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Old 07-28-2009, 04:18 PM
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Engine break-in

Just did the cam break-in on my 350sbc. Have some issues as far as a couple header tubes glowing and some not (timing is nuts on with advance plugged). Carb was transferred over from a running car (may need adjusted, not sure) but I would imagine it's probably a vacuum leak causing it.

The main thing I was wondering though, is during the 20 min break-in in the 2200-2500 range, the engine sucked down nearly 2 gallons of fuel. Is that normal for a break-in?

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Old 07-28-2009, 05:13 PM
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break in

Where was the timing set???
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Old 07-28-2009, 09:29 PM
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Timing was set to 35/36 (with vacuum advance plugged).
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Old 07-29-2009, 04:50 AM
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engine

I assume that 36 degrees was set @2200/2500rpms??

2 gals is a bit much. I have a 2 gal tank on my test stand and I get 1 and a half engines minimum out of a fill up.

Not sure what type of a carb is on your engine but holleys usually start pull-over around 2200rpms or so. If that was the case with your carb then that might explane the excessive fuel that was used. How close to 2 gal do you think you are???

Pull the dip stick and smell it and let me know if it has a fuel odor.

Keith
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Old 07-29-2009, 01:18 PM
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Timing was set at the 2200/2500rpm range.

Carb is an edelbrock 750, electric choke not hooked up and wired open.

Oil has a faint fuel odor. Mostly just smells like oil though.

Fuel used was probably close to 1 3/4 gal. It was a 2 gallon tank, not quite full; now not quite empty.
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Old 07-29-2009, 02:50 PM
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It`s not uncommon for headers to glow during break in due to no air flow around them. Some place a fan in front of the engine to keep the air moving.
If it continues to be a problem and you suspect the carb there`s a easy check by using only the accelerator pump, give the engine many good shots of fuel, if the glowing gets better the engine is too lean. If the glowing gets worse it`s too rich.
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Old 07-29-2009, 07:16 PM
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I had placed 2 electric fans on the outside of the radiator pushing.

My main concern still is why it used so much fuel.
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Old 07-29-2009, 07:39 PM
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Quote:
Originally Posted by JCS1969
My main concern still is why it used so much fuel.
I don't know the answer, but I do enjoy crunching numbers.
We know that an internal combustion carbureted motor will use fuel at the rate of 0.5 lbs per brake horsepower hour.

Let's imagine that you ran the motor for 1/2 hour and that the motor consumed 40 hp to sustain itself. 40 times 0.5 times 1/2 hour would result in using 10 lbs of gasoline. If we assume the gasoline you used weighs 6 lbs per gallon, then 10 divided by 6 would show us that you used 1.67 gallons.
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Old 07-29-2009, 07:44 PM
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I'm not much of a numbers guy myself, but what you've presented makes perfect sense to me.

I just never imagined that my engine would consume that much fuel in that little time. At least not this mild 350.
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Old 07-29-2009, 08:51 PM
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The pusher fans will have no effect on the headers with the hood open. When your going down the road the air flow from moving cools the headers, sitting still, nothing is cooling them. The hot air being pushed off the radiator immediantly rises as heat does and with the hood open up it goes. I was referring to a stand up, home or shop use fan to give the headers a direct blast of moving air. With the hood closed at a stand still they might help some, but it`s recommended to use a puller fan instead of pushers.
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Old 07-31-2009, 02:08 AM
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Drained the oil today and inspected it. Looked good to me. Could definitely tell it had alot of microscopic particles but nothing out of the ordinary.

I got it timed @ 12 with the vacuum advance plugged off with engine at idle. Hooked up the vac. advance, revved til it quit advancing and checked timing. Total is 45. Guess I need to change 1 spring in the distributor and check again...Correct?
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Old 07-31-2009, 06:47 AM
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No. Set the timing without the vac to whatever figure you desire so that it is all in by 2800 to 3k rpm. Use an adjustable vac can or an OEM can that only has about 8* of advance. Plug it to man vac and leave it.

On your glowing headers: Where do you have the power brakes and the PCV connected? If your pcv is connected to the manifold be sure you're getting vacuum from all the runners and not just two or three. Best bet is at the base of the carb.
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Old 07-31-2009, 05:38 PM
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I did time it initially with the vacuum unhooked. I set it at 12, hooked up vacuum, ran to 3k rpm and it quit advancing at 45. I thought it shouldn't advance past 32-36 and if it did then you needed to replace one of the springs for the mech. advance with a stiffer one?
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Old 07-31-2009, 09:17 PM
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You want 36 without the vac. can. 45 with the vac can is fine.
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Old 08-01-2009, 02:46 PM
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What Greg said. Running it without vac advance will make it run hotter at cruise, and too low advance with vac advance will make it sluggish power wise. When I did mine it landed around 45 degrees around 3000 with vac advance. I test drove it, since it`s quiet I could hear detonation. It didn`t detonate and ran great so I left it like that until I took the engine out years later.
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