What will it run?

-
S

Scampin

Well-Known Member
Joined
Aug 27, 2005
Messages
384
Reaction score
293
Finally going to take my 64 barracuda to the track wednesday. I have about 400 miles on it, seems fairly strong for what it is. Stock factory 64 273 longblock with 84k miles, summit .450 lift hydraulic cam, edelbrock tm5, 72 340 thermoquad and air cleaner, msd, factory exhaust manifolds, 40+yr old thrush side pipes, spec clutch, 4spdw/ 2.45 first gear, 8 3/4 w/ 3.23 posi, original d60-14 polyglass tires. I guess mid-low 15's.
 
I am going to guess on the conservative side at 15.98! My full (bracket) race 273 CID 1965 Valiant pictured did a best of 12.72 @ 108 MPH back in the 1970's.
 

Attachments

  • 8436432-1965ValiantEffortcopy.jpg
    39 KB · Views: 330
It's a slug. Didnt break anything, which is good. Couldnt get it off the line without bogging. On the street rev it up, dump the clutch, it spins and goes. At the track rev it up, dump the clutch, it hooks and bogs. Tried tightening the air door, giving it more pump shot, restrictor in the pulloff, still bogged. My g/f rode along every pass, best pass 16.9 @87mph with a earth shattering 3.0 60ft. Worse pass was a 64.99, lol. The little motor just doesnt have enough to not bog with that big thermo and tall gear. Its a shame because it got 23mpg on a trip this past weekend. Have a 600cfm carter i'm going to borrow to see what it will do. 87mph should be good for a low 15 on a decent working car... We shall see.
 
Before you pull the TQ check the secondary butterfly opening, they should only open around 80%. You can also bend the tab on the air door to fine tune secondary. I would try decreasing air door opening.
 
mderoy340 said:
Before you pull the TQ check the secondary butterfly opening, they should only open around 80%. You can also bend the tab on the air door to fine tune secondary. I would try decreasing air door opening.
Click to expand...

Yeah I have been around the block a few times with thermoquads. Bending the door "changes the a/f" though I have found it just changes the number on a/f meter and never adds up to anything on the slip. I have learned to leave the air door where the car goes the most mph, and adjust the a/f with jets and metering rods.

I tried launching anywhere from 1100 to 3800rpm. Best time was walking it off idle. Its amazing how alittle traction changes the characteristics of a car... on the street it really drives pretty darn good.
 
Scampin said:
It's a slug. Couldnt get it off the line without bogging. On the street rev it up, dump the clutch, it spins and goes. At the track rev it up, dump the clutch, it hooks and bogs.
Click to expand...

Scampin said:
I tried launching anywhere from 1100 to 3800rpm.
Click to expand...

If you were dropping the hammer at 3800 and it was still hooking and bogging with d60-14 polyglass tires I'd say there is a tuning issue for sure.

Where you doing a burnout? If so try not doing one. Some slip would probably help you at least for now.

What's the timing curve look like?

I'd still like to see you try a different carb.
 
I did a burnout the first couple runs, then realized I did not need to. lol. I'm sure if I spent enough time on it and threw the gauge on it, I could get it to do what I want, but the end result is I am trying to use a 800+cfm carb on a 8:1 273 that has a single plane, and way too tall of gear. I think I will be miles ahead throwing on a carb that more matches the size of the motor. Timing curve is 16 intial, 36 total in by 2k. Not sure what you mean by the polyglass comment? I have gone 1.54 on g70-14's... lol
 
Getting 23 mpg is awesome u should just invest 500 bucks with 100 shot and it will pick up a lot and still get same mpg and be as tame
 
Scampin said:
the end result is I am trying to use a 800+cfm carb on a 8:1 273 that has a single plane, and way too tall of gear.

I think I will be miles ahead throwing on a carb that more matches the size of the motor.
Click to expand...

I've mentioned this several times. I like the HP series carbs. A QFT or proform would serve you well too. I'm running a 950 proform on mine. My father has the 750 Qft.

Timing looks good, in a little quick for a street car but if it's working don't change it.
 
Wayyyyy too much carb and too big an intake for that little 273...
 
I was going to tell you to "Walk it out" but you did so and for the best time even. On my 4spd ride, on the street, I have to walk it out a bit. I apply as much throttle as it can take and up to the point but not beyond just radically spinning the tires. (The engine has a lot of power & and can just sit and roast the hides until the cow's come home. So it is a balance to walk.)

What size carb were you thinking about?
Try a dual plane intake. My old 318 did very well with a LD4B I think it was. Finding a intake for the old odd bolt angle LA can take time. (If that is the old head on top.)
 
Scampin said:
It's a slug. Didnt break anything, which is good. Couldnt get it off the line without bogging. On the street rev it up, dump the clutch, it spins and goes. At the track rev it up, dump the clutch, it hooks and bogs. Tried tightening the air door, giving it more pump shot, restrictor in the pulloff, still bogged. My g/f rode along every pass, best pass 16.9 @87mph with a earth shattering 3.0 60ft. Worse pass was a 64.99, lol. The little motor just doesnt have enough to not bog with that big thermo and tall gear. Its a shame because it got 23mpg on a trip this past weekend. Have a 600cfm carter i'm going to borrow to see what it will do. 87mph should be good for a low 15 on a decent working car... We shall see.
Click to expand...

You need to launch it at a higher rpm.....
 
I know it is a miss-match of parts.
When I was re-gasketing the motor I was going to throw the 2bl back on, looked over at the shelf and decided to grab a 4bl intake and carb.
I have a 750 holley set-up for blowthrough, a 750 holley d/p, a 1000cfm comp. series thermo, 2 bigblock, and 3 340 thermos all rebuilt. Intake choices were a choice of 3 71' 340 intakes, 3 72' 340 intakes, ld340, tm5, and a couple 2bl intakes. The tm5 had the smallest ports. The carb was one of the first thermos I built for the duster, flows a little over 840cfm. Threw some small jets in it and decided to see how it would do.
A buddy has some carter 600 340 carbs I will try next. I don't really want to throw any money in this, just want to get as good as combo as I can with whats at hand.
 
I have ran a very similar combination to yours but automatic Trans in my old 67 Dart. My average ET was about 16.2. It was better with a Carter afb. I did squeeze it once with a friend's 125 shot of nitrous. I cut an. 001 light and ran 13.8. At 103 mph.

I really had to spin the 273 to get it to make power and stay in the power. I would launch it at a higher rpm if you can. Launch at 5000 with a gentle clutch engage. Shift at 6500. That 450 lift solid lifter cam is not helping your launch. It is making its best power probably after 5000.

By the way I have an old LD4B sitting in the garage. It was the manifold I used back in the day.
 
when I ran my 273 dart, I launched at 5000 rpm. anything less it bogged badly!! you are right, you don't have the right gear ratio's. a 2.66 trans ratio would help some. I shifted at 6000 RPM. need to tighten air door or loosen it, depending on what it likes!!!
 
You're right about the 8.1cr. Not a lot of low-speed torque at that number.
I think the problem is in the plenum size. When you drop the hammer, the manifold vacuum drops like a stone, the airflow momentarily stalls.
A Small-port Dualplane,with a small plenum, will keep the vacuum up, and prevent the boosters from stalling, and will pull up the low speed torque.

87mph is pretty good; especially so with a passenger.
 
You must log in or register to reply here.
-

Back
Top