Stock 340 dyno tests?

-
RLF Cuda said:
Wallace Racing has a calculator for HP and ET based on inputs you provide. ET-MPH-HP Calculator
My 340 Formula S FB ran a best of 13.48 @ 105.38 pure stock with a A727, 3:55 gears, and H70x14 tires. This was essnetially at sea level in SoCal (OCIR, Lyons, Irwindale, Pomona, etc). The car weighed about 3200 and I weighed about 185 so total weight was 3385. Using the MPH/Weight estimator, I get 305.23 HP. This is the best estimate as using the ET/Weight estimator is a function of traction and ability more than engine power. Using [email protected] in the calculator yields 273.13 HP. If you put the 305 HP into the top equation which estimates ET and MPH, you get 12.99 @ 104.04 MPH. This is what a car should do with optimum traction and driving skill so it shows how much improvment is possible with the power you have.
Fun and useful information to play with.
Click to expand...


Sea level hell. At that track it was probably minus sea level. Lol. Come on now you test n tuners don’t go to the track on bad days.
 
Swinger 340 said:
The tack, chrome valve covers and chrome air cleaner makes the car faster. Those were our first Hi-Po add-ons.
Click to expand...
I've never been a chrome or sticker guy, heck I've always painted my aluminum intakes. The only chrome valve covers I've ever ran were from the factory on my 383's or 440's LOL.

Nothing flashy here, just a stock 318 with a 4 barrel on it.
IMG_4832.jpg
 
1MeanA said:
I thought the 340's 275 hp rating was realistic and not conservative as with some other engines? The 316 hp in the above mention build was somewhat believable with an optimistic dyno but getting to 400 hp with a mild cam, intake and headers is a stretch.
Click to expand...
NHRA back in the day rated the 340 4V at 325HP. This was based on 1/4 ET's, vehicle weight, gears and tires, using comparisons of thousands of runs and removal of engines for dyno tests.
The 340 six pack was rated at I believe I remember 360HP.
 
harrisonm said:
Build #1 from Post #1 is exactly my 340 except for the carb. I have a 750 instead of an 800. So I figure I am probably about 15 or 20 HP under the 392 number. That is why I say my 340 is about 375 HP.
Click to expand...
In the late '60s and into the '70s, a friend raced a Boss 302 in the TransAm series. Race regs mandated carburetor max size by throttle bore diameters, which came out at 830CFM. Holley built a secial carb for TransAm. You could purchase one through Ford and GM performance outlets, over the counter. Naturally being for a special purpose and limited production, they were expensive. The factory teams could afford this but many private teams could not. The next size they could use that was commonly available was the 780 CFM. Being commonly available it was fairly inexpensive. John's team admitted to giving up a few HP by using the affordable carb. Never found out how much, but they ran mid pack much of the time.
 
Dale Davies said:
NHRA back in the day rated the 340 4V at 325HP. This was based on 1/4 ET's, vehicle weight, gears and tires, using comparisons of thousands of runs and removal of engines for dyno tests.
The 340 six pack was rated at I believe I remember 360HP.
Click to expand...
6pk nhra rated 319 325hp
340 295 low 310hp high
never 325 for non 6pack
never 360 for 6pack
blue printed stock 340 with a 750 carb makes right around 340 hp
intake carb cam headers dizzy with a 1/2 a clue 370 to 390 hp
 
justinp61 said:
I've never been a chrome or sticker guy, heck I've always painted my aluminum intakes. The only chrome valve covers I've ever ran were from the factory on my 383's or 440's LOL.

Nothing flashy here, just a stock 318 with a 4 barrel on it.
View attachment 1716048597
Click to expand...
Just a thought, but it may be a good idea to run your throttle return spring facing the front of the car, in alignment with the throttle cable.
 
Does anyone know for sure if NHRA had a dedicated dyno facility and where it was located? I just wonder if they had/have something like NASCAR.
 
