What Carb do you guys run on the 383??

[BurnoutNova]

Originally Posted by Billla

The original stuff is going into a factory correct (but with a refit roller cam ) LT-1 I'm building...slowly...for my '69 Corvette. The others I'm just holding in trust for the right project. I love this setup for a hot 425+ HP GEN I.

are you saying you have a '69 LT1 corvette? or just putting an LT1 in your 69 corvette?

i thought they only put LT1's in corvettes and camaros from 70-72, but did some make it in 69's? also, i thought the most powerful 350 you could get in 69 was 350hp

im always eager to learn more about old 60's corvettes/ and musclecars, so im not picking what you said apart at all, just trying to learn somthing

[67_C-30]

There were no LT1's built in 1969. They were also rated 370HP in the Vette's, and 360HP in the Camaro in 1970 before the compression was cut in 1971. You are right that the most powerful 350 in 1969 was the 350HP L46 engine.

[Sport/Truck]

Ive got a SMI Qjet Stage 2. I'm not done yet so not sure what I can expect for MPG.
s/t

[Billla]

My '69 isn't an LT-1 - as noted there were no '69 LT-1s although there were LT-1 powered '69s that the press got to drive as part of the announcement of the '69 and it was show as an option in some early literature.

My 'vette is the L-46 350/350HP with a documented dealer swap to the LT-1 intake and carb - kind of a weird swap. Unfortunately, at some point the refitted factory hood was replaced with the standard hood - so I'd have a hard case to make with the NCRS

I'm building a very correct LT-1 that will look exactly right from the outside...just because I can

[BurnoutNova]

Originally Posted by 67_C-30

There were no LT1's built in 1969. They were also rated 370HP in the Vette's, and 360HP in the Camaro in 1970 before the compression was cut in 1971. You are right that the most powerful 350 in 1969 was the 350HP L46 engine.

i knew the 70 corvette had the 370hp LT1 and the camaro had 360, supposidly becasue the corvette had better flowing exaust manifolds, even though it was the same engine.

the only thing that changed was the compression went from 11:1 to 9:1 in 71 making 330hp, right? the vette and the camaro were both rated at 330, even tho the ex manifold were still diffrent

[BurnoutNova]

[QUOTE=Billla;2671473] so I'd have a hard case to make with the NCRS

QUOTE]

well if theres more 67 L88 and L72 cars running around that are " triple crown ncrs top flight bloomington gold certified" than they even produced, you shouldnt have a probleom

[space]

Originally Posted by Billla

CFM = ((CI x RPM)/3456) x VE, if you figure 383 HP then you don't need more than 600 CFM until past 6000 RPM. You'd have to turn it to 8K to need 750 CFM.

There's nothing wrong with the 1406 - if it's not "cutting it" then it's not working, configured or tuned correctly. I agree that the Edelbrock Performers, Holley Street Avenger or Street Demons are the best choices for a daily driver.

A mechanical-secondary carb is a racing carb, not a street carb. You give up driveability and fuel economy for instant acceleration performance - if that's a good trade-off, then cool - otherwise tune what you have.

Interesting thread.. I just purchased a 800 Holley double pumper because I was told by 3 different race shops my hesitation @ WOT was due to my Edelbrock 750 single pump not being able to throw enough fuel. Different jets were experimented with at different timing settings to no avail. Any comments on this?

[Billla]

Originally Posted by space

Interesting thread.. I just purchased a 800 Holley double pumper because I was told by 3 different race shops my hesitation @ WOT was due to my Edelbrock 750 single pump not being able to throw enough fuel. Different jets were experimented with at different timing settings to no avail. Any comments on this?

It's a broad question with no simple answer as every engine is different. How were they determining it was fuel starvation? Was this on the dyno?

If it's sudden WOT (drag racing) then this is more about secondary opening than the pump shot...

[space]

Yeah it was on the dyno. I also switched to a mechanical secondary as it was opening up late. It happened anytime I put it to the floor.

[67chevemall]

The most common "big" carb was the Holley 780 which was a 4150 vacuum secondary carb with a secondary metering block in place of the standard plate - like a 3310 today

Just caught this one...... the carb that came on the engine was exactly that
vacuum sec with a mettering block on the secd's and it had a choke installed.
and it was a 4150.

So maybe I should look at the 3310


hummm?

[70rs/ss]

Originally Posted by Billla

CFM = ((CI x RPM)/3456) x VE, if you figure 383 HP then you don't need more than 600 CFM until past 6000 RPM. You'd have to turn it to 8K to need 750 CFM.

A mechanical-secondary carb is a racing carb, not a street carb. You give up driveability and fuel economy for instant acceleration performance - if that's a good trade-off, then cool - otherwise tune what you have.

This formula is theoretical assuming a set of peramiters, but it is good for a starting point (buy by no means the absolute). As any modified motor will accept more fuel up to a point over the theoretical formulas suggested number. A BIG carb on a nearly stock anything isn't going to work, but a BIG carb on a motor that can handle it is OK. I daily drove a warmed up 350 with a holley 750 double pumper wth no drivability issues for about 5-6 years, heck I even had to have the car emissioned in Tucson. To say that DP are racing appl only is a little too far to the other side of of the dicussion with they are great for a dd 290hp 350 on the other extreme. There is a point in the middle of stock and full on race engines and the double pumper does fine there. An Edel, Carter, Stret Avenger, etc work good and give great drivability and decent MPG but a double pumper will put down more power on a hotter motor at the sacrifice of MPG. Just so nobody thinks I am biased, I own three Edels from 600-850 cfm, as well as an 850 Demon DP, and an 850Holley DP. I use the 750's mostly on hopped up 350-383, and the 850's on my BBC 454-496.

