people with 383 stoker with lt4 heads and intake

[redbird94]

how much did all this stuff run, how much power should i expect with headers and a mild cam. what ALL so i need to make this complete. where would be a good place to buy the parts. and do i need machine work done?

[N20LT4Bird]

Yes, you do need machine work. The block needs to be clearanced for the larger crank and the cylinders need to be bored if you want to attain 383 CID. Many guys go add 4 bolt mains for added strength. I did not, but would have like too.

ROUGH prices:

LT4 Heads/Cam/Intake - $2200
383 Stroker Kit (rotating assembly) - $1500 - $3500 (depending on quality/ strength)
Basic machine work - Clean/Bore/Hone/Clearancing/ $500-$800
Gaskets/Misc - $300
You may want to go with the splayed 4 bolt mains too, which would be another 3 or $400.

Power levels really depend on cam selection and porting (if any on the heads/ intake). My cam is very mild for a 383 and I am making around 500 rwhp and 600 rwtq.....on a 100 shot of nitrous. Without nitrous, I would expect 350-400 rwhp and 450-500 rwtq.....

[Nightrage]

N20LT4Bird, how much did it cost you to have the heads and intake ported?

[Injuneer]

Your going to get a huge range of alternatives on this. Depends how far you want to take the engine. If you just buy the LT4 heads and intake, you're looking at $1,500. But if you want them to flow better than ported LT1 heads, you will need to invest another $1,500-2,000 in them. Thats the difference between an engine that makes 425HP and one that will make well over 500HP.

Then there's the rotating assembly. For 500HP or less, you could get a cast crank, low $$$ rods and hypereutectic pistons for well under $1,000. But if you ever envision a blower or a huge shot of nitrous, you can drop $3,000 on the rotating assembly.

Figure another $1,000 for tearing down the old engine, machine work and some reassembly. Typically you will replace all the parts that are worn out, or have limited life spans.... damper, timing set, water pump, distributor, oil pump. The "cam" will have to include upgraded valve train parts - lifters, pushrods, rockers, studs, springs, retainers.

It's hard to see how you could get away for less than $4,500. And there's really no upper limit..... $15K-20K is not out of the question.

[Nightrage]

At 500 horsepower, what else would we need to upgrade on our cars? Fuel system and clutch i'm sure, but what about the rear? Isn't there a kit that can be used on our tranny's to enable them to handle 600+ horses? I really want to start adding power and even though it'll probably be a few years until i see anywhere near this kind of power N/A, i like thinking about it.

[N20LT4Bird]

At 500 horsepower, what else would we need to upgrade on our cars? Fuel system and clutch i'm sure, but what about the rear? Isn't there a kit that can be used on our tranny's to enable them to handle 600+ horses? I really want to start adding power and even though it'll probably be a few years until i see anywhere near this kind of power N/A, i like thinking about it.

Your T56 is capable of handling 500 HP. The clutch, differential, and suspension will need to be upgraded if using slicks.

[redbird94]

i have 95,000 now on the car, the paint i almost perfect, new wheels it looks great body kit ram air hood just amazing, interior is good but its cloth. i think i want to keep the car. with all the mods listed what should i do then. if i just do an Lt4 conversion will i really pick up 425 hp with a set of headers? would my bottom end hold this much power, and with that many miles arent i loosing compression already? how long will my bottom end hold out i got the car at 74,000 on it from a 45 year old woman who had it since it was brand new and the oil has been changed every 3,000 and she drove it like a granny. i have ragged on it a little bit but i take care of her.

[N20LT4Bird]

the 425 HP is really misleading.........you will need headers, larger throttle body, and custom tuning to reach that power level (and thats a maybe). Im running a few more cubic inches, and I dont think I even make that power N/A. A stock bottom end will support 425 HP, but you may want to check compression beforehand to know whether or not it needs a freshening.

[redbird94]

what do you mean by freshened? will it only hold 425? can i make that power without touching the bottom end? i plan on doing headers and i know a custom tune, the trans will be swapped by then for a heavy duty model from mad dog transmissions. would i be better off running a loyd elliot head and cam package? which is the more price worthy product?

[Injuneer]

You need, as a minimum, to do a compression and leakdown test. That will tell you whether your rings and cylinder walls are in good condition, identify burned valves, etc. It wouldn't make any sense to put new heads and cam on an engine that is worn out. There's a good chance it isn't worn out... there are LT1's with over 200,000 miles on the original block and rotating assembly.

The other concern in a high mile engine is the bearings. It isn't unusual for a cam swap to be followed closely by failed bearings. That's harder to evaluate, since you would have to disassemble the engine for a meaningful analysis. You could probably get some idea of bearing condition from an oil analysis, looking for signs of metals that are only found in the inside layers of the bearings.

The stock rotating assembly should easilly support 500 flywheelHP, as long as you aren't making that power with a radical cam and high RPM. I suspect that you would find a heads/cam package from someone like Lloyd Elliott to be more cost effective than the LT4 "conversion kit". You'll save money simply because all you are doing is the machine work to port your stock LT1 heads, and not buying a whole new set of assembled heads. And, a good port job on yout LT1 heads will flow more than a stock LT4 head. You want the LT4 head (and $1,500-2,000 worth of porting) if you are looking for something in the 500-600HP range, where you need more than 300cfm intake flow. The LT4 HOT cam is really fairly mild. You can go a bit larger than that on a 350ci engine and still pass emissions and have a "streetable" ride. Go to a 383, and you would be wasting your money on the HOT cam... the 383 would just swallow it and struggle to make decent power.

