318 with 340x heads sluggish

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tmat26

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I recently purchased a 73 Scamp that was mostly redone. The problem with it is that it is very sluggish even though the engine wants to go. The person I purchased the car from and his mechanic blamed the stall for this. He originally installed a new converter with a 3400 stall and then updated it to a 3000 stall. Its still slow.

My question is would a 2200 stall improve the get up off the line? Or is the rear end the issue? Or do I have multiple issues?

Not looking for a drag car but not a cruiser either.

Specs:
318 with 340x heads bored 30 over
mildly Aggressive Cam (do not have the specifics on lift)
performer intake
650 carb with 750 jets
Hooker Headers
904 trans (no shift kit)
3000 stall
8 3/4 rear with 3:32 gears
18' wheels
 
I think the 318 sitting under the 340-x heads is the culprit. Look for a 340 or 360 short block and get your power back! :burnout:
 
Could be a combo. Without knowing the cam or where it is installed (cam timing, "degree") that could be a huge issue as well
ANY used engine........without hard and true documentation......is a crap shoot.

Also, how do you know that the timing is "where it ought'a be" and chances are "it ain't."

Timing, distributor curve, cam specs, cam timing, and even the carb, and absolutely the intake manifold??

What does it have for exhaust manifolds / headers?

A lower RPM stall converter is the LAST thing you want for an engine sluggish on the bottom end, or did you mis--type that?
 
tmat26 said:
I recently purchased a 73 Scamp that was mostly redone. The problem with it is that it is very sluggish even though the engine wants to go. The person I purchased the car from and his mechanic blamed the stall for this. He originally installed a new converter with a 3400 stall and then updated it to a 3000 stall. Its still slow.

My question is would a 2200 stall improve the get up off the line? Or is the rear end the issue? Or do I have multiple issues?

Not looking for a drag car but not a cruiser either.

Specs:
318 with 340x heads bored 30 over
mildly Aggressive Cam (do not have the specifics on lift)
performer intake
650 carb with 750 jets
Hooker Headers
904 trans (no shift kit)
3000 stall
8 3/4 rear with 3:32 gears
18' wheels
Click to expand...

Start from the Base to determine the culprit.

Possible Culprit ....... Rear End and 18" Wheels.

#1 ....... What is the Tire Diameter ?
 
It has the low profile wheels so they only sit 24" high. The rear end might have a technically different ratio 3:42 but I measured by the revolutions of the tire vs the drive shaft to come up with the 3:23.

As for the timing aspect it seemed to be running well and idling great but not 100% sure that it was correct.

Hooker headers as well. Engine seems to be running well.
 
67Dart273 said:
Could be a combo. Without knowing the cam or where it is installed (cam timing, "degree") that could be a huge issue as well
ANY used engine........without hard and true documentation......is a crap shoot.

Also, how do you know that the timing is "where it ought'a be" and chances are "it ain't."

Timing, distributor curve, cam specs, cam timing, and even the carb, and absolutely the intake manifold??

What does it have for exhaust manifolds / headers?

A lower RPM stall converter is the LAST thing you want for an engine sluggish on the bottom end, or did you mis--type that?
Click to expand...

So I have definitely multiple issues. I will do some additional questioning to see if I can get the cam specs. I knew that was an issue. The engine is going and seem like it wants to go but the power is not to the wheels.
 
What's the true c/r
That can have a drastic effect especially with a big cam ?
 
With 3.23 gears and an aggressive cam with that 3000 stall, 340 heads on a 318, you have a recipe for a car that won't pull a greasy string outta a cat's ***.

Here is what's happening. First, your compression is LOW. The 318 had heads with smaller chambers. Installing 340 or 360 heads on a 318 lowers the compression down into the 7s. You're probably at 7.7 or 7.8:1, possibly lower. That's the first killer.

Killer #2 is the "mildly aggressive cam". That cam, coupled with the already dismal static compression, makes any left over cylinder pressure plummet. Goodbye power.

Killer#3 is that converter coupled with the 3.23 gears. What's happening there is, the converter is actually stalling up higher than it should, because it does not have the leverage of a better gear ratio. Converter slip city. If you had 3.91 or 4.10 gears, at least THAT part would be better.

The best thing you can do is several fold. Get some 318 heads back on it. Get a cam in it with around 210-216* duration @ .050". Degree it in.

Then, toss that converter and put a stock one in. You will have a completely different car.

Oh and get those stupid lookin wheels off. Mopars ain't ghetto.
 
I would sell the x heads and get magnum heads and don't worry about a couple cracked seats. Keep carb and converter but lower those gears and get a sure-grip and you're good to go! Maybe different wheels cause those low pros are gonna burn @ 24"!!! It really depends on how much time and money you want to put into it.
 
RustyRatRod said:
With 3.23 gears and an aggressive cam with that 3000 stall, 340 heads on a 318, you have a recipe for a car that won't pull a greasy string outta a cat's ***.

Here is what's happening. First, your compression is LOW. The 318 had heads with smaller chambers. Installing 340 or 360 heads on a 318 lowers the compression down into the 7s. You're probably at 7.7 or 7.8:1, possibly lower. That's the first killer.

Killer #2 is the "mildly aggressive cam". That cam, coupled with the already dismal static compression, makes any left over cylinder pressure plummet. Goodbye power.

Killer#3 is that converter coupled with the 3.23 gears. What's happening there is, the converter is actually stalling up higher than it should, because it does not have the leverage of a better gear ratio. Converter slip city. If you had 3.91 or 4.10 gears, at least THAT part would be better.

The best thing you can do is several fold. Get some 318 heads back on it. Get a cam in it with around 210-216* duration @ .050". Degree it in.

