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Discussion Starter #1
I just finished my cam brake in the other day and went to drive it to a muffler shop today. When put in reverse the car was sluggish but didn't die. But when I put it drive was bogs down and dies. All the fluids are good, no vacuum leaks, only thing I can think of is that my stock stall isn't high enough for my cam. Didn't have money at the time for a new stall so it is stock. I have a Edelbrock Performer RPM (7182) Cam (290 int./300 exh.) .496/.520 with stock rocker ratio. I changed the orignal rockers to 1.6 Roller Rockers so I think the .496 lift off slightly. The point is am I an idiot and need a higher stall or is something else wrong.
 

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That's not a terribly radical cam, and while it would work best with a slightly higher stall speed converter, you should be able to make it work ok with your stocker.
Try bumping the initial advance from the stock 6 degrees BTDC to 8 or 10.
Its also very likely that you need to reset the idle mixture screws on the carb, and possibly increase the main jet size, to compensate for the decreased low speed vacuum from the bigger cam.
What's your idle speed with the transmission in park/neutral with the engine warmed up?
 

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Discussion Starter #3
my idle advance is sitting at a4 degrees right now, won't run any more or less. I'm running a Edelbrock 600 CFM carb and have been playing with the idle scews but the motor is very picky with what it likes. I'm also not running the vacuum advance and shut off the vacuum valve for the lights. I don't have a tach. so i couldn't tell you what I'm sitting at.
 

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Can you keep it alive with your foot on it? Try putting the a$$ on stands and run it some - see what you got.....I'd suspect major vac leak or like cj says - way undersized jets. A timing light and a vac meter would really help you out when it comes time to tune/tweak it the best you can. There is a good post (I think woodsnake) on here about how to approach it.....
 

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Discussion Starter #6
It'll run in gear with some gas to it again its touchy. I'll try to see if it is a vacuum leak and slap a different carb on and what works. Just curious, what is a stock converter stall?
 

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Talked with a Trans Shop about my cam a while back asking if a stall would be required.... They told me the stock converter back then was between 1800 and 2000 already. Just a little FYI.
 

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If that is the Edelbrock performer RPM cam, I have that one in my 68 Cougar. However, you won't be able to get it right ,until you know what you have. Tuning by ear just isn't as easy as people think. I have a 5 speed in my 68, and it idles right at 850-900 rpm. If I go any lower, it will stall out and die, coming off the interstate. I have had lots of problems with that cam, I hope you have better luck than I have. Also, what rear end gear are you running? I Think they recommend at least a 3.50.
I have a 3.50, and honestly I think the motor would like a 3.89 very well!
 

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Discussion Starter #10
rebuilt 3 speed fmx, 2.73 gears for now will be going to 3.50 in a few months. same cam your talking about, it was part of their top end 400hp kit. I'm trying to keep this streetable while having the ability to take it down the strip for fun. But whatever to get it running at this point. Also was looking into getting a Revmax 3000 stall, any info on them?
 

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A few thoughts at random:

14 degrees initial timing is a lot. Maybe you need that much to help compensate for not having the vacuum advance hooked up, but why is it disconnected in the first place? Any idea what you're running for total advance?
Doesn't make sense that the engine will only run with 14 degrees initial timing. Was that also the case before the cam swap? In any event, its a good indication that something more is wrong than just converter stall speed.
Do you have a vacuum gauge? At minimum, you need to determine that you have a steady vacuum reading, and idle mixture needs to be set to obtain the highest reading. Doing it by ear is just taking a shot in the dark.
Check Craigslist and garage sales. You should be able to find an old tach/dwell meter for next to nothing. If you're tinkering with old cars, you need one.
Kinda obvious, but is the new cam ground for the same firing order as the old cam? If not, did you make the appropriate wiring changes?
Man, 2.73s and that cam are not a good match. Getting the engine smoothed out is obviously the first priority, but get those 3.50s in there as soon as you can.
 

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I know that when I put my first cam in my 69-351W, the car was SLOWER with the new cam on stock gears. The new gears allowed the engine to take avantage of the power band, and that is when I fell in love, all over again...
 

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Discussion Starter #13
the car ran the same 14 advance before the swap out as well. For total timing i'm sitting around 38. From what I've read initial timing should be done with the vacuum advance off, so that's what i followed. Will be checking the vacuum sometime this week. And this is my first build so i don't know an incredible amount about this stuff, I went with what worked for my year make model and motor. I don't imagine the firing order needing change and none of the documentation for the parts said it was required.
 

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Another thought - since you went to roller tip 1.6 rockers, what length PR did you end up with? Wondering if your geometry is on target and not coming up a bit short....
 

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the car ran the same 14 advance before the swap out as well. For total timing i'm sitting around 38. From what I've read initial timing should be done with the vacuum advance off, so that's what i followed.
Yes, that's correct but once timing is set, the vacuum advance should be immediately re-connected. I'll also point out that if you aren't using a tach, you don't really know what the initial advance is, because it has to be set at a specified rpm. Higher or lower engine speed will change the reading.




Will be checking the vacuum sometime this week. And this is my first build so i don't know an incredible amount about this stuff, I went with what worked for my year make model and motor. I don't imagine the firing order needing change and none of the documentation for the parts said it was required.
Unless you bought your cam used, somewhere in the documentation that came with it, it'll say what firing order its designed for. Plenty of cams sold for 351s are ground for the 289/302 firing order and vice-versa. Unless you know for sure that the cam you replaced was the original, it could have been either firing order. Please humor us and take a few minutes to verify that your distributor wiring matches the cam specs. There's at least a 50% chance it'll be right, but its hard to go on with diagnosing a poor running engine until all the basics are covered.
 

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Discussion Starter #16
Cam firing order is correct, no vacuum leaks. Hooked up my vacuum advance and put on a less restricting air filter and now it runs...
 

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Wee-Hoo! Glad that's what it was. Now you can fine tune things!
 

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Well, it sounds like it needs some tuning. Not a terribly radical cam but it I would start with checking the ignition timing and total advance. 8-10 initial and 35-36 total is a good starting point. You might need to check the advance stop in the distributor. Was that 38 total with 4 initial or 14? Check and see what centrifugal springs are in the dizzy, might need to go there as well. As far as keeping it idling in gear, have you tried opening the secondaries on the carb slightly? That might help get the transfer slots exposed slightly and keep the air/fuel moving while its against the converter. Just a gee whiz but that cam is a standard 351 firing order. So what distributor are you running? What size carb?
I'll be in Vegas next month if you can wait! lol...
 
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