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Discussion Starter #1
I broke in my rebuilt engine a couple of weeks ago. I ran Brad Penn Oil break in oil for my flat tappet cam. Ran it at 2000-2500 for 25 minutes.

The problem I am having is setting the timing. I can't the engine down to 750 rpm. I've set the static timing at 10deg BTDC but I can't get the rpms down. The engine is running at 1100. When I tried to set the timing 5deg BTDC it was way way down on power its like I was starting 3rd gear..it felt like I could walk faster than this car could go. And it way hot too at idel.



I have the choke open. I set 0 tdc by turning the engine over by hand using a stop. I did this a few times.



The only thing I can think of is a vacuum leak. That's my next step. Could be the base of my new carb/intake (both summit brands)? Or maybe the PCV valve is leaking? ...


Any suggestions?,


Thanks,
Dean
 

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So you can't turn the carb idle screw down after setting to 10 BTDC? I guess confused since it sounds like you can set the timing to 10deg but then you should be able to turn down the idle screw on the carb to the RPMs you want. Or is it shutting off on you?
 

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Discussion Starter #3
So you can't turn the carb idle screw down after setting to 10 BTDC? I guess confused since it sounds like you can set the timing to 10deg but then you should be able to turn down the idle screw on the carb to the RPMs you want. Or is it shutting off on you?

Yep the screw its self is completely turned out. Its confusing to me too. That's why I'm scratching my head on this.
 

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Yep the screw its self is completely turned out. Its confusing to me too. That's why I'm scratching my head on this.
That does hint toward a vacuum leak of some kind or something amiss in the new carb. We know nothing about this engine?
 

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When you hook up a vacuum gauge to an intake manifold vacuum source what does it say?

What intake manifold, carburetor and carburetor spacer are you using?
 

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Ditto, what was stated.......are the throttle blades closed when you back out the throttle idle screw all the way? Check your throttle linkage is free.
 

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Discussion Starter #7
Its a 289 rebuilt heads block is .40 over. 9.8 comp. It has a mild/moderate cam -Melling MTF-5. Valve lift is .450 intake/.474 exhaust. 107/117 overlap.


I'm using the spacer that comes with the carb (500). It might be binding I'll have to check. The plugs look good all light brown, the oil pressure is 60 cold/50 hot. But it can't run - its so soft my old six cylinder could walk it,
 

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That spacer is to keep the carb from binding.

Disconnect and cap all your vacuum sources and see if that makes a difference.

If it does, add them back in one at a time.
 

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Discussion Starter #10
:surprise:

I'm ticked. This has been by far the worst build I've been apart of. Nothing is easy with this car. Its always something. for example I pull out today to test drive it and as I'm pulling back to the end of the driveway I see a puddle that wasn't there before and trail of oil...I stop the car and I'm thinking what the H...? I must have knocked the oil line when I was taking out the plugs and can see the line had snapped at the base..ugh..this driveway has more fluid spilled by me in two weeks with this car than in 20 years. What a mess. Asphalt and oil is not a great combination - softens it up. Just another day the life of a mustang owner.
 

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I'm ticked. This has been by far the worst build I've been apart of. Nothing is easy with this car. Its always something. for example I pull out today to test drive it and as I'm pulling back to the end of the driveway I see a puddle that wasn't there before and trail of oil...I stop the car and I'm thinking what the H...? I must have knocked the oil line when I was taking out the plugs and can see the line had snapped at the base..ugh..this driveway has more fluid spilled by me in two weeks with this car than in 20 years. What a mess. Asphalt and oil is not a great combination - softens it up. Just another day the life of a mustang owner.
Feel free to go back in the posts up until last year on my 331 saga. Motor in and out of the car 6 times with as many incompetent machine shops to diagnose improper machining of a Chinese Scat crankshaft. Even when I only wanted only to have the machine shop match the flywheel end of the Scat crankshaft with the original 289 crankshaft that took 2 incompetent machine shops to do that only half-azz right. Many thousands of dollars wasted! I feel your pain!

When I hit the gas at the start of an autocross run it's worth the journey!
 

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Discussion Starter #12
Feel free to go back in the posts up until last year on my 331 saga. Motor in and out of the car 6 times with as many incompetent machine shops to diagnose improper machining of a Chinese Scat crankshaft. Even when I only wanted only to have the machine shop match the flywheel end of the Scat crankshaft with the original 289 crankshaft that took 2 incompetent machine shops to do that only half-azz right. Many thousands of dollars wasted! I feel your pain!

When I hit the gas at the start of an autocross run it's worth the journey!

I did read your story - and it was great that you were able to resolve it. I don't think I would have had the patience. Taking the engine out twice was enough..lol.. I used most of my vacation time working on this car and its an hour away so I don't have the luxury of popping into the garage to check something or fiddle with it. Ugh.
 

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What carb? Some Holley's and Summit have a secondary idle screw. The one on my summit was cracked opened and I could not get the idle down.
 

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The secondary idle screw is always cracked open slightly so that fuel is used from the secondary bowl to keep it from going stale. On Autolite's it's adjusted one turn from first contact with the stop. On Holley's I've seen them state both 1/4 and 1/2 turn from first contact but the transition slot must remain covered.

You said you're using the spacer that came with the carb... do you mean the thick base gasket or is it an actual spacer?
 

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Discussion Starter #17
It's the thick one it came with. I'll have to check the secondary idle screw. This is the first I've heard of it
 

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Discussion Starter #19
Yeh I think I will try a spacer. Thanks
 

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As has been said you probably have a vac leak. However, it looks like your cam has a fairly tight LSA which would leave it with quite a bit of overlap. If so you might not get it to idle at 750 and it might want more initial timing. I would worry more about total timing (initial plus mechanical plus vac) than initial with an aftermarket camshaft. It might idle rich and fairly high. I felt pretty good that I got mine to idle at 950 hot which I arrived at with work with the vac gauge and timing light. I only have a 110 lsa which would have less overlap than yours.
 
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