Tuning Advice

Cougar Community Classic Cougar Maintenance Restoration and Repair
21

A few questions. I have reread and found no check for cylinder pressures. Did you degree the cam and what is it installed at? How much vacuum does the engine carry under mild load which is where your misfire seems to start? It’s been 30 years since I tuned a carb but basics need to come 1st! Switching to a 5 powervalve is indicative. The last 351 cleveland (my brothers) I worked was the most fun with only 32 degrees total timing, all mechanical and that was with a custom low duration, high lift Mellings cam on 4v heads.

Brad
ps. That valley pan looks like you spilled acid on it.

22

I plan to check for cylinder pressure soon, I’ve been out of commission for a little due to a surgery but I should be getting back to it, and now that I’ve dug up my pressure gauge I’ll know soon. I had the engine built by a shop near me, if I remember correctly they installed it straight up, although I’ll have to check the paperwork from them.

As for vacuum, it’s been a while since I ran the gauge somewhere where I could read it while driving, but last I remember I had about 11" of vacuum in 1st, under light load, and then as soon as it would shift, it would nosedive to less than 5", if I let off the throttle it’ll jump right back up to 14" or so.

I’ve swapped power valves around, I believe it comes with a 6.5, and I tried both a higher number, 8.5 I think, and a lower, 4.5, and neither seemed to really change much. I did some reading around and came to the conclusion that if you can get above a certain threshold with idle vacuum than the power valve number was less critical, much of what I read seemed to indicate it was much more crucial on engines with a more radical setup, but I’m open to any changes now really.

I’ve tried a lot of different timing setups, none have seemed to fix the problem, I’ve noticed changes and small improvements or deteriorations, which led me to believe it was the carb causing the big problem, but so far I’ve gone all mechanical and it seemed to have improved.

And lastly yes, that valley pan was toast, I’ve never seen something like that happen to something that has no water running through or over it, but from what I read the high heat, low oxygen environment inbetween the pan and intake seemed to have really done a number to the oil that got trapped there.

23

I had a bit of time so I checked compression on 4 cylinders that I could get to the easiest, 1,4,7, and 8. 4 & 7 were the ones with the blackened plugs, and were the ones that would fire out the carb occasionally, but all of those cylinders were right around 160 psi, give or take a bit since the gauge I have is increments of 30. Number 8 was a tad bit higher at I’d say 170, but I believe that falls within acceptable numbers.

I also did check the paperwork from the machine shop, the cams LSA is 113, they installed the cam at 113, so straight up. Unless there’s something to cams which I missed, which is possible since this is my first engine build.

I’m currently working on stopping a power steering leak from the reservoir and trying to get the brakes to be 100%, so I have other things to keep me busy but I’m still stumped on how to get it running right.

24

Have you checked your coil? Mine had similar issues as yours, not identical, but some of the same symptoms. It felt like carb problems so I spent time/money rejetting, but no improvement. I also played with timing, but no love.

Also, it would run fine for the first mile or so, then started acting up. Turns out that as the coil warmed up it produced weaker and weaker spark. That made testing/diagnosing tough. I finally replaced the coil on a whim, and it’s a whole new car. Good luck.

25

I’ll look into that, I’ve had the opposite where after warming up my problems are less noticeable, but definitely still there. I’ve checked voltage while running and I’ve always had 12v to the coil, I replaced the stock coil with the Flamethrower 2 which requires a 12v pos.

26

I’d check primary resistance with the coil cold and then warmed up. If there’s a change, it might be your culprit.

27

I would take another look at possible vacuum leaks. Small vacuum leaks can seal as rubber and metal warms, which is consistent with your symptoms. I had an issue years ago where the idle smoothed once the car warmed up. It turned out to be a hairline crack in the intake manifold that was not discovered until it was removed.

Steve

28

Once I can drive it around again I’ll check for both the coil and the leaks, I’ve hardly driven on the newest intake gasket set that I put on, but I’d just be surprised if 3 different times, each time applying different gaskets with different methodologies, would produce the exact same result.

I just got my power steering pump and reservoir apart to chase a small leak so I won’t be driving it till I get the new seals in there, perhaps this sunday I can do more testing.

29

Didn’t find any leaks, and I checked the coil and it seemed fine, although I’ll have to check again, as the engine was already warmed up a little when I checked.

I did end up taking the carb off, since I thought perhaps my float level was a bit low. I lowered it, but I also noticed that my primary throttle blades were open pretty far, more than is necessary for the transfer slot to only have the small square opening it should from what I read. My Idle speed screw wasn’t the thing holding it there, It was a small screw on the choke side. I adjusted it so now the blades are shut more, enough that at idle the transfer slot is only showing the bottom bit, and then I opened the secondary blades just a little to expose those transfer slots since the secondary blades were shut completely pretty much.

Now, I haven’t gotten to tune it better, I still have to check the idle mixture, float level, secondary opening adjustment, and set the idle speed, but I had to stop for the night, however I did take it around the block, and It was hard to tell if anything was changed since the idle speed seemed decently higher in park, but in gear it was low enough that it died, and I had to keep feathering the throttle. Once I get it tuned I’ll see if I can fix that, but is that indicative of a specific problem? Or should I set the throttle blades back to where they were?

30

I got to tuning it a bit more, made a tool to mess with the secondary idle speed screw thats on the underside, and I put a tach and vacuum gauge in spots where I could read them while driving.

I upped my timing to about 16 degrees initial, and changed to a blue bearing which is 21 degrees mechanical advance, all in by 3000rpm, and that didn’t really do much. So after that I upped the jet size back to 70 primary and 74, which is what it came with when I got it, not much change as well.

In park, I got about 14" of vacuum, in gear it would drop to about 10-11". Under very light acceleration, I’d stay around 10", get up to maybe 1500 rpm, and the car would shift into 2nd, going back down to about 1000 rpm, but the vacuum would plummet to 5" or lower, and this is when I’d get all the stumbling and popping through the carb.

It seemed like on later trips around the block that it would recover from that vacuum drop faster, but it would always drop right as it shifted. I don’t know all the specifics of the relation between vacuum, engine load, and rpm, but it seems like in 2nd the increased engine load is dragging my vacuum very low.

Is there a chance that a shorter rear gear would help, by keeping the rpm higher when it shifts? I was planning to replace the gears in the back after I got this figured out, but now I’m wondering if swapping gears would be the fix. I’ve got an AOD, and 3.00 gears in the rear, I planned on going up to 3.50 or 3.70. I’m just wondering now since I’ve gone through so many different fixes and adjustments on timing and carb, that perhaps I’m looking in the wrong spot.

31

If you have intake manifold to transmission air hoses to tell the transmission what the vacuum is, did you check them for vacuum leaks?

I think some of those can be adjusted on the transmission.