12 second 340

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Adam, You have a lo com. 340? What about getting a set of Cometic head gaskets to bump the comp up. Slide a new cam in, and get some 4.30s? Those Cometics are pricy but are reusable. Should be a one time purchase. You will need a 750 carb.
Call Don @FBO 503 627-0728 he sells them and he could help you figure it out. Mike should call him too to figure out his problems. The guy runs a 318 with 1.81 intake valves in the 11.70s He knows his stuff and is a real nice guy.
 
Yup low compression. I'm thinking seeing it runs so strong I'll stab a cam in it, Get some thing head gaskets and a set of small chamber magnum heads.

Im planning on 4.30ss too. Had them in it before and they worked well.
 
Just remembered that I have a set of Adjustable rockers and push rods for a solid cam (273 parts)
So a solid cam is always an option.
 
Have you had the heads to confirm its a low comp? Just because its a 72 doesnt automatically mean it the lc version. My block is supposidley a 72 but it dates to july 71 and pistons sit out of the hole....mind you aftermarket.
 
No I havent had the heads off yet but it will run on 87 octane no problem.
 
Forged I think. I dont think I ever really checked it. I'll look in the morning.
 
Well if it is i imagine you would have the high compression unit. Sometime in 72 they switched to the cast crank LC in the hole pistons...4 valve relief. The balancer should tell the tale. Hell even if it is a cast crank and in the hole pistons its not the end of the world. Pistons can be changed.......If its a cast crank thats okay too. Those things should be okay for up to 400 or so hp. Probably more.
It was eatin at me when i got mine to know exactly what was inside so on the advice of a friend we took it out and i tore it down to find exactly what was in it. If you want to build it up your going to have to find out sometime :) ....a good winter project...at least take the heads off and see what bore size you have and if they are 4 valve or 2 valve relief....you might be :eek:
 
Yeah its something Ive been wanting to do. But no garage and its cold out side.
 
Yeah I dont have a choice right now. Its got a good cover on it and Im gonna get a car tent for it.
 
Just remembered its a forged crank and internally ballanced. Ive changed the converter on it and theres no wieghts . werent any on the old one and none on the new one.

Im ordering a few parts for it. SSI cam and lifters from PAW 243 @.050" .508" lift 108LSA, Timing set, and gaskets. I also have a timing chain tensioner. It needs a new chain anyway. When I took the mech. pump off I stuck my finger in the hole. Man it has alot of slack in it. And ive replaced it once already.

I'm also looking at a solid cam 284 adv. 241 @.050" .527" 106LSA. My desk top dyno realy likes this cam. Nice flat torque curve. with 9:1 COMPRESSION SMALL HEADERS AND A DUAL PLANE INTAKE IT SAYS 388 HP @ 6000 AND 387FT,LBS @ 4000

I figure if it doesnt make it faster it will atleast sound nasty. :roll: :D

When I get the heads off if they sit way in the hole I'll have them milled a bit. Once I get a set of gears in it, it should move good.
 
im rebuilding a 340 right now that did 11.30 in a 3400lb car.

KB 10:1 pistons
mopar 292 purple shaft cam
ported j heads......im going with ported eddies for a little more oomph and a little less weight
4.56 gears
4500 converter
air gap intake
cast crank, internally balanced with refurb stock rods and arp bolts
running an internal balance stock balancer

as for a timing chain its running an undersized one because my block was line bored

this combo twisted two pairs of stock axels in the car it came out of, and should put me in the high ten's on a good day when properly tuned
 
fastbackcuda said:
Just remembered its a forged crank and internally ballanced. Ive changed the converter on it and theres no wieghts . werent any on the old one and none on the new one.

Im ordering a few parts for it. SSI cam and lifters from PAW 243 @.050" .508" lift 108LSA, Timing set, and gaskets. I also have a timing chain tensioner. It needs a new chain anyway. When I took the mech. pump off I stuck my finger in the hole. Man it has alot of slack in it. And ive replaced it once already.

I'm also looking at a solid cam 284 adv. 241 @.050" .527" 106LSA. My desk top dyno realy likes this cam. Nice flat torque curve. with 9:1 COMPRESSION SMALL HEADERS AND A DUAL PLANE INTAKE IT SAYS 388 HP @ 6000 AND 387FT,LBS @
I figure if it doesnt make it faster it will atleast sound nasty. :roll: :D

When I get the heads off if they sit way in the hole I'll have them milled a bit. Once I get a set of gears in it, it should move good.
Click to expand...

