Pure stock 340 Mopar

[James L Miller]

I had planned on building a 340 to run IHRA pure stock with my 1969 Barracuda street car. The Crandall track closed, so that plan went out the door. I had bought a custom cam from Bullet for that deal, it was something like 250 degrees at .050" on a 109 LSA as I recall. The old factory spec for the 340 cam was something around 336/348 duration at .000" lift, so that gave a lot of leeway in grinding a cam. Not much different from the regular stocker cams from what I know about them. I also have an old Lunati(c) cam and an ancient CD stocker cam from the 1970s that I was going to try. I liked the idea of Pure Stock since I didn't need to put a rollbar in an original 340 car.

[Todd Boyer]

Hi James.
That sucks about your track closing.
On the factory spec cam do you mean the "stock eliminator cheater cam" with 336/348 duration at .000" lift that Mopar had, or are you referring to a factory 340 cam ? I didn't think the duration was that long on a factory 340 cam.

I'm wondering how much a custom cam will be worth.

[Chipper Chapman]

Todd, what A56 is talking about for the exhaust is that it's not the back pressure the system gives to the engine, but the velocity at which the exhaust gases have to travel in a smaller primary tube. The higher velocity (or rate of speed) will help to draw (or scavenge) the air/fuel into the cylinder during that minimal overlap period, effectively cheating the engine into thinking it has more cam duration. On the monte we ran small primary street headers (cheapo flowtechs) that achevied this, but with a 3" system and mufflers to not create excess back pressure. It went .4 under with a 100k mile engine.

[mike coates]

Todd,
The cam specs come from the NHRA / IHRA engine specs. For the high compression 340's, the specs have the 330 ish duration. They don't match the "advertised" specs. I think Danny Waters Sr. may have the specs. Terry Bell used to have them, but I don't think he does anymore.
They have to be the old specs from before they removed the duration requirements, from like 20 years ago. I have them for the '70 340. I am not sure if they are the same for the earlier ones.
I have an ISKY stock grind that is around 348 @ .050. with .478 lift I think. It is the dwell nose type. The higher lift works because I run the stamped rockers and the ratio is off from the 1.5, so the actual lift at the valve is still a little short. It is supposed to be a good cam for a regular stocker, but I think it is too much for a pure stock. I run stock valve springs per the rules and I only get 6200 - 6300 rpm. If I were to get another, I would get one that works more to that rpm range.
Some time ago, I talked to the guy with the pure stock demon. I think he was only shifting @ 6000 and 4.56 gears and he was running around 12 flat. I don't know what his specs were. But as I said, I built my engine and I think he had someone build his. I know there are probably several items that could be improved on mine.

Mike

[GTX JOHN]

I WOULD GUESS only a few hundred between productionheaders of the two sizes.. I have run the Flowteck 1 5/8 from summit on 318 or 360 engine and they were not bad and only $119 at that time. Of course Mark's Perf. Welding are much faster than any mass
produced piece!

[Todd Boyer]

Originally Posted by Chipper Chapman

Todd, what A56 is talking about for the exhaust is that it's not the back pressure the system gives to the engine, but the velocity at which the exhaust gases have to travel in a smaller primary tube. The higher velocity (or rate of speed) will help to draw (or scavenge) the air/fuel into the cylinder during that minimal overlap period, effectively cheating the engine into thinking it has more cam duration. On the monte we ran small primary street headers (cheapo flowtechs) that achevied this, but with a 3" system and mufflers to not create excess back pressure. It went .4 under with a 100k mile engine.

Thanks Chipper, I'm beginning to figure this all out. You want velocity, but not back pressure. Did you use an X-pipe or H-pipe with your 3" system ? What class were you running ?

[Todd Boyer]

Originally Posted by GTX JOHN

I WOULD GUESS only a few hundred between productionheaders of the two sizes.. I have run the Flowteck 1 5/8 from summit on 318 or 360 engine and they were not bad and only $119 at that time. Of course Mark's Perf. Welding are much faster than any mass
produced piece!

