Chevy race engine problems

[canned_civic00]

Ok here is my setup:
350 sbc .060 overbore
summit cam hydraulic Duration 292/ 302, Lift .488/ .510,
1.5 roller rockers
Speed pro forged flat tops (4 eyebrow)
Double hump heads (stainless 202 valves, screw in studs port matched)
Victor Jr intake manifold (port matched)
Forged pushrods
Stock valve springs
Hei distributor with ACCEL super coil
hig flow water pump and oil pump
650 holley double pumper
2 inch spacer
accel thundersport wires

My problem is from a dead stop, if you floor it it will stutter and stammer. If you let back off the gas it will stay running but if you keep it floored it will go dead. After you get started you can put it to the floor and not have any problems. The timing is perfect no question. What i thought it may be is my ignition. HEI uses a vacuum advance and with this cam it has a lack of vacuum, therefore not advancing it enough to take off. Thats the only thing i can come up with. If anyone else has any input please post cuz i need this thing running right.

[Jet-Lee]

how're your wires and plugs? mixture good? maybe manually advance your timing a little? not enough to make a big difference normally, but enough keep it running good on take-off.

['Cuda66]

I had the same problem in the Barracuda a few years ago. My solution was higher octane gas and a small bump in the timing. Now it launches very hard.

[Bad Asp]

Ditch the Holley and try an Edelbrock. I think you're pushing too much fuel with the DP. If you must keep the Holley (yes DP are kick ass when TUNED correctly) try a few things.

Is this a new carb, rebuilt, or just plain used?

First check the fuel level in the bowls. There should be a small "sight" plug on the side of the carb remove it. If fuel comes out level is too high, lower fuel level by adjusting the top nut/set screw (it's been a while and I'm guessing here) the fuel level should be at the bottom of the sight plug if you rock the car a fuel should only dribble out of the plug hole.

Next check the accelerator pump clearance with a feeler guage go to the Holley web site for proper adjustment clearance.

You may have a blown power valve which older Holleys are notorious about blowing if your engine back fires. Don't even ask me how to rebuild a carb I would just trash the Holley (or sell it to me if you want to sell?) and go with an Edelbrock 750cfm you cannot beat them out of the box.

I'd consider removing the 2" spacer too just to see how the engine reacts.

IMO
I also see you're running a Victor Jr. intake, pretty healthy intake for the street, I tend to stay away from open plenum intakes and go with dual plane, just my preferece.


What is this engine in and what are your goals? Drag racing, hot street car etc? Just curious.

Hope some of the info helps.

['Cuda66]

Originally posted by Bad Asp@Jan 16 2006, 01:36 PM
IMO
I also see you're running a Victor Jr. intake, pretty healthy intake for the street, I tend to stay away from open plenum intakes and go with dual plane, just my preferece.
Yes, dual plane for the street.

[Brandon R]

sounds like a lean condition or a combination of lots of things to me. I'd try adjusting the accel. pump and check the float levels.
Set the timing at about 15-10 initial. I like as much as it will take and still be able to start while hot.

Also you never mentioned what kind of car (big n heavy?) or what gear your running. It could be that you need to get vaccum sec.

['Cuda66]

Originally posted by DuBBeD00L@Jan 16 2006, 09:40 PM
Also you never mentioned what kind of car (big n heavy?) or what gear your running. It could be that you need to get vaccum sec.
Thats right, I forgot I also changed to a softer spring for the vaccum secondaries.

[StreetLethalCamaro]

While this might not have to do with your problems, i'd seriously consider getting some aftermarket springs with that big of a cam. I have a comp cams xtreme energy 268 in my firebird. (224/224 @ .50 .477/.480 lift). I broke 2 valve springs before i swapped them (I thought the first one was just a weak spring). I got lucky. You don't want to be spinning 6 grand and drop a valve.


EDIT: Also, i'd post on a few different boards besides this one if you haven't already. This board doesn't have many people that run SBCs.

[Bad Asp]

Thats right, I forgot I also changed to a softer spring for the vaccum secondaries.

It's DP so it doesn't have vac secondary springs ;)

Double hump heads (stainless 202 valves, screw in studs port matched)


I hope he already has new valve springs on those heads, but good sugguestion if they are older heads!!!

EDIT: Also, i'd post on a few different boards besides this one if you haven't already. This board doesn't have many people that run SBCs.

Ditto.

Canned Civic, Can we hear back from you to see if any of this advice works and if not, what did, or what else have you tried?

[SmokeyTheBear]

def. sounds like an ignition problem. check the disty, plugs, wires, coil, and your HEI thing (idk a lot about SBCs) my probe had this and it was a bad internal coil. id def. check out all your ignition stuff.

[StreetLethalCamaro]

Originally posted by Bad Asp@Jan 17 2006, 08:13 AM


Double hump heads (stainless 202 valves, screw in studs port matched)


I hope he already has new valve springs on those heads, but good sugguestion if they are older heads!!!


Yeah, he said he had stock valve springs, which aren't a good idea with that big of a cam.

[badco]

i just read this, i build and dyno motors for a living.
.
first, your intake is too big for the cam your running, so the spacer just makes it worse. if you could, trade the victor jr. for a performer rpm or a rpm air gap intake.

second, find someone that has a advance timing light and set you TOTAL timing at about 2500 rpm.

third, change the acc. pump cam on the rear bbls, maybe even the sqirters.

your stumble is probly because of the fuel drop it has for such a small cam. the vic jr is from 3500-8000 rpm then you add the 2inch spacer and it raises it at least 1000 rpm, so now your intake is 4500- 9000 rpm! from what you listed, you motor would quit pulling at 6500 or less.

that summit cam is also junk, they are not good cams at all, if you want it to pull good, and want to stay with a hyd cam, keep it below .500 lift.

another thing that comes into play is the converter, what do you have in it?

[canned_civic00]

The motor is in a 72 chevy pickup. it has a 2500 stall, and sadley 3.08 gears. havent had a chance to try yalls advice out due to its in the process of getting the trans rebuilt

[Brandon R]

Too much cam Too much intake, not enough converter and gear. And probably too much carb(dp vs. vs)

[canned_civic00]

Well its only a 650 carb i figured that was pretty small. i have seem them run on stock motors with no problems.

[badco]

i think the carb is fine. but everything else is a mismatch

[BDP]

Thats exactly how my 350 .30 did when timing was at 7deg When it was adwanced to 35 or 40 deg is the only time it would run.

It was the first 350 I built and all I did was put it together, my timing was right and it was the second and third time as well. I had #1 so far against the firewall it was prolly pointing to the passenger. But I could street race and shoot flames all day with that setup, change it back to 15, 10 or 7 and it just shudders and spurts.

I parked it and figured I'd finger it out later, I already had a race-built 468 in my 4x4 and my turby talon, didnt really care about a baby 350 at the time. Just glad Its still around now.

[Brandon R]

Your gonna be hard pressed to get a double pumper to work good out of the hole with that big of a cam in a truck with a tight converter and 3.08 gears.

just my .02!

[canned_civic00]

Well i do plan to get some 3:73 gears soon