1965 30-30 versus LT1 cam

[Timothy B.]

Re: 1965 3030 verces LT1 cam

My question is to Michael Frost, if you have a 340hp 63 car why are you using the 30/30 over the 097. With the other related 63 parts why not use the original camshaft.

I would spend my time maximizing the compression ratio with the head gasket/quench distance and keep the engine componits original spec.

That's one reason why these over cammed engines need to idle so high because they have no dynamic compression ratio. Combine that with close ratio and 355-370 gear..

[Joe C.]

Re: 1965 3030 verces LT1 cam

My question is to Michael Frost, if you have a 340hp 63 car why are you using the 30/30 over the 097. With the other related 63 parts why not use the original camshaft.

I would spend my time maximizing the compression ratio with the head gasket/quench distance and keep the engine componits original spec.

That's one reason why these over cammed engines need to idle so high because they have no dynamic compression ratio. Combine that with close ratio and 355-370 gear..

Nope.

It's because of valve overlap, which lowers idle vacuum. This in turn provides a weak signal to the carburetor, which makes air/fuel ratio much too lean, to the point where idle cannot be sustained without stalling unless the speed is increased, which then boosts the vacuum signal, which then pulls in more fuel. It's a classic feedback loop. One way to help overcome idle issues is to use a carburetor with more sensitive booster venturis. The Holley 585 CFM 4150/4160 series carburetors used on the SBC engines from 1964-69(?) employed the weakest booster arrangement possible.....the straight leg booster. Much stronger and receptive to low vacuum signal, is the downleg booster (used on all 750 CFM carburetors) and stronger still is the annular booster, which was once solely used for the "Dominator" (4500) series from Holley, and its clones, but which is now popular with Holley 4150 series in small capacity sizes, like 650 CFM...................

[Joe R.]

Re: 1965 3030 verces LT1 cam

I'm all for better connecting rods and todays better oils but that's for a completely different reason. I don't think that trying to make more HP in these old cars is in any way logical.

Michael,

I'm with Duke on this one. As an engineer, I like the idea of making my engine more powerful, while appearing (and sounding) bone stock. Not everyone just put-puts around the drive in hamburger joint on cruise night. Some of us like to drive them hard on occasion. I know I did, before the engine blew up. I say to each his own!

Joe

[Clem Z.]

Re: 1965 3030 verces LT1 cam

Michael,

I'm with Duke on this one. As an engineer, I like the idea of making my engine more powerful, while appearing (and sounding) bone stock. Not everyone just put-puts around the drive in hamburger joint on cruise night. Some of us like to drive them hard on occasion. I know I did, before the engine blew up. I say to each his own!

Joe

if you want more power use a roller cam as it can be manufactured to give a lot more power with out a loss in drivability and you don't have to worry about and cam lobe wear.

[Stuart F.]

Re: 1965 3030 verces LT1 cam

Well, for me; I have a son with whom I cruise who keeps buying newer and more powerful Vettes. I could take his old 78 P.C. L-82 4 speed's w/o too much trouble (he had 3 different ones), then he got a 96 G.S. w/LT-4 and 6 speed which made me hustle to stay with him, now he has a 08 P.C. w/LS-3 and 6 speed. I can still keep him in sight (he can't run away from me), but I'm dreaming of a new 383 crate motor now. There is only so much an old L-76 can/should be made to do, specially w/stock rods.

I used to have my way with most any newer Vettes w/performance axles (mine is 3.36). Then they came out with the 6 speeds. Now it's foolish to try.

Stu Fox

[Michael H.]

Re: 1965 3030 verces LT1 cam

Michael,

I'm with Duke on this one. As an engineer, I like the idea of making my engine more powerful, while appearing (and sounding) bone stock. Not everyone just put-puts around the drive in hamburger joint on cruise night. Some of us like to drive them hard on occasion. I know I did, before the engine blew up. I say to each his own!

Joe

Joe,

I think you may be missing my point. If you want to hot rod your car, and if you think an LT1 cam increases horsepower, then by all means, go for it. I'm not saying that everyone has to use the correct cam.

But some here feel that they must convince everyone that owns a small block Chevrolet engine that they need an LT1 cam. That's like telling everyone that they should like chocolate instead of vanilla.

Many have come here asking where they can purchase the correct original cam for their restoration project only to be told that they need the LT1 cam instead. That's not what NCRS is all about.

When these cam discussions come up here, it usually winds up sounding like a discussion over at the CF.

I've spent more than a FEW hours with Chevrolet engines on dynos so it's not possible to convince me that an LT1 cam actually produces more HP than the 30-30 cam, but, as I mentioned, that's not the point.

[Duke W.]

