stock48

iTrader: (16)

Back in the late 90's I had one of those trucks with a 383, ported factory heads, and 217/225 cam. I had alot of trouble getting enough fuel. I never did get it to run right, and ended up pulling it out. You might get away with the heads and a little more cam but I wouldn't push it too far. If you go with a RAMJET, or marine intake you could get away from that, but it's going to cost you some $$$. Maybe you can find the stuff used if you look around. I don't know about the tuning but some guys have done it.

6789olds

the L31 fuel injection will top out at 400hp at the fly wheel . ported stock vortecs and a LT4 hot cam with 1.6 rockers long tubes and a tune should get you 375-390 hp fly wheel hp . if you want more power then that you will need to swap to a marine intake . or just spray a small 50-75 shot that will get you 450 hp . also if you swap your springs out for beehives i have heard of people getting by with .525 lift with no machineing on the heads . but should always check to make sure .

1320 OTTER

There you go. Or.....dare I say this on here....take off the FI and carb it. A nice 650 mechanical secondary, Holley blue pump, and don't wory about anything. Shure MPG isn't as good but who cares? The objcet is to go fast. Simple to tune and all. You'll need a HEI ( not computer controlled ), intake manifold, CARB, fuel pump, air cleaner, and the linkage to hook the TV cable to the carb. It will be cheaper in the long run to go faster this way. Just break out the timing light, a flat head screwdriver, some jets and tune it. Learn oldschool techniques like reading plugs, setting timming, carb ajusting, lisstening to what the motor is telling you. I'm so pumped up about this I just might go carb my 06.

laoutlaw

How much hoursepower can I expect out of a set of aftermarket heads.

dirty_old_chevy

stock vortecs are worth an extra 30-40 horsepower over l98's with a middle-of-the line cam. In fact vortecs were kinda a shock to the aftermarket, because when people found out how much they flowed, they also found they outflowed many aftermarket heads.

laoutlaw

What size heads would be good for a stock 350 with a full exhaust and no cats and a cai. I talked to a guy a patriot and he said that the stock vortec heads flow 180cc. He said the biggest he would go was 190cc. What do you guys think. I will have a stock cam and I want to put 1.6 roller rockers in the heads also.

dirty_old_chevy

They don't flow 180cc, that is the intake runner volume. Ideally you want a smaller runner with high flow. This is where the vortecs do well. Thats how they make good power and torque. Chevy Hi-Performance magazine flow tested numerous SBC heads and documented the flow numbers. You can find it on their website. Its worth looking at. If you spend a huge wad of cash on different heads and keep the stock cam, I think you will be dissapointed.

1Bear

iTrader: (1)

The fellow from Patriot was telling you the intake port volume, not the maximum flow of the intake ports. The intake ports are considered very good for a factory casting, as most stock 062 Vortec heads flow somewhere in the 228cfm range, whereas a very mildly ported set with stock sized valves can easily flow 10cfm more, all while having reasonably small valves at 1.94 & 1.50 respectively. The problem is, if you consider it a problem and don’t address it is the exhaust side. The Vortec heads in a stock configuration only flow about 60% or so Int/Exh ratio, whereas most would consider a 75% or more Int/Exh ratio better for producing good power. One of the biggest returns in time and effort would be opening up the exhaust valve seat, as most stock Vortec heads have an exceptionally wide seat, usually over .090” wide. If you were to have the exhaust seats opened up with a radius cutter and a .074” seat width to substantially increase the area in the port throat under the valve, you would be opening it from 1.2” to 1.295”. That may not appear to be very much, but equals a 16% increase in area with the same size valve. Another area the shows good results for increasing the flow past the smaller valves is reshaping the guide bosses, as in factory form they are fairly large and impede flow. The last thing I would concentrate on is reshaping the port floor in the short turn radius area by blending it to make a smooth continuous radius. On a side note, some of the early Vortec heads came with straight down 90 deg cut under the 45 deg seat on the intake side, instead of the typical 60/75 deg bottom cuts of the typical multi-angle valve-job. If you by chance have a set of these heads with the 90 deg cut, the only thing you can do to is move up to a larger intake valve, in which case I would have the seats cut for 2.00” intake valves and then open up the pockets to match, with an 85% ratio pocket to valve seat size. Also, I wouldn’t have the heads cut anymore than what would be necessary to get them straight, as they are a thin wall casting and are already crack prone if heated. Prepping the heads in this manor will normally net you a 25+ hp gain over the bone stock castings. In a mild build-up like your considering, you could use steel shim gaskets for the best compression ratio possible, but for most builds, I would normally just recommend going with a 39cc compressed thickness composition gasket.

