camshaft for mild 340

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j.d.duggan

j.d.duggan

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what cam could I run for a mild street build?don't want to worry about valve clearance,or pushrod lengths.just a little more power and maby a little lope.340,.060 over,915 j 1.88 heads.any thoughts?:lol:
 
Comp Cams 268AH-10

It's basically a stock 340 cam with a more modern split grind. I love it in my 360. It's 9.4:1cr with 1.88/1.60 Jheads.
 
Another consideration for your cam selection is what rockers you’ll be using.
Fast rate cams require higher spring loads than cams with smoother lobes....... and the typical 100,000 mile variety stock rockers don’t always enjoy a long life when used with a fast rate cam and the matching springs.
Pushrods seem to poke holes in them.
 
sireland67 said:
This one will give you some lope, and still have decent vacuum.
I have it in my 340.

Lunati Voodoo Camshafts 10200703
Click to expand...

This is what I run and agree with the other but you will need to top the guides and run proper springs. Both the summit and melling are good choices. Honestly with any cam you should check pushrod length and degree it with a quality chain and tensioner.
 
without knowing his compression you guys are pissing into the wind
all could be good suggestions depending
the summit is an old crane/ cam dynamics grind
melling could be a stock 340 or any variety of chevy copy
voodoo line works but which one depends on your build and desires
btw lope and broad power range are incompatible given what you want to change- go for power- change your mufflers if you want sound
post your compression, gears carb and headers and you will get another round of opinions that are closer to the mark
stock 340 cam in low compression motor leaves a lot on the table without converter and gears
 
Wyrmrider says:
btw lope and broad power range are incompatible given what you want to change-
Click to expand...
I disagree

go for power- change your mufflers if you want sound
post your compression, gears carb and headers and you will get another round of opinions that are closer to the mark
stock 340 cam in low compression motor leaves a lot on the table without converter and gears
Click to expand...
I agree with everything above except, how do you know it is a low compression engine? Not because he has J heads is it?
What do you consider low compression?
 
pistons are .013 out of hole,felpro 8335 head gaskets .049 compressed thickness I think.wiend stelth intake,holly 750 carb.long tube headers with 3" tubes to the bumper,323 rearend gears,833 4 speed,915 j heads with 1.88 intakes.thats about all I know.
 
Wooooo/Weeeee!!! We got some squeeze going on there! If the J heads are uncut, your about 10.5-1 by my guesstimate. If you were at zero deck while being .030 over bored & a .039 gasket with open chambers you would be right in 9.8-1.

Your at .060 & positive .013! Whooo who who wee!
Yikes! So much for “ASSUMING” your a low compression mill!!!!!
:rofl:
 
dartfreak75 said:
I agree but this cam does require valve guides to be cut. Or at least it does on my 360 heads! Im going with one size smaller. The lunati voodoo 10200702.
For stock heads I agree with toolmanmike and RRR
Click to expand...

My “X” heads cleared with no issues.
 
j.d.duggan said:
what cam could I run for a mild street build?don't want to worry about valve clearance,or pushrod lengths.just a little more power and maby a little lope.340,.060 over,915 j 1.88 heads.any thoughts?:lol:
Click to expand...


Hey JD,

Here's what I used with my previous 340 build, factory rockers and pushrods, LD-340 intake, hooker headers 1 7/8 " pipes I think (JUNK..don't buy!! )10.5 compression, 650 cfm Holly carb, 4-speed ,2.65 first gear, 3.91 rear , 275/15 inch rear tires. This was a great street setup , not an overly powerful setup but great street manners and fuel economy was not too bad either. Great idle sound as well.

Hope this helps!

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Late to the party but I get 9.3:1 static CR with 71 cc unmilled J heads, PT8553 head gaskets .050" thick and 4.18 " bore hole, and stockish high compression type pistons with 2 eyebrows and .013" out of the hole. The 1 unknown is if these are the 2 or 4 eyebrow pistons. With 4 eyebrows it could be 8.9:1. (But I doubt that they would be .013" out of the hole for the lower CR 4 eyebrow pistons.)

So 'medium'-ish compression at best.
 
nm9 all I,ve found on the 915-j-1.88 heads say there 65cc and I would think they were surficed,I didn,t cc them but they had good clean face.
 
rumblefish360 said:
Well, I'm actually kind of partial to the solid roller @ 274@.050 w/ .650 lift myself.....
:rofl:
Click to expand...
I didn't quote the cam, gears, and single plane I'd strap on it, I like stuff that comes to life at 3000 RPM and up!
 
j.d.duggan said:
nm9 all I,ve found on the 915-j-1.88 heads say there 65cc and I would think they were surficed,I didn,t cc them but they had good clean face.
Click to expand...
The 65 cc is probably an NHRA spec. What that means is that 65 cc is the minimum combustion chamber volume which these heads can have after modification and still be competition legal; in other words, it is a competition spec, not a production head spec. The production chambers have been repeatedly measured and come out in the 70-73 cc range with consistency. Having a clean face may or may not mean they have been milled. So until these are cc'd, you really don't know what you have.

This is why the advertised 10.5 static CR for the early 340's is not the reality in most cases; it is based on some minimum production or NHRA head chamber spec, not typical production heads.
 
nm9stheham said:
The 65 cc is probably an NHRA spec. What that means is that 65 cc is the minimum combustion chamber volume which these heads can have after modification and still be competition legal; in other words, it is a competition spec, not a production head spec. The production chambers have been repeatedly measured and come out in the 70-73 cc range with consistency. Having a clean face may or may not mean they have been milled. So until these are cc'd, you really don't know what you have.

This is why the advertised 10.5 static CR for the early 340's is not the reality in most cases; it is based on some minimum production or NHRA head chamber spec, not typical production heads.
Click to expand...
You'll never know exactly where you are until you measure it while assembling the engine.
 
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