360 does not seem to be making power and is slow in the 1/8. Need help and/or suggestions

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440BelII

440BelII

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Hello FABO racers,
We are having some issues with our 360/727 combo in our 72 Demon. It seems to have a hard time making power and is extremely slow in the 1/8 mile.
We initially set out to build the car to run at our local 1/8 mile track. We set out to get the car to go mid 7s (7.40s-7.60s). Here is the combo:
360 bored .030 and zero decked
KB107 flat top pistons
Stock crank and rods with ARP hardware
Howards flat tappet cam .510/.510 lift 247/247 @.050'' with 108* lobe separation
Edelbrock Performer RPM intake, topped with Proform 750 race carb (unsure of jets; carb came off of a 69 camaro with a healthy 383 stroker). Based off of compression calculators; the motor should be around 9.9-10.0:1 compression.
Heads are J heads with a just a little bit of clean up work done. Also have Ferrera 2.02/1.60 Stainless valves and new Valve springs to support the cam.
Fuel pump is a Carter Muscle car fuel pump, 5/16 line that provides 6psi of pressure at idle
The trans is a 727 with built internals, a turbo action reverse manual valve body. The converter is a 10 inch converter that was rated for like 3500-3800 stall but on this it flashes to 3000 rpm.
Rear end setup is an 8.75 with Moser 30 Spline Axles and a Strange 30 Spline spool with Richmond 4.30 gears.
As previously stated, the we were shooting for mid 7s (7.40s-7.60s) in the 1/8 mile with this combo. We set out to test the car at the track and the best time the car turned was a 9.03 @76mph with a 2.05 60 foot time; which seems extremely low even for this combination. My son said The car seemed to be breaking up at 4000-4200 rpm and up when he was making his test passes. We had a hi-rev 7500 ignition box from jegs on the car with an Accel distributor that was similar to a stock Chrysler distributor with lighter advance springs in it. When it made its best pass of 9.03, the timing was set at 34* total, my son built the converter up as high as he could at 2,000 rpm and he said it seemed to want to push right through at 2100 and the car was super slow out of the hole, seeming to be laboring itself down the track. We have been recommended a few different things to get to the mid 7s range with it (11.70 or so in 1/4 mile). We have been told it may not hurt to change to an MSD ignition setup, also change the Cylinder heads to aluminum heads to raise the compression and get better flow. Also people said to change the fuel system to 3/8 line and pump. and last but not least; changing to an 8 inch 4500-5000 stall; along with different heads, fuel system, and MSD setup to get to mid 7s versus the 9.0 we are at. Any help and suggestions would be appreciated. Would it be more beneficial to go to Edelbrock or TrickFlow heads, would a 4500-5000 stall be too much or just right, and What other changes should we make? We can try to send a video of the run and pictures of time slips if that would help.
Thank you for your help in advance.
 
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I agree, it's very slow for what it is. I agree, your expectations were realistic. I strongly disagree in throwing parts at it such as heads. Fix the issue at hand. Get it to run what you expected it to run, then add better performing parts. Way too many folks just throw money and "upgraded parts" at their projects to substitute a real underlining issue(s). Tuning and tweaking is time consuming and a learning process, but it's worth it.
 
MOPAROFFICIAL said:
What heads and what has been done to them ?
Click to expand...
Whoops totally forgot to put it in the post, sorry about that. They are J heads with a just a little bit of clean up work done. Also have Ferrera 2.02/1.60 Stainless valves and new Valve springs to support the cam. Will add that into post now
 
318willrun said:
I agree, it's very slow for what it is. I agree, your expectations were realistic. I strongly disagree in throwing parts at it such as heads. Fix the issue at hand. Get it to run what you expected it to run, then add better performing parts. Way too many folks just throw money and "upgraded parts" at their projects to substitute a real underlining issue(s). Tuning and tweaking is time consuming and a learning process, but it's worth it.
Click to expand...
Very true, not sure if it is just one issue or multiple ones. Some say it is just fuel line and pump is too small, others say ignition needs to be updated. We plugged a stock ignition box to see if there would be any difference and my son said it seemed it may have been slightly better than even the high rev 7500 box from jegs on a basic street pull. obviously wont be able to tell until we hit the track again
 
440BelII said:
Whoops totally forgot to put it in the post, sorry about that. They are J heads with a just a little bit of clean up work done. Also have Ferrera 2.02/1.60 Stainless valves and new Valve springs to support the cam. Will add that into post now
Click to expand...
Going off your description..They could be peak flowing anywhere from 200-230 cfm. Not great, not horrible..just lacking and the no.1 in line for things to upgrade.

There is something wrong with the 60'
That's tune or chassis issue.
 
What are you using for traction? Slick's or drag radials? Are you using super stock Springs an a snubber or caltracs or what?
 
Will need a real convertor to run 11’s
I went 11.60’s in a heavy car with stock fuel tank and 5/16 line
The line diameter isnt an issue. Maybe the fuel pump could be, but you can go FAST with 5/16 line.
Making sure the thing isnt breaking up and will pull cleanly to 5500-6000 grand iswhere i would start. If it wont do that, nothing else matters until it will
 
It sounds like the converter is hurtin' for sure...
what does the car weigh??
 
Take the carb apart and see what jetting is in it.....start with stock jetting....probably not the problem but you need to eliminate things

most likely the off the self converter.....
 
