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340 Advice

M

Mopar4Speed

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Hi all,

To all those that replied or viewed my previous thread on my 318 issue, I ended up just getting a 340 for the extra cubes and power potential.

Just wanted some advice on what the correct pushrods would be for my 340. I was able find a beautiful like new set of original 273 adjustable rocker arms with the original banana groove shafts. The stock 340 stamp steel rocker pushrods measure approx 7.5" tip to tip. I read somewhere that people have luck with the Sum-g6420 (7.389") pushrods on La's with hydraulic lifters and adjustable rocker arms. Comp cams also makes some pushrods for this application (cup and ball 7.389") but they have pressed tip whereas the summit ones are welded for less money. Should I upgrade the carb or if the 600cfm is enough for my setup? Was leaning towards the the new Avs2 eddy.. Let me know your thoughts/opinions..

Specs of the engine are:

1969 340 block bored 0.030" over
Mahle Powerpak Forged Flat Top Pistons & balanced to crank
MP high volume oil pump and full groove main bearings
MP purple cam P4452992 280/.474
Original Forged 4 speed crank with factory windage tray
Pocket ported X heads, Manley Stainless valves, Comp 901 springs, Hardened locks & retainer
Tti Headers 1 5/8 step to 1 3/4 with x pipe 2.5" duals
Edelbrock Air gap intake
Edelbrock 1406 Carb
Petronix Billet Distributor with Ignitor 3
Edelbrock dual roller timing chain
 
Mopar4Speed said:
Hi all,

To all those that replied or viewed my previous thread on my 318 issue, I ended up just getting a 340 for the extra cubes and power potential.

Just wanted some advice on what the correct pushrods would be for my 340. I was able find a beautiful like new set of original 273 adjustable rocker arms with the original banana groove shafts. The stock 340 stamp steel rocker pushrods measure approx 7.5" tip to tip. I read somewhere that people have luck with the Sum-g6420 (7.389") pushrods on La's with hydraulic lifters and adjustable rocker arms. Comp cams also makes some pushrods for this application (cup and ball 7.389") but they have pressed tip whereas the summit ones are welded for less money. Should I upgrade the carb or if the 600cfm is enough for my setup? Was leaning towards the the new Avs2 eddy.. Let me know your thoughts/opinions..

Specs of the engine are:

1969 340 block bored 0.030" over
Mahle Powerpak Forged Flat Top Pistons & balanced to crank
MP high volume oil pump and full groove main bearings
MP purple cam P4452992 280/.474
Original Forged 4 speed crank with factory windage tray
Pocket ported X heads, Manley Stainless valves, Comp 901 springs, Hardened locks & retainer
Tti Headers 1 5/8 step to 1 3/4 with x pipe 2.5" duals
Edelbrock Air gap intake
Edelbrock 1406 Carb
Petronix Billet Distributor with Ignitor 3
Edelbrock dual roller timing chain
Click to expand...
Sounds like a potent small block, many upgrades over a 318. When I rob a 273 of its rockers, I always get the pushrods too. It's the same basic engine and adjustable.
 
I would give it a 1407 Edelbrock 750 cfm carb and let that 340 cid eat! 440'
 
Mopar4Speed said:
Hi all,

Just wanted some advice on what the correct pushrods would be for my 340. I was able find a beautiful like new set of original 273 adjustable rocker arms with the original banana groove shafts. The stock 340 stamp steel rocker pushrods measure approx 7.5" tip to tip. I read somewhere that people have luck with the Sum-g6420 (7.389") pushrods on La's with hydraulic lifters and adjustable rocker arms.
Click to expand...
Let’s stop right here! You need to measure your pushrod length. I have 2 sets of “Stock” 340 pushrods that are from two different companies at two different lengths.
This is not a place to cheap out on or just do “Good enough” though there is a minor amount of room for play in the over all spec length. The adjuster can take up some length but that should be most minimal.

