L695speed

I am at the point where I really need to get started on an engine. Now, those who're on some of the same boards I'm on may have noticed I was initially planning a 383 build with 500+ HP. Well I sat down and talked to a local builder, and realized that might be overkill. My goal was to have a car that was capable of mid to low 12s on street tires, 11s on slicks. 500 HP at the flywheel is definitely overkill in that respect. Considering an LS1 car I rode in had 374 at the flywheel and was also running 12s; I'm overhauling the whole engine build philosophy. While I want to run 12s at the strip, this is not a strip car. This is a fast, excellent handling street car for the twisties and road courses. I might autocross too.

Drop the power level to 400-450. Somewhere over 400 HP would be nice. This is easily done with a 350. Several people out there are running 350s with 400 HP+ on pump gas. It would also be cheaper as I wouldn't need clearance work on the block for the stroker. Now here is what I want and what my car is so far.

I have an 84 Trans Am. PHS documentation showed shipping weight of 3200lbs. The suspension has been built with UMI parts and Koni shocks/struts. I have PBR rear brakes going on, and LS1 Fronts. HPS pads. I will put on SFCs when I can get it on a drive on lift and have someone weld them in. I swapped the original 15x7 wheels for a set of 16x8s to retain the sleeper look as I wanted it to appear original to those who don't know all the details about these cars. I will run 255s on all four corners.

The driveline is the original 10 bolt with 3.73 gears that was rebuilt to factory spec maybe 60K miles ago. I put in a set of Mosler axles because I knew I might snap one of the axles if I left the factory ones in. I will upgrade the rear when it blows up on me, they're easy enough to do. The original T5 has been swapped out for a 97 LT1 T56 converted to work with the mechanical speedo.

Now here is what I have in mind for the engine. I would like something that can cruise on the highway in 6th and have a redline at over 6000RPMs (I'm thinking 6200-6400) running on pump gas. Get a Vortec 350, put in some flat top pistons. Port and match the heads and intake. The valves will get a 3 or 5 angle valve job. At the moment I am unsure if I will use the 1.94/1.5 or 2.02/1.55 combo. Run a roller LT4 Hot Cam, and use either LS1 or LS6 valve springs with the appropriate retainers and maybe roller rockers. Switch to the mechanical fuel pump if its not already one. Ditch the FI system for a RPM Air Gap intake and a 750cfm carb, HEI iginition. I've read the truck ignition runs hotter than the car one. So I might just retain the stock truck ignition.

I think this might make what I want easily and for much less than the cost of getting a 425 horse GMPP 383 crate motor. Any input on that engine combo? Power figures? Thanks for all opinions, but please don't start a flame war or insist that I go the LS or LT route. I am leery of that optispark among other things on the LT and the LS while I thought about it, I relented because I flat out suck at electrical work. Besides I'm too far along setting up for a carb motor to justify starting over for an LS motor. Thanks guys.

L695speed

Now here is what I have in mind for the engine. I would like something that can cruise on the highway in 6th and have a redline at over 6000RPMs (I'm thinking 6200-6400) running on pump gas. Get a Vortec 350, put in some flat top pistons. Port and match the heads and intake. The valves will get a 3 or 5 angle valve job. At the moment I am unsure if I will use the 1.94/1.5 or 2.02/1.55 combo. Run a roller LT4 Hot Cam, and use either LS1 or LS6 valve springs with the appropriate retainers and maybe roller rockers. Switch to the mechanical fuel pump if its not already one. Ditch the FI system for a RPM Air Gap intake and a 750cfm carb, HEI iginition. I've read the truck ignition runs hotter than the car one. So I might just retain the stock truck ignition. I will be running headers but as for the rest of the exhaust I'm not sure yet.

So no one knows if this combo will make 400+ HP?

InfernalVortex

iTrader: (4)

Theres not much available in 255/50/16's anymore. Good luck with that.

Skinny Z has vortecs with a an xr276 and makes aruond 376hp. He does 12's, traps at 107 with a 3700lb car.

LT4 hotcam is great with Vortecs too, it makes around 350.

I think you should go 383. You'll be wishing you had that power down the road. Good heads are the key to keeping it a good street car.

L695speed

You're right, I probably will wind up just running 245/50s Just because of that. Just putting it out there what I wanted to do.

I probably will stroke that motor eventually, but I'd like to get this thing running. The idea I had was to build the top of the 350 so that when I do decide to stroke it, I don't have to do much to the top end. The point the engine builder I talked to was making, is 12s in a 3500lb car max is easily done with less power. No need for a 500+ horse motor that could kill you in the rain. I've been looking around and it seems that my thoughts on the Vortec 350 are in line for the power I want. Builds reporting 412-440 HP have been done for relatively little money on a Vortec 350. I need to fine tune the parts list or cam choices.

L695speed

I was given a major lead on a whole engine if I pull it myself I can get it for 120 bucks. If I can nail down the upgrades needed for 400-450 HP then I'm golden.

InfernalVortex

iTrader: (4)

In my opinion anything above about 350hp (especially at stock displacement) needs to have a fresh bottom end. Mainly because to get more than 300-350hp from a 350 you need to spin it fairly high. Not super high, but definitely high enough that stock rod bolts are going to be a liability. This is why I think building up 305's isnt too smart. The RPM's necessary put the bottom end at risk.

