I currently have a crate GM Performance 350 /330 hp. Below are the specs from Jeggs where I bought the motor. 330 HP @ 5000 RPM
380 ft/lbs torque @ 3800 RPM (Max Recommended RPM: 5500)
Compression Ratio: 9.1:1
Cast Iron 4-Bolt Block with One-Piece Rear Main Seal
Nodular Cast Iron Crankshaft
Cast Aluminum Pistons
PM Steel Connecting Rods
Cast Iron Vortec 64cc Cylinder Heads (1.94" Int/1.50" Exh valves)
Chrome valve covers
Dual Pattern Cam (Lift: .435" Int/.460" Exh, Duration @ .050": 212° Int/222° Exh)
1.5 Ratio Rocker Arms What would give me say just over 400hp? Head change/cam? which ones, dont want to break the bank . not a cheap skate either..........Thanks

 

One more thing I don't want to get into crank / piston change.... thanks

 

I've been working on here for some new numbers.

http://www.compcams.com/Pages/409/camquest-6.aspx

 

With that low of compression that would be kind of your biggest restriction a bigger cam may help on the top end but may hurt the low end, If the heads are the mexican casting we have found them to have a runner volume of only 158 to 159 CC's as the older non mexican casting have appox 170 CC's, Those stock heads will not accept much more lift then you have.

A single pattern cam might pick the torque up a little and bring it down to a 110 lobe sep.

 

thanks northern77 I will check that out. blockman what abouut aluminum heads

 

You can get there with the vortec heads. I'm not sure what you consider expensive, but these are some options that I dont think would break the bank. a felpro 1094 head gasket will bump your compression a bit to prob around 9.5:1, stock springs can hold .490" lift, so those are your boundaries as far as a cam and rockers go. I'd think a cam with duration in the high 220's-230 range @ .050 should give you a decent improvement in power without too much low end loss. 110 LSA is good for a street motor like Blockman said. full roller rockers will free up some power too, but if you up the ratio you might have to clearance the push rod holes. An RPM Air-Gap manifold will fit that cam and rpm range well and flow better than the one the motor came with. You can probably do all of that for $600 or less (+ new gaskets). after that, synthetic oil, a windage tray and switching to an electric fan will give you a couple more if youre not quite there.

do you know which vortec heads you have? on the accessory end they'll either have a single pyramid, or 3 pyramids ("saw tooth"). You want the saw tooth ones. If you dont have those, maybe a set of Scoggin Dicky vortecs. They'll have better springs and machined down valve guides so you can throw more lift at it.


lots of different ways to go. those are just my thoughts.

 

The Dart 180 heads will set you back about 1100.00 but I think your heads are fine with more compression and a better cam would surely make a differance.

The quench on those engines are probably around .080 or so. Those heads are suppose to be 64 CC chamber but I bet are closer to 65 or 66 CC's

 

found an old Carcraft magazine article on the web. they were actually upgrading the same motor I have. here is what they said. what do you think Please excuse my form. my enter button crapped out hot hydraulic roller cam kit pn 12480002 roller lifter kit 12371042 comp cams beehive valve springs. have to elongate push rod holes on inboard side to use 1,6 roller rockers ........ http://www.carcraft.com/techarticles...ine/index.html They say the achieved 401 hp

 

All good info provided above..
You haven't mentioned anything about your exhaust system though?
What do you have on the car now?

A free flowing exhaust system will definitely allow some more real horsepower to get to the rear wheels....
trade off will be finding an acceptable noise level.

cheers
tom

 

I was in the same boat. Just take the heads off mill it down to 10.5 compression and get the it ported.
Get better cam, but without changing stock vortec springs you will limit yourself to .500 lift.

I have 355 roller with 10.5 compression ratio, ported vortec heads (280cfm @500 lift), air gap intake and XR276HR cam with 1.5RR and it should make 400HP easly.

Be sure that you have right gears for the cam and good exhaust.
S.
ps. Don't waste your $$ on other heads, you can make 400HP with your vortec.

 

I was under the impression that its not the springs, but the height of the valve guides that limits lift to .500"

on that note, ive heard/read reports of valve lift limit on the vortecs being as low as .480"

can anyone clarify any of this?

 

Fast burn heads and the hot cam kit from GM.

