For you average V-8, what improvement in performance should I expect to get when installing headers, porting the intake and polishing the head. What mods should be done to the cams?
headers and improved exhaust system-maybe 10-20 hp roughly on a stock engine.
port polished heads-20-40hp depends on the extent, on a stock engine.
headers and improved exhaust system combined with ported heads on an otherwise stock engine-40hp +/-.
Nothing you can do to modify the cam, except replace, the pushrod engines have one camshaft, if by cams you have a modular then yeah you have two to four cams. A cam could add another 40+/- hp depending on the intended rpm or where the cam was designed to peak power wise. When it comes to trucks or another street vehicle, think torque.
I ask for the mods since I have two choices, for the same money, swap to an unmodified 351W, or get a 400M and put headers, polished heads, etc, but I still worry about getting a better mileage than my current stock I-6 300 (8MPG!)
My stock cammed 351w with a performer intake and performer 600 cfm carb with shorty headers and true duals gets around 11 mpg through a 3 speed and 3.55:1 rear gears, if I had overdrive it would be even better.
I am not familiar with the 400m but would have to guess, that would be the way to go if you could get a modified version for the price of a stock 351w, if hp and tq is what your after. later
Actually you can leave the heads alone on a 400. With a 4 barrel intake and 750 holley along with a decent RV cam, you will out pull anything on the road. If you want some compression to get the full advantage of the new cam find a set of 4V cleveland heads for the 400.
__________________ Cody, Calgary AB Chapter Leader 82' Flareside: 2/4 Drop, 350hp 351W, Custom interior 81' 250 mudder: home fabbed lift & dana 60 SAS , 450hp 400, 4sp/205, 38" tsl's
If your after more HP, then of course you can port and polish the heads on the 400, or any engine for that matter. I've yet to hear of a engine that wont perform better with porting and polishing, done correctly of course.
i would use 600 - 650cfm carb for the 400 (btw its a 400 not 400m) that engine needes to breathe and when it does it can pull your house off its foundation keep the heads as they are close to the best for that engine port the exhaust side if you want to help them read the 335 forums you will find a plethora of info on this great engine. ive heard of 14-15 mpg on slightly built 400's but expect 11-12
Help: Headers, porting, polishing, etc more HP?
Mods to decide between a 351W and a 400M
351W, Custom interior
, 450hp 400, 4sp/205, 38" tsl's
