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Old 11-04-2008, 06:43 PM
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Here's What I have. Need Help with Rest

Ok guys I know you are all probably watching the election results but I need help with my decision. Here is what I have to work with. Please make suggestions with what I have because it is all I got for now.

1989 Chevy S10 (inside stripped to lessen weight)
No factory glass, all lexan and plexiglass
Tubbed & Narrowed w/ Frame boxed
9" Narrowed Rear w/456 gears & Auburn Full Spool
33x16x15 Hoosier Slicks
BBC 402 (numbers say it came in a 72 Camaro)
781 oval port heads
Offy Tunnel Ram w/ (2) 600 Edelbrock Carbs
TH400 Tranny w/Transbrake

I do not know much about the motor other than it does run fine. As far as the cam specs, that is unknown too. I have to assume the motor and heads are stock because I can't afford to tear it down right now to see. I am just trying to get back to the track by next season. My question is, what would be the best cam & stall converter for this setup? I am to the point of wanting to install the tranny to get the driveline complete but I don't want to put too big a stall in nor too small a stall. My "guess" would be a 3000 - 3500 stall. What do you all think. I would like a good lopey idle with the cam. All help would be appreciated. Thanks
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  #2 (permalink)  
Old 11-05-2008, 03:59 PM
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Quote:
Originally Posted by S10 Racer
Ok guys I know you are all probably watching the election results but I need help with my decision. Here is what I have to work with. Please make suggestions with what I have because it is all I got for now.

1989 Chevy S10 (inside stripped to lessen weight)
No factory glass, all lexan and plexiglass
Tubbed & Narrowed w/ Frame boxed
9" Narrowed Rear w/456 gears & Auburn Full Spool
33x16x15 Hoosier Slicks
BBC 402 (numbers say it came in a 72 Camaro)
781 oval port heads
Offy Tunnel Ram w/ (2) 600 Edelbrock Carbs
TH400 Tranny w/Transbrake

I do not know much about the motor other than it does run fine. As far as the cam specs, that is unknown too. I have to assume the motor and heads are stock because I can't afford to tear it down right now to see. I am just trying to get back to the track by next season. My question is, what would be the best cam & stall converter for this setup? I am to the point of wanting to install the tranny to get the driveline complete but I don't want to put too big a stall in nor too small a stall. My "guess" would be a 3000 - 3500 stall. What do you all think. I would like a good lopey idle with the cam. All help would be appreciated. Thanks
Can someone help me here?
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Old 11-05-2008, 04:24 PM
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I don't know much about BBCs, but maybe can help a bit.

Do you know what your compression ratio is?

I would start looking at cams with at least 230 degrees of duration at .050, maybe up to the mid 240s. If your compression ratio is low I think a cam on a 108 LSA could help.

Call a few cam companies they know some stuff!
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Old 11-05-2008, 09:16 PM
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If you have "stock " 781 heads they will need modification and valve spring up grades to handle any kind of valve lift that a worthwhole racing BBC deserves.
If the motor has the stock 1972 compression ratio you are very limited to cam duration. Big cams don't work with low compression.
The tunnel ram needs a fairly big cam to work. If you want it to actually make power.
So if you expect it to go fast, you cannot afford not to tear it down and set up the heads and cr properly to use a bracket racing cam. Bone Stock #781 heads valve springs won't handle more than about .440 lift and will not work at high rpm.
This is a situation where you are best to leave it in the garage until you are able to do it right.
I would use no less than a 10" "3500 stall" converter.
You want 10:1+ compression. 1972 402 stock is 8:1.
With 10:1 and a 3500 stall and the right valvetrain a Comp cams 294S magnum cam # 11-219-4 would be good. Requires new Hi lift long slot (or roller) rockers, valve guide, retainer clearancing, new valve springs, retainers etc.
Does not work with a stock valvetrain. Won't work with low compression.
The only way to determine the real cr is to take the heads off and measure what you got. The only way to determine the valvetrain and max lift limit of what you got is to dissassemble it and look for yourself. Gaskets are cheap compared to bent valves and smashed pistons
There is no good short cut (with a decent outcome) with this combo.
But when done right the first time, it will make very good power.
You can do it right now or do it over after you bend all the push rods and valves. (stock valvetrain)
Get a paper route and get the money to do it right. racing costs money, get used to it.

You can look up these cams specs online to get an idea of what that motor/combo will want for a camshaft.
Comp #11-604-5 , 11-219-4 11-679-5
Isky #396255
Lunati Voodoo #60242 or #60243
Crane # 134691 #134261
These are all solid flat tappet cams. They all require specific matching valvetrain and cylinder head machining.
Thes are about the largest cams that will/should fit as far as valve to piston clearance is concerned on a typical BBC with stock or typical aftermarket pistons.
Anything larger will most likely require piston valve relief notching.
valve to piston clearance must be checked before you fire it up reguardless.
Don't waste your time with a hyd cam on this one.
The 781 heads will need some porting for best results.
The stock valvetrain is not compatable with any kind of real performance camshaft. If you attempt to mickey mouse it, it will just cost you more.
From the looks of the picture, you're a long way to being track ready so......

Last edited by F-BIRD'88; 11-05-2008 at 10:08 PM.
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Old 11-05-2008, 09:21 PM
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because of your limited compression and lack of rear end traction I would go with a 2500 stall, it'll help keep the tires planted on the launch.
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Old 11-05-2008, 10:03 PM
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You should really look for some closed chamber large oval port heads. Using 781 heads on a 402 is almost impossible to make decent compression without having to use mega dome pistons.
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Old 11-05-2008, 10:20 PM
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Quote:
Originally Posted by baddbob
You should really look for some closed chamber large oval port heads. Using 781 heads on a 402 is almost impossible to make decent compression without having to use mega dome pistons.
Changing the pistons is the cheaper solution. If this motor has stock 1972 pistons, then even a closed chamber head will not get the cr up high enough.

This is the piston you would need
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