Okay, there is a really good chance you have the high comp. pistons. Find out for sure before putting in a different cam. You gotta at least take the heads off this winter and find out.
 
OK this is what Im gonna do. The thing runs to good and I dont want screw it up.

Im gonna order a set of gaskets and a timing chain and switch to some 1.6 rockers for now. Any recomendation on a good set of rockers ?

The car needs gears bad with its currant cam so I'll swao the 3.23s for a set of 4.10s or 4.30s ( I like alot of gear :mrgreen: )

I been thinking of replacing the 727 with a low gear set 904. That alone should free up spme power. Add a loose 10" or tight 9.5 3500 rpm converter and it should run good for a mostly stock (?) 340 with out breaking the bank. :afro:
 
I wish i was 26 again....hell i'd settle for 45 :salut: ......I have a stick so am not too familiar with the autos...Why the 1.6s?....your gear change is gonna be HUGE! I've got 3.55s now and they are sure a nice middle of the road. Will be putting the 3.91s in though. Man you go out on the freeway with 4.30s your RPMs are gonna wear that thing out in no time. Just my 2cents....Merry Xmas!
 
I'm pretty sure its got the stock 340 cam in it wich only has.429/.444" lift. The 1.6 will give me alittle extra lift without worrying about loosing what little torque I have for now.

I dont do any highway driving and I had 4.30s in the car before. They worked well and they arent all that bad on the highway. I figure if the car cant spin at 3000rpms for more then 20 minutes at a time its not gonna last being shifted at 6500 on the drag strip.

Merry Christmas.
 
Thats a pretty stout cam. Does it not have a lope at idle? What rpm does it idle at? The guy i bought my dart off had the 3.91s in it and said he had to shift into second in the middle of the intersection...This from a stop light or stop sign. So put the 3.55s back in. Mind you he was almost as old as me. :drunken: ....Sometime though take those heads off and see whats in there. Take care of that puppy and finger the ricers. :thefinge:
 
littlecampbell said:
Thats a pretty stout cam. Does it not have a lope at idle? What rpm does it idle at? The guy i bought my dart off had the 3.91s in it and said he had to shift into second in the middle of the intersection...This from a stop light or stop sign. So put the 3.55s back in. Mind you he was almost as old as me. :drunken: ....Sometime though take those heads off and see whats in there. Take care of that puppy and finger the ricers. :thefinge:
Click to expand...

Better late then never. LOL

It has a pretty good lope at idle now that I changed to a Holley. With the Edelbrock it was pretty smooth. Idles at 750 in gear 850 in park.

I picked up a set of 3.91s so there going in and a 904 with a low2.77 first gear and tight 8" converter.
 
check ebay for the low gear set, i got mine for $55 shipped

as far as gear.....i went 4.56, and if I could do it again I would. 4.30's would really wake it up ;). no comparison from a set of 3.91's to the new gears.
 
Yes its easy to get a 340 A-body in the 12's. If your on a tight budget like me you dont have to use alot of high dollar parts. I like the MP .474 cam myself as I used one years ago in my girlfriends 340 Dart. I also used the stock non adjustable rockes as I also did in the 383 that used to be in my sons Dart. You can drop in the .474 cam and mill the heads if needed to get an honest 9.5 to 10.0 comp. The heads on her car were all stock 2.02 valve heads milled .010 for a true 10.0 and NO porting at all.Then use rocker shims to set lifter preload. Thats how I set up my girlfriends car. Then it used the old LDP318 intake and a 650 Holley DP. Had the stock dist and stock ign box. Used 1-3/4 Hooker headers and 2-1/2 pipes. Stock 904 and convertor from a 318. 8-1/4 rear with 4.10's. This car ran 13.40's @ 105 on slippery street tires back in 1979. It could have run easy 12.80's with slicks or a good drag radial which was not around back then. Not to mention if it had a decent convertor and it was still stock bore and pistons. This car had mostly all stock internal parts other then the cam and like I said with 105 mph it would have been in the high 12's on a good tire and it was built on a tight budget. Good luck on whatever you decide. Ron
 
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