Better 258 head flow & mileage

rollbar

See if it's right MC. This is for a 258 head or any head that the problem exist. This is to fix an AMC flaw. To gain better head flow & mileage U must match the ports on the head to the gasket U install. 1. To do this (with the head removed, if possible) stuff rags in the head. 2. Lay the intake gasket on the head (glue if U have to so it will not move). 3. Repeat step two w/the exhaust gasket. 4. Once the gasket is on the head take a drummel tool & match the heads intake/exhaust opening to the gasket. You can go step further & do the intake/exhaust it's self. 5. Clean everything up. 6. Install the head. 7. Tuning the carb is easier cause the gaskets won't get saturated w/fuel. Result-Better head flow & better gas mileage by 5MPG & up to 25% better flow. The TJ's have matched intake/exhaust ports to get better mileage. This recommendation comes from an ole machinist here in Ft. Pierce that does this kind of engine work. P.S. Makes since don't it. How many times have you done the head work on an engine & when you put the gasket on the heads intake etc. is smaller than the gasket by 1/8" or so.

jeepsr4ever

Yes sometimes you can gain MPG and with a simple port match. However a port match rarely does much of anything if it isnt ported all the way to the valve. I would say maybe 10% if you had a very bad port. Every little bit helps though! :t:

rollbar

Thanks :t: , were gonna do a head next week & see what happens. We have the MPG now of the old head (leaking some) so we will compare the two in a few weeks. I'll let you know what happens, unless I forget. 111!!!

CJim7

Or.....just swap it out for a 4.0L head. Problem solved :t:

rollbar

NA, FI injection :shock: , I like my carbs, quick & easy.

CJim7

rollbar wrote
NA, FI injection :shock: , I like my carbs, quick & easy.

Me too, but not neccesarily NA....
My previous settup: 258 w/4.0L head, XJ header, 260* comp cam, 833 pistons, TFI ignition, Clifford intake, 500cfm 4bbl Edelbrock.

Would smoke any 4.0 out there and most stock V8's :t: