gears and converter for an L78 cammed big block

[aaronkl84corvett]

what do you all recoomend for minimum converter and gears for a
BBC with the L78 cam, oval ports, iron intake, tuned qjet, manifolds.

i'm not having a ton of "smile" with 3.31s and 2400 converter in a Monte!

Cheers

[L78steve]

454?

[earntaz]

A Monte is pretty heavy -- even with a 454 makin' goobs of torque. Back in the day we ran a 3:91 and they pulled real well ... TAZ :burnout:

[aaronkl84corvett]

yes 454

[MailOrderMotion]

I know this is splitting hairs, but in a 454 that is an LS6 cam.

[luzl78]

I know this is splitting hairs, but in a 454 that is an LS6 cam.

same cam

[WILMASBOYL78]

I would think a 3.55 - 3.73 range with a quality convertor 2600-2800 would do the trick. You might want to check with ATI and give them your specs and possible rear gears and see what they recommend. Another thing to consider is the transmission...is it bone stock? shift kit? performance governor?...

The original L78/LS6 packages had a HD TH400, 6 lug convertor and a special governor that allowed for high rpm shifts...around 6200 rpm.

If the rpm's don't scare you, then 4.10's will really make it jump.

-wilma

[aaronkl84corvett]

yes it is the LS6 Cam..

its an Elgin copy - E905P (if i remember correctly - but the specs are spot on)
i have it degreed in 2advance

i have the old log type manifolds on the car which I'm sure is killing it above 4500 rpm - really don't wanna go with headers, but i'd consider going with the long branch corvette style that I believe will fit.

i have a set of 3.73s for the car - will install them this summer.

converter now is a B&M holeshot 2400 - but it could probably be much happier with a 3000 converter for quick starts - i just don't like that slippery converter feel for a nearly daily driven vehicle.

[earntaz]

I would think a 3.55 - 3.73 range with a quality convertor 2600-2800 would do the trick. You might want to check with ATI and give them your specs and possible rear gears and see what they recommend. Another thing to consider is the transmission...is it bone stock? shift kit? performance governor?...

The original L78/LS6 packages had a HD TH400, 6 lug convertor and a special governor that allowed for high rpm shifts...around 6200 rpm.

If the rpm's don't scare you, then 4.10's will really make it jump.

-wilma

If you put the 4:10 gear in it -- it will really haul donkey ... good luck!! TAZ :scholar:

[aaronkl84corvett]

ok - well do you uys tend to believe that the L78/L72/LS6 etc. cam is the end all be all street-strip cam for a 10:1 BBC?

i'd happily consider a cam swap to something a little more favorable to a heavy car with taller gears - but i'm not interested in a crazy roller setup or one of those super aggressive ramp profile grinds that all the cam companies want to sell

cheers

[luzl78]

A truck torque pulling cam would work great. Eric (vintage muscle parts) can set you up well.

[WILMASBOYL78]

yes it is the LS6 Cam..

its an Elgin copy - E905P (if i remember correctly - but the specs are spot on)
i have it degreed in 2advance

i have the old log type manifolds on the car which I'm sure is killing it above 4500 rpm - really don't wanna go with headers, but i'd consider going with the long branch corvette style that I believe will fit.

i have a set of 3.73s for the car - will install them this summer.

converter now is a B&M holeshot 2400 - but it could probably be much happier with a 3000 converter for quick starts - i just don't like that slippery converter feel for a nearly daily driven vehicle.

You need to consider that the street mechanical cam that Chevy used in the L78/LS6/L72 was designed to be used on engine with cast iron exhaust manifolds. Of course, headers really help...but I'm not sure I agree with the power being killed above 4500 rpm's. There are lots of folks running that cam in various stock class cars that haul the mail quite nicely.

As for your concern about a 'slippery convertor'...you get what you pay for. The B & M stuff is entry level at best [imho]...as I mentioned, call ATI, give them your information and they will get you the right convertor. We have a 3,000 rpm 'Streetmaster' behind a fairly well built big block in a 68 Nova and it performs excellent. Around town or cruising it behaves very well...give it the gas and it does the job!

www.atiracing.com

-wilma

[aaronkl84corvett]

Yes. I just ordered a converter from cliff ruggles. I trust it will be top notch

Power isnt killed at 4500 rpm, but it doesnt feel like the motor easily revs under load at and above that rpm. Could just be that the heavy car x 3.31 gears and restrictive exhaust are holding it back too much.

Once I get the new converter in, ill re-evaluate but ill probably go with 3.73s

If that doesnt really wake it up. Ill consider a slighlty smaller cam more suitable to my combo!

