Heads, let's talk....

big_mike · Jul 26, 2017

I was watching a video from a engine builder and he was going over the stock casting verse aftermarket/non-vortec and mentioned a "step" or "ramp" at the lip of the vortec head where the intake mates to the heads, supposedly adds a little extra intake port volume where the aftermarket do not. He went over the back cut valves, port design, chamber design, ect..

I'll probably end up going with the GM heads. I'm guessing I won't see much performance increase though if the are unported stock castings. I also read the exhaust side is the only area the stock casting could use work, any truth to that?

TylerZ281500 · Jul 26, 2017

my .02 you already arent using all the vortecs have to offer, going bigge ris gonna hurt more than help. if you end up going GM replacement let me know i can figure out how to use my discount, id research into pro topline as well. but if its as tame as you say, grab a slightly better cam without going over lift, put 1.6s on it, and run stock heads, clean them or buy new stock.

making something like darts efficient on something like that would require a very aggressive build and a completely differenet intake and injection unit, mileage will suffer, driveability will suffer, you simply dont need them.

TylerZ281500 · Jul 26, 2017

DONT TOUCH THEM! you wanna grab your nice carbid bit and remove some casting flash and pores be my guest dont go hogging them out. theres a point you will start losing power. on the same token. Im running consistant 10.60s with stock vortecs, press in studs on .550 lift (not sure how still) and minimal port work. 5 angle titanium vavles and alex springs

big_mike · Jul 26, 2017

TylerZ281500 said:
my .02 you already arent using all the vortecs have to offer, going bigge ris gonna hurt more than help. if you end up going GM replacement let me know i can figure out how to use my discount, id research into pro topline as well. but if its as tame as you say, grab a slightly better cam without going over lift, put 1.6s on it, and run stock heads, clean them or buy new stock.

making something like darts efficient on something like that would require a very aggressive build and a completely differenet intake and injection unit, mileage will suffer, driveability will suffer, you simply dont need them.

Yea, it's gonna be a pretty mild build. I know there are better intake, cam and head combos out there but cost rises significantly over what I'm shooting for on this build.

I had heard that too, something about the design of the vortec 5.7 head was really aimed at making its power/torque with smaller cams, hence why it only came in the 350 trucks/suv from the factory. Too much porting, too large lift a cam and you won't see expected gains. I'm not super experienced in porting myself so a slight debur/cleanup is all I'd ever attempt myself unless I had a junk set to play with and practice.

Makes sense to me since my LS build had 5.3 heads on 5.7 block to bump compression. But they were also worked to match my small cam selection of a 224/224 .581/.581 114 . We did put larger intake valves in but the person who did the work back cut the intake valves to flow more at lower lift. So it made surprising power once assembled for such a small cam.

TylerZ281500 · Jul 26, 2017

that wasnt really my point at all, notr what i meant to imply

big_mike · Jul 26, 2017

TylerZ281500 said:
that wasnt really my point at all, notr what i meant to imply

I think I got what you we're saying though. The stock heads can do more than what the stock cam, intake and spider allow them to do. Correct?

So if my stock heads aren't cracked, a little clean up work and rebuild of them will be plenty fine with the 395 cam I wanna run. Then the stock intake/injector setup will be the limiting factor.

And if they are found to be cracked then those GM vortec replacements are the ones to get, not aftermarket since I'm not really pushing the motor or racing it.

slowburb · Jul 27, 2017

A more efficient head needs less cam. The vortec head is the most efficient factory head for the old school sbc. They weren't designed for a smaller cam, they were designed to work better, or move more air/fuel than anything factory attached to an sbc. A result is that it takes less cam to make x horsepower. There is no need to touch/alter/modify the design of ports or chambers, because as cast, the heads will support well over 400 horsepower. I've seen, driven, and ridden in many sbc/vortec powered cars that rev 6500-7000 rpm's with carb/intake/cam/exhaust. My buddy's Nova comes to mind. L31 longblock, GM HOT cam/Crane 1.6 rockers, Performer RPM intake, headers, TH350 with a loose converter, and 4.11 gears. Stab the throttle at 40 mph and burn 'em down until you let off.

The injection setup starts to fade out around 400 horses. The intake limits airflow and rpm.

TylerZ281500 · Jul 27, 2017

^ that. now if you decide to go balls to the wall there better avenues than spider injection. put your cam in, clean and redo the heads. clean your intake and such, replace spider if needed, but i wouldnt be going all out thinking itll do a ton. it wont. tune it or swap to 0411 and tune and call it done

big_mike · Jul 27, 2017

TylerZ281500 said:
^ that. now if you decide to go balls to the wall there better avenues than spider injection. put your cam in, clean and redo the heads. clean your intake and such, replace spider if needed, but i wouldnt be going all out thinking itll do a ton. it wont. tune it or swap to 0411 and tune and call it done

That is pretty much the plan, I was just curious since those dart castings we're about the same price. I figured if they were better why not upgrade but if the GM castings are better given the build criteria then that is the route I'll take. I'm getting the new MPFI spider to eliminate the poppets for sure. Also the 0411 is a sure swap along with some shorties, Jegs offroad pipes w/thunderbolt hiflo cats added, thrush welded di/do muffler for the exhaust. Probably gonna do some minor work on the stock tb and clean the lower intake up with egr delete.

TylerZ281500 · Jul 28, 2017

keep egr, cant really mod a tb

Heads, let's talk....

big_mike

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TylerZ281500

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big_mike

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big_mike

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slowburb

all motor

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big_mike

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