Posted By: scatpacktom
Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/22/14 11:19 PM
Both cars are equally shifted and geared, have about the same options and weigh within pounds of each other. Which car is faster and why?
Street Race a Stock 70 340 Duster vs 71 340 Duster
Posted By: B5 Bee
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/22/14 11:41 PM
Thermoquad puts the '71 first to the finish line.
Posted By: ScottSmith_Harms
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/22/14 11:55 PM
71, TQ AND Intake design.......But thats only if everyting is truely stock. Toss on a stealthy 800 cfm AVS, port the intake, etc. and the 70 might come out on top, of course the TQ car could then up the ante with a bigger TQ and ported intake as well. BTW, if anyone thinks the pass side exhaust manifold difference would give an edge to the sexier 70 design, I've dyno tested both, 1-2 hp difference, so basically nothing.
Posted By: dvw
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 12:34 AM
Assuming proper tuning the 71 has a bigger and technologically superior carb and matching bore manifold. I believe those are the only differences. 71 wins.
Doug
Doug
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 03:29 AM
71, too bad no 6 pack option back then oh well..
Posted By: 340wedge
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:19 AM
1971 wins, better stripes and sharktooth grill add 10HP 
Posted By: ScottSmith_Harms
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:19 AM
Quote:
71, too bad no 6 pack option back then oh well..
Well there was......Sort of
*BTW, I got the chance to drive the car in this article, it was the tightest nicest Demon I ever drove and it was very fast for a stock 340 Six Pack.
Posted By: TJP
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:21 AM
Quote:
71, TQ AND Intake design.......But thats only if everyting is truely stock. Toss on a stealthy 800 cfm AVS, port the intake, etc. and the 70 might come out on top, of course the TQ car could then up the ante with a bigger TQ and ported intake as well. BTW, if anyone thinks the pass side exhaust manifold difference would give an edge to the sexier 70 design, I've dyno tested both, 1-2 hp difference, so basically nothing.
I agree and was there in the day, Scott nailed it
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:27 AM
"BTW, if anyone thinks the pass side exhaust manifold difference would give an edge to the sexier 70 design, I've dyno tested both, 1-2 hp difference, so basically nothing."
I wouldn't have guessed that. The outlet is like 2.5 vs 1 7/8 plus the pipe diameter has the be smaller as well.
OK so we think 71 is king, how much better do we think a TQ is over a AVS? Take my Duster that has run a best of 13.20 how much faster is it if I were to swap out the intake and carb? A tenth? Two? If it is 5 to 10 hp it won't even show up on the strip.
I wouldn't have guessed that. The outlet is like 2.5 vs 1 7/8 plus the pipe diameter has the be smaller as well.
OK so we think 71 is king, how much better do we think a TQ is over a AVS? Take my Duster that has run a best of 13.20 how much faster is it if I were to swap out the intake and carb? A tenth? Two? If it is 5 to 10 hp it won't even show up on the strip.
Posted By: ScottSmith_Harms
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:33 AM
Tom, only one way to find out for sure 
In a real world test on the same car/engine I'd guess you wouldn't see a huge difference but on paper the 71 should be the winner (by whatever margin). It may come down to the individuals skills in carb tuning as well, AVS's are pretty basic/easy to tune, TQ's are a bit more complicated and need to be tuned properly to work at their peak, something that can take a bit of practice.
In a real world test on the same car/engine I'd guess you wouldn't see a huge difference but on paper the 71 should be the winner (by whatever margin). It may come down to the individuals skills in carb tuning as well, AVS's are pretty basic/easy to tune, TQ's are a bit more complicated and need to be tuned properly to work at their peak, something that can take a bit of practice.
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:44 AM
I know Scott
Posted By: ScottSmith_Harms
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 04:58 AM
I know you know, so go do it man!
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 05:11 AM
I had read that the hot lick back in the day was to put a 440 carb on a 340. I stuck a 69 440 carb on the Duster and took it for a spin. I didn't run it at the track but it seemed to do nothing. I put the correct carb right back on. I may have to revisit that test at the track. I remember I had to stack a couple of thick gaskets up so the throttle blades would clear the intake.
I know in Stock Eliminator the 71 car is clearly better than the 70. In stock form I'm just not sure. Doesn't seem to me a stock engine can use the TQ to its fullest potential. I keep thinking my car is second fiddle to a 71 but I'm just not really sure it is.
I know in Stock Eliminator the 71 car is clearly better than the 70. In stock form I'm just not sure. Doesn't seem to me a stock engine can use the TQ to its fullest potential. I keep thinking my car is second fiddle to a 71 but I'm just not really sure it is.
Posted By: ScottSmith_Harms
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 05:33 AM
Quote:
I keep thinking my car is second fiddle to a 71 but I'm just not really sure it is.