 

I changed my vortec springs to Comp cams springs/retainers without modifying anything else and now I can go to .550 lift with no problems. if you want more lift you have to machine the valve guides or install special beehive springs/retainers.
S.
ps. He doesn't need new heads for 400HP.

 

The shortblock is a pretty solid foundation and 400 (flywheel) horsepower is a pretty reasonable goal. The article is a good reference, but always remember that HP is great for racing - torque is king on the street. I would note that with the cast pistons and PM rods, 425HP or so would be my very top HP target. Don't even think about NOS

The Vortec heads are some of the very best entry-level heads out there with flow numbers that rival most of the entry-level aftermarket heads - especially in mid-range flow. Peak flow is around 240/148 @ .500, which is certainly capable of delivering 400 HP from 350 CID (1.14 HP/CID). A head change isn't required for your power goals; as the article noted "Vortec heads are certainly capable of a streetable 400 hp as well as excellent low-speed and midrange with 428 lb-ft at 4,200." The heads on this engine are P/N 12558060.

Generally, I'm not a big fan of upgrading the stock Vortec heads as they run out of flow at about .475 lift or so, and stock they're lift-limited to no more than that number and often a bit less. In this case, however, I'd spend the $$$ on the CompCams 26915 springs that allow you to get a bit more lift without removing the heads to machine the guides. We're kinda stuck with 1.5 rockers unless you want to remove the heads to open up the pushrod holes. Roller-tip rockers are a good investment as we go over .500 lift as they have a better geometry and are stiffer; full rollers really aren't needed unless we're going to extremely high spring pressures or consistently turning over about 6K RPM - which is not the case here.

This leads us to the best investment - a hydraulic roller cam. A roller cam is perfectly matched to the Vortec heads - they provide more power throughout the RPM range but especially midrange, which is right where the flow and I/E ratio of the Vortecs is the best. As the article you linked noted, the block is all set for a roller cam with the factory spider, which is good to about .525 lift - more than what we need. The factory-type spider and cam retainer can be purchased from GMPP or CompCams, and then we just need the timing chain, cam and lifters. The relatively low CR really isn't an issue here with the level of cam we can run.

Cam selection requires more information on your transmission, gears and usage - are you going racing, or just want more "grunt" down low?

I agree with Tom as well that you need to look at the whole system and ensure you've got headers and a free-flowing exhaust. You also don't mention the intake, carb or air cleaner; hood clearance is always an isssue, but a low-rise dual-plane is going to be a damper for sure.

Finally, budget to invest in a good dyno tune - there's a fair bit of power and driveability in the right timing curve and the right carb tune.

You can do this whole thing with the engine in the car and it's about 4-6 hours work.

 

FYI, the 350/330 ships with head gasket P/N 10105117 which has a compressed thickness of .028; combined with an average .020 -.025 deck height this gives about .048-053 quench. Above the ideal of around .040, but given the CR not something that needs attention at these power levels.

If you end up removing the heads, then swapping to an MLS-type thinner gasket makes sense - but I wouldn't pull the heads just for this change.

 

To get the standard retainer-to-seal clearance something like .460 is a realistic limit if you want to "bolt on" with no worries at all...although you should *always* measure.

I've worked with dozens of sets of the GMPP Vortecs and they've all been a bit different....

 

You can change your valve locks to 10 degree ones from comp cams to give you additional 0.05 clearance or do "ghetto grind" on your retainers. But most of the time if you install bigger cam you will need to change springs to increase the pressure because of valve float at higher rpms.

My springs cost me only $100 (with retainers and locks), and changing them is easy (even if the engine is still in the car.
S.

 

If they used standard Fel-pro head gaskets, you can ditch them and use .018 gaskets and gain 1/2pt in compression.. Its a cheap way to gain a little power and very often over looked..

 

.5 point of compression at this power level is worth maybe 1-2% power...although with a different cam there might be another 1% or so in there.

Great David Vizard article; most of this stuff is more racing-oriented but the chart is useful.

http://www.popularhotrodding.com/tec...ech/index.html

 

AFR 1034 aluminum heads with 64 cc combustion and 195 runners. Trick Flo track max cam, 1:6 rockers, Edelbrock torker intake, Holley 750 double pumper + gaskets, etc.
Total cost just under 3 grand.