Advice on moving forward

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69dodgedart360

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Getting ready to go back to the strip and need a little advice. I have a full weight 69 Dart with a 360/727. The 360 is about 12 years old and has about 40,000 miles on it. Dry wet compression tests show 170/195 except #6 Was 160/195. The motor has an edelbrock 650carb, edelbrock air gap, x heads, tti headers and a comp xe284 thats been advanced an additional 4 degrees.the 727 has a 2400rpm stall w/ a shift kit. 3.55 gears and 235's. The car has run 13.40-13.60 @102-104 on drag radials and 60 ft's were bad, 2.10's.

I have an opportunity to buy a 3.91 gear 3rd member for a decent price. Would it really help me much over my 3.55's? In a perfect world, I would buy a better converter and rebuild the 360, but I'm broke and wanna try and get into a high 12 before I rebuild this thing. Any advice or suggestions are appreciated. Thanks.
 
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The 3.91 will help all the way down the track, but the 60' times are where you can drop the ET the most. Tires, suspension, weight transfer, what ever it takes to hook up and not bog. Get a 1.75 60' and you are in the 12's.
 
If you have enough compression to run the cam you have listed then I think you need more carburetor . See if you can borrow a couple different carbs from buddies and go out and do test and tune .
 
More gear would help as well as carb cfm.
Your not spinning tires are you?
Bogging at the line?
What is the launch rpm?
Foot braking the car?

What is your rear suspension?
Stock leafs?
What about your shocks?
What is the ignition and how is it set up?
 
Getting ready to go back to the strip and need a little advice. I have a full weight 69 Dart with a 360/727. The 360 is about 12 years old and has about 40,000 miles on it. Dry wet compression tests show 170/195 except #6 Was 160/195. The motor has an edelbrock 650carb, edelbrock air gap, x heads, tti headers and a comp xe284 thats been advanced an additional 4 degrees.the 727 has a 2400rpm stall w/ a shift kit. 3.55 gears and 235's. The car has run 13.40-13.60 @102-104 on drag radials and 60 ft's were bad, 2.10's.

I have an opportunity to buy a 3.91 gear 3rd member for a decent price. Would it really help me much over my 3.55's? In a perfect world, I would buy a better converter and rebuild the 360, but I'm broke and wanna try and get into a high 12 before I rebuild this thing. Any advice or suggestions are appreciated. Thanks.
Figure out what your issues are now WITHOUT going one step further. You should already be in the 12's with ease.
 
Thanks for the replies, no spinning off the line last time I went, I think it is just a real soft launch due to the converter and at the end I'm only trapping like 4700-4800 because of my gear. I would footbrake it to about 1800 and launch from that and it would flash to about 2400. The car has SS springs, cheap local auto store shocks all the way around, stock MSD ignition. I will look for an old slip.
 
Looks like the issue is in the launch. I think the 391 is a good idea, but i also think the carb and timing is part of it. I was able to drop over a second with just a different carb, and timing, and shift points. Your converter sounds like it's working ok.
 
Which case? For a 742 or 489 case it would be worth it. 741 case maybe, not because everyone thinks they are weak, but because new ring and pinions are very limited in the 741 case. Strip only car and I see 4.10's in you future. 6200 rpm at the stripe with 26.5 tall tire.
 
3.91's are my favorite gear for a street car, 489, 742 or 741 don't matter. Buy it and have fun.
 
remove hood. play with timing, jetting, tire pressures first. I wouldn't change anything.
 
Thanks for the replies, no spinning off the line last time I went, I think it is just a real soft launch due to the converter and at the end I'm only trapping like 4700-4800 because of my gear. I would footbrake it to about 1800 and launch from that and it would flash to about 2400. The car has SS springs, cheap local auto store shocks all the way around, stock MSD ignition. I will look for an old slip.
Here is the problem: The converter is getting the blame, as is the gears. So, people will throw more gear and converter at it and the 60 ft times will come down, as will the E.T. Then they say, problem fixed! WRONG! Problem MASKED is the correct answer.
  • Example: I just cut a 2.0 60ft with 2.45 gears, 15" tire, stock stall, tranny, and basically an almost 100 % stock 360 with manifolds in a full weight Duster. No, I don't want a cookie :D ! Just pointing out that better gears and stall will help, but your masking a power loss. Yes, I'm aware my cam likes a lower RPM, but your converter and gears are worth more than anything that my cam is offering under 2500 rpm's. That is why I said above "don't change a thing, fix (tune) the car as it is now"; it should go 12's
 
The 3rd member is a 741 case and yeah it isn't the most ideal case for a ring and pinion. I just ordered an edelbrock carb tuning kit and will give that a go when I make it back to a track and can actually test the changes. I do have a spring and bushing kit for my MSD distributor and will bring that with me too when I can test it out. I hear what you are all saying about not making any changes but the range of my cam is 2300-6500 so maybe my torque converter just isn't putting me where I need to be? Couldn't find any old slips but I do remember 60 ft times were in the 2.10-2.18 range. I recently changed the distributor springs to the lightest ones and at WOT it pinged pretty bad so I changed it back to stock for now.

