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What will it run 410 stroker 71 Duster.

Posted By: moparjoe360.4

What will it run 410 stroker 71 Duster. - 06/30/22 03:57 AM

I have a 71 Duster,full interior, steel hood, 73^ disc brake swap. 410 stroker 360, CAST Scat crank, made 467hp and 506 ft lbs on the dyno pulling it to 6k ,727 forward manual VB, 3000ish stall 10in b&m holeshot conv. 4.30 gear, 275/60/15 Et street pro (28ish in. tire)I’m slightly worried about trap rpm and how tight I can safely twist the cast crank, what is a safe max rpm for this crank, and what does everyone think it should run?



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Posted By: J_BODY

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:10 AM

Think the 10” converter gonna hurt the situation but that’s just a hunch. I’ve gone 10.80 in Vegas with our “bracket Betty” iron headed 360 smile
Posted By: AndyF

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:12 AM

Should be fine. If you run mid 11's at 115 mph then the engine will be spinning around 6500 rpm in the lights and the driveshaft maybe spinning at 6000 rpm. 6500 might be a little past your peak power point but it shouldn't hurt anything. You'll just have to play with it and see what it wants. The car might run better with 4.10 gears but no reason to make any changes until you gather some information.
Posted By: Neil

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:14 AM

Something like that would be good for 11.50 something around here at 2800 feet based on someone I know who has a later model Duster set up set up kinda similar.

Think 6000 - 6500 would be a good rpm limit. You'll have to run it with those gears and see what you get thru the lights. Too much rpm and a gear and/or tire size change may be required.

I know of people who have broke cast cranks, but they were in cars raced hard every weekend for several years in a row.
Posted By: topside

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:52 AM

At 6000, was it still making power, or had it leveled off ?
With decent valve springs I wouldn't worry about 6500 RPM, but that might not be necessary.
Posted By: rb446

Re: What will it run 410 stroker 71 Duster. - 06/30/22 08:53 AM

Yep 6>6500rpm with slip although I doubt you'll get too much with that converter.
At a guessing weight of 3400lbs@the line and an honest 450fwhp/28" tyre your ticket could look like this if it hooks good>

60 Foot E.T. : 1.59 Seconds
1/8 Mile E.T. : 7.21 Seconds
1/8 Mile Trap Speed :94.25MPH
1/4 Mile E.T. : 11.43Seconds
1/4 Mile Trap Speed :117MPH
1/4 Mile Trap RPM :6054RPM+slip and with 4.10's 5772+

We got a street/strip Demon here with a mild 340/416 running 11.2's/118+ with similar hp, .500" hyd. cam, stock J heads, TR with 2 x 650DP's, Hughes 3500stall, SS springs, 3.91's/10x28's at approx 3250lbs, shifts@5500 traps@6000-ish.
Posted By: Locomotion

Re: What will it run 410 stroker 71 Duster. - 06/30/22 11:10 AM

FWIW, Scat and eagle are cast steel. Certainly stronger than cast iron,but OEM 360 cranks are pretty strong already. Mine have been stock stroke, but I've run cast steel cranks to 7,000 for years. Strokers shouldn't need that much even if they can handle it.
Posted By: DusterKid

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:32 PM

If you knew the weight that would help a little more, but my guess is it'd be right around 11.70s. Could be pushing the lower 11's but I think the 10" convertor will hold it back some and may actually help keep the rpm down a little as well. We ran a 28" tire and 4.56 gears for a little while on a stock stroke 360 with 8" convertor. It was spinning to 67-6800. We later put a 30" tire on it and dropped the rpm down to 62-6300.
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:41 PM

Originally Posted by topside
At 6000, was it still making power, or had it leveled off ?
With decent valve springs I wouldn't worry about 6500 RPM, but that might not be necessary.


It was starting to level off at 6k but I think it might’ve had a couple more hp left in it.

Judging from driving it around this thing twists up very quick, I’m going to guess it will trap between 6200 & 6500 from the messing around I’ve done on the street, but I currently have my rev limiter set at 6k so I’m not sure. The first couple times at the track I plan to leave the exhaust on it so I know it won’t be max effort. I’ll let everyone know what it does once I get it to the track.
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:44 PM

Originally Posted by Locomotion
FWIW, Scat and eagle are cast steel. Certainly stronger than cast iron,but OEM 360 cranks are pretty strong already. Mine have been stock stroke, but I've run cast steel cranks to 7,000 for years. Strokers shouldn't need that much even if they can handle it.