[70rs/ss]

PS Billa, if you want to come off one of those repop LT1 intakes, my 70 RS/SS Camaro would appreciate it!! Mine came with the L48 300hp/350 which is the same block and heads, different rods (not "pink" like the LT1) and the non-solid lift cam, mine has an iron intake with a Q-jet. I am going to say something about the HP #'s from 70 to 71, but no flames, please. There was a compression drop, but the real reason for the drastic "drop" in HP wasn't really a drop at all, GM switched from gross to net, 70 and back was at the flywheel with no accessories, 71 up at the tires in full running order, with accessories. So the drop is there, but it looks huge because it is now at the tires. So in reality the late 90's early 00's Z28 buried even the hottest 69 and 70 Z's number.

[67chevemall]

Well I've been jacked. no prob. I alway figure it out somehow.

http://cgi.ebay.com/ebaymotors/750-H...QQcmdZViewItem


I am liking the looks and price of this one......what do ya think???

[space]

67chev, I'll have my new Holley put on this weekend, my Edelbrock 750 will be for sale 1st of the week if you're interested. It's the kind shown here: http://www.jegs.com/i/Edelbrock/350/...0002/-1/743603

[70rs/ss]

Originally Posted by 67chevemall

Well I've been jacked. no prob. I alway figure it out somehow.

http://cgi.ebay.com/ebaymotors/750-H...QQcmdZViewItem


I am liking the looks and price of this one......what do ya think???

Wasn' jacking just trying to say that the formula is one way of determining your carb size, I would even go so far as to say don't go smaller than the formula, but bigger has its advantages. I have never used an avenger, but hear on here they are great. I like the edelbrocks for a DD and kinds performance carb. Good luck with whatever you decide. BTW Edebrock has a great tech line, and can give you a good guestimate based on elevation, and other factors where to start with rods, power valves and you can fine tune from there.

[70rs/ss]

That one looks good here it is a summit with 411 shipping it might be a better deal? the other is a factory reman'd one. Good luck either way.

HLY-0-3310S Holley Model 4160 Adjustable Float Carburetors
Carburetor, Model 4160, 750 cfm, Square Bore, Manual Choke, 4-Barrel, Vacuum, Dual Inlet, Silver, Each
Today $264.95


HLY-65-3310S Holley Remanufactured Carburetors
Carburetor, Remanufactured, Holley, 750 cfm, 4-Barrel, Square Bore, Vacuum, Dual Inlet, Silver, Each
5/1/08 $235.95

[Billla]

Originally Posted by 70rs/ss

As any modified motor will accept more fuel up to a point over the theoretical formulas suggested number.

To say that DP are racing appl only is a little too far to the other side of of the dicussion

a double pumper will put down more power on a hotter motor at the sacrifice of MPG.

As usual, I find myself on the other side of this discussion. I'll note that I disagree with virtually all of this and move on

[70rs/ss]

Agreed. As a concession, I run both, but the DP is not DD anymore, weekend warrior status now. I have FI and diesel DD's!

[BurnoutNova]

Originally Posted by Billla

As usual, I find myself on the other side of this discussion. I'll note that I disagree with virtually all of this and move on

i'll agree with this...you dont gain any power richening your fuel mixture... so more fuel can hurt you.

a bigger carb doesnt always mean more fuel either, CFM is air, not just the amount of fuel you consume

[BurnoutNova]

Originally Posted by 70rs/ss

I am going to say something about the HP #'s from 70 to 71, but no flames, please. There was a compression drop, but the real reason for the drastic "drop" in HP wasn't really a drop at all, GM switched from gross to net, 70 and back was at the flywheel with no accessories, 71 up at the tires in full running order, with accessories. So the drop is there, but it looks huge because it is now at the tires. So in reality the late 90's early 00's Z28 buried even the hottest 69 and 70 Z's number.

true, the gross vs. net hp diffrences can be debated and argued all day long, but the truth is the 71 LT1 did have less compression, and that alone makes it so that it does make tremendously less power. heck, i bet the '70 motor made more like 330hp at the wheels by the time it was thru the drivetrain, and with the accesories. its only 40 hp anyway.

and about the LS1 camaros smoking the 302 and LT1 Z28's... i personally have been in a restored 71 camaro Z28, with a 70' spec LT1 (just bumped up compression otherwise bone stock) and spanked LS1 camaros time and time again. those things RUN. Mint68 here on the board has the camaro ive been in, belive it or not i think LT1's run better than they were given credit for. and other than headers, its a bone stock car. down to the numbers matching heads/intake/ carb, ect. it even has a stock air cleaner.

maybe his car is just setup right, and just has the right combo of parts, maybe he knows how to drive it? but thats part of the reason why i LOVE old school muscle

[Billla]

Chevy factory ratings were DRASTICALLY understated towards the end of the 60's, and the move from gross to net in '71 had an impact for sure - but the change was much more than 370 to 330 HP.

For example, the L-88 was rated at 430HP in 1969...which was sheer fantasy Part of the intent was to keep buyers from checking the "highest horsepower" box on the order sheet and so was rated 5 HP *below* the L-89 Tri-Power, which was far more streetable as the L-88 was a racing engine, pure and simple.

Probably a little OT, but I used to restore Corvette engines - so I had some history here I'd estimate the 1970 LT-1 at a lot closer to 425 FWHP with headers. My build target is just under 500 with a "secret" solid roller cam and heavily ported heads.

[67chevemall]

Well it is the end of summer and the truck got 0 kms this summer
bummer.
Tearing the whole thing apart now.
Air bags/ wheels/ cab mounts/
NEW CARB....holley avenger 670