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Old 06-30-2012, 09:06 AM
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help with 385 sbc

Hello everyone this is my first time posting on the forum but have read many educating threads i recently built a 385 for my 88 camaro and have been through a few issues but recently it has been a bear to deal with i can't seem to find the perfect tune here is a brief description of what i have

385 sbc 350 bored .40 over .200 speed pro dome pistons w/ moly rings
Lunati bare bones cam & lifters lift.465/.488 duration @ .050 .224/234 lobe seperation 112
hardened .100 over 5/16 pushrods
pro comp 7000 series distributor
pro comp pc-91 coil
pro comp 10.2 mm spark plug wires
pro comp fuel pressure regulator set at 6lbs
Ac delco R45ts spark plugs gaped at 30
summit racing headers 1 1/2" primaries 2 1/2" collectors 3" piped out the back
M55 standard volume oil pump w/ 7qt oil pan
edelbrock performer 1407 700cfm carb
edelbrock torker ll intake manifold
882 heads
eagle 3.75 2 piece rear stroker crank
5.7 forged i beam bushed rods
5 peed borg warner w/c trans
borg warner 9 bolt rearend not sure of gears

now on to the issues when i put a vacuum gauge on the carb i get 10hg around 750rpm around 12hg at 1000rpm when i drive up the road at cruise it gets a jerking or jumping when at wot it's cutting out changed plugs this morning and all were carbon covered wondering if my carb is to big or if i have the idle mixture screws are out to far just really looking for some new ideas and other points of view thanks for evryones time and help

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Old 06-30-2012, 09:08 AM
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forgot to post timing is at 14 Btdc

Last edited by 88camaro385; 06-30-2012 at 09:27 AM.
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Old 06-30-2012, 09:29 AM
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Assuming specs not shown, I estimate your c.r. at 12.6, high for a pump gas motor, is the motor detonating? What's your cruise rpm and speed? Did you adjust your idle mix with a vacuum gauge?
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Old 06-30-2012, 10:52 AM
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heads are 76cc chambers the pistons list 11.1 c.r. with these heads i recently switched from a edelbrock performer 600cfm to the 700cfm i don't have very much experience useing the vacuum gauge to tune i run 93 pump gas and it ran pretty good with 600 but felt like it was starving for fuel in the upper rpm range theres not really any ping or detonation i get the highest idle with about a 1/2 turn out on the idle mixture screws
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Old 06-30-2012, 11:10 AM
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Not to beat a dead horse, but have you checked the Pro Comp distributor and coil to make sure they're doing the job? Haven't had good luck with that distributor myself.
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Old 06-30-2012, 11:16 AM
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yeah i'm getting good spark have checked every wire with a timing light to be sure and when i unhook the coil wire and hold it away from the body it can jump to about a inch or so away i have checked and rechecked the timing to be sure it's holding time
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Old 06-30-2012, 11:22 AM
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also the engine will rev up fine and holds idle ok in the driveway but as i stated when driven on the road it jerk and jumps at cruise and i rechecked the plugs after i replaced them this morning and they are already getting a carbon look
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Old 06-30-2012, 02:01 PM
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well i think i'm going to switch the 1407 750cfm back out for my 1406 600cfm and recalibrate to a 1405 any suggestions greatly appreciated thanks all
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Old 07-01-2012, 01:38 PM
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FWIW
As far as the "jumping/jerking" it could be too much vacuum advance. For a quick check, disconnet the distributor vacuum advance hose from the carb, and plug the fitting on the carb. Give it a test drive and see if the jerking/jumping is gone. If it is you might look into limiting the total vacuum advance with a plate(crane cams pn 99619-1) and/or changing the advance rate with an adjustable vac. advance can(not familiar with that distributor, so I can't give you a pn).
If the "jerking" dosen't stop it could be pre-ignition(trying to turn the engine backwards), and needs imediate attention.
You may have too much total timing? With 14* initial and say 24* mechanical(typical) you have 38* total(don't count vacuum adv. at WOT) which is probbaly too much IMO. You should look into mechanical adv. limiting bushings to decrease the mechanical adv by about 10* for a starting point.
Then increase the initial timing a little at a time until you hear detonation while accelerating from low rpm in high gear. Search around the web for custom ignition advance rates/amounts and fine tune the ignition before you mess with the carb.
Then again with 11:1 you may have to run racing fuel(100+ octane) to keep it from detonating.
If I were you I'd open up the plug gap to at least 0.035".
ssmonty
PS I would have said something sooner but I couldn't log-in. Also forgive the spelling as it seems there is no longer a spell checker?
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Old 07-01-2012, 02:48 PM
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recurve the distributor for 24deg inital base at idle
and 34-36deg at max mech advance.
limit the mechanical advance travel stop to 10deg.