Skep, I wish my car ran 7's in the 8th lol.
 
Skep, I wish my car ran 7's in the 8th lol.
Oh yea! Skep gettin it done!

Yes, your stock converter is an issue. Get that done later. It is pricey and not a huge issue. Just part of the jigsaw puzzle.
If you can get the gears easy enough, I'd do that. Keep tuning everything. Carb, timing, tire pressure, weight balance.
What do you have for rear springs?
 
Rumble, I have SuperStock Springs with just some regular monroe shocks in the back. No pinion snubber. I am gonna ask about that 3rd member and see if I could pick it up this weekend. In the meantime, just waiting on some parts and then hopefully when it is not 90 plus degrees, go to the track and test stuff out. There is Mopar Magic up in Sacramento on the 10th of September that I would like to get some runs in.
 
Getting ready to go back to the strip and need a little advice. I have a full weight 69 Dart with a 360/727. The 360 is about 12 years old and has about 40,000 miles on it. Dry wet compression tests show 170/195 except #6 Was 160/195. The motor has an edelbrock 650carb, edelbrock air gap, x heads, tti headers and a comp xe284 thats been advanced an additional 4 degrees.the 727 has a 2400rpm stall w/ a shift kit. 3.55 gears and 235's. The car has run 13.40-13.60 @102-104 on drag radials and 60 ft's were bad, 2.10's.

I have an opportunity to buy a 3.91 gear 3rd member for a decent price. Would it really help me much over my 3.55's? In a perfect world, I would buy a better converter and rebuild the 360, but I'm broke and wanna try and get into a high 12 before I rebuild this thing. Any advice or suggestions are appreciated. Thanks.

What gas are you running? And what power-timing?
To get the 168psi, I back-worked the calculator and came up with this
Static compression ratio of 10.2:1.
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 8.30:1 .
Your dynamic cranking pressure is 167.70 PSI.
V/P (Volume to Pressure Index) is 145...........................................................145
You may be into detonation! A Dcr of 8.3 with no Q in the openchamber heads will/can do that.
Part of the problem is the 100* install.This brings the ICA to 62*.

Here is the same combo with the Ica @66*
Effective stroke is 2.74 inches.
Your dynamic compression ratio is 8.04:1 .
Your dynamic cranking pressure is 160.92 PSI.
V/P (Volume to Pressure Index) is 134..............................................................134
This is about the limit for pump gas and full timing
Notice tho that the VP has fallen to 134. This makes the bottom end with a 2400 very soft.
This increases your 60ft right there.
Then there is the small matter of the totally wrong gearing to tire size to trap speed. 103 calculates out to about 5100 with 5% slip. Your 4700/4800 means that 2400 is at about ZERO-slip, so the rest of my numbers will be using zero-slip. The problem is that 284 is just waking up at about that rpm. That cam probably power peaks around 5200, and will want the 1-2 shift at about 6600, and the 2-3 at about 6200, and I bet you weren't shifting it there?? So that means at 6200 in second gear you would be hitting 90 mph, and going into third this would be 4270rpm. where it has just woke up. It will want to trap at about 5700.
But I'll almost bet you short shifted both gears at 6000. If you did that, the Rs drop to 3540, and 4140, And with a VP of 145 She'll still be a lil soft down there.

So by my count, your combo is suffering in 5 areas

1) power-timing and possible detonation
2)the 2400 with the VP145
3) the shortshifting
4) trap gears.
5) the little 650 carb

I offer the following solution;

1)Check for signs of detonation and back up the cam to as far as 106 if you have to
2)More TC, a lot more
3)Increase your shift rpms to 6600 and 6200, and run some loops
4) the gear you want is probably 4.10s to get you 5700 on the nose at 104. The 3.91s might get you the same 104, but at 5450ish, IMO a hair low. But if the above mods pick up the trapspeed then 3.91s will work, and are good to maybe 109mph.
5) this would be my last mod, but that engine will like a 750

