340 Six Pack Engine Specs

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MICHAEL J KLOCK

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Hello,
I've been searching online and I can't believe how hard it is to find the factory MOPAR engine build specs for a 340 six pack motor. I even looked in my 1970 Chilton manual and they don't even list it! Does anyone have a factory spec sheet for this motor? I'm looking for specifics as far as compression, cylinder head chamber volume, cam lift, etc. Many thanks!
 
MICHAEL J KLOCK said:
Hello,
I've been searching online and I can't believe how hard it is to find the factory MOPAR engine build specs for a 340 six pack motor. I even looked in my 1970 Chilton manual and they don't even list it! Does anyone have a factory spec sheet for this motor? I'm looking for specifics as far as compression, cylinder head chamber volume, cam lift, etc. Many thanks!
Click to expand...
You're not gonna find a lot, because not much is different spec-wise from a 4bbl. 340. The heads are the same J castings in every respect except they drilled the pushrod
holes further out to allow for max crossection porting if needed, and used the offset adjustable rockers along with that. Same with the Hydraulic cam specs, ditto pistons
& rods, valves & springs 340 H.P. again. I have a couple of Chiltons that list it....for '71 LOL, they do list the cam lift for the 4bbl/6bbl, but I can't say I trust those to be
100% accurate, they differ slightly from what the DC/MP performance books list, which have also been known to include erroneous info. I had/have a 340 H.P. stick here
somewhere, and I'm sure I checked it out like a million years ago, never used it for anything and forgot the numbers it checked at. Good luck over at the registry, and see
what Allpar has in it's smallblock section, haven't cruised that site in a little while.....................
 
Any idea what the lift on cam was? I'm reading that the 4bl and 6 pack cams were the same.
292° Hydraulic: P4120233 seems to be the cam that keeps coming up in rebuild articles. Not that its factory correct, but seems to work. I just don't want to spend $$ on a cam and have issues later. :O
 
same as a 4 barrel 340 except for heads have offset rocker and are mechanical rockers...it has an aluminum 6 pac intake with 3 holley two barrels instead of cast iron intake with a carter avs.

crank rods pistons and valves...valve springs .cam ..compression all the same....but uses a dual point distributor.
 
Here is something to get your heart pumping. It was a labor of love to get it to look like this. Yes it's mine!

20160404_195801.jpg
 
MICHAEL J KLOCK said:
Any idea what the lift on cam was? I'm reading that the 4bl and 6 pack cams were the same.
292° Hydraulic: P4120233 seems to be the cam that keeps coming up in rebuild articles. Not that its factory correct, but seems to work. I just don't want to spend $$ on a cam and have issues later. :O
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Good grief Heavens no, that's waaay big for stock, I did a set of T/A heads for someone running that cam w/a 6bbl, 9"vac is about the best You will get at idle & You'd need
at least a 9.5" TC or smaller. If that engine had been in a duster instead of a stock AAR, w/a 904 based trans, that 340 would've been running 11's with just a set of slicks.
According to the racing manual from DC/MP, it looks like this;
The majority of 340's came with a 268deg/.450" cam PN 2899206
The H.P.'s came with a .460" lift no part# given
For one Year only, the '68 4spd option was a 276deg/.460-.465" lift stick PN P3412044
According to the other sources, all 340's Intake valve open specs are 22deg BTDC except the '68 4spd's, which are 26deg BTDC.
The lift from these also is listed the same 4bbl & 6bbl at .429" Int/.444" Exh actual valve lift.....................

Take it all for what it's worth, but that cam You listed is the biggest Hyd. Purple Shaft Mopar sold,LOL!!!
 
Looking at past forum posts, someone listed the MOPAR camshaft P/N 2899205 for a 1968 340 manual car with 276,284 .444, .453.
Anyone know if they reproduce this? Or anyone have a NOS in their basement? :)
 
MICHAEL J KLOCK said:
Looking at past forum posts, someone listed the MOPAR camshaft P/N 2899205 for a 1968 340 manual car with 276,284 .444, .453.
Anyone know if they reproduce this? Or anyone have a NOS in their basement? :)
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There has been a search here before for that cam so it can be duplicated. A couple members were working on it and the info is buried in a thread. Let me see if I can find it.
 
