cam question

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ltrripp11

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gentleman

got a cam question here?? got a 72 340 duster with an all stock motor. anyone know what the cam specs ma mopar gave this motor when built (lift,duration) without removal?? im looking to upgrade but not sure on what to get for a good street performer with a little lope to it. (no dragstrip).also were the cam specs different between the first 340's and the last in 73?? i know the compression was but anything else?? thanks for any help.
 
The 72 and 73 specs were similiar, however there is a difference between some of the cams used behind a standard tranny and an auto - which do you have? In 68 there was a hotter can in the 4 speed engines, and after 1970 there was a drop in compression and I believe cam specs. Do you know what you have in there for rear end gears, because that will make a difference to how much cam you can handle.
 
hi, the mopar specs are;268/276 dur, .429 int,, .444 exh. lifts. ground on 112 LCA. the only 340 cam different was the 1968 340 manual trans cam.as for a cam, the comp cams extreme energy grinds work very well. the xe 262H or xe 268H are very good grinds. in your low comp. motor, I would use the xe 262H cam. I've used the 262 in low comp. 340 motors.
 
thanks for the above. heres a little more info::::

the rear gears are 3;55. the tranny is a 727 with a mild shift kit. it has the stock x heads and manifold. unsure on the convertor. this motors very virgin. on the manifold however i would like to swap it for an edelbrock performer. with this manifold would the comp cam 268 be compatible? in the future i will be doing a total rebuild back to the older 10:5:1 specs keeping the above mods. but in the meantime im just looking for some simpler less expensive additions for a little more steam. the motor has 84000 original and runs way to nice to tear it down yet. in light of that what do you guys suggest on these 2 proposed mods?? thanks again.
 
sounds good to me, although there may not be any lope with the xe-268 maybe slight at best. there is a seeming different opinion on the lope in this cam. it seems to depend on the setup as to wheather or not it lopes. there is a thread on here about the ex-268 that was asked not too long ago read it it may help you decide. here is the link to it:

http://www.forabodiesonly.com/mopar/showthread.php?t=13623

if you go on and do the complete rebuild with the higher compression ratio then change the convertor out to a 2400 stall (min) and go with the ex-274. i think you will be happier. just my 2 cents.....
 
thanks demon

i was reading your posts earlier. you seem to have a same car and similar set up to me. i will consider that other cam later. we'll see how it runs. i thought of this after the post!! think there would be any valve to piston clearance issues on the 268??
 
i think not , as it is almost the same spec as the stock 68 cam. i am not an expert by any means though. there are alot of great guys that can give you the full detailed info that you need. good luck !
 
WARNING; The use of the Performer is a waste of your time on a 340 or larger CID engine and will cause a loss in performance. Use the Edelbrock RPM or weiand Action plus (As to keep a T-Q on top if so equiped)
On cam choice, what ever you decided to run, make it a split duration cam. IE; More exhaust duration and lift. This type of cam will add power to your engine set up with stock heads or mildly ported heads over a single pattern cam.
Hint; The lope of a cam is due to a smaller numeric centerline. 110 vs a 114. The 110 will have a chop to it. 108's and less become difficult to tune at idle.
 
Lot sof reason 2 motors with the same cam will have differant idles. Intake, carb, ignition timing, exhaust even torque converter.
 
rumblefish

the thermoquad was recently replaced due to it being a little tired (floats sticking etc) but retained. it was replaced with a holley 650 w/vacum secondaries. i was under the impresssion that the regular performer manifold would give me a little more bottom end over the rpm and that the rpm was only benificial in the upper rpm range. i want to keep the bottom end as much as possible. that is why i was leaning towards the regular performer. correct me on this if my thinking is wrong. thats why im picking everyones brain before purchase. i was also considering the air gap but was concerned about hood clearance issues. any comment on that idea??
 
7demon2 said:
there are alot of great guys that can give you the full detailed info that you need. good luck !
Click to expand...

speaking of which here are 2 guys now that can help you alot: adam and rumble!

hey rumble are you saying that the stock 340 cam is ground on a 114 center not 112?
 
I personnaly do not know about hood clearance on an "A" body.
Click the link I gave you for T-Q service. David is excellent with these carbs.
The Performer should be shelved. The stock intake is a better intake. Hands down.
 
I dont have any experience with ThermoQuads but I have always wanted to try one. It wont work with a RPM or Airgap unless you run an adapter though. Then it really wont fit under the hood. Also I dont think the air gap is much taller then the RPM.

The problem with the Performer is the port size is for a 318 not 340/360 so its killing some air flow. I think a stock thermoquad intake would give better results then the perf.
 
hi, the reason I give for using the XE262H is, when you put long duration cams in low compression motors, you will loose cylinder pressure, which will in turn loose torque,= lose of power!!! the 268 will have plenty of "rump".
I just went through this with a guys 73- 340. he had the mighty mopar 509 cam in it. it couldn't spin a tire on wet pavement.his motor builder told him, this was the cam to use!!!! we replaced it with a EX262H. it now will spin the tires, it has a lot better power, and will pull 6000 RPM.
 
ltrripp11 said:
it has the stock x heads and manifold.
Click to expand...

The original engine from your 72 Duster shouldn't have X heads on it. Should have J heads. 69 was the last year for the X heads. If it has X heads you might want to do some checking to see if it's the original engine. Someone may have replaced it with an older 340 and it may be higher compression than you think. On the other hand just the heads may have been changed which won't affect compression.
 
fishy68

good eye but i have checked the numbers and they are correct. therefore im not sure what to think on that. perhaps they were changed at some point or ma mopar slid in a few x heads on these and we aren't the wiser for it. i appreciate all the feedback and knowlege. it has been invaluable. i will shoot for the rpm intake and still not sure on the cam--- 262 or 268? ill keep you all posted.
 
I think the 340 intake is just as good or better than the performer intake, you just lose a few pounds. I would stick with the factory intake and swap to a 340 man trans cam. I used one in my little 273 and liked it alot.
 
oldvart

yes there is an X cast into the head at the plug hole-- thankfully.
 
I run an XE263H in my mild tune 360 (9.0 Compression). With 3,23 gears it performs well and has a powerband that you can use. Pretty clean idle with just a hint of 'rump'. According to comp cams this cam will make HP up to approx.5,500rpm. particularly fun when manual shifting from 2 to 3!
 
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