Re: 1965 3030 verces LT1 cam

Some want to maximize average torque/power across the rev range just as some want better body fit and paint quality than St. Louis provided. Most restorers want their car better than it was built.

For mechanical lifter small blocks,the best configuration that acheives maximum average torque/power from off idle to 7000+ revs using pump premium and all the OE external components and that can pass Flight judging deduction free and a PV is the LT-1 cam with massaged heads and a maximum true CR of 10.5:1. The slight improvment in average power that the 30-30 cam might offer in the 5500-7000 range is more than offset by the loss of low end torque unless the engine is for a real race car.

The dyno tests are on the Web.

So I recommend the LT-1 cam and head massaging for all mechanical lifter SB restorations and even L-79 if the owner wants more power and revs. I'm still trying to find a vintage racer who will run my system engineered vintage racing configuration, which uses the Rochester FI system and the 30-30 cam retarded four degrees, but so far, I've got no takers.

For a road engine one must consider the full operating range from off idle to peak revs and the bottom end is important because road engines spend most of their time in that range. My requirement is 80 percent of peak torque at no less than 2000, and the LT-1 cam is the best design for this set of requirements.

For a road racing engine the requirement is maximum average power in the upper 30 percent of the rev range with 80 percent of peak torque at the lowest revs that the engine will see on the slowest corner which is usually in the 3000-3500 range. For this applciation the 30-30 cam is the best choice among the OE camshafts.

Duke

[Michael H.]

Re: 1965 3030 verces LT1 cam

Some want to maximize average torque/power across the rev range just as some want better body fit and paint quality than St. Louis provided. Most restorers want their car better than it was built.


Duke

That's true. But we don't tell them that they should make the bodies and paint quality much better than original. We let owners decide for themselves.

[Joe C.]

Re: 1965 3030 verces LT1 cam

Some want to maximize average torque/power across the rev range just as some want better body fit and paint quality than St. Louis provided. Most restorers want their car better than it was built.

For mechanical lifter small blocks,the best configuration that acheives maximum average torque/power from off idle to 7000+ revs using pump premium and all the OE external components and that can pass Flight judging deduction free and a PV is the LT-1 cam with massaged heads and a maximum true CR of 10.5:1. The slight improvment in average power that the 30-30 cam might offer in the 5500-7000 range is more than offset by the loss of low end torque unless the engine is for a real race car.

The dyno tests are on the Web.

So I recommend the LT-1 cam and head massaging for all mechanical lifter SB restorations and even L-79 if the owner wants more power and revs. I'm still trying to find a vintage racer who will run my system engineered vintage racing configuration, which uses the Rochester FI system and the 30-30 cam retarded four degrees, but so far, I've got no takers.

For a road engine one must consider the full operating range from off idle to peak revs and the bottom end is important because road engines spend most of their time in that range. My requirement is 80 percent of peak torque at no less than 2000, and the LT-1 cam is the best design for this set of requirements.

For a road racing engine the requirement is maximum average power in the upper 30 percent of the rev range with 80 percent of peak torque at the lowest revs that the engine will see on the slowest corner which is usually in the 3000-3500 range. For this applciation the 30-30 cam is the best choice among the OE camshafts.

Duke

The Rochester fuel injection system is a poor choice for a "systems engineered" SBC using the 30-30 cam. At about 650 cfm the induction system is weak. A much more potent induction system is the Z28 inlet manifold topped with a 750 cfm carburetor.

Some people seem to think that using the old rule of thumb calc:

Max Carburetor CFM required = engine displacement x maximum RPM x VE

is all that should be considered in a "systems engineered" design, but don't consider the ideal situation, which is to approach, as near as possible, Zero in-hg @ WOT in the intake manifold. The 585 Holley or 650 Fuel Unit is pulling closer to 1-2 in-hg @ WOT.

[Duke W.]

Re: 1965 3030 verces LT1 cam

I don't tell anyone that they should do anything that would result in a judging deduction or I make clear that it might or will result in a NCRS ding of some kind. I do make recommendations based on the end result that the owner is looking for that won't result in judging deductions or PV failure, and the dyno tests, Top Flight and Duntov awards are now on the Web and in the NCRS award files.

Duke

[Joe C.]

Re: 1965 3030 verces LT1 cam

Joe,

I think you may be missing my point. If you want to hot rod your car, and if you think an LT1 cam increases horsepower, then by all means, go for it. I'm not saying that everyone has to use the correct cam.

But some here feel that they must convince everyone that owns a small block Chevrolet engine that they need an LT1 cam. That's like telling everyone that they should like chocolate instead of vanilla.

