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Discussion Starter #1
Hi, I have a '68 XR7 with a 302. I have replaced the stock heads with Flo Tek aluminum heads, replaced the 2V intake with a 4V Edlebrock performer Z89 and have a Holley 650 4 barrell carb. I have also replaced the stock points and condensor ignition with a Petronix ignition and coil. Full headers and Flowmaster exhaust.
I am not getting the power I think I should and wonder if the timing might be off? I know I should know this, but don't. I think turning the distributor counter clockwise will advance the timing? When I moved it that way the idle increased and the off the line pickup seemed to be better.
I have found that stock timing is 6 BTDC. I'm not sure if I need to remove the vacuum line from the vacuum advance when checking the timing. I read somewhere that, this is the thing to do and to block the end of the vac line? It didn't specify if I remove it from the carb or from the vac advance. You would think I should know this but I guess I was absent the day they went over this...
You would think that after all these mods that I would be able to smoke the tires at will. Not the case... Any suggestions? Timing with vac advance attached is at approx 10 BTDC. Thanks in advance for any and all help.
Charlie
 

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Charlie - the idea is to not have a vac leak when you remove the line - so plug it at the carb and then you have the advance killed until you set the timing. Going from a 2v to a 4v doesn't make a world of difference - but heads and cam would wake it up quite a bit once you get everything tuned and flowing smooth. Sounds like you have good exhaust flow - so that's not the issue. What cam are you running?....
 

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Discussion Starter #3
I knew that question would be coming.... When I rebuilt the top end, I did it with the engine in place, so did nott swap out the cam. In hind sight, probably not the best idea. The guy I bought the car from told me he had had the engine rebuilt, problem was he left it sitting for 10 years after the rebuild and I wound up with a car with poor compression in 2 cylinders and were issues with the intake valves not seating. This is what prompted me to rebuild the top end. Getting back to the cam, I was told it had an "upgraded cam" I could not find any paper work on the cam. What I can say is it feels like a mildly upgraded cam, what many refer to as a nostalgia cam. I know this is not the answer you want but the best I can come up with, since I did not change it. Paperwork on his rebuild showed solid work on lower end and new cam ( bushings or bearings) cant recall what it has but that area looked strong and cam was not too lopey just mildly so. Enough to be able to tell it was 't stock but not so much that it bounced the car around. I wish I could be more specific, but this is the best I can do at this time. I know, I really should have pulled it but didn't. Hope this description helps, maybe a little...
Charlie
 

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Well, as far as your tuning goes, you are going to have to have timing light, so that you know what you are working with. The 6 degrees the book calls for, doesn't actually work very well for performance or economy. You will also need a vacuum guage to dial in your carburetor. Vacuum needs to be plugged when stting your timing, I.E., disconnect from the vacuum line that goes from the carb to the dist. at the dist. Plug that open end. I would say start at 10 degree's inital, and see if it pings under a load. If not, then go 12 degree's. Also, your 650 sounds about right for your motor. You need a REALLY small flat head screw driver to get to the idle mixture screws on both sides of the front metering block. Screw the passenger side in, until you get the highest number of inches of vacuum at idle, and then do the passenger side. Your engine idle speed can then be set, so that you get the 650 r's pm in drive. (I think it's 650 in gear?).
Then test drive, and see how it does!
 

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Yep - peaking your vaccuum will get you best performance. Also - when you hook up the vac advance to the carb - be sure to use the ported vac port on there. It's the one higher up on the carb body on the right side. There are some tuning tricks to set that holley up for good performance - free on thier website - I'd step through that as well. (you may want a kit)
 

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Discussion Starter #6
I have the timing light, an older one with dwell and a tach built into it. I don't have the vacuum meter. Any suggestions on where and which one to get? Tuned lots of motorcycle carbs but they don't look like what is on the car. I'm sure the operation is similar just more pieces and laid out differently. Hopefully between the timing and the vacuum, I will be able to get it to brake loose. Thanks for help. Appreciate the info. Not sure what the vacuum meter looks like so would appreciate any help in picking one out. Sure I may need a few pointers getting it hooked up, once I have it.
Charlie
 

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Discussion Starter #7
Just checked timing with vac advance off of distib and line plugged. It says it is at 16. Checked with another light to be sure, 16 is where the marker is pointing. There is no ping, wonder if that could be correct?
Charlie
 

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A vacuum gauge will help. If you are in a real hurry, they can be found at Harbor Freight or most any auto parts store. Can't comment on parts store, but the Harbor Freight ones are cheap junk. As is their oil pressure gauge. I doubt they have any kind of dampening, they jump all over.

What I did was hit ebay and turned up a oil filled gauge and added a nipple and coupler from Home Depot. The oil filled gauges give much steadier readings.
 

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You would think that after all these mods that I would be able to smoke the tires at will. Not the case... Any suggestions? Timing with vac advance attached is at approx 10 BTDC. Thanks in advance for any and all help.
You didn't mention it but since you have a 302 I would guess you have, at most, a 3.00 rear. Frankly I don't think you will find it that easy to smoke the tires at will regardless of your timing, carb, intake, heads or headers. You are going to need a lot more torque than you have, or a much lower gear then you have, or maybe both.
 

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