Factory 68-71 340 puts 325HP on GM Dyno

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dustoff440

dustoff440

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I just heard from an old guy who lives near here that GM engineers got their hands on a factory 340 in 68 and put it on the dyno and it yielded 325 horsepower but was advertised at 275 horsepower for insurance reasons. He said that the engineers were stunned that an engine that was in the form of the 273 with 235 horse the previous year had jumped nearly 100 horsepower with only one year of refinements. Do you think there is any truth to this? Has anyone here actually seen an early factory 340 on the dyno using the methods from that era to dyno the engine???????
 
I have always heard that the 275 horsepower was a joke and they made around 325 horse but I have nothing to back it up just reading in books.
 
demon seed said:
Wouldn't surprise me, those 69-71 340's used to stomp 383 and 440's in Challengers and Cudas all the time.
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not to mention all the 327's, 350's, 400's, 351's, etc. etc. etc.:toothy10:


btw, I remember reading about Car Craft 'testdriving' a Boss 429 because they thought Ford had warmed up the one they were sending to magazines a little too much. They thought Ford was lying about the power.
They pulled the motor and dynoed it. It was rated at (iirc) 385 hp. The one they pulled out of the showroom put down 525. Ford was lying about the power lol.
 
Mopar may have been truthful on others though, I saw one of the car mags about 6-7 years ago rounded up all the original factory pieces and put together a 383/335 horse and used factory specs and the dyno rating procedures of the era and the engine put out exactly 335 horsepower!
 
dustoff440 said:
Mopar may have been truthful on others though, I saw one of the car mags about 6-7 years ago rounded up all the original factory pieces and put together a 383/335 horse and used factory specs and the dyno rating procedures of the era and the engine put out exactly 335 horsepower!
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yep and later on I remember them putting a .528 cam,headers,carb on it and making 425hp

I heard the story about gm and the 340 before.
 
Well if you design the base engine (273, etc) to be bad-*** then it's easy to hot-rod it. Chrysler's motors were ALL good, not just the high-performance ones, which I think says a lot. Seems like GM had to spend a lot more time developing their performance engines because they had to change so much more than the Chryslers to make them fast.
 
Per the old Direct Connection Chassis Manual back then for Super Stock NHRA factored the 1968-1970 (AVS) 340 at 295, 1971 (TQ) at 305 and 1970 (6 Bbl) at 325, and the 1972-1973 (TQ) at 275.

Prior to SAE net ratings in 1972 most horsepower figures were pure ballyhoo driven by the marketing departments.
 
MOPEkidD-3 said:
Well if you design the base engine (273, etc) to be bad-*** then it's easy to hot-rod it. Chrysler's motors were ALL good, not just the high-performance ones, which I think says a lot. Seems like GM had to spend a lot more time developing their performance engines because they had to change so much more than the Chryslers to make them fast.
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''

Yup ma moapr was THE hot ticket back then as they not only built powerfull engines/cars that were the ones to beat but they were very reliable as well.

If you wanted cheap you bought a ford,lol!
 
When I was a kid 68-70 I remember going to drags and the guys that drove in put slicks on uncapped headers. The small block a-bodies were always quicker than the big blocks,Kevin.
 
I've heard the same thing over the years that the earlier 340's did indeed put out over 300 H.P. but advertised as 275 H.P. for Insurance reasons.I believe it!
 
factory 375hp/327 chev.. and yes it made that and then some..
NO factory smallblock or most bigblock mopar could compete
with that engine.

flame away.
 
Damn, what were the specs on that 327??? (Cam, compression,...) Thats some crazy power out of such a small engine!
 
11:1, 460ish cam (lotsa duration), 2.02 "fulie heads", and mechanical
rockchester fuel injection. not bad for 1964. was a
corvette optional engine iirc.
 