Many have come here asking where they can purchase the correct original cam for their restoration project only to be told that they need the LT1 cam instead. That's not what NCRS is all about.

When these cam discussions come up here, it usually winds up sounding like a discussion over at the CF.

I've spent more than a FEW hours with Chevrolet engines on dynos so it's not possible to convince me that an LT1 cam actually produces more HP than the 30-30 cam, but, as I mentioned, that's not the point.

Duke never says this!

In Duke's defense, what he says is, is that the LT1 makes for a more "drivable" powerplant because it delivers more torque lower in the rev range. Actually somewhat analogous to the 327/300 horsepower engine. He realizes that the LT1 makes less peak power than the 30-30, and does not deliver the come-on-the-cam kick in the ass that the 30-30 delivers at around 4500RPM. This is why he recommends the 346 and NOT the 178 for his (almost) all-out vintage race engine, with weak Rochester fuel injection induction system.

[Mike R.]

Re: 1965 3030 verces LT1 cam

It could be quite a while before I can get my head around this....




I don't think that trying to make more HP in these old cars is in any way logical.[/quote]

[Duke W.]

Re: 1965 3030 verces LT1 cam

Vintage racing rules vary depending on the sanctioning organization. Some allow the use of modern parts, and doubtless, there is a lot of fudging going on.

My vintage racing engine configuration is truely vintage and would be a good configuration where the rules require vintage parts like the OE rocker system and flat tappet cams. Some organization allow roller cams and roller rockers, but in my mind, that's not vintage.

As far as induction systems go, some organizations do not allow the use of the Z-28/LT-1 manifold. The best that can be used is the Edelbrock Performer, but NOT the Performer RPM manifold, and most rules allow the use of a 750 CFM carb.

The Rochester FI manifold is more efficient than any of the above manifolds and the air meter can be modified to flow about 750 CFM at 1.5" Hg. depression - same as the allowed carb - so FI has the potential to make equal if not more power than an allowable manifold and 750 CFM carb. Another advantage of Rochester FI in vintage racing is that you can run the OE cold air induction system, but such is not allowed with a manifold and carb.

Consider that power increases about one percent with every 10 degree drop in inlet air temperature, then compare ambient air temperature with underhood temperature and there's probably at least a five percent improvement with cold air induction.

A lot of C1 vintage racers use FI, but few C2 vintage racers use FI. This has always disappointed me because I think the '63-'64 FI system, if properly massaged and setup with the legal cold air induction will make more power than allowable carb/manifold combinations - all other things equal.

In search of competitive power, many vintage racers are running very aggressive dynamics cams/gorilla valve springs and this raises hell with the OE valve train, so durabililty is poor and guys spend a lot of time in the paddock fixing broken valve train components and maybe don't get to run all their available track time or even make or finish the race.

A properly built engine to my vintage racing configuration with a design speed of 7500 revs could easily go 25 hours before teardown/inspection with nothing more than minor tuneups including lash checks. At the typical two hours track time per weekend, that's 12 races, which would probably be two to three seasons.

Actually, I'd like to see a very high compression, full race ported heads, FI vintage racing 327 dyno tested with the LT-1, 30-30, and ...140 cams to see what the real differences are. I don't think they would be huge, and if a track has a lot of low speed 3000 rev second gear corners, the LT-1 cam might actually be best.

I've worked with a C1 vintage racer who is running the 2x4 carb system and has actually learned to make it work as far as being responsive with no flat spots or stumble, but the FI cars alway beat him off the corners. He could close the gap down the straights, but it wasn't enough to beat the FI cars to the next corner. The way he had the 2x4 system configured it was a very good 9000 rev induction system, but he only revs his 283 to 7000-7500 and didn't want to shorten the axle and rev higher.

We talked about a different cam, but once I realized how his 2x4 system was configured, I knew it was the reason the engine was a stone below 3500. The first thing I recommended was to reconfigure the 2x4 system and see how it worked. The result was noticeably more grunt coming off the low speed second gear corners with no noticeable loss in top end power, so there was no need to go to a shorter cam.

Duke

[Joe C.]

Re: 1965 3030 verces LT1 cam

Vintage racing rules vary depending on the sanctioning organization. Some allow the use of modern parts, and doubtless, there is a lot of fudging going on.

My vintage racing engine configuration is truely vintage and would be a good configuration where the rules require vintage parts like the OE rocker system and flat tappet cams. Some organization allow roller cams and roller rockers, but in my mind, that's not vintage.

As far as induction systems go, some organizations do not allow the use of the Z-28/LT-1 manifold. The best that can be used is the Edelbrock Performer, but NOT the Performer RPM manifold, and most rules allow the use of a 750 CFM carb.

