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Old 04-16-2010, 09:40 AM
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350 combo

small block 350 , the engine block was from an 84 corvette, stock crank, rods, pistons. i put on a set of edelbrock performer heads ,are SB-Chevy 302-400Ci Performer RPM Aluminum Cylinder Head
185cc Intake Ports
70cc Combustion Chambers
2.020''/1.600'' Valves
1.460'' Valve Springs, .575'' Max Lift
3/8'' Rocker Studs
Straight Plug, a comp cam 280H cam with .480 .480 int ext lift .050 duration. hydraulic lifters. .100 long push rods, comp cams 3.5 roller rockers, edlebrock performer intake, with dual four barrel 650cfm performer carbs. full up mallory ignition system to include a hyfire6A ignition box, an Ecoil, and a mallory magnetic breakerless distributor, 8.5 mm mallory spark plug wire into accelle short header spark plugs vacum canister with guage for power brakes, and a set of hooker full length race headers 3.5 out let.

does this combination sound good or not this is how im currently running and not faring to well all opinions and suggestions
welcome

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Old 04-16-2010, 09:59 AM
How fast is fast enough?
 
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Needs more compression and that intake is hurting you.
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Old 04-16-2010, 10:25 AM
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more compression as in a higher or lower number? whats wrong with the intake do you figure??
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Old 04-16-2010, 10:39 AM
How fast is fast enough?
 
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Quote:
Originally Posted by UPandComing
more compression as in a higher or lower number? whats wrong with the intake do you figure??
low rise dual 4 bbl intakes are for looks only, not performance. And more compression means a higher number, what pistons are you running? What is your head to piston clearance?
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Old 04-16-2010, 10:43 AM
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What is this motor in?

What is the issue? details........

we are not mind readers
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Old 04-16-2010, 11:08 AM
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if i read this correctly, that you have dual 650 carbs that would be 1300cfm @ WOT then that is way to much induction unless you plan on turing this 350 to 9000+RPM, a single 650 would be just fine
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Old 04-16-2010, 11:13 AM
How fast is fast enough?
 
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Quote:
Originally Posted by my87Z
if i read this correctly, that you have dual 650 carbs that would be 1300cfm @ WOT then that is way to much induction unless you plan on turing this 350 to 9000+RPM, a single 650 would be just fine

That's not the problem. for a dual carb setup on a 350 650's work fine in most caes, the problem is most of the low profiles dual carb intakes suck. If you go to a tunnel ram that's a whole 'nother story but the ones made to fit under your hood just don't deliver.
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Old 04-16-2010, 11:14 AM
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Quote:
Originally Posted by my87Z
if i read this correctly, that you have dual 650 carbs that would be 1300cfm @ WOT then that is way to much induction unless you plan on turing this 350 to 9000+RPM, a single 650 would be just fine

There is a big difference between the carb(s) flow rating and how much air the engine will draw thru it at WOT.
The 650's are not too big if you know how to set them up,and set up the car to take advantage of their power potential.
They have a adjustable secondary air door to aid smooth secondary throttle transition.

They will make more power than single carb.
Is this on the RPM hi rise dual quad manifold or the C-66 low rise manifold?.
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Old 04-16-2010, 11:45 AM
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hey good stuff this is in an 81 trans am, the issue is i cannot seem to get it to run right, it will sit and idle nice instant response if you snap the throttle, but it has no bottom end to get out of the hole and once its warmed up and you shut it off you cant restart it for an hour or until the water temp hits zero otherwise you just sit there cranking till the batt is dead ill try and include a pic, the pistons rods and crank are stock for an 84 vette they pistons are flat with the half moons for the valves with stock 350 heads its was making 9.5:1 now its making 10.5:1
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Last edited by UPandComing; 04-16-2010 at 02:04 PM.
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Old 04-16-2010, 01:39 PM
How fast is fast enough?
 
