Quote:
Originally Posted by cg285
i'll let you know after i finish playing with another eng for one of my trucks. i am going to start off slow and change a few items at a time so i can compare to a baseline vs making multiple changes at once.
what i can assure you is changing to an hei will have absolutely no affect on your mileage or hp. (and here is where a bunch can chime in to tell me i am wrong - but i am not) what you will get, by changing to hei, is loosing the periodic points replacement (although points will last 50k + if matched to the correct condenser) but that will be replaced by changing the module, periodically, while you are stranded dead in the water - UNLESS you use only delco components - especially the module - and follow the directions with the heat paste. and use plugs with a gap of .045 vs .060
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I'll actually agree that when I put the HEI in mine the other day it didn't really seem to do much of anything (kind of what I figured). I gapped the plugs all the way out to 0.060.
A big carb will just (potentially) increase top-end power and if anything I'd probably expect worse mileage.
I stuck a vacuum gauge in my truck (stock '71 250) a while ago and IIRC I had to wind it up to 3,500RPM+ before I really saw any vacuum at WOT. How often do you have it wound up past 3,500RPM with the throttle on the floor?
Small-tube headers will probably add a little power (not sure how much). Might be able to effectively use a slightly larger carb with them. Large-tube headers are not what you want.
Jetting/tuning the carb will probably help, as would reworking the distributor advance curve.