750 Mighty Demon

[Badasspen]

I have an Eddy performer Dp manifold on a .040 mildly built 360 truck motor. It is a spread bore and I installed an adapter plate to fit a Holley 4160 square bore and it seals fine. With this setup I was able to get just under 15 sec at the 1/4 mile track. I was hoping to get closer to 13 on my next visit to the track.
Now, I have a brand new in the box Demon with all the fittings I need to install it on my fresh 360 sitting on the shelf. I noticed there is a vacuum leak somewheres in the intake causing a stumble at low RPM and I am thinking of changing out the Performer for an Airgap at the same time. Will this get me the 2 secs I want, or should I just leave it alone?

 

[bremereric]

I have an Eddy performer Dp manifold on a .040 mildly built 360 truck motor. It is a spread bore and I installed an adapter plate to fit a Holley 4160 square bore and it seals fine. With this setup I was able to get just under 15 sec at the 1/4 mile track. I was hoping to get closer to 13 on my next visit to the track.
Now, I have a brand new in the box Demon with all the fittings I need to install it on my fresh 360 sitting on the shelf. I noticed there is a vacuum leak somewheres in the intake causing a stumble at low RPM and I am thinking of changing out the Performer for an Airgap at the same time. Will this get me the 2 secs I want, or should I just leave it alone?

Here's M2C...fix your vacuum leak and leave it alone....750 is going too large for your 360.....:director:

 

[res1vw21]

I agree the 750 will be a bit much, if it was a 340 ir would be a different story but the 360 is a long stroke motor. The air gap might might help a bit though.

 

[jimmyray]

How did you diagnose you have a vacuum leak? Did you spray carb cleaner on the intake gasket and notice a change in idle rpm? A low RPM stumble could be a variety of things: Misadjusted accelerator pump, wrong metering rods/jets, wrong metering rod springs, timing, etc.

What convertor do you have? What is the rear gear? What is the 60 foot time? What RPM are you shifting at? What is your rpm when you cross the finish? Headers? Cam specs?

It is possible the carb is holding you back, but unless your motor is designed for higher rpm (5000+), a bigger carb may raise your ET, not lower it. We can help, but need a good bit more info.

 

[Badasspen]

How did you diagnose you have a vacuum leak? Did you spray carb cleaner on the intake gasket and notice a change in idle rpm? A low RPM stumble could be a variety of things: Misadjusted accelerator pump, wrong metering rods/jets, wrong metering rod springs, timing, etc.

What convertor do you have? What is the rear gear? What is the 60 foot time? What RPM are you shifting at? What is your rpm when you cross the finish? Headers? Cam specs?

It is possible the carb is holding you back, but unless your motor is designed for higher rpm (5000+), a bigger carb may raise your ET, not lower it. We can help, but need a good bit more info.

Carb has been rebuilt to specs by me.
Idle changes with starting fluid at #6 and #8 at intake to head gasket.
Timing is a little advanced at 8btc with vac advance disconnected and plugged.
Converter is 10" unknown, most likely a 2500 stall.
Rear gears are 4.10 to 1. Hooker headers. Cam is .273 / .476
I shift by ear at around 4500 rpm reaching about 6000 at finish at 91 mph. No Tach.

 

[bremereric]

What intake gasket?

I stand by a Felpro 1213 intake gasket it is like a printo-seal one...I still use a little black stuff on both sides at the water openings...and I mean a little...

http://www.summitracing.com/parts/FEL-1213/

and if you want a better run try 10 degrees before tdc and get your distributor recurved to throw in another 24 degrees at 2500 rpms....34 degrees total timing...right now you don't know what you have

 

[jimmyray]

Carb has been rebuilt to specs by me.
Idle changes with starting fluid at #6 and #8 at intake to head gasket.
Timing is a little advanced at 8btc with vac advance disconnected and plugged.
Converter is 10" unknown, most likely a 2500 stall.
Rear gears are 4.10 to 1. Hooker headers. Cam is .273 / .476
I shift by ear at around 4500 rpm reaching about 6000 at finish at 91 mph. No Tach.

I misread your original post, and thought you were running an Edebrock (carter) carb. With 4.10's, I would think you should be running much better times, even with a mild 360.

FWIW, the vaccuum advance is worthless at WOT, but helps street economy. Do you know the total timing? What are your 60 foot times? How do you launch - load the converter or punch at the green? You definitely need a tach to know shift points, the ear can be deceiving.

 

[Badasspen]

[ the ear can be deceiving.[/QUOTE]

Not when you built the engine yourself kiddo.

Still has the stock 1.88 intake valves and dished pistons, but I built it for an all around roadtripper/weekend warrior.
It sure likes that TRICK racing fuel!

Eric, I used the big fat blue felpros like always with a light coating of copper hi temp.

Ross, how do you feel about Holley carbs? My ol" Man swears they are junk and he has been building Mopars way before either of us were on the potty. I'm just not getting the same throttle response that I got with my 340 and it only had an Eddy 550.
The vac. secondaries don"t do it for me either.

 

[res1vw21]

Ross, how do you feel about Holley carbs? My ol" Man swears they are junk and he has been building Mopars way before either of us were on the potty. I'm just not getting the same throttle response that I got with my 340 and it only had an Eddy 550.
The vac. secondaries don"t do it for me either.

I don't use anything but Holleys I never have been able to get a webber or eddy tuned in right. I pretty much only use 4150 DP's though but all my stuff is 4spd cept the newport which I just picked up a vac secondary 600cfm holley for, I am gonna pull off the 4150 650cfm dp and put that on.

 

[jimmyray]

...the ear can be deceiving.

Not when you built the engine yourself kiddo.

Well, you obviously don't need my help, then. But I am mystified how building one's own engine obviates the necessity of a tachometer.

 

[1980volare]

your carb is to big. try a 600 edelbrock, or holley......sell the demon and buy 3 or 4 holleys or edelbrocks. properly tuned it should be in the high 12's easy.


i go 15.2 at 93 with a BONESTOCK 318 leanburn and 2.7 gears. you should be way faster.

 

[Badasspen]

Well, you obviously don't need my help, then. But I am mystified how building one's own engine obviates the necessity of a tachometer.

No offence meant at all. There are only 3 positions of throttle as far as I can tell. 1 is idle, 2 is shift (just before nose over) and 3 is redline, WOT, standing on it, or whatever you want to call max power. I will install a tach as soon as I get the guts to cut up my cluster bezel.

 

[Badasspen]

Hey guys got a question, is it OK to let the wife drive the R/T ? I am afraid she may not give it back!

 

[bremereric]

Hey guys got a question, is it OK to let the wife drive the R/T ? I am afraid she may not give it back!

My worst fear is that she may wreck it...:icon_batman: