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Discussion Starter · #1 · (Edited)
If you need one more dyno and drag test to look forward to...

1970 MC
4110 lbs
Original TH350 and converter
Locked, 2.56 12-bolt

Current 467 (estimated 450-460 hp) showing about 380 hp running 13.0 @ 108 mph, best 60’ 1.98.

In case you’re wondering about the disparity between max hp and hp shown in the quarter, think about the gap between the stock stall and peak hp with 2.56 gears. 1st gear, 5400 rpm is about 66 mph, the trap comes at about the same rpm in 2nd gear. The car is nearly a dead hook with the 255/60 Kelly Charger radials.

Anyhow, here’s where it gets exciting...placed an order with Mark (VortecPro) for a stock-appearing stroker. He’s confident it will still go over 600 hp with headers, even with the cast iron intake and QuadraJet carb.

I’ll give updates along the way, as things get closer, in the meantime, I’m open to your thoughts on the challenge.

Fuel system seems to be high on the list. I want to see how this pans out.

Maybe driveshaft/u-joints? I won’t be anywhere near a critical rpm, but the driveshaft/u-joints will be putting in overtime if the tires hook up.

For quick reference, 6000 rpm = 74 1st gear, 120 in 2nd with a 26.5” tire.

The question we will hopefully answer this year...will it run 11s or quicker as the car sits? Once this is determined/confirmed, will it run 11s with exhaust manifolds in stock appearing trim?

Needless to say, I’m fairly excited.
 

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Anyhow, here’s where it gets exciting...placed an order with Mark (VortecPro) for a stock-appearing stroker. He’s confident it will still go over 600 hp with headers, even with the cast iron intake and QuadraJet carb.
Talk about burying the lede!! Congrats on your purchase!!

That motor gonna be happy running around on a 2.56 gear? I'm assuming you talked it all through with Mark. I think I see what you're trying to do -- make your torque with a MJ big block instead of via gearing. Be careful with torque converter selection.

-Dave
 

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Discussion Starter · #3 ·
Talk about burying the lede!! Congrats on your purchase!!

That motor gonna be happy running around on a 2.56 gear? I'm assuming you talked it all through with Mark. I think I see what you're trying to do -- make your torque with a MJ big block instead of via gearing. Be careful with torque converter selection.

-Dave
Thanks Dave.

There are a few things which will make this engine a little different from Mark's typical 650 hp, 496, things to broaden the power band (as if it really needs it lol) to work with the factory converter, and eventually manifolds.

Hopefully, the lack of real traction prevents driveline catastrophes. I’m imagining a smooth roll-on start and a long, steady thrust back into the seat.

A TH350 with 2.56 gears, in this case, acts like a power glide with 3.90 gears at the stripe, more or less. I’m hoping the shallow combined first gear and extended time in the upper rpms allows the engine to apply enough average power to run the number.
 

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A smooth start doesn't make for a good ET. The most important part of a pass down the track is the first 330'. After that, not much will change the resulting ET unless you're Top Fuel or the like!
 

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Discussion Starter · #5 · (Edited)
A smooth start doesn't make for a good ET. The most important part of a pass down the track is the first 330'. After that, not much will change the resulting ET unless you're Top Fuel or the like!
Thats what makes this idea intriguing, can it be done? My best guesstimate is that I need a 60’ in the low 1.7s to get in the high 11s. So, the whole idea boils down to is there 0.3 of a second improvement in the 60’ between what I have now and what Mark delivers (and I can put down in the first 60’). After 60’, Mark’s hp will do what it will do, and that’s add mph.

I can tell you there’s about 0.3 of a second difference in the 60’ between 14.1 and 13.0, with both passes applying the same hp after 60’. If the 60’ improves by 0.3, the rest should take care of itself.
 

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You will achieve your goal and then some. I ran a [email protected] mph with 2.56 gears in my 70 SS454 many years ago. I did have 1 3/4" primary headers,2.5" exhaust and a B&M 2400 Holeshot convertor. 60 ft. was 1.83 using a 235/60/15 BFG drag radial.
 

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You'll certainly have enough engine. I'm looking forward to the results. Big fan of the MC's too. Post pictures along the way if you can.
 

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I like the way your thinking. Using the th350 as a power glide and having third gear as an overdrive. I’ll be interested in whats learned with this. Are you thinking high stall to get off the line? Or stock tight to maximum your power band ? Seems like an ideal street strip set up if you can get it done. Drive on the highway at low rpm to the track and click off 11’s then drive it home, all while being able to hear your self think. I’d say that’s just about ideal.
 

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1971 Chevelle. Carb’d 6.0 LS Th350 3.90 12 Bolt. 1972 Greenbrier Wagon 489, 700r4 3,73 12 bolt
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Sounds like fun...I think it will be tough to pick up .3 in the 60’. Thats alot of weight to get going. You are good at getting the car off the line now, I think you will get your 11’s.
 

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You probably have enough engine to pull it off, but that just seems like it's gonna be such a lazy start, even if you get your 1.7 60' -- I just noticed you said you're keeping the stock converter?? I wish you the best, but I predict that will be your Achilles heel.

-Dave
 

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It will run 11.90's with the right converter and 2.56's, that part is the key to good times. Good luck, if I can run 11.20's with an 8:1 BBC and a 3.70 effective gear I think you can do it, especially with one of Mark's engines.
 

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Discussion Starter · #12 · (Edited)
I like the way your thinking. Using the th350 as a power glide and having third gear as an overdrive. I’ll be interested in whats learned with this. Are you thinking high stall to get off the line? Or stock tight to maximum your power band ? Seems like an ideal street strip set up if you can get it done. Drive on the highway at low rpm to the track and click off 11’s then drive it home, all while being able to hear your self think. I’d say that’s just about ideal.
I’m planning on giving it an honest effort with the cast iron intake, QuadraJet, and headers with the original converter. In any case, this will be done on hard tires with a possible attempt on a 255/60 ET Street R if the hard tires spin in vain.

