update, supercharged 383?

[custom442]

Been a while since I posted on here, am getting married so the whole big $$ cutlass thing isnt going to work out at least not anytime soon.

I have the 383 still its been 2 years now since I built it, still got low mileage. I'm just at the point to where the car can be inspected and be on the road. Which is a huge step, its really going to be gratifying driving my ugly terd around whipping up on everything on the highway. I've been tweaking the holley 770cfm 4160 now for months and finally got it to where it runs perfect. I literally had to replace just about every piece you could replace for tuning. This was the ultimate b*tch of anything ever done...but to everyone who thinks you can't run a XR282HR cam with 2.14 gears and a 3000 stall I've done it, runs like a scalded dog up to 70mph in first gear. I'm afraid to redline it in second being so not street legal. One of the tricks was to curb idle it twice what you'd do for a normal vehicle, and tune the accelerator pump to shove fuel at that high rpm range where the cam is breathing.

The 3000 stall is going to be thrown out for a 1000 rpm stall sometime. Wish I had a manual. The car is going in a different direction. My idea is to make a ton of top end power, at least as much as I can on these internals and with this cam and setup. It's going to now be made for high speed, and decent mileage, maybe 15-17mpg. Just because thats easier and less breaks, and I'll be able to eat corvettes for lunch and maybe a lambo or ferrari from time to time.

The car weighs now 3000lbs. It goes without saying I need suspension.

So the engine has between 440-480 hp after putting everything in all the calculators I could find. The stock internals - 2 bolt main- hypereutectic pistons are supposed to hold 550hp. Heads are patriot performance 195cc intake runners, 76-78cc combustion chambers, 2.08 intake 1.60 exhaust. I'm running sort of low compression for a small amount of boost, estimate 8.5-9.5 comp. When I bumped up the supercharger psi in my 4.3 truck from 9 to 12 the vortech s/c broke. It needs a rebuild. I'm thinking about taking the whole system, gauges, meth kit and all, and shoving it in the cutlass for 3-4psi boost on my current setup. 4.3L and gen 1 sbc have the same front bolt patterns. This would make somewhere in the neighborhood of 550 hp. I would need to run the carb before the centrifugal s/c and run the outlet side of the s/c to the intake manifold. Then manifold reference my powervalve and tune it rich, step cooler plugs, get the right nozzle for the water/meth, and should be ready to go with a few other things.

Question is will it hold? what do you think. What am I overlooking? I dont care about the rear I'm keeping it stock 7.5 until I figure out what to do with the car.

This idea would be nice because my dd truck would be more reliable, and the cutlass would have a lot more power. I think it'll be somewhere between muscle car and supercar territory at higher speeds with 550hp and 3000lbs and that low numerical gear...which is key, I mean theres no other car on the road that can wind out their torque curve this much.

 

[jrm81bu]

I've done something similar before. Blown 383 with a bigger cam, and at different times, a 2000, 2500, and 3000 stall, with 2.41 gears. With the low-end grunt from the small roots blower, that i'm still running, it would pull those gears just fine.
Two issues I see with what you want to do is number one, hyper pistons. Yes they are rated for the power but not forced induction. That said it may still be fine, i'm getting away with cast pistons, but it's possible for it to go bang at any time.
Second, I wouldn't bother trying to make it a draw through system. Just go with a blow through. Yes all that time spent tuning will be wasted but hey what else you got to do?

 

[custom442]

I've done something similar before. Blown 383 with a bigger cam, and at different times, a 2000, 2500, and 3000 stall, with 2.41 gears. With the low-end grunt from the small roots blower, that i'm still running, it would pull those gears just fine.
Two issues I see with what you want to do is number one, hyper pistons. Yes they are rated for the power but not forced induction. That said it may still be fine, i'm getting away with cast pistons, but it's possible for it to go bang at any time.
Second, I wouldn't bother trying to make it a draw through system. Just go with a blow through. Yes all that time spent tuning will be wasted but hey what else you got to do?

Ya, going to have to run one or two o2 sensors with these pistons and no more than 3psi, there's no other way around it. Should be good for 550hp.

The reason I'm using a suck-through carb is I don't have another reasonable low cost option. My supercharger is front mount, centrifugal style. Going to use secondary injectors (2x 85# injectors) off a separate fuel line/electrical pump in order to fine tune top end fuel. Have to use things already laying around to make it cost effective. Most likely what I'll do is switch out the 770cfm holley for a spreadbore or tiny carb, tune it well without the blower. Should be able to trade down with my fairly new street avenger vs something else.

It'll have a bracket that will relocate the carb off the intake manifold entirely, a big cold air intake under where the cowl will go, cold air to the carb, and run air tube from the carb to the front mount supercharger inlet. From the outlet side of the s/c will be a pipe to the intake manifold. In that pipe where the carb would normally sit are my injectors. In this area will also be a healthy shot of methanol injection. I'm not wasting my time with a bunch of aftermarket timing computers. Just take back initial timing some, and run however much advance it runs. The methanol should help out a little for extra octane security, since its only 3psi and I'll richen up the AFR pretty well so it won't need water.

It'll take a lot of tuning time. One good thing is there won't be backfire issues. With the suck through carb, the centrifugal s/c acts as a one way valve. And on backfire/coming off boost it will go through a bypass valve between the manifold and after carb/before supercharger allowing pressurized manifold air to go through an open loop when throttle is let out.

It sounds crazy, but I actually want a 450 economaster, holley 4360. Either that or 390cfm holley. With a 750 qjet or my current 4160, the secondaries are so big it will make tuning the injectors much harder. And this low of boost doesn't care if it has a restriction at the intake, the supercharger will pull air regardless, and throttle body injectors are there to compensate. The gas mileage potential is about the same with the 750qjet vs the 4360, vs maybe the 390cfm holley, the primaries look to be similar size.

But those gigantic qjet secondaries will be so off the charts , I mean they'd have to be tuned at higher rpms when boost is coming on, which will make it hard to do at the same time with extra injectors. So the idea is if I have the little 450 or 390cfm, the primaries will be for gas mileage, the secondaries a transition through lower mid-range to where the extra injectors take over all the way till redline. Removing the choke horn, choke, and some milling work on the 4360 will help a little with airflow, along with a good cold air intake. Tuning idle with any of these is going to be different :shock:

These injectors allow for tuning to start at around 12" mercury. Which is amazing, I mean I don't even need to run a 4 barrel. Most of the 390cfm 4bbls floating around are used in race applications for cfm regulations and expensive, but usually flow very well. If I can get a clean trade with my 770cfm 4160 I'm going to do it. And the reason I'm not considering a 2bbl is restriction at the intake. Basically the carb is only going to be used for idling and low rpms.

 

[custom442]

jrm81bu - I took the car for a drive yesterday, in 2nd gear in the th350 I was roasting the one wheel peel under 2500rpm from a stop, just burning it into the pavement with no brakes and not going anywhere at all. I think I'd start to get traction somewhere around 70 mph with these tires :lol: . I really have no business adding 80-100 more hp, but if it's an option it's always the right thing to do

 

[upandaway84]

Adding more horses is never a wrong thing to do.

 

[custom442]

Adding more horses is never a wrong thing to do.

haha ya it at least gives me something to do. Probably won't start this project till the summer. Gota get the car inspected first, getting ahead of myself.