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TB Spacer material


NAXJA Forum User
Plymouth Indiana
I'm having my TB bored to 60mm by a machinist friend and buying a TB spacer as well already have a Homebuilt FIPK kit and Magna Flow muffler
my question is there are several spacer manufacters out there my machinist friend tells me to but Phelonic spacer it will keep fuel cooler then the aluminum.Any thought on this or recomendations of a brand.
Phenolic resin is a hard dense plastic material. I don't know what it's resistance to heat is. It can get pretty warm under the hood.

Fuel is injected with the air into the cylinders. Not at the TB. I doubt that the material of the TB spacer would affect air temperatures as it still has to work it's way through the hot intake manifold.

If you do go phenolic let us know how it works out!

If you had throttle body injection I believe there would be more advantage to this, better atomization but in your jeep no fuel passes through the TB. I have heard of people manifold spacers attached at the block where the injectors are located but at considerable expense. With the right angles the air has to run on the Jeep manifolds, I doubt the spacer would effect much but I'm no physicist or expert. Getting colder air in the first place (isin't there a plate on the radiator bracket that can be removed?) and less restricted air (some tubes have baffolds inside them) would help.
An aluminium spacer will do fine. All the spacers on the market are the same thickness and do the same job. In this case, it raises the TB 1" further away from the plenum floor so it allows airflow velocity to be increased, especially at lower rpm, with a small gain in torque. Gas mileage may also improve slightly.
If you want to reduce the temp. of the air entering the cylinders, insulate the underside of the intake manifold. That area becomes scorchingly hot due to radiant heat from the exhaust manifold, so adding a Thermotec heat blanket will reduce intake air temps. and underhood temps. substantially. I did this in my Jeep and now I can touch the intake manifold without burning my fingers:


It's a great mod.
maybe 1 hp or so. Its not really worth the install. If anything you will just get an annoying whistle that will make you take it out. Aluminum, steel... id imagine you could make one out of anything really. Just cut and bore and your done.
aardvark4x4 said:
A bit off thread topic I knoe but what kind of gains in BHP / torque can you expect after fitting a 1" TBS to a stock 4.0 HO motor?
Anyone got any opinions on who makes the best ones?

From my own experience, I'd say 2hp/3lbft peak gains with a 5lbft gain at lower rpm would be about right. I also gained 0.8mpg over long term testing.
Choose any TBS you like. They're all much the same. The best place to look is on ebay. The helix bore is just a marketing gimmick so if you remove it from the spacer, the whistle might go too.