Cheers

[scuncio]

3.31s should pull pretty strong with a decent converter in an A-body. 3.73s will feel snappier but you'll hate them on the freeway.

[RALLY]

Call ATI converter and tell the tech what your combination is for best converter performance. They are good knowledgeable people. Yes the L78/ LS6 cams are the same. I say go with a 4.10 gear for the street. I use one in my street SB Nova, nice gear.

[GreenLS6]

I Extensively test and dyno with the LS6/L78 cam.. with the Oval port heads and Manifolds in a 454 with 10.1 comp and a decent intake. you should have 525ish ft. lbs. of torque. DO NOT ADVANCE that cam in a 454 or it WILL NOT pull past 5000 rpm.
If your repro cam has the 114 lobe separation RETARD 2* ..with the oval ports it will loose No torque but will pull to 6200rpm.. minimal loss to vacuum.
Don't be afraid of the exhaust manifolds - I have made way more power than you think in my Pure Stock motors and pull to 7k + in my L89/396 ... 6800 rpm in my LS6 making North of 550hp with UNPORTED HEADS AND MANIFOLDS.

consider a Yank 11" convertor , they work nicely.

[earntaz]

Good info Tom -- thanks ... TAZ :scholar:

[HawkX66]

3.31s should pull pretty strong with a decent converter in an A-body. 3.73s will feel snappier but you'll hate them on the freeway.
Couldn't agree more. I have 3.31s in my BB 69. Very nice happy medium for the street and highway. I do have an M21 though.

[1971ls6]

Listen to green LS6!

The corvette passenger side manifold is worth something, or the boys would not have brought it up when I showed up at the race with it on. The drivers side is better, but the passenger could not be any worse

[aaronkl84corvett]

I Extensively test and dyno with the LS6/L78 cam.. with the Oval port heads and Manifolds in a 454 with 10.1 comp and a decent intake. you should have 525ish ft. lbs. of torque. DO NOT ADVANCE that cam in a 454 or it WILL NOT pull past 5000 rpm.
If your repro cam has the 114 lobe separation RETARD 2* ..with the oval ports it will loose No torque but will pull to 6200rpm.. minimal loss to vacuum.
Don't be afraid of the exhaust manifolds - I have made way more power than you think in my Pure Stock motors and pull to 7k + in my L89/396 ... 6800 rpm in my LS6 making North of 550hp with UNPORTED HEADS AND MANIFOLDS.

consider a Yank 11" convertor , they work nicely.


i pulled the car apart this weekend - 1) I have a new 9" converter from Cliff Ruggles that has a 3200-3400 stall speed - he swears by em - so thats what I went with.

I also had a Crower 01244 cam waiting to go in - i was worried about the LS6 cam being a bit too much for my engine considering i'm not even 100% certain its 10:1 - i'm guessing a bit closer to 9.5:1 which is probably still ok = i just hate being on the line. The crower is a 290/298, 232-244, 562/571 on 112 - and I have Rhodes lifters for it.

As for an intake, i was running the low profile LS5, and now will be running the aluminum version of it which was used on 427/390hp Corvettes... if nothing else, i'll save the 100lbs :D

when I pulled the timing cover - i checked the LS6 degree at it was indeed advanced 2* so thats right in line with what you said.... but the car just didn't have the "umph" i was hoping for - and i'm certain it wasn't at 500ft/lbs. it would barely break the tires loose flashing the converter at 2400 - barely... you could feel the cam "switch on" right about 3000 rpm but felt flat from about 4800 on up....

fwiw - it was an Elgin E-905p variety - if that makes any difference -

i can knock out a cam swap in a Monte Carlo in about 6 hours - SO, if this Crower is a dud then i'll happily go back to the LS6 - but i think i'd use the Crane or a SpeedPro version as I know they are accurate blueprints- unless i could find an original that isn't junk

will report back soon...

i hope i'm simply not expecting too much from this motor.

also - to be clear - the heads on this are 702 1966 castings and they cc-ed at 94cc.
with the stock 1971 LS5 flattops, and a steel shim head gasket - my math gets me 9.7:1 anyone car to check? stock deck height.

[aaronkl84corvett]

well the Crower 01244 and Rhoads were a bust -
even with the new converter I think the car was quicker/torqier with the 178 cam advanced 2degrees,

back to drawing board!

or at least back to the GM cam

[GreenLS6]

Cant tell if any of these pm replys are getting thru..
just call.. tim 517-605-421 eight