how to get 340 into 12,s

-
M

matty wardle

mopar dedicated
Joined
Aug 12, 2007
Messages
109
Reaction score
4
Location
brisbane
just a quick rundown of the parts in my brothers 340 which we thought would run a mid 12,but only ran a 13.2 last night at the drags.

ENGINE 340 60 thou over 4.1 inch bore
CAMSHAFT hydraulic roller 292/292 dur @50 248/248 lift 570 110
HEADS mopar performance ally heads,straight out of the box 179 cc,matching springs for cam,flow the same as stock eddys
MANIFOLD mopar single plane with an inch spacer
CARBEURETER 750 holley hp series
STROKE stock 3.31 inch
RODS stock 340
HEADERS headmans
CONVERTER 3500 stall
TRANS torqueflite stage 2 transgo
the car has good street ets on it,the car is extremly boggy down low,runs great and goes hard when your into it it miled an hour consistently at 105 last night but the 60ft,s are a terrible 1.9,how do we make this challenger go hard off the line and can we get it into the 12,s,the car is about 3600 with driver,it can hardly do a burnout off the line,just so doughy:burnout:
 
probably only leaving the line at 3000 rpm,i think you gotta rev the crap out of this motor to make it go,the cams pretty big
 
hi, what is timing set at?? total timing that is and rpm it comes in at?? launch rpm ??
 
You need to do some port work on the heads just like the eddy heads to make them really flow (FYI Eddy makes the aluminum heads for Mopar).
 
Also what gears and tire size does he have?I leave the line at 2200 rpm with a 4500 stall,4.56 gears and 29 inch tire...60fts are in the mid 1.4,s
 
compression is 10.2 to 1 and rear end is 3.91 8/ 3/4 his wheels are widened ralleyes 15 inch,with mickey thompson street ets,about 9 inch,s wide i think,i think he,s scared to rev it,the motor was well built,everything measured and puttogether right,does the mile an hour suggest a better time from this car you think
 
105 mph is about a 12.50 pass.I think his 60fts are hurting due to the bogging off the line.Need to find out why the bog?A 750 vacuum secondarie carb(3310)may help.JMO
 
need to get the 60 ft time down...as said 105 should easily be in the 12s...either spinning times or engine is bogging...
 
this hp series holley was brand new out of the box and and seems to squirt a god awfull amount of feul when u crack it ,maybe it needs jetting down,maybe thats why its so doughy off the line,i think it will be off to the dyno
 
not jetting down...adjust the squirter....either smaller squirter or adjust accelerator pump cam..
 
The compression - was that measured or assumed? Which pistons? HP Holleys are wet flowed, so it's larger than the "normal" 3310s and 750 cfm 4150s. You will need to do some tuning, and tuning starts with timing. Set timing first, then set carb. For what you have, I'd be looking for an inital figure of 18°, centrifical in the 20-22° area, for a total of 38-40. Once you;ve gott aht set, then you can mess with the carb which IMO is too large.
 
CONVERTOR - CONVERTOR - CONVERTOR!
Invest in a good convertor, nothing off the self. Make a call to the any mfg. & they can custom build one for you.
It will the best money you ever spent.
I have ran several 340's, twelves is nothing for one.
 
Im with Moper, start with tuning. What is your cranking compression? What is your vacuum at idle? I dont think your carb is too big but if youre bogging and cant hardly get off the line then you dont have it tuned right. You should be able to stab the throttle without any hiccups, coughs, or bogs. Also, are you open to changing parts? If so, I may swap an Eddy Air-Gap intake in place of the M1.
 
matty wardle said:
how do we make this challenger go hard off the line and can we get it into the 12,s,the car is about 3600 with driver,it can hardly do a burnout off the line,just so doughy
Click to expand...

only way is to cut weight:
aluminum rims
aluminum drive shaft
rear seat delete (but not for street)
small front wheels (but not for street)
lightweight bucket seat (but probably not for street)
fiberglass hood / fenders / trunk lid (but not for street)
use lexan windows (but not for street)

etc.
 
mikedevore said:
CONVERTOR - CONVERTOR - CONVERTOR!
Invest in a good convertor, nothing off the self. Make a call to the any mfg. & they can custom build one for you.
It will the best money you ever spent.
I have ran several 340's, twelves is nothing for one.
Click to expand...

WINNER!

It's gonna want a GOOD 4500+ converter.

That car is a dog off the line and where you are losing at least .15 right there which is maybe .30 at the other end.

The car should run about a 12.50-12.60 for that MPH.

With that camshaft and the heads, IMO, it's missing at least 5-8 MPH. That's a 430-450hp set up. It's a mid high 11 sec set up at 3600#. Just as an example... this engine with a shelf hughes 2500 converter ran 103.50 mph in a Demon at 3250 pounds

360, J heads with 1.94 valves and blending only, Comp XE268H, ld340, OOTB 750 DP, dougs headers, MSD, 2.94 gears and BFG T/A's. The carb was never tuned for conditions, was a bit fat. Engine made ~350hp/400tq on the dyno.

Where is the engine shifted? That cam will want every bit of 6200-6500+ shift points.
 
Yeah, cam kinda big. Are the secondaries bogging it? What rear suspension? Like they said, start with timing, then carb adjust. that doggy 60 is in timing, carb, not leaving hard enough, or spin.
 
matty, i think you have enough motor to into the 12's easy. like the others said the mph is there and that tells you the motor is making the hp. also like was said get timing set first. next adjust the pump cam arm, open the throttle all the way up with motor off and see if a .016" feeler gauge fits between the cam and arm. if it does you're good to go, if not adjust it. next with the motor in park or neutral and running. take your hand and open the trottle as fast as you can. there should be instant throtte responce without any hesitation. if there is you need to add squirter size until it's crisp. now hit the track. idling in first stab the throttle it should respond cleanly without bogging. if it bogs add more squirter until you're happy. all this is because you have an intake with a large plenum and a 1" spacer on top of it. that's a lot af air that is moving rather slow at idle and it will need alot a gas shot into it to richen it up to get the hotrod to move quickly. try and find a holley book on tuning and you will read about alot of neat things about tuning a carb.
 
thanks guys alot of good info to digest here,of course we will do the simpler things first like timing and carb adjustments,when we bought the converter we gave them all the cam specs ect and they apparently built it accordingly at 3500,i get a feeling this engine could run the numbers just a successfully with a dual plane and a vac secondary,this big single plane and spacer obviously needs big revs and lots of air speed to get it to be affective off the line,from what i,ve read a vac sec is better with an auto,a dp is hard to get off line,probably extra hard with this big cam we got
 
Another vote for the converter, somethings not right with it with that combo you should be able to pull a sparkplug wire off and still run 12's
 
tune it right and it will run. get the ignition right and then start working on the accpump and squirters.
 
A stock 340 will go 12s with converter, gear and slicks in an A body.
 
You must log in or register to reply here.
-

Back
Top