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Discussion Starter #1
I have a 1968 mustang with a 1969 302 in it. I am having trouble tuning it to run properly. I bought the car with lots of modifications already done to the engine and have taken the top half of the engine completely apart and back together to try to fix the problems but they are still there. I have tried tuning the carb with different jets and rods, and adjusting the timing but the car still struggles to go especially at low RPMs and some dead spots in the throttle. I doesn't really seem to have the power it should have. I tuned the carb with a vacuum gauge and got to a max of 11-12 at 1000 RPM which i think is the correct idle for the cam i have but i do not know for certain what cam i have in there. I am wondering if i should open the engine up again and check the cam and bring it back to stock as this will be a fun street car when done. Distributor curve maxed at ~3000 RPM initial timing at ~15 degrees i have thrown some money at it to fix it but i don't wont to spend any more until i know what the issue is.
Any wise engine sages that can help me out? :shrug:
Engine mods are:
MSD pro billet distributor with 6AL box
Edelbrock Performer cylinder heads,
Edelbrock Performer RPM Air Gap intake manifold,
1406 Edelbrock 600 CFM carburetor,
Possibly Edelbrock Performer RPM Camshaft ?????
engine pistons, rods and crank and all stock as far as i can tell.
all attached to a T56 magnum transmission with a ford 9 housing 3.25 gears

PS: while taking the heads apart i noticed quite a bit of gunk on the top and bottom of the valves
 

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Describe junk. I’m not a Edelbrock carb guy, but several here are. Sounds like you might be a little rich though. Need to know your cam specs that determine where you should be on vacuum. When you say max timing, what is it? Any smoke out the exhaust? If so, what color?
 

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Take a look at the lifters and the cam lobes through the holes in the lifter valley. (Pull lifters out one at a time for examination) Look for signs of the cam being wiped due to lack of proper lubrication (ZDDP)

If cam and lifters are ok, degree the cam to see what it is. Decide if that cam works for your intended purpose.

If so, check the timing set to see if the crank and cam gears are lined up properly and the timing chain slack is within spec.

Next check to see if the preload on the lifters is within spec.

Check the plugs for signs of fouling and double check gap

At that point the distributor and carburetor should come into the mix.

If the carb hasn't been gone through (rebuilt) in the recent past, rebuild it and make sure the fuel filter is new as well.
If there is lots of junk in the float bowls, the gas tank and fuel lines are suspect, clean or replace as needed.
Check the distributor and vacuum advance for proper and full function

Hopefully your issue(s) are somewhere in this list. In any event. let us know when you sort it out.

Good Luck
 

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Discussion Starter #5
Describe junk. I’m not a Edelbrock carb guy, but several here are. Sounds like you might be a little rich though. Need to know your cam specs that determine where you should be on vacuum. When you say max timing, what is it? Any smoke out the exhaust? If so, what color?

Performance Camshafts Cam Card Locator - Edelbrock, LLC. Here is the cam card of the cam i think it might be, i checked the exhaust and intake opening and closing degrees and they match if that means anything to confirm its identity. The timing i am talking about is the initial timing and the point at which the total advance occurs in terms of RPM. The initial timing is 15 and the total is 33 at ~3000 RPM. as for smoke i haven't really payed attention but it think white if any. the junk on the valves is black oily shmoo on top of carbon buildup
 

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Discussion Starter #6 (Edited)

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That RPM cam is little bit too much for street cruising, it does not work very well on lower rpm like under 2000. Vacuum reading is correct for that cam, i had same on '66. Timing on my setup was 18 on idle and 37 at 3000rpm. I changed to roller cam and car worked much better, duration 220 .50 and .544 lift. I would suggest to get that RPM cam out and change it something that has less duration.
 

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I think you know why it was for sale:)
So it runs OK mostly but is gutless?
Eddy carbs have a rep around here of being plug and play, nearly foolproof.
I dont know that combo but street warriors often dont build for the big picture. It may only be good while spun up, like it needs to live above 2K rpm. Cruising around does it have consistant pep above 2500rpm?
Does the dizzy have a vac advance? If so loosen it up. I think you might want more total but more important is the rate and increments of the progression that you should be able to see with a light.
 

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How about a compression check? It's cheap and easy and will at least rule that out if the numbers are good.

BTW - I have the Eddy RPM cam in my 351W daily driver and it's just fine (=fun!) for the street.
 

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Have you tried setting your initial timing to 10-12 see how it runs? Are you running a vacuum advance? A wideband AF guage will tell you right away where your at at part throttle, etc and makes it very easy to tell what your changes are doing to the car.

I have had this one since 2016 works great:
AEM (30-4110) UEGO Air/Fuel Ratio Gauge https://www.amazon.com/dp/B00N3VGPYS/

Not as advanced as the ones that let you collect data and import it to your computer but good enough for tuning.
 

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Sound suspiciously like a 302 I had once that wore down three cam lobes. I was bound and determined it was something else (I don't remember why) but it passed all the basic tests. Even measured decent compression. I didn't give in until I finally broke down and measured the cam lift at the suspect cylinders.
 

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You’re getting some good advice here. Don’t know if this helps or hurts, but the single greatest tuning I ever did to my car was to junk the Edelbrock carb and put a Holley on it. Car ran great with the stock heads and cam, but I could never get it to run right after adding heads and cam until the Holley.
 

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Worn engine with "speed parts" added?
There is some mismatch to the parts that are on the engine, but
it's not damning.
The vacuum reading seems really low to me...... 7" less in mercury
for 6 degrees more cam than I have. Sum-ting not right there.
Look closely at the cam lobes.
 