Should I upgrade the carb or if the 600cfm is enough for my setup? Was leaning towards the the new Avs2 eddy.. Let me know your thoughts/opinions..
Click to expand...
The 750 would only be about 10hp greater than the 600. It’s hard to speculate the throttle response between them. I’d rather an AVS style up top but there not available new in a 750cfm. Only in a OE 440hp application. Edelbrock has them in the 650 & 800 sizes only. (Bummer!) While it is possible to add an electric choke to the old carb, that call is yours to make.

My choice would be a 750 cfm carb though a 600 may and should offer a slight hair better mileage and throttle response.
 
Jerry Hall said:
Sounds like a potent small block, many upgrades over a 318. When I rob a 273 of its rockers, I always get the pushrods too. It's the same basic engine and adjustable.
Click to expand...

Right on, the guy didn't have the pushrods for it. Also they wouldn't work anyway because I have a hydraulic cam not a solid.
 
As for the carb, I was thinking the 750cfm performer or the avs2 650cfm since for some reason edelbrock doesn't make the avs2 in 750cfm only 800cfm..
 
Mopar4Speed said:
Right on, the guy didn't have the pushrods for it. Also they wouldn't work anyway because I have a hydraulic cam not a solid.
Click to expand...
If you have access to a lathe, pushrods for a solid can be shortened to length required for hydraulic. Once I even made a set from shortened slant six pushrods. You can make them EXACTLY the right length once you measure what is required with a checking pushrod.
 
70chall440 said:
Get new ones from Smith Brothers
Click to expand...
ABSOLUTELY.....call them, discuss your plans and expectations specifically your intended cam and the adjustable rocker arms, RPM range, valve springs, etc.
Smith Bros. Pushrods
2895 SW 13th St
Redmond, OR 97756
1-800-367-1533
Fax 541-389-8840
ORDER CALL800-367-1533
TECH LINE 541-388-8188
www.pushrods.net

Just my opinion of course.
BOB RENTON
 
RJRENTON said:
ABSOLUTELY.....call them, discuss your plans and expectations specifically your intended cam and the adjustable rocker arms, RPM range, valve springs, etc.
Smith Bros. Pushrods
2895 SW 13th St
Redmond, OR 97756
1-800-367-1533
Fax 541-389-8840
ORDER CALL800-367-1533
TECH LINE 541-388-8188
www.pushrods.net

Just my opinion of course.
BOB RENTON
Click to expand...

Thanks, Just ordered a set of custom length pushrods from Smith Bros! Excited to recieve them.
 
Anybody have any suggestions for carbs? Car is mainly meant to be a performance street car, not a dd. I'd like a carb I set it and forget it.
 
Mopar4Speed said:
Anybody have any suggestions for carbs? Car is mainly meant to be a performance street car, not a dd. I'd like a carb I set it and forget it.
Click to expand...

Personally,.....if it were my choice, I would use an origional CARTER AVS, from a '69 - '70 Mopar 440 cubic inch engine. It flows just as much air as the previously suggested Edelbrock/Carter (aka "Eddy"). IMO...the Edelbrock AVS is a hermaphrodite, using secondary booster venturi and an adjustable air valve, whereas the origional AVS uses just the air valve. The Edelbrock tuning kits are readily adaptable with prudance and can be used on the Mopar AVS ..... OR.... with the right manifold, the Carter Thermoquad, which provides 800 CFM, would be an excellent alternative. Not exactly sure why the general consensus seems to prefer the Edelbrock unit. But the Holley R3310-3 or -4 @ 750 CFM would be a great candidate to consider and tuning parts are available just about everywhere......but the choice is yours..... Just my opinion of course.
BOB RENTON
 
I’m a fan of the old carters so you see where I stand.. AVS is my personal favorite... this is one of those conversations that get interesting!
 
Thanks guys keep it coming. Also forgot to mention that i would like something with electric choke, since i'm already setup for it, with the rpm air gap (no crossover) and still want to have a working choke for colder days and ease of starting.
 
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