The carb being formely used on a Chebbie is always suspect... so yes check the jetting.
 
That 60 ft is abysmal. A decent converter would be my first change after covering the tune up basics.
 
Since its breaking up the first 2 things I'd check is fuel and fire! Is the distributor hooked into the vacuum properly? Timing? Starving for fuel ? Etc that's where I'd start.
 
I strongly disagree in throwing parts at it such as heads.
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I agree.

There appears to be two issues, which may or may not be related.
A- won’t rev
B- 60’ sucks

I wouldn’t make any changes to the “combination” until you figure out why it won’t rev, and then fix that.
Most likely some sort of ignition issue.

After that’s solved, go back to the track and see what it runs.
There should be a big improvement in MPH.
If the 60’ times still suck, and it’s not spinning, it’s likely time for a converter.

But imo, step one needs to be getting it to pull cleanly into the upper rpm.
 
Have you tried leaving from idle? It won't in the 7's but your converter may work better and pick up some 60'.
 
Some easy things to check, make sure you don't have any plug wires too close to one another (specifically, ones that are in line on the cap, don't let those wires touch if possible). Many years ago I had a miss up high in the RPM range that was nothing more than that....easy fix.

Check jetting, vacuum leaks, does it get full throttle, fuel pressure, etc.

While I agree it should be faster, I would not be too surprised if it ran low 8's with the current setup. To me, it sounds like you have a few things going wrong at the same time.
 
If there is a chassis dyno service not too far away, after you get the high rpm issue taken care of, it might be worth making a few pulls as a baseline test to see how the converter is working, along with monitoring the fuel curve at WOT.
 
I didn't read all the answers. But I read of your input. You need a much higher converter. It should brake stall no lower 3500 with a small block you need a 4500 converter to do that. Get and 8 inch converter. I run a 5500 on my 340 and Foot brake to 3000 . Here it is on a foot brake

 
Oldmanmopar said:
I didn't read all the answers. But I read of your input. You need a much higher converter. It should brake stall no lower 3500 with a small block you need a 4500 converter to do that. Get and 8 inch converter. I run a 5500 on my 340 and Foot brake to 3000 . Here it is on a foot brake

Click to expand...


where a car will footbrake to wont make a lick of difference in how fast the car will ET.... in most cases, assuming the convertor flashes just past peak torque, where it should.
In other words, i currently have a convertor that flashes 5100.
I can footbrake it( without rolling through the beams comfortably) to around 3200. That is partly because of the convertor, partly how good the brakes are. Both are a factor.
I can leave at 1500, 2000,2500 or 3000, and the car ET’s virtually the same. I use the rpm to adjust my reaction time, nothing else. In all those cases, the convertor is still going to the 5100 flash before it “ hooks”
In fact, every convertor i have ever had, the above is true. Where ever i leave at rpm wise, the ET Doesnt change.
In fact, if the convertor is specced correctly, i havent seen any difference off the foot, or using a brake. If there is a notable difference, i submit the vert is off somewhere.
Some convertors might be “ tighter” to where you cant bring it up off the foot holding your foot on the brake anywhere near the above example. That could be the case and yet the convertor could be correct for the car.
Example a mild combo might like a 3500 flash convertor that will try to creep At maybe 2200 rpm..
Nothing wrong there, just might be what that combo needs to run best.
I have often found not pushing the convertor as far as the brake will hold it is wise. It allows the suspension to be “ relaxed” and not tense. Particularly noticeable with a leaf spring car.
In short, there is seldom any advantage ET wise to push the convertor to the limit the brakes will hold it, before launching the car.
Just my experience..lol
 
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B3422w5 said:
where a car will footbrake to wont make a lick of difference in how fast the car will ET.... in most cases, assuming the convertor flashes just past peak torque, where it should.
In other words, i currently have a convertor that flashes 5100.
I can footbrake it( without rolling through the beams comfortably) to around 3200. That is partly because of the convertor, partly how good the brakes are. Both are a factor.
I can leave at 1500, 2000,2500 or 3000, and the car ET’s virtually the same. I use the rpm to adjust my reaction time, nothing else. In all those cases, the convertor is still going to the 5100 flash before it “ hooks”
In fact, every convertor i have ever had, the above is true. Where ever i leave at rpm wise, the ET Doesnt change.
In fact, if the convertor is specced correctly, i havent seen any difference off the foot, or using a brake. If there is a notable difference, i submit the vert is off somewhere.
Some convertors might be “ tighter” to where you cant bring it up off the foot holding your foot on the brake anywhere near the above example. That could be the case and yet the convertor could be correct for the car.
Example a mild combo might like a 3500 flash convertor that will try to creep At maybe 2200 rpm..
Nothing wrong there, just might be what that combo needs to run best.
I have often found not pushing the convertor as far as the brake will hold it is wise. It allows the suspension to be “ relaxed” and not tense. Particularly noticeable with a leaf spring car.
In short, there is seldom any advantage ET wise to push the convertor to the limit the brakes will hold it, before launching the car.
Just my experience..lol
Click to expand...
I reference his combo. His stall is to low for that motor with that cam and compression. 4500 would work a lot better. If the car don't 60 foot a higher stall converter will be the way to go. This is just experience I have had.

The video above the car went 10.79 and weighed 3850 with driver. stereo playing, spare in the trunk through the mufflers, LOL Barely got it wound up in drive, 5500 stall . What gears do you think?
 
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