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Old 11-01-2008, 02:03 AM
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need help between 2 cams

Ok I posted here early about upgrading my motor in my 1968 firebird. I ended up buying a different motor. Here are the specs Chevy 400 bored .30 over stroker to 418 eagle h beam rods , je pistons , dart 230 heads with 2.08 intake and 1.60. Exhaust 11 to 1 compession , holley intake and. Holley 750 with pro form main body. it needs a cam though I think I have it narrowed down between two and wanted some advice.there both solid flat tappet cams, first is a comp magnum 12-224-4 intake @ .50 248 exhaust@.50 248 lift 525 for both intake and exhaust. Comes on at 2500 rpm to 6500 rpm the second cam is a lunati intake @.50 248 exhaust @ .50 259 lift on intake 525 exhaust lift 534 comes on at 3500 rpm till 7000 rpm this car will have a turbo 350 with 3500 stall convertor and 373 gear but with 25 inch tires.I want a cam that sounds nasty and performs great at the track. Sorry for the long post thanks for all your help

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Old 11-01-2008, 07:22 AM
How fast is fast enough?
 
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those are two pretty different cams, but of the two I would go with the Lunati grind. split cams seem to do better on the 1/4. With those heads that may be a little excessive exhaust duration though.

The split pattern also allows you to add nitrous later if you want- nitrous almost always does better on split cams- though I'm sure someone has one or two examples of it doing ok with a single pattern cam.
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Old 11-01-2008, 04:01 PM
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Are Lunanti good cams vs. comp.
thanks
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Old 11-01-2008, 04:55 PM
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lunati

Joe Lunati has been building cams from the 70's if not earlier. You can't have the best of both worlds, if you drive on the street, the first cam is iffy. Youv'e still got a lot of variables to deal with, carb size, gearing ,(more gear for bigger carb, heavier car, size of tires both height and width, you can't just take a motor and dump it in a car, and expect great things. everything has to blend together. Back in the day, people put the optional z-28 cam in their cars to run on the street with a 750 carb, sounded great but cam didn't come in till 4500 -5ooo rpm and the 750 would dump too much fuel too soon. Getting the picture. if you have a heavy car, a smaller carb will make it run crisper and smoother. Low rpms , your dumping too much raw fuel in the cylinders with the bigger valves. If this is strictly a drag car, and your around 3600 lbs, your going to need a 5:38 gear or better to launch it. hope this helps.
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Old 11-01-2008, 07:20 PM
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so what are you saying for the strip I would be better off with the lunati cam
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Old 11-01-2008, 08:15 PM
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Both of those cams are going to have a pretty rough idle. For the street I'd probably go with the first cam. For the strip I think the lunati will probably get you down the strip a little quicker. Your going to sacrifice a little torque with the Lunati, but if your looking for performance at higher RPMs I think its the one to go with.
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Old 11-02-2008, 08:48 AM
How fast is fast enough?
 
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I would consider either of them streetable... but I'm kind of sick in the head like that

Lunati is a great cam company, many would say better than Crane or Comp.

A 750 Holley may actaully be too small for your car if you plan on using it at the strip, and 4.10 or 4.56 gears would be much more suited to your power range for the 1/4... I hate to actaully say this, but just ignore pretty much everything hemihonker said. Seems like a nice guy but his recomendations seem to be for a highway cruiser on the carb sizing and a 1/8 mile car on the gearing- neither of which is what you have.
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Old 11-02-2008, 03:51 PM
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Well I appreciate everyones advice as this setting up a motor with the right parts and your whole car for that matter is new to me. The gear did seem very deep for the 1/4 but he did make some good points. I think im going to go with the lunati cam. We will see how it ends up running. I imagine what ever one I get I would be happy with both of them.
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Old 11-02-2008, 07:55 PM
How fast is fast enough?
 
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Quote:
Originally Posted by Pontiac68bird
Well I appreciate everyones advice as this setting up a motor with the right parts and your whole car for that matter is new to me. The gear did seem very deep for the 1/4 but he did make some good points. I think im going to go with the lunati cam. We will see how it ends up running. I imagine what ever one I get I would be happy with both of them.

That is an excelletn attitude and outlook. I, and I'm sure the rest of us on here, wish you the best on your hotrod buildup.
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Old 11-02-2008, 09:37 PM
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firebird gears

i guess old school knowledge and experience, don't count. If your not sure, call a local speed shop that actually races a car, and they can help you in the ball park as to your setup. If you want to drive it on the street, your limited to your gearing, which doesn't allow you the use of the engine you have which will slow you at the strip. That's what I was getting at. And I will guarantee you a smaller carb will launch quicker and smoother. All in all,. do what you feel comfotable with , good luck.
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Old 11-03-2008, 07:27 AM
How fast is fast enough?
 
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Quote:
Originally Posted by hemihonker
i guess old school knowledge and experience, don't count. If your not sure, call a local speed shop that actually races a car, and they can help you in the ball park as to your setup. If you want to drive it on the street, your limited to your gearing, which doesn't allow you the use of the engine you have which will slow you at the strip. That's what I was getting at. And I will guarantee you a smaller carb will launch quicker and smoother. All in all,. do what you feel comfotable with , good luck.

A smaller carb will lauch better with a tight stall, but it will also slow him down on the top end. your advice isn't bad for 1/8 mile tracks, but it'll be done before he ever gets to the end of a 1/4 mile.

And anecdotal knowledge does count, but technical knowledge does as well. Neither can be shrugged off.

I wasn't trying to insult you and I really hate saying that anyone is wrong, but to my understanding he was talking about a hot street car set up for the 1/4 mile and your advice would have left him a little short.
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