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Old 02-05-2005, 06:25 PM
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SBC engine issues HELP

I'm New to the forum and I'm in need of any ideas out there with my 350.
I built a 350, .060 over, Comp .525 lift 300 dur cam, Iron Eagle 230cc - 2.08 intake heads, Air Gap intake, Holley 650 dbl pump, forged .200 domed pistons, 10:1 compression, fuel pressure regulator at 5lbs.

I started and ran the engine for breakin, it ran great and very strong. I needed to replace the 750 with the 650 and also replaced the Mallory ignition with an MSD.
I have TDC by using a manometer (clear tube with fluid plugged into #1) Timing is right on TDC and I tried adjusting each way.

The engine will start but basically just chugs, I pump the gas to get it going but it just spurts out the carb.
I have a new power valve in the carb and the floats are adjusted.
Why is it spurting and why does it just chug?
I set the valves when I assembled the engine, could they need backed off now?

Any help is greatly appreciated. I'm stumped.
JZ

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Old 02-05-2005, 06:30 PM
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good place to start.

Try resetting the valves.
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Old 02-05-2005, 07:43 PM
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You changed both the carb and distributor? Try replacing one then the other.
As it is now do you have spark? does the accelerator pump squirt?
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Old 02-05-2005, 07:48 PM
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too low

your fuel pressure is too low. you have it set at 5psi? you need 5psi at full throttle and you wont get it that way. jump the pressure up to 9 psi and try that.
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Old 02-05-2005, 08:37 PM
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Sounds to me like your timing is way off. The distributor is the only thing you changed that would cause it to backfire through the carb.

Reset the valve lash/preload as well to be sure.

Larry
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Old 02-06-2005, 08:22 AM
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Sounds like the distributor, if you have not touched the valves since assembly and you have changed the carb and distributor I would say it is one of the two. Last time I did an engine swap I removed the distributor and when I put it back in the engine ran just as you discribed. I also was using the same carburator.

To fix it I removed the distributor and the #1 spark plug. I rotated the crank until the #1 cylinder was at TDC. Then I used a screwdriver to turn the oil pump shaft so when I set the distributor down in the rotor was on the #1 cylinder in firing. This is not dead on accurate and will require some adjusting. You could also used this two check to see where you are. If you set the cylinder and just observe where the rotor is relative to the distributor cap it can tell you quickly if your timing is way off.
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Old 02-06-2005, 03:29 PM
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Thanks for all the replies.
I have TDC and the dist is pointing to #1.
Holley float valves are set at approx 7lbs so 9 lbs would blow past the valve. I had this problem before I regulated the pressure down to 5lbs.

I swapped the carb for a 750 Holley that I know is good and it made no difference.
The problem seems to have started after breakin and got progressively worse.

I used a manometer to find true TDC. This is a clear tube filled with ATF and bent in a U shape and fixtured into #1 spark plug hole. When I turned the crank by hand the compression stroke of #1 cylinder pushes the fluid up the U. When it stops moving up you have TDC.
Thing is, when I stop turning the crank the fluid drops back down to level. This seems to me to mean the cylinder isn't holding pressure "leak down".
I believe this is the valves being too tight.

Could the valves cause this problem as I described it?
Thanks so much for your help.
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Old 02-06-2005, 04:41 PM
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As mentioned above, Reset the valve lash.
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Old 02-06-2005, 06:48 PM
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I'll do that this week and repost the results.
Thanks guys.
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Old 02-07-2005, 01:19 AM
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Good luck!
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Old 02-07-2005, 11:53 AM
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The nexxt thread will start with,

How do I get 85 cc of ATF outa the cylinder that hydro locked?
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Old 02-07-2005, 12:09 PM
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Re: SBC engine issues HELP

Quote:
Originally posted by viperjesse
I'm New to the forum and I'm in need of any ideas out there with my 350.
I built a 350, .060 over, Comp .525 lift 300 dur cam, Iron Eagle 230cc - 2.08 intake heads, Air Gap intake, Holley 650 dbl pump, forged .200 domed pistons, 10:1 compression, fuel pressure regulator at 5lbs.

I started and ran the engine for breakin, it ran great and very strong. I needed to replace the 750 with the 650 and also replaced the Mallory ignition with an MSD.
I have TDC by using a manometer (clear tube with fluid plugged into #1) Timing is right on TDC and I tried adjusting each way.

The engine will start but basically just chugs, I pump the gas to get it going but it just spurts out the carb.
I have a new power valve in the carb and the floats are adjusted.
Why is it spurting and why does it just chug?
I set the valves when I assembled the engine, could they need backed off now?

Any help is greatly appreciated. I'm stumped.
JZ
You should always reset your valves after break-in, but I don't think that's your problem. You ran it and it started fine during break-in, THEN you changed ignition and carb. That tells me one of those two caused the problem.

I also think fuel pressure has nothing to do with it. If you're running low pressure, you'll see the problems after you get the car going, not when you're at idle or just above.

Your issue is timing, you're probably at least 10 degrees too far advanced. You changed your distributor and the new one is simply too far ahead. I would also look for a vacuum leak, particularly around your new carb install. If you change stuff, then you have problems, 99% of the time the problem is with the stuff you changed.

K
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Old 02-14-2005, 10:33 AM
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Well I think I found the culprit. I disassembled the intake with care not to disturb the gasket as much as possible.
I had antifreeze leaking into the #2 cylinder and probably the #1 also.
When I assembled the engine last fall and installed the intake I applied silicone around the water ports on the head, put the gasket on. Tha tube was empty and I couldn't find my new tube so I had to hitail it to the auto parts store for more silicone.

I got back and finished the assembly. The silicone musta set up a bit too much and when I removed the intake it was pretty evident that the, too thick silicone had failed and started seaping through to the intake port.

This explains why it ran great at first, it was still sealed, and got progressively worse as the leak appeared and then gradually got worse.

I should be ready to run and tune this weekend and I'm sure it will scream again.
Thanks for all your ideas.
JZ
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Old 02-14-2005, 03:05 PM
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In my experience, the only place to use silicone on an intake is at the corners of the intake gasket and the end seals. Anywhere else on the intake gasket is asking for trouble.
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Old 02-14-2005, 06:14 PM
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Quote:
Originally posted by 1ownerT
In my experience, the only place to use silicone on an intake is at the corners of the intake gasket and the end seals. Anywhere else on the intake gasket is asking for trouble.

Edlebrock recommends using it around the water ports for aluminum manifolds.
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