IQ52 said:
Does anyone know for sure if NHRA had a dedicated dyno facility and where it was located? I just wonder if they had/have something like NASCAR.
Click to expand...
Good question! I was allways under the impression they did there factoring based off of weight/mph calculations. Teams would try to avoid going too fast and getting "re-factored"
 
mgoblue9798 said:
"treated to a performance valve job by JMS Machine"

Open to interpretation I guess, but it isn't a stock type valve job. At least 3 angle possibly more. Either way doesn't make sense to do a 3 angle and leave the ledge without blending it into the bowl.


www.motortrend.com

How To Resto-Spec Build A 340 Engine - Mopar Muscle Magazine

Check out the second part to building our resto-spec 340 Swinger engine for a 1970 Dodge Dart. Tune in for more details and photos only in Mopar Muscle Magazine
www.motortrend.com www.motortrend.com
Click to expand...
Ummmmm.......a stock factory valve job IS a three angle......at least in the head. I love when shops act like they're giving you more than a regular valve job when grinding three angles in the head, because they all come like that. lol
 
IQ52 said:
Does anyone know for sure if NHRA had a dedicated dyno facility and where it was located? I just wonder if they had/have something like NASCAR.
Click to expand...

Maybe the first few times the cars were on track they used the factory rating, after that, they never based the ratings on actual factory HP in stock elim. It was always a level the playing field approach. If one car ran significantly under the index, it got re-rated. Nothing to do with an observed dyno output, except track data. Same thing they did in pro stock. One engine/combo dominates, factor it out of existence by adding weight to it so no longer competitive.

They are still rated at levels for many combinations, far below the current outputs.
 
RustyRatRod said:
Ummmmm.......a stock factory valve job IS a three angle......at least in the head. I love when shops act like they're giving you more than a regular valve job when grinding three angles in the head, because they all come like that. lol
Click to expand...
You sure about that?
 
I dug up my old Direct Connection Performance Book from 1980 and used the Weight/HP vs MPH chart to calculate the HP my 340 made when new.
The '68 FS FB 340 weighed 3050 or so with the back seat out. I weighed 185 or so back then in 1970. The car turned consistantly 13.50's at 105 with a best of [email protected]. Using the DC chart, 105 MPH converts to 11.5 lbs/hp. With a weight of 3250, this translates to 285 HP. The DC book on page 1332 shows a stock 340 should produce 275-290 HP, so this is about right.
Interestingly, Chart 6 on Page 1332 show what ET is possible with the proper chassis and transmission setup. A stock 340 with a race weight of 3250 should turn 12.70's in the quarter mile. Stock with tires, torque converter and good driving. Not bad.
 
I raced my 69 340 Dart GTS in 1972.
It had 3.55 gear, cheapy headers and was otherwise bone stock.
Went 14.23@99 mph at US131
My first ever outing
 
Usually when we talk HP in older cars it's gross hp in dyno trim which a 340 should easily produce 300+ hp, as for net we know the lesser 340 is rated 245 so with the higher cr and 2.02 got to worth 20 or so net hp, 275 hp is fairly close to the net rating.
 
Dyno tests usually have no alternator, fuel pump, water pump, air cleaner or fan and are run through headers.
And if the dyno has a happy 5% error the results could be wrong by 50hp plus!
 
From what I have seen, within dyno runs the repeatability is quite good, probably 1% or 3-5 HP. It is repeatability between dynos that is the issue. Two different dynos in different locations and under different conditions will give very different results. Here I would say that 10% difference would be common. For a stock 340, this could mean 27-30 HP difference.
 
ir3333 said:
Dyno tests usually have no alternator, fuel pump, water pump, air cleaner or fan and are run through headers.
Click to expand...
True But that's the number were generally talking about Eg.. We say a stock 5.9 magnum is 300 hp engine, that's it's dyno trim number.
ir3333 said:
And if the dyno has a happy 5% error the results could be wrong by 50hp plus!
Click to expand...
Your math is a little wrong unless were talking 1000+hp engine, more like 10-30 hp for 200-600 hp engines.
 
273 said:
Usually when we talk HP in older cars it's gross hp in dyno trim which a 340 should easily produce 300+ hp, as for net we know the lesser 340 is rated 245 so with the higher cr and 2.02 got to worth 20 or so net hp, 275 hp is fairly close to the net rating.
Click to expand...

Note that when the 340's compression ratio dropped two full points and got a smaller intake valve, it dropped from (supposedly) 275 gross hp to 240 net.

The 318 went from 230 gross all the way down to 150 net with NO loss in compression.

Draw your own conclusions.
 
65 Cuda 340 said:
Note that when the 340's compression ratio dropped two full points and got a smaller intake valve, it dropped from (supposedly) 275 gross hp to 240 net.

The 318 went from 230 gross all the way down to 150 net with NO loss in compression.

Draw your own conclusions.
Click to expand...
The 318's 230 hp rating is grossly exaggerated by the factory, 340 wasn't. That's why they were made to switch to net.
 
You must log in or register to reply here.
-

Back
Top