The Rochester FI manifold is more efficient than any of the above manifolds and the air meter can be modified to flow about 750 CFM at 1.5" Hg. depression, so it has the potential to make equal if not more power than an allowable manifold and 750 CFM carb. Another advantage of Rochester FI in vintage racing is that you can run the OE cold air induction system, but such is not allowed with a manifold and carb.

Consider that power increases about one percent with every 10 degree drop in inlet air temperature, then compare ambient air temperature with underhood temperature and there's probably at least a five percent improvement with cold air induction.

A lot of C1 vintage racers use FI, but few C2 vintage racers use FI. This has always disappointed me because I think the '63-'64 FI system, if properly massaged and setup with the legal cold air induction will make more power than allowable carb/manifold combinations - all other things equal.

In search of competitive power, many vintage racers are running very aggressive dynamics cams/gorilla valve springs and this raises hell with the OE valve train, so durabililty is poor and guys spend a lot of time in the paddock fixing broken valve train components and maybe don't get to run all their available track time or even make or finish the race.

A properly built engine to my vintage racing configuration with a design speed of 7500 revs could easily go 25 hours before teardown/inspection with nothing more than minor tuneups including lash checks. At the typical two hours track time per weekend, that's 12 races, which would probably be two to three seasons.

Actually, I'd like to see a very high compression, full race ported heads, FI vintage racing 327 dyno tested with the LT-1, 30-30, and ...140 cams to see what the real differences are. I don't think they would be huge, and if a track has a lot of low speed 3000 rev second gear corners, the LT-1 cam might actually be best.

I've worked with a C1 vintage racer who is running the 2x4 carb system and has actually learned to make it work as far as being responsive with no flat spots or stumble, but the FI cars alway beat him off the corners. He could close the gap down the straights, but it wasn't enough to beat the FI cars to the next corner. The way he had the 2x4 system configured it was a very good 9000 rev induction system, but he only revs his 283 to 7000-7500 and didn't want to shorten the axle and rev higher.

We talked about a different cam, but once I realized how his 2x4 system was configured, I knew it was the reason the engine was a stone below 3500. The first thing I recommended was to reconfigure the 2x4 system and see how it worked. The result was noticeably more grunt coming off the low speed second gear corners with no noticeable loss in top end power, so there was no need to go to a shorter cam.

Duke

That's because the "fuel" unit works so poorly with the 30-30 cam when it is lashed properly. When set to .030"/.030" per Engineering's "band-aid" fix, it will idle reasonably well with the fuel unit with bumped-up idle speed. This tweak, as you know, diminishes peak power and delivers marginally more low/midrange torque................a "plus" out of the corners, and a "minus" down the straights!

When lashed according to the original design paper, at .025/.025 (which is actually your .023/.023 when the 1.44 rocker ratio is taken into account) the 346 delivers its design horsepower, and performs the way it was designed to. The 097 cam works beautifully with the Rochester system.

Agree about the Rochester cold air induction being a BIG advantage, and when you add to that the fact that certain experts can port them to deliver more than 700 cfm, the even fuel distribution and runner velocity, and instantaneous throttle response in the corners, it's a mighty tempting combination. Maybe the rules limit cold air induction only to those P/Y's that were available with the air box? A well set up, MODERN 4BBL carb will also deliver instantaneous response in tight corners. Add to this the fact that a race 750 cfm unit (without choke horn) is conservatively rated and can be "undercover" ported to deliver in the neighborhood of 850 cfm (provided that the downleg boosters are not swapped out for annulars) wet flow and you have a fairly insurmountable edge going down the straights......................

[Duke W.]

Re: 1965 3030 verces LT1 cam

Idle speed/quality isn't an issue on a vintage racing engine. One just sets the idle speed high enough and rich enough to be stable so you can get from the paddock to the track and back through the paddock without the engine stalling. Something near 1500 is usually okay for most configurations.

With the clearances set at .023" and the ...142 or equivalent valve springs this configuration will make competitive power - at least compared to legal engines where OE rockers and flat tappet cams are required - in the 5500-7500 range (with a valve float speed of 8000+) while still being fairly easy on the OE valve train and acceptable torque at 3000-3500. Torque below 3000 isn't an issue on a vintage racing engine. If revs drop below 3000 in second gear on the slowest corner, the axle ratio is too tall.

Header primary pipes should be nominally 1 7/8" ID, 32-34" long with minimum 3" open side pipes 36-60" long.

At the last Willow Springs race of the season late last year, the 283 vintage racer changed his axle from 4.11 to 3.70 on the suggestion of a retired race driver. It was a dog, and the 4.11 is back in. He runs a 4.56 at Monterey.

Duke