While I sincerely believe you could reap the benefits for a more aggressive camshaft, if you wanted to stick with a factory piece, but still use a unit that will show some improvements over stock, I would consider using one of three available camshafts from the General. At a minimum, I would look for the old 14093643 camshaft that came in the ’87 L98 350 Corvette’s and IROC-Z Camaro’s, and had 202/206 Int/Exh duration, .403/.415 Int/Exh lift with a 1.5 rocker ratio, with a lobe centerline of 115 degrees. This cam with 1.6 rockers would net you a .430/.443 Int/Exh lift, with the only issue being it’s so old, it may be harder to find now. Next up, I would consider the 12551705 ’95 – ’97 Corvette and Camaro LT1 cam, which had a 201/208 Int/Exh duration @ 0.050”, .447/.459 Int/Exh lift with a 1.5 rocker ratio. This cam with 1.6 rockers would come in at a .477/.490 Int/Exh lift. Lastly, you could use the factory 12551142 LT4 camshaft that was advertised as being a 203/210 Int/Exh @ 0.050”, .476/.480 Int/Exh lift with a 1.6 rocker ratio, on a 115 degree lobe centerline. The only thing you would need to do to run a camshaft that was designed for an LT1 or LT4 in an older small-block would be to shorten the dowel pin in the end of the camshaft about 0.030”. The LT1 / LT4’s have the dowel pin set at about .620” from the end of the camshaft. Lastly, I would consider replacing the valve-springs with a set of Comp 915 springs and appropriate retainers to handle the amount of lift any of these cams will put out with the 1.6 rockers, as I'm sure you have heard all the stories of not being able to run much more than between .450" to .470" of lift depending on the individual Vortec heads. Now if you use Comp 915 Beehives that are designed for LS1's at an installed height of 1.800", instead of the factory SBC height of 1.750" you can obviously run more lift without the retainer hitting the valve guide or seal. To run LS1 style Beehives in a SBC designed with 11/32" valve stems, you will need to use a hybrid retainer. Comp makes such a retainer Part # 787-16. Also to get the installed height of 1.800" you will need a +0.050" steel lock/keeper and Crane makes just a jewel: Part # 99095-1, coded Yellow. If you just install the springs without the +0.050” locks, you will increase the spring pressure over what they are rated to and obviously reduce the amount of lift they could otherwise handle.

Of course if having the heads reworked, you could just as easily have the guides cut down for typical guide seals and fitted with the appropriate sized regular conical springs. The main thing is whichever way you go, that you measure to make sure that you end up with at least 0.060” of clearance between the retainers and valve-seals for safety.

If you didn’t mind going aftermarket on the cam, Comp Cams has the 252XFIHR13, specs are 202/212 .518/.513 113 w/1.5 rockers. It has a RPM range of 1000 to 5000.

If you want a little more bump and performance:
I've always liked the cams Lingenfelter has ground for the older SBC's.
Part # 74216 is a Hyd. Roller listed as: 213/219 .493/.506 112 w/1.6's.
You could run it with 1.5's and come up with a lift of .462/.470 and be safe.

dirty_old_chevy

My buddy used a Comp 8-500-8. It performed well with no added programming.

dirty_old_chevy

That was in a 97 silverado.