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Quote:
Originally Posted by UPandComing
hey good stuff this is in an 81 trans am, the issue is i cannot seem to get it to run right, it will sit and idle nice instant response if you snap the throttle, but it has no bottom end to get out of the hole and once its warmed up and you shut it off you cant restart it for an hour or until the water temp hits zero otherwise you just sit there cranking till the batt is dead ill try and include a pic, the pistons rods and crank are stock for an 84 vette they pistons are flat with the half moons for the valves with stock 350 heads its was making 9.5:1 now its making 10.5:1
Its not making 10.5:1, If you have stock dished pistons its not even at 9:1, if they are stock 4VR flat tops then you're probably around 9.2:1. That's not great, but its not so terrible it won't work. What is your initial timing at? What is your total timing at, and when is it all in by?
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Old 04-16-2010, 02:01 PM
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the pistons are flat across the top with the individual indents for the valve faces, there is no dish unless im not following you. from my research on an 84 vette with the 350 its specs came out to 9.5:1 the description that came with my new heads for my combo should be making 10.5:1 i could be wrong, i dont know how to check on that. the timing marks cam to crank are dot to dot. crank dot in the 12o'clock position the cam dot in the 6 o'clock position which put the piston tdc both valves closed i didnt have a degree wheel to degree the cam. with the engine running idle at 700rpms the mark on the balancer was at 0 degrees at 3000rpms up round 32-34 degrees advanced
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Old 04-16-2010, 04:06 PM
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The engine is hard to restart cause its getting too hot from incorrect idle spark advance.

Recurve the distributor to allow 24deg at idle and 34-36deg at full mechanical advance. That means you are going to limit the mech advance travel from 20-22 deg stock ot just 10-12deg. You cannot do this just by changing the advance springs. you must rework the distrbutor.
Yank it out, tear it apart and fix the advance curve stop limit.
The increased idle spark advance will increase the manifold vacuum making your vacuum canister pretty much unnessessary.
Re set the carb idle speed once the distributor is properly recurved.
If the intake manifold plenum heat passages are open, you want to block them off.
Edelbrock carbs tend to get way to hot if the heat riser passages are open.
Wood carb spacers help a lot too. You must keep the carbs cool.
To aid hot restarting install a ignition power interupt switch to allow cranking with the spark disabled, crank it over 1-2-3 then throw the spark and it will fire easily without starter strain.

You need a 3500-3800 rpm stall converter and 4.10 gears in that 81.
make these changes and it will idle nicer. have much better low rpm response and will run cooler overall. It will restart much easier.

The low rise C-66 manifold is not near as good as the newer Performer RPM air gap dual quad intake. If you want serious dual quad power this is the one you want.

Last edited by F-BIRD'88; 04-16-2010 at 04:18 PM.
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Old 04-16-2010, 06:27 PM
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Quote:
Originally Posted by F-BIRD'88
The engine is hard to restart cause its getting too hot from incorrect idle spark advance.

Recurve the distributor to allow 24deg at idle and 34-36deg at full mechanical advance. That means you are going to limit the mech advance travel from 20-22 deg stock ot just 10-12deg. You cannot do this just by changing the advance springs. you must rework the distrbutor.
Yank it out, tear it apart and fix the advance curve stop limit.
The increased idle spark advance will increase the manifold vacuum making your vacuum canister pretty much unnessessary.
Re set the carb idle speed once the distributor is properly recurved.
If the intake manifold plenum heat passages are open, you want to block them off.
Edelbrock carbs tend to get way to hot if the heat riser passages are open.
Wood carb spacers help a lot too. You must keep the carbs cool.
To aid hot restarting install a ignition power interupt switch to allow cranking with the spark disabled, crank it over 1-2-3 then throw the spark and it will fire easily without starter strain.

You need a 3500-3800 rpm stall converter and 4.10 gears in that 81.
make these changes and it will idle nicer. have much better low rpm response and will run cooler overall. It will restart much easier.

The low rise C-66 manifold is not near as good as the newer Performer RPM air gap dual quad intake. If you want serious dual quad power this is the one you want.

awesome response thanks much ill track down a shop to have the distributor reworked and see what happens
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Old 04-16-2010, 10:56 PM
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If the block was from an 84 Corvette and the pistons, crank and rods are all original to that engine then it would have had 9:1 compression. Depending on the heads that originally came on the engine you could have gained or lost compression. If the old heads were 72 cc then you would have picked up a little. But if the original heads were 64cc then you will have lost compression. What were the original heads that were on the engine?

http://www.motorera.com/corvette/1980/vet84.htm
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