340 Rebuild reccomendation

[LAA66]

 Start with a solid bottom end (balanced of coarse) and see what $ are left over for the heads and valve train. That area can be upgraded later as funds become available without pulling the whole motor. 10.5:1  pistons still work in mine with todays 91 octane fuel.

 If you guys keep it under 6000 RPM the original rod forgings should work OK. I would size the cam and ultimate build accordingly.

[71chally416]

No need to bother with the balance if the pistons are the same weight. And under 6,000 for a small block rod? As long as you have good bolts and you get them resized they're good to 7,000 (Not that the motor will make power there with unported heads..)

[LAA66]

 You may be right. I don't remember exactly what RPM mine let loose.

[71chally416]

The rods in my old 318 (resized 340 stockers with ARP bolts) saw over 7K more times than I can remember. It was also re-ringed 3 times with the same bolts. They were very good stock forgings though, with equal meat all around the big ends (where you check the side clearance) and balance pads all about equal size. I also deburred and polished the beams. I have seen some that were either just bad forgings or had sloppy factory machining with the big end looking off-center. I wouldn't use those.       

[sleepychallenger]

thanks guys, keep the inputs coming. what cam would you reccomend for what he is wanting, he still wants a lope, but something that will allow good vacuum too

[71chally416]

As it is in every case, the cam depends on your compression, the pistons you use and the notches they have and what's done to your heads. Stock heads break over (stop gaining flow) at around .500" lift, so any more than that is kind of a waste. You have to consider the valve spring installed height too and what cam lift it can accomodate. 

[73cuda-project]

Hey guys I really appreciate your inputs, Drew and I will make sure to take them into consideration when the time for the rebuilt comes. I can't wait to start taking the engine apart, but first there's a couple things I need to do. ( like getting an engine stand and lift and so on)

   Thanks a lot all!!!

[sleepychallenger]

i dont know about David, but i was thinking anywhere between 9.5 - 10:1 compression and maybe a 45? - 485 cam? what do you guys think?

[71chally416]

I'd try to get the compression up around 10.5 and use a cam around .480"/.500" lift. CP can give you a specific Lunati or Engle grind.   

[sleepychallenger]

thanks, i wasnt sure if 10.5 would be too much to run 91 octane or not.

[71chally416]

With the right cam it should be alright.

[sleepychallenger]

thanks, i was really thinking of like a 488 cam, just didnt want to seem overzelous

[71chally416]

My 318 did 12.70's @ 109+ with less than 8 to 1 comp and a .470" lift cam (MP) so something like a .48X" should get the job done. I'd use as much lift as a reasonable valve spring will allow.   

[Chryco Psycho]

I use the Engle K 56 or K 58 a lot , with approx 10:1 compression all will be good