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Discussion Starter #15
Thanks for all the great feedback guys. As excited as I am to open the top end of the engine for a 4th time, I am hoping that it is the cam and I can replace it and be done with it and drive around. I have done a compression test already as Rorin67 mentioned I should do; the cold numbers are 125psi average with no outliers. I read that the air velocity inside the intake runners is very important with large cams, could the Edelbrock performer rpm air gap intake be too big for my engine? As to changing the carb I am hesitant because I am no carb expert and even without using a Holley I know they are inherently more difficult to tune right because there are just so many more adjustments to be made... and mess up. Anyway thanks again for all the replies guys, ill try messing with the timing again and if that doesn't work then Johnny 5 disassemble!
 

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I don’t think you want/need more than 32 total with those heads. I’ve got largely the same heads and was steered towards data indicating 28 total is the mark.

Your initial, curve, and total look good really. The AirGap isn’t too big IMO. Your combo will have to get buzzed a little to make power but don’t choke the heads swapping to a smaller intake.

As has been stated, vacuum looks about right (doesn’t Edelbrock state 11” for the RPM cam?).

An interesting side-note: I picked up nearly 4” of vacuum just switching PCV valves. I tried a few including a specific “low vacuum” part & infamous GM “nothing but a small hole” deal. I think quality construction matters a lot...the winner was a NOS Ford EV50 from the early 70’s....shouldn’t be but it is indeed.

I’ve got a pretty big solid flat tappet cam but I knew 8” was too low. I don’t have any power accessories but it was more about idle quality which is definitely better without a vacuum leak. :)

Compression does seem a bit low but since it’s consistent and given what you mention I would try a different known good carb if possible. You could well have a cam going South but a carb swap is easy in comparison!

If you can cure the hesitation stuff (like above - what do your plugs look like??), it may still be a bit of a stem-winder to make power. 2V pistons, ~60cc heads, and a decent amount of overlap...needs winding!
 

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Thanks for all the great feedback guys. As excited as I am to open the top end of the engine for a 4th time, I am hoping that it is the cam and I can replace it and be done with it and drive around. I have done a compression test already as Rorin67 mentioned I should do; the cold numbers are 125psi average with no outliers. I read that the air velocity inside the intake runners is very important with large cams, could the Edelbrock performer rpm air gap intake be too big for my engine? As to changing the carb I am hesitant because I am no carb expert and even without using a Holley I know they are inherently more difficult to tune right because there are just so many more adjustments to be made... and mess up. Anyway thanks again for all the replies guys, ill try messing with the timing again and if that doesn't work then Johnny 5 disassemble!
Yours is NOT a "big" cam. Not even close.
Compression, at 125 psi average, no smoking gun there. (unless you
have major disparity between cylinders)
Your intake is fine. Your cam profile doesn't really match the head,
particularly if they're not flowed. Performer RPM heads would be
a closer match and RPM's ported would be even better because you're
still dealing with small CID displacement and not a ton of CR.
 

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There could be something wrong with that Eddy carb if it's old and not checked. Otherwise Eddy carbs are very reliable and perfect for street cruising and some mild/moderate performance engines. I recently got Eddy thunder AVS2 carb to my car and absolutely love it how smooth acceleration is. RPM cam is fine if you wanna do spirited driving, had it many years on my car.
 

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Discussion Starter #19
I finally had time to take apart the engine today and found nothing too dramatic from what i can tell. I did figure out that the camshaft is a Edelbrock performer-plus camshaft . The Lobes didn't look terrible but then again I don't have the knowledge to know what to look for. But interestingly I found that while taking the camshaft retaining plate that it was not installed correctly, it was installed upside down which baffles me because it literally says which direction to install it stamped on it ..... the oil passage therefore was blocked off and i don't know how there wasn't more damage it might be a long shot, but could it be possible that this could create some of the problems i am having? Does anyone have a definitive way to tell if the camshaft is worn? Also i noticed that the Edelbrock cam cards say not to use double springs yet all of the springs in my heads have a normal spring and a smaller spring inside like a sheet metal coil. How critical is the spring poundage and single or double spring setup?
It's a lot of questions i know, sorry, but thank you for all of your help so far guys!
I would post pictures but it seems that the file size of pictures is very restricted here.
 

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I finally had time to take apart the engine today and found nothing too dramatic from what i can tell. I did figure out that the camshaft is a Edelbrock performer-plus camshaft . The Lobes didn't look terrible but then again I don't have the knowledge to know what to look for. But interestingly I found that while taking the camshaft retaining plate that it was not installed correctly, it was installed upside down which baffles me because it literally says which direction to install it stamped on it ..... the oil passage therefore was blocked off and i don't know how there wasn't more damage it might be a long shot, but could it be possible that this could create some of the problems i am having? Does anyone have a definitive way to tell if the camshaft is worn? Also i noticed that the Edelbrock cam cards say not to use double springs yet all of the springs in my heads have a normal spring and a smaller spring inside like a sheet metal coil. How critical is the spring poundage and single or double spring setup?
It's a lot of questions i know, sorry, but thank you for all of your help so far guys!
I would post pictures but it seems that the file size of pictures is very restricted here.
I could be wrong, but it sounds like your heads have "booster" springs which are what machine shops sometimes install inside old springs when they're worn and can't quite muster enough spring pressure. This of course makes no sense on new, Edelbrock heads. Please try to post some pictures.

Check the tops of the valve stems. Can you see any wear marks? The rockers should be contacting the tops of the valve stems directly over the center area. If whoever assembled the engine didn't check the valve train geometry, you could easily have the wrong length pushrods which would cause the rockers to hit the valves on the edges of the valve stems. Again, try to post some pictures.

Do the lifters look OK? Closely inspect the area which contacts the cam lobe. It should be smooth and not mushroomed or scuffed. Yep, pictures!

Be persistent. You'll get there!
 
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