at a local muffler shop, you can gain some power for a reasonable price. Many years ago I put headers and turbo mufflers on my Monte Carlo (355ci/325hp) and had a complete dual exhaust system fabricated to fit the car. The gain was amazing. But, to be practical I would recommend a good exhaust system with a stubby turbo muffler. Don't even consider a glasspack! A little exhaust sound is ok but blat blat is very uncool.

Your cheapest horsepower (and gas mileage) gain will come from a good tuneup with stock spark plugs and new gas and air filters.

You can replace the fan with fiberglass or electric.

Synthetic oil will also help.

You can get into exotic parts, but it gets really expensive

My 4.0 has enough power for me and my HO 4.0 (like yours) has more than enough power for my needs.

I had considered more horsepower for my commuter car a few years ago. All I wanted was better 50-70mph passing power. I did most of the above and wanted a little more. I came to the conclusion that an electric turbocharger was the right way to go. I suggest you look into this and decide if you want to spend the money for a little more power.

Just remember that "cheap horsepower" is an oxymoron.

Merrill

Why do you call it a truck ??