Hey guys.
I'm in the process of getting my LT1's bottom end built. I've done some research on what to expect on my horsepower figures, but I wanted to get some estimates from my beloved C4 brotheren prior to dyno tune time....car is a 93 C4 6 speed with stock 3.45 gears.
OK, here are the mods...
Stock block bored .30 over. SCAT forged rotating assembly. 11.0:1 CR.
Stock LT1 heads ported and polished with 3 angle valve job. Valves are stock. From what I remember as far as peak flow, was almost 250cfm at .5 lift, I believe.
1.6RR
LS1 beehive springs
Cam selection, not complete yet, but will be a hydraulic roller and will be biased more on max power under the curve as opposed to peak HP.
Ported LT1 intake
52MM TB
K&N with cut air lid and TB bypass.
EM long tubes, Bullit cats, and Corsa cat back
MSD opti, coil, and 6A ignition box
SVO 30# injectors
Meziere electric water pump
Cloyes true double roller timing chain

I think that is about it. I'm hoping for 500chp.
Those with similar mods, I'd appreciate some feedback.

 

motor also has underdrive pullies. Don't want to forget those.
I know cam specs are important for determining the power...probably going to go with a custom grind....think more along the lines of an aggresive cam with a good balance of meat under the curve along with some peak HP...

 

You cannot estimate power levels until you have selected a cam.

either way, 500chp is wishful thinking with your heads.

 

You'll need a healthy camshaft to reach that goal.

 

So with a head that flows 250 at .5 do you think he would need a cam around 260@.050 to get 500chp?

 

Maybe you'll ge there but you will have no driveability and extreme difficultly to tune.

 

I know, I was just throwing a number out there and seeing what you guys thought. My opinion was LOTS of duration with that head flow.

 

Since he keeps emphasizing torque over horsepower, his cam choice will probably be on the somewhat conservative side. I'm guess something in the area of 230/236 or 236/242 both at .050.

So I'd say 1.15 to 1.2 per cubic inch.

Jake

 

But he is talking 500chp out of a 250cfm ported stock headed 383 LT1. Those HP numbers lead me to think LOTS of duration.

 

http://www.eportworks.com/

This is where Im headed for heads and cam. I do not think you will reach your goal with the head specs you listed. What about a 396 with aftermarket (trickflow,AFR, etc.) ported heads and cam?

 

I've researched the 383 vs 396 debate, and my conclusion is that the 383 should be able to rev quicker due to a longer stroke plus it is cheaper to build (parts and machining the block). I talked to AI and my engine builder on this.
My cam being selected will actually be selected based on the new AFR Eliminator heads not yet out. I will eventually be getting these. I'm hearing flow numbers of over 300cfm at .5 lift, and that those numbers are on the conservative side.
Anyway, I've got cam specs at work, but I forget what they are.
But I do remember that the specs are more radical than the examples given above of either 230/236 or 236/242 both at .050.
I know a 110lsa, and I'm going to take a stab at this anyway....a duration of around 240/244...242/246 (I think. I wish I remembered for sure). Cams are still a bit of a black art to me.
The plan is to have the car dyno tuned by PCMforless. They've done my tunes in the past.
I based the 500chp being comparable to 425whp.

 

I've heard great things about AI also. Tell them what your looking for and I'm sure they'll get you there. Search camaroz28.com there are plenty of people over there running similar engine setups with dyno's and ET's posted. Although with the vette your times will be even quicker with similar mods.

 

Nope, he might as well skip that plan, not unless he installs a power adder. 500 HP out of heads flowing 250 CFM is a bit of a stretch.

Jake

 

If you can tell the difference on how quickly a 383 revs vs a 396 you’re a hell of a lot better than me. Owned three 3.875 stroke 39x motors and one 3.75 stoke 385. All larger motors made more power. Even tried light flywheels vs stock dual mass and I can’t tell the difference in those either if that means anything. Neither can the dyno as it showed no loss or gain in flywheel weight regardless of what the people whom sell them to you say. Usually the decision is more budget oriented and value based vs which one rev’s quicker. The larger motor will always make more power if built to apples to apples.