68 340 4 speed cam:

276°/284° duration
.444"/.453" lift

Int open: 26° BTDC
Int close: 70° ABDC
Exh open: 78° BBDC
Exh close: 26° ATDC

Overlap: 52°

Per the 68 factory service manual...
 
Pretty much any cam company can grind you a cam if you have the specs. Camcraft is one company.
 
I just found a post that said that Oregon Cams has a darned close copy.
 
MICHAEL J KLOCK said:
So someone can grind these?
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Yes, cam companies will grind anything You want, customs cost more though. That's why some members are looking for a quality pattern example to have a re-grind
in a group-buy scenario, it cuts the cost per unit down some.............
The "P" part number I posted was a "re-issue" of that cam, long since no longer available, through Direct Connection at the time.
 
Unless You're going for a 1000 point resto, I wouldn't be too hung up on that particular cam, especially from a grind standpoint. A smaller overall duration modern grind
will idle better and perform as well or better than that piece. The bottom end with that cam probably lost a little when put in an auto unless You put a little looser torque
converter in, is Your ride a stick, or....?
 
Killer6 said:
Unless You're going for a 1000 point resto, I wouldn't be too hung up on that particular cam, especially from a grind standpoint. A smaller overall duration modern grind
will idle better and perform as well or better than that piece. The bottom end with that cam probably lost a little when put in an auto unless You put a little looser torque
converter in, is Your ride a stick, or....?
Click to expand...
I have a stick, I'm going to give Oregon Cams a call tomorrow and see what they charge.
 
They are very friendly to deal with from what I've read, as toolmanmike said, they may already have a grind that is a near match to that cam. A Comp 270 Magnum is
probably the closest single pattern cam, and they show a nostalgia repro of the 268/276 cam# 20-309-4, but the footnote says You cannot use the OE valve springs. Lift
is listed at .470 for the Mag & .464 for the repro, they spec their 901 springs, pretty close to the red 340 H.P. springs w/damper.
 
MICHAEL J KLOCK said:
Looking at past forum posts, someone listed the MOPAR camshaft P/N 2899205 for a 1968 340 manual car with 276,284 .444, .453.
Anyone know if they reproduce this? Or anyone have a NOS in their basement? :)
Click to expand...

MICHAEL J KLOCK said:
So someone can grind these?
Click to expand...

toolmanmike said:
I just found a post that said that Oregon Cams has a darned close copy.
Click to expand...

I bought a replica custom grind 68 340 4 speed cam from a member many years ago... Another member asked me if he could copy it, so we sent it to Ken at Oregon Cams to duplicate...

Ken was able to copy it to be exactly on lobe centers, but the intake lift is .006" less than stock, but is very close...

the exhaust is dead on...
 
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MICHAEL J KLOCK said:
I'm going to order the Promax Carb mods for my 6 pack, lots of $$$ but much easier to tune!
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Be forewarned, the throttle bodies are very tight to the shafts, You must barely snug them down when installing the outboards or the shafts will drag/bind. This leads to the
front & rear not working in unison. And the next issue is the jetted metering plates, use the thickest bowl gaskets You can, because they won't tell You,......but the float toes
will make contact with the thicker design metering plates. This leads to erratic flooding &/or fuel starvation, after having discovered this, ProMax said,"Oh Yeah, that happens
all the time". But My Customer had sent them back to ProMax twice because of a fuel issue and they said nothing. It won't show on the dyno because the movement & fuel
sloshing shifts the float fore & aft contributing to the interference's erratic behavior. The pieces are nice quality, but You need to be aware of these things.
 
So I heard from Ken today from Oregon Cam grind, his exact words were, "I am convinced that the cam you are looking for never existed." ie P/N 2899205.
:O
 
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