zak91rs

Just got a new toy guys! Bought an 84 z28 with a 350ho, msd wires, distributor, igniton and box, headers, 700r4 with shift kit, and for some reason a REALLY small carb and air cleaner. Pics will be coming when its light out, stupid insomnia. Not sure of the cfm on the carb, but i'm upgrading to a 750 and a cowl hood to fit an air cleaner thats not dumb. After that comes panhard rod, subframe connectors, and strut tower brace and hopefully lowering springs.

Now for the motor. It seems like its not making as much power as it can. Somethings holding me back here, it feels like it has maybe 290 horse. (sorry for the butt dyno readings)

Now I'm hoping this is just the carb being a piece of junk. Or maybe stock exhaust combined with headers is just restricting the whole power flow. But other than that, what upgrades do you recommend for a 350HO? I was thinking maybe like a zz430 top end kit (which should bolt right up, right?) or some other combination of a roller cam, heads, and a shiny new intake manifold. What do you guys think?

If all else fails, 100 shot of nitrous is gonna have to be the way to go lol.

And dont worry, yes I'm gonna put in a new rear even know theres a new posi carrier in the one I have.

TL;DR:
What should I do to upgrade my 350HO? also, why is it possibly losing power? Sometimes when WOT is pressed, it sounds like to motor bogs down for a split second before the power is delivered.

Guest

Your L69 is only 190 HP, and a 750 is way too much carb for it. Start with the basics, headers and a 3" cat-back, head porting, and a sensible cam. Maybe an XE262 at most. Even then, a 600 cfm carb is plenty large.

zak91rs

Dude it's not an l69... didnt you read GM 350 Ho? Thats a 330 hp crate motor, not a 305 l69

JamesC

iTrader: (5)

Sounds like you "may" need to fiddle with the spring, if the carb has vac secondaries.

EDIT: BTW, my 350HO Deluxe is equipped with a Holley 600 CFM Vacuum secondary w/ electric choke. The car, IMO, runs like a bat out of hell with that carb.

JamesC

TreeFiddy

Could be accelerator pump(s) too.

zak91rs

Hmm i'll look into the accelerator pump thing. Any other ideas to upgrade the 350ho as soon as i get it sorted out?

InfernalVortex

iTrader: (4)

Are those the ones with Vortec heads? Or do they have some 70s era smog head like the Goodwrench 350?

That will make all the difference. If they're vortec heads you could make 400hp without messing with new heads. Just get hte valve guides cut down and get a nice big roller cam. If you get mechanical secondaries, 650 cfm, if vac secondaries it doesnt much matter if its set up right. It'll flow as much as you need, period. I doubt you need more than 625-700cfm. What intake does it have? The GM Performance Parts intakes are made by Edelbrock, one is a crappy Performer intake, and the other is a Performer RPM intake. See if you can figure out which one you have.

http://www.summitracing.com/parts/NAL-19210007/

Looks like it doesnt even include one... So what intake do you have? An Edelbrock Performer RPM is the ticket for the most part. You can go air gap if you want but it doesnt really accomplish anything if you ask me.

What alarms me is you're stuck at 9.1:1 compression, probably have dished pistons. You can but a bigger cam in it but it may not get you too far. You can still probably put a bigger roller cam in it. The stock cam is pretty small and is your biggest bottleneck. .435/.460 lift.

If the pistons are dished (they have to be to get you to 9.1:1 compression with 64cc chambers you may want to consider having your heads shaved a little, or getting heads
with 58cc chambers and a roller cam. Problem is you have some of the best affordable heads around. You'd do well to leave them there unless you want to buy some AFR's or Trickflows etc. I dotn think there's a GM head out there that's really better. The Fastburns arent really much if any of an improvement, and the Corvette L98 113 aluminum heads on the zz4 aren't an improvement either.

So I think your best bet is a roller cam, maybe a thinner head gasket, and make sure you've got a good intake. Try to get a cam that doesnt go too far above .470 lift, the only real limitation of vortecs is the airflow past .470 lift drops off drastically and actually hurts performance.That also happens to be about as much lift as a stock vortec head can take.