The better heads you have ,the more displacement you have, the slower you need to spin the motor to hit your power goals. If you want streetable, go 383.

Also, be aware, the rules about power dont change. Power is ALL in the heads, intake, and camshaft. You put a given set of heads, cam, and intake on 350, and it will make the same power as those heads/cam/intake on a 383 - but the 383 makes it at lower RPMs. There's some effect of volumetric efficiency, so it's not going to be exactly the same, but it's not going to vary very much either. So if you're expecting to throw a 383 under the same top end and make 50 more hp, it's not going to happen that way. But a ragged edge barely streetable combo on a 350 will be a lot more tolerable with a 383.

L695speed

Well I am thinking if I get this motor out of the yard, then at least I already have stuff like the rear main seal housing, oil filter fitting, the heads, etc. All that little stuff adds up pretty quick. If I can get a motor that already has all that stuff I am already ahead.

I just don't see the sense of going 383 right away. I am figuring if I can build the top end up of the 350, I can stroke it any time there after. At least then I can actually enjoy the car and work on it at the same time. I will probably wind up with the stroker, but not right away at the start. I know a vortec headed car can do the job. I also know the RPM Air Gap intake and a 750 carb can do the job on both. The LS1 or LS6 valve springs will likely work on both as well. As would 1.6 or 1.7 rockers. Its the cam that would change I think. The LT4 Hot Cam will be the starting point there. If I could just swap the cam out of that whole top end on the 383 switch then that would be good.

I've had many people tell me theres no sense in going with the stroker for a street motor at 400-450. But I've had people tell me that it doesn't make sense to go with a 350 at 500+. Most of the car guys and builders I talked to around here have said to stick with the 350 but build the top end that way I can drive it while waiting for winter to build the bottom end. THen when I switch I will maybe gain some power but mainly it will be more streetable.

I know the peak power will be higher up in the range, but it won't be spinning that high on the street too long. For a street motor it might be fun. This is not a daily driver either.

L695speed

I know the JY Vortec is not the best setup for the power I want. It is a place to start which I sorely need. If I have the motor I could even just drop it in and go and have fun with the car while building it up.

InfernalVortex

iTrader: (4)

I will repeat... a stroker will not make more power with the same heads/cams/intake as a 350. It will make about the same power. The advantage of a stroker is you can go way more aggressive on heads/cam/intake and keep it streetable.

To me there's no point at all in building a 350 these days. I regret not stroking mine fairly often. You can make good power with a 350, but making more than 350fwhp gets really hard unless you spend big money on cylinder heads. Vortecs are GREAT but they wll NOT get you to 400-450hp on a streetable combo. With a 383 and a larger cam you might be able to pull that off.

L695speed

Ok, lets say I do this.

Stroke it, use a set of flat top pistons, run a 274 or 276 (282 might be too much) roller cam with a set of RHS Vortec 2.02/1.55 heads (or I could keep the stock valve size or have the heads I get on the motor done for the 2.02/1.55 size) ported and bowl work done if needed and port the RPM Air Gap to match, LS6 beehive springs, 1.6 roller rockers I'm not going to not use the vortec heads when a friend of mine is running Vortec heads on a 477 horse 406. That was dynoed and at the flywheel.

No sense for me to go with AFR aluminum heads at 2 grand at this time. I just want this thing running again. Like I said, I may run it with the air gap intake and carb on the 350 motor til winter then do more work on it. I don't really need all forged stuff if I'm staying within 400-450 HP on a street motor. What is cast or forged in the production motors? I read somewhere, but I forget.

InfernalVortex

iTrader: (4)

No need to spend a ton on an air gap intake. The runners in the air gap are the same as the runners in the RPM. As far as airflow is concerned they're identical. All the runners heat up to temperature just like a regular intake, it just takes a little longer, so dont expect any power gains. There will be some before the engine is up to temperature perhaps, but youll have to tune the car around that... just kind pointless. I think it's a bit of a gimmick personally. They DO look cool, though. If you get a deal on one go for it, but I dont think the philosophy behind it holds much water.

L695speed

Ok, I will look into switching to the usual RPM Performer then. Any other advice on valve springs, rockers and cam? I'd rather go with the roller cam in this motor than a flat tappet one.

IroczFan

i think what you wanna do is the smart way to go build the 350 over summer so u can still enjoy the car then next winter tear the motor down and do the 383 kit that way you can still enjoy the car and gain performance over time

L695speed

I do and would rather go about it that way. But I want to have that parts list nailed down so when I do it, I'm not waiting on parts. I may have this thing running if I find a decent donor from a vortec truck. Will be at the yard tomorrow but might not get anything at that time for a motor. Weather isn't optimal for that kind of stuff. Going after other things like sway bars and etc. I think I'm in line as far as parts go but as Infernal Vortex pointed out, the air gap increase is miminal for the price increase. He says the RPM performer will get the job done just as easily. I will look into that and probably will take his advice on that. I would like similar input on the rest of the setup I had in mind. I think (not certain) I can run my TA's HEI dizzy on that motor. If I can, I think it might work just as well as an aftermarket one. Unless I keep the truck dizzy. The TA's HEI just plugs right into the wiring harness though. Its lil stuff like that that I just want some input on. Cam choice as well.