24 at idle 10deg advance curve ='s 34 to 36deg at max mech advance.
not that hard.

reinstall the stock default jetting in the 750carb and replace the power step springs with a 3" or 4" rated springs.
fuel pressure should be 5 psi at idle.

The 750cfm carb is not too big.

Ditch that intake manifold at first opportunity
a performer RPM dual plane is way better in every respect including
drivability and max power output.

The 882 heads are about the crappiest lame *** head you can use.
As long as you are using these heads you will be down 80-120 hp from everyone else.
What the point of building a stroker motor only to cripple it with the worst SBC head known to man.?

Use a AC delco R42T or Champion RV8c spark plug gap .035"
in those crappy heads.

Jumping jerking at cruise. ignition fault, bad engine ground, carb flooding, fouled spark plugs, excessive vacuum advance and or distributor cap rotor
phasing out of wack.

high rpm starvation ='s low fuel system flow. possible weak valve springs too.

You do not need a fuel pressure regulator at all when you use the right fuel pump.
mechanical pump with not rmore than 6psi pressure at idle
or Carter electric pump #p4070 ( no regulator is required) 3/8" fuel line and a simple $10 3/8" in out paper element fuel filter
is all you need for this motor.

your chinesium regulator is probabily restricting fuel flow at WOT and or your fuel pump fuel lines-tank pick up tube are restrictive

Last edited by F-BIRD'88; 07-01-2012 at 03:02 PM.
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Old 07-02-2012, 07:58 PM
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Yea I already planned to ditch the intake for a rpm I don't have bottomless pockets kind of limited to what I can spend what would you suggest for a cost efficent set of heads preferably something I can continue to run 93 pump gas with to keep street drivability thanks

Last edited by 88camaro385; 07-02-2012 at 08:22 PM.
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Old 07-02-2012, 10:47 PM
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To be perfectly honest you would have been much better off to have spent the money you dropped on the stroker kit to get a decent set of cylinder heads. Your biggest issue is going to be getting a set of heads that will keep your compression in pump gas range with those pistons. As of right now, you are on the ragged edge of pump gas with pop ups and iron heads. A newer, more efficient combustion chamber shape and flat tops would have been a little more forgiving than pop ups with 882's. That said, Jegs has some aluminum cylinder heads in your choice of runner volume and combustion chamber size for 550 apiece. Vortec heads aren't an option given your pistons, as they would definitely put your way over pump gas compression and would likely have P2V clearance issues. Look around on CL for some decent heads, perhaps for cheap. Otherwise, save up your nickels and dimes and shell out for a decent set to match what you already have.
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Old 07-04-2012, 09:26 PM
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385 small block

I saw these Dart heads at: Dart 11121111P Dart SB-Chevy Pro 1 Aluminum Heads I don't know all you did when rebuilding. But one thing to consider with those domed pistons is your quench (the measurement from the top of the piston to bottom of head). Do not measure dome. This will help with running pump gas. If your block has not been decked most likely your piston will be .020-.025 down in the hole + compress gasket thickness. You will need to be around .040. You could always have a machine shop machine the piston domes down for the head cc you buy.

Last edited by cdminter59; 07-04-2012 at 09:27 PM. Reason: correction
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Old 07-05-2012, 10:26 PM
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I switched back to the edelbrock 1406 today after rebuilding and recalibrating to 1405 and cleaned the plugs took it out and running pretty good burning the tires from a roll in 1st through most of second will drive it as is for now but will be using vacation time to buy a set of dart 72cc heads talked to my machine guy he said that the 882s were closer to 74cc than 76cc and that a good flowing 72cc should work fine since the 882s are working with 93 pump gas
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Old 07-09-2012, 11:13 AM
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Well i'm looking at different heads and wondering if 235 intake runner 2.08/1.6 valve heads would be good or would I be better to use a smaller intake runner head thanks all
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