My GTX performs so-so at best (for a mild 440). It has poor performance off the line and until the RPM get up there. Carb, cam, converter and gears seem to be the problem (see below). This car is 100% street and I don't care about gas mileage.

If I go to 3.91's and maybe a ~3000 converter would that wake up my combo or do I need to get more drastic?

Here are the specs:
'70 GTX
Mild 440
Stock compression forged pistons
Polished and balanced rotating assembly
Mildly ported 906 heads
284/484 MP cam
Eddy RPM Performer intake
Stock manifolds, 2.5" exhaust
FBO electronic ignition
727 w/340 convertor (guessing 2300-ish?)
3.55 Suregrip
275/60-15 rear tires (28" tall)

I would leave the Gears alone and just change the Converter. You say its 100% Street, and the 3.91's will have you buzzing down the freeway ~3300 rpms.

are you sure you don't have any problems? Even that combo should boil the hides pretty good. I have 3.91's xterme energy cam (.492 lift I think)and a 3,400 stall and it decimates my drag radials and blows ls-2 vettes away. I would think your combo would be better than you describe.

First problem is the TQ as that cam needs a 3000 to 3500. 3.55 to 3.91 gear change will give a little but not much.
I'll bet your cam could use degreeing and a little advance from suggested intake centerline install.
If it is the 108 lobe separation and a 106 intake install it would really respond to 103 or 102 intake install.
often when a 484 108 lobe center is lazy the cam is in at a slightly retarded position.

My main reason for thinking of this was because of this thread I started on my carb. Most folks said to change the cam (not what I want to do) or add gears and a converter.

https://board.moparts.org/ubbthreads/show...rue#Post5253122

I would get the converter upgraded. (changed)

If your sure your combo is healthy a stall should help alot. My car is 100% street and with a good converter running a 3,000+ stall should not be a problem. I was a little concerned myself about a higher stall on the street but it drives like a creampuff until you stand on it. The 3.91's with a 28 inch tire isn't terrible on the highway if you stick to 60-65, it does get buzzing pretty good over that though. My combo is just a little bigger cam, stall and gear more than yours but it sounds like worlds apart as far as performance, your sure theres nothing else wrong?

I think you should finish one car before you
tear apart another.
Don't you have 2 or 3 projects going on right now?
Or you could sell me your Demon.

What is your compression ratio? If your tune is good, the right converter and cam will do wonders with 3.54's.

What do you have the timing set at, initial and total? What do your plugs look like? You can easily change the cam and lifters with the motor in the car without removing the intake. You can always contact Dave over at Hughes Engines and talk to him about your set-up and see what he recommends.

Nobody thinks the stock exhaust manifolds might be an issue? I had a 440 in my 69 charger with 10:1 flat tops, stock heads, Crane .484 cam, Torker 2 manifold, 850 dbl pump, Cyclone headers , 2 1/4" exhaust, accel dual point mech dist and 3:23 gears...that thing would roast the tires if you wanted to and would eat 5.0 mustangs and 350 vettes for breakfast back in the day....

Make torque power. Go 3.55 gear at most with a 4 speed. Let the 3.75" crank pull you, but compensate with a timing curve. Keep a performer dual plane at all cost. Try a 800 AVS thunder, or 650DP both manually actate the secondaries. Also taylor top end with a spacer.

probably low on CR maybe in the 8.5 zone, that doesn't help with that cam, the exhaust manifolds are not the problem many F.A.S.T. cars running low 11's with them. maybe advance the cam, make sure the FBO stuff is working.

why that cam with a stack compression ?

Torq converter cam make a world of difference. Not sure who's good now, but I know dynamic used to make a good street/strip converter that'd flash stall to 4-5k yet drive basically normally during regular driving. Something like that would be a night and day difference for your car. If you go to a high stall like that, you can leave your rear gears as-is. If you do the stall, the gears won't make much of a difference.

Quote:

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the exhaust manifolds are not the problem many F.A.S.T. cars running low 11's with them.

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True, but the fast guys are also going to be running ported manifolds, higher compression and often stroker cranks. But for his application HP manifolds should do the job decently.

You could also get a shorter tire 26" a 275/50/15 They are a little wider i think about a 1 inch off the top of my head.

284/484 MP cam <--- that be your problem... and if you have a carterbrock carb. 3.91's and more conver will help. or you can swap the cam out for something a more street friendly. I'd do the cam...much easier and cheaper.

The mani's are NOT the issue. While tha manis are not the best for performance, that cam is what is making the car poo poo. Trust me. Swap the cam out, even with a summit 488 cam and you will be much much happier. You won't need 3.91's (although they'd help) and you won't need to change your convert. That 484 cam sucks compression and won't start workingh until 3200rpm. Which means it's DOG off the line. Plenty of cams will work w/ your set-up get one that will work and you won't need to drop the trans or pumpkin.