No…..not another exaggerated AFR flow number post!! Please tell me it ain’t so. I bid 320 cfm @ .400 lift. What’s yours? Ok, let’s try 350 cfm @ .300 then.

The black art of camming a car is what are you going to use the car for? How many rpm’s do you want to turn? (remember the stock computer is limited to 7200 rpm) What static compression are you running? What stroke length? Rod length? What is the intake to exhaust flow ratio of your heads. What is the head intake volume? Stick vs automatic? Vehicle weight? How many ci and what is your drivability tolerance?

If you will get your block done and your heads, I’d then call some of the cam companies or someone like Bret Bauer as the cam is the last thing you pick out. No black magic and no magic beans that grow giant bean stalks. Common sense, experience and science based mixture.

Literally just left a dyno session with Lloyd Elliott and the guy (think it’s Brian) from PCMforless tuning cars and saw Lloyds personal car on the dyno being tuned. If that doesn’t give ya a hint or two regarding mail order tunes and what the pro’s really do. Lloyds 383 likes around 34 degrees of timing while my 398 likes 39 degrees on the top end. I’d say that’s one hell of a difference to try and tune either car without seeing what each combo wants. Also mine likes a leaner mixture. Every engine has variances that are particular to that individual set-up and you can never get it properly tuned remotely. Do a mail order tune only if you do not have access to a dyno and a good tuner.

Fyi..........Lloyd's 383 made 438 rwhp and it's an automatic using his older cam designs and heads. Newer stuff would be better.

 

My motor is out and in the shop. I also have a '93 torch red 6 speed. I'm doing the 383 with ported polished LT4 heads with the LT4 intake. I was running the Hotcam with the LT4 top end 52mm TB and EM long tubes with the PCM for Less tune before. I don't think I'm going to run the hotcam with the 383. I too would be interested in a good cam selection....

 

I think the biggest mistake is keeping the stock valves. Go with bigger valves.

 

Going to take a stab without any information but being you have a hot cam tells me you’re a bit conservative. No....you don't want to be that conservative in a 383 and make the mistake of using such a small older technology cam.

Made 445 rwhp around 6100 rpm in a 383 using Lloyd Elliott LT1 heads with 208cc intake ports, ported LT4 intake and GTP 6 233/242 cam on a 114 with 1.6 rockers and 11.8 to 1 compression. Very, very smooth running combo that idles smoother than a hot cam in a stock block. Good gas mileage, good power, etc. If you want to be a little more aggressive, I'd tighten the lobe separation but remember, it really is a SYSTEM and ALL details are needed to optimize your combo.

Don't screw around with the heads. LT4 are terrific castings with huge potential. Have them ported by someone whom really knows what they are doing. Do not settle for less than 300 cfm and have them flowed again AFTER you receive the heads by someone independent to ensure flow as there are now people getting 300 cfm from LT1 casting even. Head porting has improved light years in the last two to three years.

We also now know there is 8-10 hp gain in high hp combos in a properly welded/ported intake. Right above the injectors is a restriction and needs more material welded into that area on the outside to enlarge the inside enough remove the restriction. Simple porting won’t do it.

Nothing magical about cams regardless of what you hear, the cam can be off a little and honestly won't make that much of a difference if you don’t get just plain stupid. The numbers and variables of cams make it confusing for most but when it's all said and done, don't try and reinvent the wheel as there are several good cams to choose from with proven track records.Saw a professional built 383 dyno yesterday with a 107 lobe separation cam, mid 230 duration with no split on duration cam and about the same(or a little better) LT1 heads. Made about the same power as my conservative 233/242 on a 114.

Don’t believe the BS that there is a magical grind that would make a huge power difference. If your close on your numbers; there isn’t, however to optimize and get close on the numbers, you need to take in the total system.

 

The Lt1 heads are temporary. Youll be fine. I agree with 48mclain on staying away from the conservative Hotcam and 300cfm minimum on heads. I wouldnt go larger then 200cc intake ports as Im a believer in port velocity. Let LE or AI help you with cam selections for your desires and you should see 425rwhp with the correct cam. Looks like you have all the right supporting mods. Good luck. Let us know your dyno#s.