John, did you run the Flowtechs in an A-body? I'm wondering how they fit?

[X-TECH MAN]

Originally Posted by mike coates

Todd,
The cam specs come from the NHRA / IHRA engine specs. For the high compression 340's, the specs have the 330 ish duration. They don't match the "advertised" specs. I think Danny Waters Sr. may have the specs. Terry Bell used to have them, but I don't think he does anymore.
They have to be the old specs from before they removed the duration requirements, from like 20 years ago. I have them for the '70 340. I am not sure if they are the same for the earlier ones.
I have an ISKY stock grind that is around 348 @ .050. with .478 lift I think. It is the dwell nose type. The higher lift works because I run the stamped rockers and the ratio is off from the 1.5, so the actual lift at the valve is still a little short. It is supposed to be a good cam for a regular stocker, but I think it is too much for a pure stock. I run stock valve springs per the rules and I only get 6200 - 6300 rpm. If I were to get another, I would get one that works more to that rpm range.
Some time ago, I talked to the guy with the pure stock demon. I think he was only shifting @ 6000 and 4.56 gears and he was running around 12 flat. I don't know what his specs were. But as I said, I built my engine and I think he had someone build his. I know there are probably several items that could be improved on mine.

Mike

I still have the Dodge specs up to around 1973. Dont forget that in Pure stock you are supposed to run the OEM type trans that came with the engine combo that you are claimming. No manual valve bodies either but I know of a few who are cheating and geting away with it using a 904 instead of the 727. Early 340's are suppposed to use a 727 Torqueflite and NOT the 904. No back cut on the valves either unless it was factory like the 455 SD Pontiacs and newer Vettes, etc. 99.9% of the current tech guys wont know the difference so if you have no morals go for it.

[mike coates]

Terry
I do run the 727, but have a manual valve body. When I was putting it together, there was a debate on this and I believe Dwayne said it was OK.
there was also a debate on the transmissions and at the time, it was worked out that if you ran a 904 (or any non original trans in other brands) you had to use the current HP rating, but if you ran the original (727, etc) you would get a 10 hp reduction for carbs (5 for FI cars).
Like I said earlier, I haven't raced for awhile so I don't know if anyone still uses this, but it was never made official and I still use the rated hp because of that. So I am at a disadvantage due to that....plus my valves are stock with no back cut...probably why I only run .1 to .2 under, among other things...
Mike

[Ross Family Racing]

Todd,
I ran my '72 Cuda in Pure Stock for several years.I set a couple of records early on and went through teardown with the old stocker style cam.(I actually had an old cam I bought and used from Ed Hamburger back in the early 80's).
The 904 was run in my car after a call to Mike Baker at IHRA.I asked if the 904 could be used in place of the 727.He asked me if it was the same number of forward gears(to which I answered yes) and he told me it was fine to run that transmission.
At Norwalk in 2005 when I qualified #1 in Stock is when some turds hit the fan. It was then decided to let the cars with the stock trans have a 10HP deduction. We were several times checked to see if we had the mechanical fuel pumps,as were others. The rear tire size is limited to 29.5 and when Mickey Thompson came out with the 29.5 radil slick we used that.Truman Fields actually ran the 29.5 Mickey radial before anyone else because he was testing the tire for M/T.We could not yet purchase that tire.
I ran the Hooker 13/4 Super Comp headers with Flowmaster mufflers with turndowns right off the end of the mufflers.
I decided to step up to Stock Eliminator with the associated cost of a 10,000 engine,$4700 Transmission,and $2700 Headers (from Mark and worth the money).Pure Stock is a great place to run and very cost effective. All of the S/SS associations around our area let these cars run as they are a part of IHRA Stock Eliminator.
I am putting together an '80 Aspen 318 4bbl.car for Pure Stock and local brackets.The 318 HP combo uses many of the same parts(heads,cam ect.) as the 340 and 360.
Good luck with your car.
Jeff Ross
IHRA G/SA 313
NHRA F/SA 3313