That’s good to know. Thanks. I’m probably worrying about the rpm more then I should be, I just don’t want to hurt it after putting the last 4-5 years of my free time into getting this car together.
Posted By: an8sec70cuda

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:46 PM

467 hp on a chassis dyno? If so, I'd expect it to run in the 10s.
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:48 PM

Originally Posted by rb446
Yep 6>6500rpm with slip although I doubt you'll get too much with that converter.
At a guessing weight of 3400lbs@the line and an honest 450fwhp/28" tyre your ticket could look like this if it hooks good>

60 Foot E.T. : 1.59 Seconds
1/8 Mile E.T. : 7.21 Seconds
1/8 Mile Trap Speed :94.25MPH
1/4 Mile E.T. : 11.43Seconds
1/4 Mile Trap Speed :117MPH
1/4 Mile Trap RPM :6054RPM+slip and with 4.10's 5772+

We got a street/strip Demon here with a mild 340/416 running 11.2's/118+ with similar hp, .500" hyd. cam, stock J heads, TR with 2 x 650DP's, Hughes 3500stall, SS springs, 3.91's/10x28's at approx 3250lbs, shifts@5500 traps@6000-ish.



I’d be very pleased to see a slip that looks like that! Honestly I was figuring 12.10s-11.80s
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 06/30/22 12:56 PM

Originally Posted by an8sec70cuda
467 hp on a chassis dyno? If so, I'd expect it to run in the 10s.


It was an engine dyno, I wish it was wheel hp.

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Posted By: B3422W5

Re: What will it run 410 stroker 71 Duster. - 06/30/22 01:33 PM

Should run mid 11’s easy enough. Would run better with a good convertor.
Posted By: Kiddart

Re: What will it run 410 stroker 71 Duster. - 06/30/22 01:34 PM

I would think 11.3 to 11.6 all day pending track condition and the how it hooks
Posted By: Cab_Burge

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:29 PM

Using the peak HP or peak torque RPM may not be what your motor wants to be shifted at, I learned that on my last pump gas stroker BB motor. It had several different sets of heads on it with a low deck six pack set up, I engine dyno tested it multiple times on three different engine dyno, it always made peak HP between 5500 and 5600 RPM, peak torque between 4500 and 4600 RPM.
At the track it wanted to be shifted at or above 7000 RPM shock That stupid motor was an over achiever from day one, I learned a lot from it bow
My message is go test different shift points, maybe start at shifting it at 5500 RPM, then 6000 RPM and then 6500 RPM as long as it is going quicker and faster move the shift point up until it doesn't go quicker or faster by 500 RPM increases, once it stops gaining try splitting the shift rpm by 200 to 300 RPM above and below where it went the best for you. Not all tachs read the same RPM as all other tachs also shock shruggy
Good luck, have fun and test, test and test some more up wrench scope
Posted By: bobby66

Re: What will it run 410 stroker 71 Duster. - 06/30/22 04:43 PM



Nice looking hot rod. Good luck with it! up
Posted By: DusterKid

Re: What will it run 410 stroker 71 Duster. - 06/30/22 05:52 PM

Being an engine dyno and not chassis dyno I'm going to guess 12.00s.
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 07/12/22 04:04 PM

Well I finally made it to the track for the cars first Test n Tune last Saturday, I was happy with the results considering it was in street trim with the exhaust still on it and bouncing it off the rev limiter on shifts. I still have a lot of learning to do and there are a few minor tweaks that need to be made. These are the time slips from the first 2 passes.

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Posted By: FurryStump

Re: What will it run 410 stroker 71 Duster. - 07/12/22 04:21 PM

Is it spinning? 60’ is soft. 4:10 might help a bunch. Mine is a low gearset 904, but I run a 26” tire with 4:10’s, with a 9.5” ptc converter that slips 3-4% at the stripe. If flashes to 3500 rpm. Crosses at 6500-6700 rpm using the same crank. I have 1000’s of runs on it and dragweek and 60,000 street miles. It has been balanced to 1/2 a gram by a real old, very picky guy. Oh, with that hp in a sorted out combo you with be in roll bar territory. Low 11’s
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 07/12/22 05:28 PM

Originally Posted by FurryStump
Is it spinning? 60’ is soft. 4:10 might help a bunch. Mine is a low gearset 904, but I run a 26” tire with 4:10’s, with a 9.5” ptc converter that slips 3-4% at the stripe. If flashes to 3500 rpm. Crosses at 6500-6700 rpm using the same crank. I have 1000’s of runs on it and dragweek and 60,000 street miles. It has been balanced to 1/2 a gram by a real old, very picky guy. Oh, with that hp in a sorted out combo you with be in roll bar territory. Low 11’s


I didn’t feel any spin, honestly it seemed to be dead hooking. The track was very well preped because they had their Friday heads up series the night before. I think the converter is holding me back, it seems to start pushing through the brakes ( I’m foot braking it) around 2000-2200 rpm. I had my revlimiter set at 6300, plan to bump that to 6500 or high next time out, it was either starting to bounce off of it or float valves around the 1000-1100 ft mark.
Posted By: fast68plymouth

Re: What will it run 410 stroker 71 Duster. - 07/12/22 07:31 PM

Quote
I had my revlimiter set at 6300, plan to bump that to 6500 or high next time out, it was either starting to bounce off of it or float valves around the 1000-1100 ft mark.


If it’s some type of hyd cam, it’s certainly possible(and not uncommon) to experience valvetrain control issues before ever getting to 6300.