[N20LT4Bird]

. Go to a 383, and you would be wasting your money on the HOT cam... the 383 would just swallow it and struggle to make decent power.

C,mon now. I dont own the fastest car in the world, but I like to think im making "decent" power. The LT4 Hot cam is very mild with 383 cubes, but it makes for a car that is very streetable with a nice idle and over 20mpg on the highway. It also seems to like the nitrous......so on a 100 shot, im making over 125 HP and 200 ft/lbs to the wheels.

I would like to step up to a cc306 though.

[Injuneer]

... The LT4 Hot cam is very mild with 383 cubes, but it makes for a car that is very streetable with a nice idle and over 20mpg on the highway. It also seems to like the nitrous......so on a 100 shot, im making over 125 HP and 200 ft/lbs to the wheels.

Sorry... didn't mean for it to sound so negative.

In all honesty, I think I can say the same thing about mine.... streetable, silky smooth 800rpm idle, 20mpg on the highway. But its a 230/242 114LSA 0.590 I/E. To me, its still too small, but we picked it to pass emissions. Heck, people are running the CC306 in 350's and looking for something bigger. The next thing I'm going to do, since it isn't street driven any more, is go bigger on the cam. But for a "daily driver", the one I have is fine.

I was sort of surprised you had the HOT cam, but it comes down to a personal definition of "streetable" I guess. Don't you ever get tempted to try and pick up another quick 35-40HP?

Again, no criticism intended.

[N20LT4Bird]

Yes, Like I said I would like to go to a cc306 cam. I didnt pick the cam, it was in the engine when I bought the car and I was a bit surpised to find it in there when I opened the engine up last spring. But, I dont have a lot of money, so even the extra 300 bucks would have put a strain on the budget for that build. So, I went with the same cam (it was in good shape).

I also dont know how another cam would work with the nitrous. I know I could make more power N/A with another cam, but the hotcam respnds well to the juice. Id rather make a little less power N/A and lots more power on the juice. How does your cam work with the juice?

And....no criticism taken.

[FireFinder20]

this is perfect...hopefully, i'll be doing this next winter and expected to spend around 6 grand...i hope to make the right choices...just kinda mad that I can't undo some mistakes already made, like my Edel cam sitting in the box...

[Injuneer]

The main way the cam is going to affect nitrous power is determined largely by how much nitrous it allows to escape during the overlap period, when both the intake and exhaust valves are open. That's why people usually look for a 114LSA on the cam. I would think that becomes more critical as the duration of the cam goes up. If you were running a cam with more overlap and losing some via overlap, you just spray more nitrous.

Second issue is the concept of "how much nitrous you're spraying". Basically, you start with a jet size that is "typical" of say 150HP, and you put it in. Then you jet the fuel to match. There are a couple of variables in how much power you can actually make with the nitrous. First, you have to total all the pressure restrictions in the system to determine how much nitrous actually flows. You may say you're going to use an 067 jet for a 150-shot. But how much nitrous will actually flow depends on the type of valve you have on the bottle, whether you have a filter and what type, whether you have an electric bottle valve, how long the hoses are, what size hose you use, what solenoids you are using, etc.

I know I bought a new, "super" high flow bottle valve, to replace the high flow valve that was giving me some problems. When the shop saw the valve, they told me not to use it, because it would actually alter the tune. With the super high flow valve, there is less pressure loss, so more nitrous flow through the sytem.

The point I'm trying to make is, that just because you put a 067 jet in the system, doesn't mean you are spraying 150HP. If you have a lot of losses in the system, you might only be spraying 125. If you have a well-designed system, you might be flow well over 150HP. Run it overly rich for safety, and you lose power. Run it leaner to make max power for the amount of nitrous available, and you're "on the edge". Sort of a tradeoff.

Bottom line is, I wouldn't necessarily judge the efficiency of the cam by the amount of measured rwHP vs. the size of the jet you put in the system. I never really looked at the jet size vs power. We just kept drilling out the two jets until we felt we were at the point where the engine would go unstable and risk detonation with any more juice. All that was done on an engine dyno. Later, when I asked them to add more nitrous, they just started enlarging the jets some more... but this time they were using a more detonation resistant fuel (C16 plus another ingredient). The shop tends to be VERY conservative in their tunes, so I expect most people would have been willing to push it a bit more. But since I was spraying 60% of the NA power, vs. their normal standard of 50% max, I didn't push the issue any farther.

That's one of the reasons I want to bump the NA power.... the more power you can make running NA, the more nitrous you can spray. If I could make 600flywheel instead of 500, I could maybe spray a 350-shot rather than a 300. 600+350 sounds like more fun than 500 + 300. But I will need a much bigger cam, and I'm not even sure my heads will support 600flywheel. The intake is good, but the exhaust really sucks. That's why we picked the lobe lift on the cam to produce the same 0.590" gross lift, with 1.6's on the intakes and 1.55's on the exhaust. If it needs more exhaust, we have the option of going up to 1.6's for 0.609" gross lift.

And I understand the "money" issues.... I can't afford to upgrade the heads... unless I could get some decent (there's that word again ) $$$$ for the LT4's.

Long-winded as usual.