I'm building up a replacement slant-6 pulled from a '68 Dart for my D-150; this is my first rebuild project. The tranny is an A833-OD.

I have no plans for racing, but I want to improve towing power and acceleration for entering the on-ramp or passing another vehicle without worrying about a semi coming up behind me. I'll be dressing it out with a GM TBI system and a dual exhaust (Dutras or headers).

The head has been cleaned and magged. I'm getting ready to have the head machined for over-sized vales and to increase the C/R. I haven't decided if I want the head ported as well. It will cost about $600 extra.

For my situation, will the porting be worth the investment?

Any other suggestions for building up my engine is welcome.

I just don't want to invest in overkill.

Thanks - TJ.

Get them to Bowl Hog for the bigger valves.....you should sweep the chambers around the valves.....use your $600 for that. ....then deck the block and/or head for compression. You should do some searches.

As soon as you said "bigger valves' you stepped into överkill"


What cam?

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Porting is going to be over kill. However, $200-400 should get some bowl blending and gasket matching, that's all you should need. Spend the other $200 on a dencent cam. Last, mill the head .1 to up the compression to 9.2:1 and you'll have a hot little engine.
Porting on the slant is a difficult job to justify on the slant, and to perform. Grinding the heck out of the head means you got to somehow get the intake to match which can be dangerous. Next, enlarging the cross section of the port can cut down on torque. The 302's love a giant port cause all they have is horsepower. You got a truck, so realise you want to maximse your torque and and only pep up your horsepower.

Full porting may be overkill, but porting valve bowl area is certainly not. My oversize valve bill was about $400 and that included the new valves and machine work. The head surfacing was expensive because the machinis didn't believe that 1cc=.0066". He stopped the milling process and checked the chamber volume at least once. I do my own porting and have probably $300 invested in tools including a flex shaft Dremel that isn't made any more (Foredom still makes 'em though), carbide cutters and misc supplies.

Do check the piston deck height, CC the combustion chambers and calculate the CR. My '73 225 was about 7.7:1 stock. Taking .100" off the block and .080" off the head with a .040" thick head gasket gets me my target of 10:1. Your truck shouldn't go much above 8.5:1. One of your biggest performance gains is going to be gears around 4.1:1. With the overdrive the overall high gear ratio is only 2.99 which is fine for economy. I would do a Super Six 2 bbl., 2 1/4" exhaust, a cam with about 256° duration, 8.5:1 CR and some careful tuning. You'll end up being much peppier than stock and still get good mileage and have the torque your truck needs.

_________________
Joshua

Thanks, all. A lot of good info for me to digest.

I'll keep you posted as I progress.

Regards - TJ