When two cars are so closely matched it's really hard to prove either as superior. Running factory tires (i.e. traction issues) would probably make it even harder.
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 05:50 AM
I would say the intake is the bigger plus more than the carb on the 71's. I really don't think you would see much difference on the time slip. The 71 aircleaner slowed my car down 2 tenths but my sb is more like 400hp.
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 07:34 AM
Quote:Couple weeks away myself
Quote:
71, too bad no 6 pack option back then oh well..
Well there was......Sort of
*BTW, I got the chance to drive the car in this article, it was the tightest nicest Demon I ever drove and it was very fast for a stock 340 Six Pack.
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Posted By: bigblock340power
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 10:13 AM
Hummmmmm, what should I pick? 70-71? 70-71? Ok, I'll go with the '71 
Posted By: Cab_Burge
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/23/14 07:54 PM
I remember watching the 1971 NHRA Winternationals stock qualifying in the classes the 340 ran in, the 1971 where quiet a bit faster than the 1970 cars in the same classes 
I didn't know at that time that the 1971 340 had different carbs than the 1970s did 
NHRA put the 1971 cars in the higher classes, weight per HP rules, later that year I beleive
I didn't know at that time that the 1971 340 had different carbs than the 1970s did NHRA put the 1971 cars in the higher classes, weight per HP rules, later that year I beleive
Posted By: RV2
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 02:44 AM
Was there a compression ratio difference between 70&71?
Posted By: 383man
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 02:55 AM
I think some books state the 71's at 10.0 and the 70's at 10.5 comp ? I also dont remember if it was 71 or 72 when they started putting EGR jets in the bottom of the intake manifold ? Ron
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 03:02 AM
10.3 for 71 down from 10.5, but not sure how that was reached maybe the j heads have a couple more cc's? My early 71 intake has no jets in the floor, also remember reading the auto trans having a higher shift point due to a governor change??
Posted By: Cab_Burge
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 03:14 AM
Quote:I beleive the 1973 Thermoquad intakes where the first SB 4 barrel intakes to have the EGR jets in them
I think some books state the 71's at 10.0 and the 70's at 10.5 comp ? I also dont remember if it was 71 or 72 when they started putting EGR jets in the bottom of the intake manifold ? Ron
The NHRA blueprint speces for the 1968 to 1971 340 4 barrel motors are the same on all the specs. 
I use to help and consult with one of the more successful NHRA Mopar SB racers in SO CA., he could swap the intake and carbs. on his Challenger and add weight so he could run 6 different NHRA stock clases,(C/SA through G/SA) with the same long block and still be legal
Posted By: RSNOMO
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 03:14 AM
Properly dialed-in, my money's on the '71...
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 04:16 AM
X heads may be a tad better than a J head
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 06:06 AM
Maybe but I think most 71's had the j's
Posted By: Cab_Burge
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 06:36 AM
Quote:Not on the dyno testing I've done, with the same flow numbers on both
X heads may be a tad better than a J head
The X have the valve eyebrow protrusion issues that need to be resolve on a blueprinted all out stocker motor, the J heads don't Or maybe I have it backwards It's been close to 20 yrs since I've touched a competetive SB MOpar stocker motor
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/24/14 01:54 PM
X head flows a little better than the later J head, just by a smidge. The X was designed as a 2.02 head, the J a 1.88. They put 2.02 valves in the J's for 71 but you know what that does to the short turn. If you had the choice of the two you would choose the X head for 1970
Posted By: ademon
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/27/14 02:36 AM
wouldn't it have been nice in 1971 if Ma used the 69 4-seed cam with the X heads and the 70 exhaust manifolds with the 71 t-quad and intake.. or 6 pack 
Posted By: Sublime70
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/27/14 02:49 AM
By the way, J heads were phased in during 1970 model year,and not just on AAR's and T/A's. They had 2.02 intakes etc. Some argue that the J's flow marginally better, but from what I have seen it is a wash.
The earliest 340 4bbl J heads that I have seen are dated October 1969. I am always looking for older dates, I have been trying to figure out when they started using them in 1970. If anyone has pictures of earlier non -T/A J heads please send me a picture. Thanks.
The earliest 340 4bbl J heads that I have seen are dated October 1969. I am always looking for older dates, I have been trying to figure out when they started using them in 1970. If anyone has pictures of earlier non -T/A J heads please send me a picture. Thanks.
Posted By: sawdust
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/30/14 03:38 AM
What about the 1968 340 four speed? From what I remember they had a bit different cam and thus better performance.
Posted By: scatpacktom
Re: Street Race a Stock 70 340 Duster vs 71 340 Duster - 04/30/14 02:16 PM
68 4sp had a lumpier camshaft. Maybe a 4sp 68 notch would be the hot ticket.