A-BOMB360 said:
factory 375hp/327 chev.. and yes it made that and then some..
NO factory smallblock or most bigblock mopar could compete
with that engine.

flame away.
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I wont flame you. I'll simply point out that MOPAR was King of the dragstrip at that time. A little 327 wont stand a chance against a Max wedge etc. That being said,they do give a lot for thier cubes.
 
That's actually a true story. It's in a recent Mopar mag. Don't remember which one. I know I've read about that story in the last year or two. GM was tryin to get some info to help their performance program. It didn't work. LOL We knew a guy when when I was in school had a '65 365 HP corvette with a 4 speed. that was the highest rated 327 ever besides the fuelie talked about above. real hot little motor. 11.5:1, "duntov" solid cam the whole works. his son bought it new in '65 and was sent to Vietnam and was killed in action. the old man kept the car and we'd go by to check it out form time to time. he was real nice too. Would come out and show it off, start it up open the hood....the whole bit. it was a wicked soundin STOCK small block. I have respect for any make builds a factory car like that.
 
So 3400-3500# A bodies were running in the 104 range in the 1/4 back in the day, off the lot? Few, if any ran 100mph.

There's a reason lots of those 350hp GM cars got killed by 275hp mopars, it's a little of one being aggressive and other meek with hp ratings.

Even today, XE268H cammed, stock headed 340's with a better intake, carb and headers are really making 330ish.

I'll Dulcich credit on this one, the stock rating he got in one article regarding a 69-70 340 engine was just about spot on for HP.
 
All the stock 340's that I've pulled have been 290ish...that's all stock except with a 3 angle valve job and a 70 degree plunge cut in the bowls.
The one that did creep up to 300 hp was with an old Cam Dynamics stock replacement street plus cam 210/221@50 with 429/444 lift.
Then we put a set of super comp headers on it and it went 315 hp.
But stone stock 340's with an electric water pump and msd 7 series ign on the dyno make 290hp.
 
Never had my '69 340 dyno'd but I can tell you my '69 Swinger 340 ran 14.28 @ 98+ mph pure stock with a 727 and non-Sure Grip 3.23 rearend. Plug that in your calculators and see what horsepower is required.
It surprised a bunch of big-block Chevelles on Whittier Blvd. back then.
 
Mine ran 13.86 at 101 , has 3:55 sure grip , headers , stock manifold and carb , not sure of the cam as not sure what previous owner changed . Will see what it runs in the next few weeks with the new motor that has been on the dyno with 389 HP and 412 lbs torque .
 
14.30 is what the stock 340's turned with a 3.23. Ive got and old mags somewhere where the car mags tested one. In the mid seventies when I started driving I had a buddy with a bone stock one with 3.91 and with some minor tuning and good driving techniques ran a 13.90. He was smoking 396/350 horse Chevelles, I even saw him beat a 360 horse 70 Z28, not by much. But I saw him get smoked by an RT B body with a tuned 440 six pack. The Dart beat him out of the hole and part way but when those six pack carbs were fully open he walked off from the Dart. He said that his car would turn 12.90. in 1970, Ronnie Sox,Mr. "Four Speed", was recruited to test a six pack car for one of the car mags. I cant remeber which B it was but he was able to turn 13.00 flat.
Ive got a warmed over stock 360 Mag with an air gap, 2 1/8 Mag RT exhaust manifolds which I had the machine shop hog out the outlet to 2 1/2, 512 lift cam, reverse 904, 3.91, and a 3500 converter, MP distributor and a 750 With a Proform Carb body. I'm looking for 12.80's without a 200 horse nitrous system, and 11.30's with the gas.. I have a buddy with the 550 horse Stang who has been running his mouth because he turned 11.80 at Bithlo raceway. As it were my Dart will be a daily driver, the only real giveaway will be the 10 inch rubber under the rear, and Patriot side pipes. I'm going for the 70's look and plan to waste the new Stangs and Vettes running 11.70 off the showroom for a fraction of the cost.
 
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