We’ll see where this ends up with headers, then swap to manifolds and 2.5” exhaust to get closer to FAST class legal. Hopefully, it’ll still run 11s with manifolds, on FAST class legal tires.
 

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I tried to get a Qjet to run on one of Mark's mill; and it runs, but NOTHNG like a race Holley. I;ve yet to fiddle with all the tuning tricks Eric built into the Qjet.

They have a hard time handling this power level, FOR SURE!
 

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I’m planning on giving it an honest effort with the cast iron intake, QuadraJet, and headers with the original converter. In any case, this will be done on hard tires with a possible attempt on a 255/60 ET Street R if the hard tires in vain.

We’ll see where this ends up with headers, then swap to manifolds and 2.5” exhaust to get closer to FAST class legal. Hopefully, it’ll still run 11s with manifolds, on FAST class legal tires.
If your trying to do this all stock appearing All the better. To me seeing what looks like a stock classic run effectively at the strip is much more impressive than a “race car” running 11’s. I’m eager to see if you can get the 60 down especially with a hard tire and that gearing.
 

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Discussion Starter · #15 ·
You probably have enough engine to pull it off, but that just seems like it's gonna be such a lazy start, even if you get your 1.7 60' -- I just noticed you said you're keeping the stock converter?? I wish you the best, but I predict that will be your Achilles heel.

-Dave
Dave, honestly, I’m not sure if the original converter is an asset or liability.

On one hand, it’ll help keep the engine out of the highest torque peak before the chassis has reacted, and that’s good for traction in the first 3’. However, before adding the locker, I found that taking off from a stop light without partially spinning a tire was nearly impossible on smooth blacktop surfaces. The engine had a slight part-throttle stumble that translated into a sudden-but-small climb in rpm which would spin a tire.

This leads me to believe a tight converter might actually be worse in traction-challenged applications, because it causes the tires to respond too quickly to engine input, i.e., almost a direct drive of the wheels before the chassis can react.

This could make driving it out of the hole with hard rubber a major challenge, especially when you have an engine bringing major sauce. I guess what I’m saying is, a high stall convert can act somewhat like a shock absorber, or accumulator, allowing you to better modulate the launch.
 

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Discussion Starter · #16 · (Edited)
You will achieve your goal and then some. I ran a [email protected] mph with 2.56 gears in my 70 SS454 many years ago. I did have 1 3/4" primary headers,2.5" exhaust and a B&M 2400 Holeshot convertor. 60 ft. was 1.83 using a 235/60/15 BFG drag radial.
Your Chevelle gives me hope that running well into the 11s on street tires with a mild gear is doable. You have a few advantages though; converter (4K) and gear (3.31) jump out as major differences. You have a better intake (square port) and carb arrangement (Holley), too. I’m also thinking you’re slightly lighter (3925) going down the track as well.

You’re probably several tenths slow running exhaust manifolds compared to headers, and obviously, I’ll have that same challenge soon enough.

Are these things enough to keep me out of the 11s? I don’t know...but we will see soon enough.
 

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Dave, honestly, I’m not sure if the original converter is an asset or liability.

On one hand, it’ll help keep the engine out of the highest torque peak before the chassis has reacted, and that’s good for traction in the first 3’. However, before adding the locker, I found that taking off from a stop light without partially spinning a tire was nearly impossible on smooth blacktop surfaces. The engine had a slight part-throttle stumble that translated into a sudden-but-small climb in rpm which would spin a tire.

This leads me to believe a tight converter might actually be worse in traction-challenged applications, because it causes the tires to respond too quickly to engine input, i.e., almost a direct drive of the wheels before the chassis can react.

This could make driving it out of the hole with hard rubber a major challenge, especially when you have an engine bringing major sauce. I guess what I’m saying is, a high stall convert can act somewhat like a shock absorber, or accumulator, allowing you to better modulate the launch.
There is no way its an asset here. You're going to be making a lot more torque, even at idle, than a stock motor and the converter is going to try to transfer the extra torque. It's gonna be lousy-to-miserable at a stop light, as its going to be pulling against the brakes. Your 2.56s will make it that much worse. Before you put it all together, call your favorite converter company and spend a few minutes talking with them as a sanity check.

Also, you say stock TH350. With 600hp and a 2.56 gear, you're gonna put some stress on that thing.

I will say, you are trying for 11s in about the hardest way imagineable -- cast iron (!!) intake, Q-jet, 2.56 gears, stock converter, in a whale of a chassis, with an absolute powerhouse of an engine :) I'm interested to see how your experiment pans out this season. Good luck, I'll be following.

-Dave
 

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1971 Chevelle. Carb’d 6.0 LS Th350 3.90 12 Bolt. 1972 Greenbrier Wagon 489, 700r4 3,73 12 bolt
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I would think a 600 hp motor would blow thru the stock converter. The 454 in the wagon would blow thru the stock 700r4’s converter...the upcoming 489 should annihilate it.
 

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I've seen several people run 3.08 rear gears with some of Mark's 570-600 HP 468s....but I believe all had a custom converter....which is what I would do in this situation.
You really want to run a stock TH-350 converter (one that could otherwise work with a 160 HP 307) in front of one of Mark's big blocks?
That said, sincere congrats on getting a Vortec Pro Motor.....and no one can accuse you of not coming up with something cool to follow.
Best of luck....and keep us all updated!
 
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