Hey everyone. I am sending out my first forum post ever. I just can't figure out what is going on.

I have a 1974 Plymouth Scamp. I just bought it off some guy who knew nothing about it. When I got under the hood I found a 1992 360 v8 small block with less then 10k miles on it. It has a bunch of after market parts and an automatic transmission. It has a holly red fuel pump and Edelbrock 7577 Air gap intake with a 1405 manual 4 barrel carb on it. I have the silver step up springs in it with the 7052 rods. I have also done the timing at 10 degrees with no vacuum advance.

I have tried changing the springs and went through each and then I started changing the rods one at a time. Nothing seems to work. Right now I have the worst of both worlds. She is sucking gas and can't break loose meaning no power. MPG is between 6-8. I would like to get decent power or better gas mileage but can't seem to get either. Any thoughts?

Sherlock Mcnett

 

I would start with a compression test, then check the cam timing !!! Check the valve clearances (push rod length)

 

A Magnum engine with all those HP carb parts on it from a guy who knows nothing about it would make me very suspicious. What TV says is what I would do plus actual TDC.

I don't understand how an engine is sold with no knowledge of it. Most car nuts like me can go on and on about every nut bolt timing and all until someone tells me to shut up about it.

 

I did the compression test. But I will check the clearance. The guy I bought this car from had never worked on a car in his life and had bought it from someone who put a lot of time and money into it. It sat in a garage for at least the last year and this guy had screwed the timing and had a hole burned into one of the plug wires. So he is useless.

Thanks for the help I will check into it.

 

Have to start somewhere and make sure the motor is solid !!! What was the compression ???

 

Your initial timing is way off, put it at 14 and go from there. Your mpg will improve significantly with vac advance. These two items are simple and basic, start here and report back (I'll be here waiting for the high five).

 

i dont know what manifold that is. but did you put a square bore carb on a spread bore manifold? if you you did that may be your trouble. the Edelbrock does NOT know how to jet carbs. i will give a short hint on jetting. i will find my long ver and post it latter. 1. do NOT change rods AND jets at the same time. 2 . change the rods first. 3. Edelbrock makes the rods with to much step between the cruse and power steps. DO us the rod with the smallest step. unless its a race engine. remember this. with a jet of .060 goes bigger by .001 is less change than a .100 jet increased by .001. i have a program that calculates these by %. ill try to find how to find the program on my sons site. hope this helps.

 

i found it it might say its the short ver but i think its the long ver.
http://clarkehackworth.com/files/JetsAndRods.html
my sons pro to cal jet %

Title: AFB and edelbrock carb / the short verson.

setting an AFB carb takes time. make only small changes. and give it time, dont make changes in an hour or two. drive it in different ways over a day or two. on AFBs or AVSs change only the jet OR rod at one time. and start with the jets. a .003" change can be felt if you try. dont forget .003" on a .060" jet is less change than .003" on a.100" jet. Then start changing the rod. A little is a LOT. i do have a computer program to cal any combo of changes. but it is lost in some main frame of my sons. Sometimes you can set the float level to 5/16”. the stock setting is 7/32. if at 5/16” at idle the fuel runs out of the main discharge nozzle reset to the stock setting. NOTE: do NOT change jets AND rods at the same time. Do not put the jets in tight, just snug is fine

 

1........Do not assume ANYTHING. Do not assume this has decent pistons, decent cam, correct cam timing, or correct ignition timing

2........AFTER you "don't assume" all that, do not assume the carburetion is anywhere close, but you have to "do" all of no1 FIRST

3.......Very very first job is to get a piston stop and determine true TDC, then map out what you have for initial and mechanical advance. If you don't know how, post back here

4........I would not waste time. You don't seem to know what the cam "is" so the very next job is to get some idea of what the cam "is" and whether it is in time Once you get the timing marks confirmed, get (or print) a degree wheel and make a graph of cam timing. You can estimate this at the rocker, but this is not very accurate. More accurate would be to pull off no1 rockers, and make up a junk pushrod into an adapter to operate your dial indicator.

One way to do this is to cut a pr, which leaves an open tube. "Affix" something such as threaded rod, even if you have to clean it and JB weld (epoxy.)

Now do something with the top of the rod, IE drill a small dimple, etc to catch your dial indicator.

Make a small plastic bushing to go over the outside of the rod and take up the space in the push rod hole.

If you are careful, this gives you a tool which you can use to REASONABLY accurately map out the cam profile. You can then compare it with some popular grinds and see if the cam timing is "anywhere close"

Bear in mind that advertised cams don't always work that well "as specked" for timing.

Here's an excellent example......."This cam" in "this engine" was a real dog. We moved it ahead quite a bit and it turned it into "a whole different animal"

http://www.forabodiesonly.com/mopar/...d.php?t=244033

This thing went from something on the order of 110CL (due to the old cam drive being off that much) to advancing it up to about 105 with a new advance /retard timing set.

5....After you get the cam checked for "degree" and possibly adjusted, see if your distributor needs recurved. ANY performance engine "wants" a fair amount of initial timing. This seems to be greater, nowadays, because of alcoholized gas. Even a stock 340 probably does well around 15* initial, and some cams like more than that.

Make sure your total (no vacuum) is in reason

THEN there are the "usual"

Is the engine running up to temp? Is it OVERheating?

Exhaust? Good exhaust system? Nothing plugged? Heat riser stuck

Run a compression / leakdown test.

Then after you get all that done, you can play with carburetion.

What do the plugs look like?

 

I agree with all the above said.... I approve this message !!!!!!