I usually sneak up on the rpm on the dyno to see if I can determine where the problem starts........ then you know.
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 07/12/22 09:57 PM

Originally Posted by fast68plymouth
Quote
I had my revlimiter set at 6300, plan to bump that to 6500 or high next time out, it was either starting to bounce off of it or float valves around the 1000-1100 ft mark.


If it’s some type of hyd cam, it’s certainly possible(and not uncommon) to experience valvetrain control issues before ever getting to 6300.

I usually sneak up on the rpm on the dyno to see if I can determine where the problem starts........ then you know.



It’s a .508/292 Mopar purpleshaft cam,with Smith Bros push rods, Harland Sharp 1.5 rockers, I feel like the week point might be the valve springs themselves, it has whatever Areohead (Indy cyl head) installed on them, they were supposed to be good to .509 lift. We were only pulling it to 6000rpm on the dyno and never went past that.
Posted By: B3422W5

Re: What will it run 410 stroker 71 Duster. - 07/13/22 12:22 AM

Originally Posted by moparjoe360.4
Originally Posted by fast68plymouth
Quote
I had my revlimiter set at 6300, plan to bump that to 6500 or high next time out, it was either starting to bounce off of it or float valves around the 1000-1100 ft mark.


If it’s some type of hyd cam, it’s certainly possible(and not uncommon) to experience valvetrain control issues before ever getting to 6300.

I usually sneak up on the rpm on the dyno to see if I can determine where the problem starts........ then you know.



It’s a .508/292 Mopar purpleshaft cam,with Smith Bros push rods, Harland Sharp 1.5 rockers, I feel like the week point might be the valve springs themselves, it has whatever Areohead (Indy cyl head) installed on them, they were supposed to be good to .509 lift. We were only pulling it to 6000rpm on the dyno and never went past that.



You don’t need to go past 6k with a stroker like yours to get it to ET extremely well.
I shifted my stock stroke 360 at 6k, it went 11.20’s. My stroker has been 10.68 now, at 3350 pounds, I shift it at 6300, if I shifted it at 6 it wouldn’t slow down much at all.
I didn’t see what heads you are using, what are they?
The convertor is most definitely a liability regards making more optimal ET
Switching to 4.10gears from 4.30’s would be a waste of time. It’s about 250 rpm at the stripe difference. And ( assuming it doesn’t hook, it probably does) it very likely wouldn’t hook with 4.10’s either
That dyno number is enough to run close to a second quicker than you are.
Post exactly the entire combo, would enjoy looking at it and making recommendations
Pretty car, btw
Posted By: moparjoe360.4

Re: What will it run 410 stroker 71 Duster. - 07/13/22 06:59 PM

Originally Posted by B3422W5

I didn’t see what heads you are using, what are they?
The convertor is most definitely a liability regards making more optimal ET
Switching to 4.10gears from 4.30’s would be a waste of time. It’s about 250 rpm at the stripe difference. And ( assuming it doesn’t hook, it probably does) it very likely wouldn’t hook with 4.10’s either
That dyno number is enough to run close to a second quicker than you are.
Post exactly the entire combo, would enjoy looking at it and making recommendations
Pretty car, btw




I’m running 974 casting iron heads that I ported and polished myself, I got the stroker kit from scat, they balanced it, it has icon flat top pistons and cometic MLS head gasket (.040 thickness if I remember correctly) it has about 11-1 comp eddy RPM Airgap , proform 750 dp, Holley blue pump, 8an fuel lines, MSD Digital 6AL . I think that basically covers the combo between what I mentioned before and this.
I
Thanks, my dad and I have completely re built it in his garage, the only thin we farmed out was the machine work on the engine. I built the entire drivetrain and he did the body and paint work (about 30-40% of the gold is original paint)
Posted By: B3422W5

Re: What will it run 410 stroker 71 Duster. - 07/13/22 07:13 PM

Originally Posted by moparjoe360.4
Originally Posted by B3422W5

I didn’t see what heads you are using, what are they?
The convertor is most definitely a liability regards making more optimal ET
Switching to 4.10gears from 4.30’s would be a waste of time. It’s about 250 rpm at the stripe difference. And ( assuming it doesn’t hook, it probably does) it very likely wouldn’t hook with 4.10’s either
That dyno number is enough to run close to a second quicker than you are.
Post exactly the entire combo, would enjoy looking at it and making recommendations
Pretty car, btw




I’m running 974 casting iron heads that I ported and polished myself, I got the stroker kit from scat, they balanced it, it has icon flat top pistons and cometic MLS head gasket (.040 thickness if I remember correctly) it has about 11-1 comp eddy RPM Airgap , proform 750 dp, Holley blue pump, 8an fuel lines, MSD Digital 6AL . I think that basically covers the combo between what I mentioned before and this.
I
Thanks, my dad and I have completely re built it in his garage, the only thin we farmed out was the machine work on the engine. I built the entire drivetrain and he did the body and paint work (about 30-40% of the gold is original paint)



Sweet. if the heads are pretty good, the car has a bunch more in it, especially with a good convertor. Pretty car, I like it. Good luck!
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