Then, toss that converter and put a stock one in. You will have a completely different car.

Oh and get those stupid lookin wheels off. Mopars ain't ghetto.
Click to expand...

Thanks for all of the info. That makes a lot of sense about the 340 having the lower compression. Everyone kept driving towards that converter but thats only part of it. I will start looking around for some 318 heads to begin with.
 
RustyRatRod said:
...

Here is what's happening. First, your compression is LOW. The 318 had heads with smaller chambers. Installing 340 or 360 heads on a 318 lowers the compression down into the 7s. You're probably at 7.7 or 7.8:1, possibly lower. That's the first killer.

Killer #2 is the "mildly aggressive cam". That cam, coupled with the already dismal static compression, makes any left over cylinder pressure plummet. Goodbye power.

Killer#3 is that converter coupled with the 3.23 gears. What's happening there is, the converter is actually stalling up higher than it should, because it does not have the leverage of a better gear ratio. Converter slip city. If you had 3.91 or 4.10 gears, at least THAT part would be better.

The best thing you can do is several fold. Get some 318 heads back on it. Get a cam in it with around 210-216* duration @ .050". Degree it in.

Then, toss that converter and put a stock one in. You will have a completely different car.

Oh and get those stupid lookin wheels off. Mopars ain't ghetto.
Click to expand...

I used to build 70's 318's with 360 heads, they were cheap, and they always ran good. Always milled the heads, block side, .020 or .040, and intake side, .019 or .038. If you need new pistons, get some 9.0:1. The rest of the recipe was as RRR has outlined for you, although I usually ran 3.23 gears. The cheapest solution is to try and tune what you have first. I have seen timing marks off, over 10 degrees. The cam usually is usually not that far off, but you need to know what you have and that it is installed correctly. There are lots of threads here, that tell how to time and adjust your carb for max power and efficiency.
 
Pretty much what RRR said. But - I don't think the heads or convertor need much. You need to figure out the camshaft and address that. Then tune it properly. Having owned and built several of these years ago - the cam choice is critical. Go big and it sucks. Stay conservative and you can run crap gas and it will be no softer than a 340 built similarly.
 
RustyRatRod said:
With 3.23 gears and an aggressive cam with that 3000 stall, 340 heads on a 318, you have a recipe for a car that won't pull a greasy string outta a cat's ***.

Here is what's happening. First, your compression is LOW. The 318 had heads with smaller chambers. Installing 340 or 360 heads on a 318 lowers the compression down into the 7s. You're probably at 7.7 or 7.8:1, possibly lower. That's the first killer.

Killer #2 is the "mildly aggressive cam". That cam, coupled with the already dismal static compression, makes any left over cylinder pressure plummet. Goodbye power.

Killer#3 is that converter coupled with the 3.23 gears. What's happening there is, the converter is actually stalling up higher than it should, because it does not have the leverage of a better gear ratio. Converter slip city. If you had 3.91 or 4.10 gears, at least THAT part would be better.

The best thing you can do is several fold. Get some 318 heads back on it. Get a cam in it with around 210-216* duration @ .050". Degree it in.

Then, toss that converter and put a stock one in. You will have a completely different car.

Oh and get those stupid lookin wheels off. Mopars ain't ghetto.
Click to expand...
x 11ty billion , nothing more
 
Can't you cut the heads down to bring up compression ? Wouldn't that be better than putting 318 heads on it ?
 
jerry6 said:
Can't you cut the heads down to bring up compression ? Wouldn't that be better than putting 318 heads on it ?
Click to expand...

That's what we did, but you can only go so far before they get thin and tend to warp and/or blow head gaskets. At .040 J heads are about 65 cc's
 
Now you are killing the next guy that buys x heads to put on his 340. Now you need to address intake on how much you mill.When you keep making mistakes to try to remedy an original blunder it sometimes snowballs. Just get some 318's you will be much more happy.
 
d5667 said:
Now you are killing the next guy that buys x heads to put on his 340. Now you need to address intake on how much you mill...
Click to expand...

66fs said:
I used to build 70's 318's with 360 heads, they were cheap, and they always ran good. Always milled the heads, block side, .020 or .040, and intake side, .019 or .038...
Click to expand...

If you are milling heads, this makes it a no brainer.
 
I know this sounds so basic and stupid, but I have seen it happen a lot. Is the carb opening up all the way? I have seen it quite a few times, somebody brings car in and and complains it wont get out of its own way. Not saying that is the problem, but check it to rule it out before you do anything else.
 
340swinger70 said:
I know this sounds so basic and stupid, but I have seen it happen a lot. Is the carb opening up all the way? I have seen it quite a few times, somebody brings car in and and complains it wont get out of its own way. Not saying that is the problem, but check it to rule it out before you do anything else.
Click to expand...

True!
 
340swinger70 said:
I know this sounds so basic and stupid, but I have seen it happen a lot. Is the carb opening up all the way? I have seen it quite a few times, somebody brings car in and and complains it wont get out of its own way. Not saying that is the problem, but check it to rule it out before you do anything else.
Click to expand...

I will definitely add the carb to my check list as the prior owner made some adjustment to the jets. It seems to be dumping gas and running rich but this maybe from the potential low compression.

Work in progress..
 
It takes about a .070" cut to equal one compression ratio. You'll have to mill over .100" to get compression on the high side of the 8s. Then you'll have to have the intake milled to match. That's a LOT of cuts for the machine shop, because they cannot do it all in one pass. It's not gonna be cheap, plus, you'll have an intake that you can ONLY use with THOSE heads. Get a clue. That's not the right way to do things. DO it right, or take up solitaire.
 
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