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Tuning Troubles on Rebuilt 289

1232 Views 29 Replies 12 Participants Last post by  D10E
I've got an A-code 289 that was taken from a 67 mustang that I rebuilt and installed recently. The engine had clearly been redone before as it was already .30 overbore and had forged .30 over pistons to match. The cylinder bores were in great shape (no excessive taper or wear) and I just quickly cleaned the bores with a 120 grit ball hone. The cam bearings were replaced at my local machine shop and my main bearings were installed and measured for oil clearance. I'm using the factory ford heads that are ported and polished with pinned rocker studs. I'm using a comp XE 262H with the 351w firing order and Trick Flow TFS-16942-16 valve springs. The ignition resistor wire has been bypassed for my 12v ready-to-run electronic distributor. Finally, it's topped off with a Weiand Street Warrior intake and 600cfm Edelbrock AVS2 carburetor.

I have run the flat-tappet cam break-in process with no perceived issues. The valvetrain has no clatter and the rockers kept their adjustment. The oil pressure was a steady 60-65psi at break-in rpms and also had no overheating issues. I've since run it in park and attempted to work on my timing and carb adjustments. The motor sounds great and revs very responsively and clean.

However, I'm having some issues finalizing my tune. I cannot get the car to idle below 1100 rpm while sitting in park and the engine stalls under load. The engine will sometimes die when turning the wheel and using the power steering pump in park. When shifted into gear (C4 auto), I have the give it a lot of throttle to keep the engine from stalling. Additionally, the engine will stall when braking to a stop. With a vacuum gauge attached while idling at 1100 rpm, it quickly fluctuates from about 16-19 in of Hg.

I've tried retiming the engine, making more adjustments to the carb, plugging all of the vacuum ports and spraying carb cleaner around the intake and carb base gasket. Checked my fuel pressure and spark plug gaps. I'm not sure where to go from here. Any advice would be appreciated!
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Verify your spark plug wires are in the 351W firing order counter clockwise from #1. Once verified, do a compression check on all 8 cylinders and post your numbers.
 

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Discussion Starter · #3 ·
I'm positive I have my plug wires in the correct sequence (1-3-7-2-6-5-4-8 counter clockwise). I've triple-check that. I'll run a compression test tomorrow. Would a compression test be accurate with new moly rings that haven't seen any miles yet? And is that sort of vacuum normal with that mild aftermarket cam?
 

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List all of your current tuning specs. Ok, the basics, it idles at 1100 and dies when placed in drive? You offer the changes you've made, but, none of the actual specs. What carb tuning have you performed?
 

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Lord.....recently went through the exact same thing....a year or so later, I am still fine tuning. My issues were the carb itself. I tried two Autolite 4100's, one rebuilt be myself and one built by a "professional". The Autolites just would not idle on the idle circuit.......I ended up buying a Summit Racing 500 CFM carb and it runs GREAT! I am finally actually on the idle circuit at idle. What power valve do you have in your carb? What is your manifold pressure reading, operating temp, C4 in gear? Your power valve should be 1/2 plus .5 if I am correct. Like you I could NOT find a vacuum leak at all. The only other place I can think there would be a vacuum leak is on the C4, passenger side, that little S type hose that is about 3" long. I never checked mine to see if it was leaking there.....probably should, but it is part of the vacuum system that comes off the intake manifold and goes to the transmission. Just thinking out of the box here. Good luck, please post your findings once you get it!
 

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Lord.....recently went through the exact same thing....a year or so later, I am still fine tuning. My issues were the carb itself. I tried two Autolite 4100's, one rebuilt be myself and one built by a "professional". The Autolites just would not idle on the idle circuit.......I ended up buying a Summit Racing 500 CFM carb and it runs GREAT! I am finally actually on the idle circuit at idle. What power valve do you have in your carb? What is your manifold pressure reading, operating temp, C4 in gear? Your power valve should be 1/2 plus .5 if I am correct. Like you I could NOT find a vacuum leak at all. The only other place I can think there would be a vacuum leak is on the C4, passenger side, that little S type hose that is about 3" long. I never checked mine to see if it was leaking there.....probably should, but it is part of the vacuum system that comes off the intake manifold and goes to the transmission. Just thinking out of the box here. Good luck, please post your findings once you get it!
he said he has an edelbrock AVS2 it has no power valve

Ck timing you need 15 -17 degrees as mentioned above

ken
 

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Discussion Starter · #9 ·
List all of your current tuning specs. Ok, the basics, it idles at 1100 and dies when placed in drive? You offer the changes you've made, but, none of the actual specs. What carb tuning have you performed?
I checked to see if the springs for the metering rods were enough and they were planted at the bottom by vacuum at the 1100 rpm idle. So the metering rods were not enriching my fuel mixture at idle. I adjusted the idle screws to the highest rpm and highest vacuum reading after screwing them inwards. I adjusted the idle speed screw to the lowest rpm it would stay at without stalling and check the idle screws afterwards. This is a new carb out of the box, so I know it has the stock jets, metering rods, float adjustment, etc.
 

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1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
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If it is, I haven't found it yet. The car has no power brakes or any crazy vacuum routing. The only lines from my carb and intake are for the vacuum advance, pcv, and the transmission.
Just for the hell of it, I’d plug all the carb’s vacuum fittings. See what happens
 

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Discussion Starter · #12 ·
he said he has an edelbrock AVS2 it has no power valve

Ck timing you need 15 -17 degrees as mentioned above

ken
I have a mismatched balancer on the car so I had to make my own timing marks. According to my marks, my initial timing is 14 degrees btdc. I have tried increasing and reducing timing and it hasn't help my running condition. It currently starts up quickly and and there's no "delay" with the starter you can hear with too much advance.
 

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1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
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Ok, then you’re doing it right. Options:

1) try a different carb, borrow one if necessary.
2) pull intake and re-seal (possible gasket problem)
3) pull timing cover, verify cam timing

In order of easiest to… not easy
 

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Discussion Starter · #18 ·
Ok, then you’re doing it right. Options:

1) try a different carb, borrow one if necessary.
2) pull intake and re-seal (possible gasket problem)
3) pull timing cover, verify cam timing

In order of easiest to… not easy
I forgot to mention this, but I did already pull the timing cover and check. I have a coworker who is gonna let me borrow his carb, just haven't gotten around to it yet.
 

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Good luck. Issues like this are so frustrating but it is probably something easy. This may sound stupid but I wonder if it is super lean. You can't get it to idle down, it dies if you put it under a load. Yes a vacuum leak could cause this but it also could be how you have adjusted the idle even though it sounds like you did it right. Try richening up the idle and see what it does.
 
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