Now on a budget, numbers 1 and 3 are cheap,
>Detonation will kill your power, so that's the first place I would look. Easiest thing is to back off 4 degrees and see if you go FASTER in MPH. If yes, then go another 4 then start to work your way back.You can get around this for test purposes by running some anti-detonant in your premium. If she traps higher, you're on the right track.
>As to shift loops, work your way up from 6200 in first/5800in second, in 200 rpm increments atta time, and only work one gear atta time starting with the 2-3 shift. Anytime the car slows down, and it's not detonating, go back to the last shift rpm.
>But the TC is the big issue. I would drop that thing like a hot-potato. And here's why;
Your engine won't start pulling until somewhere near 4000, am I right, maybe even later. But with zero tirespin, 4000 is 34 mph. That's why. And the 2400 is making your hot-cammed 360 take off like a warmed up 318. That's why. That 2400 is putting the clamp on your engine at maybe 120ish hp, whereas a 3600 might launch you at 200ish hp ( yeah I'm guessing) but the point is you could be blasting off with a lot more horsepower. And that will really boost the 60ft, and that will knock down the ET, while not doing a lot for the Mph.
Try to get your combo working with the cam in at the current timing, cuz the drop from 145 to 134, will really be felt. And if the 2400TC is staying then the 145 is needed. But if you put a bigger TC in, then retard it!; Solving for detonation trumps everything else. A bigger TC would allow you to retard the cam without loosing the bottom-end cuz you're no longer stuck down there.
>As to the 3.55s, they are making your engine stay in the low-zone for just too long, and robbing you of putting down good average HP. But this is further down the list than the first three.Concentrate on the first three points first, and maybe it will be quick enough for you.
>As to the carb, I would do this last. I wouldn't be in any hurry to swap it out, cuz really it's only barely too small for this combo, and even then only at the very top of the powerband. Mathematically it's not too small at all; (360x6400)/3450 x.85VE(guessing)=568cfm. But mine seemed so much sloower with a 600, and didn't wake up until the 750 or TQ went on it.

Any way, that's all I got,
 
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AJ/FormS: I can't thank you enough for the wealth of information. Same goes for everyone else on here helping me out. I have the MSD 6AL chipped at 6000 so I have been shifting somewhere between 55-5900 rpm. I did have detonation issues on pump 91 and had to bring back the timing. But before I could even do any follow up runs, the differential started to make some whining and then I punched a pushrod through the stock rocker arms at the time. Comp Pro Magnums and a new sure grip have gone in since then but I haven't made it back to test. I do a lot of freeway driving so the torque converter has to be somewhat mild for me. Luckily for me, paypal bill me later sent me an email reminding me of my credit line. So I bit the bullet and bought a turbo action 17805 tight converter. I know it is lower than ideal, but will probably stall around 3000-3200, its rated at 3800rpm. I think it should help over what I have now. I also ordered MSD pills from 6100-6900 and will put in a 6500rpm to allow for a higher 1st and 2nd shift point to see if that helps with the rpm drops in between gears. If I could swing a deal on some 3.91's, I will change them but I am pretty broke, planning a wedding and sinking all my money into that and other bills. Bill me later is amazing and also a problem lol.
 
So was I close? lol
You are now well on your way. But I think tires will be next,cuz
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Here's my combo
Static compression ratio of 10.9:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.72:1 . Aluminum heads
Your dynamic cranking pressure is 178.73 PSI.
V/P (Volume to Pressure Index) is 153..................................................153
Notice my VP is only 8 points higher than yours. And this engine is a tire fryer with street295s or 325/50-15 BFG DRs, hence my 2.2 60fts.
I have a starter gear of 3.55x3.09=10.97
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You have a starter gear of 3.55 x 2.45=8.70
But your new TC could have an instantaneous internal hydraulic ratio of up to maybe as high as 2.0, so that 8.70, could be up to a 17.40 at Zero mph, or rather 1 mph. But this torque multiplication rapidly decays as the vehicle moves out. And the beauty of it is that it happens automatically. So bottom line is yours will be a tire-fryer too. You're gonna love it.
Since you admit to having detonation issues with 91,And if the new TC doesn't solve it: If it was mine, I would reset the installed centerline to about 104/ICA of 66* as earlier indicated. This will bring your Dcr, cylinder pressure back in line with 91 gas.If you can't get 104, you can go a little more retard but not advance; then you'll be set up for 3.91s right away. Yeah, I'm guessing 104 is the smallest ICL. You need to get the power-timing back close to 34/36 , even if that means bringing it in later after 3200/3600rpm. With the new TC, you may be able to run some more Idle timing too. So basically a whole new tune.
 
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