383 Con Rod Bolt Doesn't Clearance Cam Nooo :(!!!

Unfortunately not an uncommon experience even when the tech guy on the phone or e-mail says "no-problem".

I would never recommend that you buy a prebalanced kit, as it seems that in 10 to 15 percent of the cases there are clearance problems with the cam when using these. This is often the result of either factory "fixes" to a block that didn't machine to spec the first time down the line; or result from align boring/honing upon rebuild, or the use of a lumpier cam thean the guy hat designed the kit counted on anyone using. So there is a risk with what the tech guy says as blanket truth.

Covering your contingencies with a small block stroker is to purchase a non-prebalanced crank, a set of cap bolt rods in whatever length and beam style you prefer, and pistons/rings separately. Then check assemble the engine with the cam you will use and inspect for clearance issues. I recommend cap bolt style rods as the clearance will come off the upper end of the bolt boss where the loss of material will not affect strength. Where-as conventional nut and bolt type rods dictate the removal of material from about the bolt head, which is carrying a lot of load in that design. If modification to the rods and possibly the piston skirts becomes necessary, afterwards you can send the bottom end parts to the balancer.

The other choice is to use a small core cam. First you need to know how the motor will be used. Small base diameter cams tend to have greater force issues between the lifter and the tappet, a somewhat typical problem from years past which can accelerate wear in this area. If the answer to the above question is "no problem", then the next step is a cost estimate of a small dia cam plus longer pushrods, is it the less costly option to tearing the bottom end apart, making necessary mods and having it rebalanced. Nice thing is, it's getting lighter so if anything needs to be done, it will be the removal of material rather than having to add Mallory metal to the counterweights.

Going back to my basic advice, buy the stroker in pieces, not a prebalanced rotating assembly, that way if there are assembly problems, my experience 10 to 15 percent have them, then the money for prebalancing isn't wasted when it has to be redone. The other is go in with the expectation that the bottom end will have to go together at least twice and maybe three times to work out the bugs before final assembly.

Bogie


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Dont use a small base circle cam if you can avoid it. They are weaker and the flex causes other valve event issues. Dont damage the cam buy turning the engine. DO remove the rods that hit, I think number 2,6,7 are the worst, and grind enough off to provide .050 MINIMUM clearance. You do NOT have to rebalance. The oil allowance used in the bobweight calculation is generally 5 to 25 grams depending on which engine builder you ask. And FYI, a nickel weighs 5 grams.

Hey guys thank you both very much that relieved me a lot of stress becuase I can't afford the time and or money to have it all balanced again!! You are right it is the CAPSCREW type ARP series that I have ie. they dont have a nut on the other end. I went ahead and grinded the first rod that was contacting (I think there are only 3 that contact ) and I took off enough material so that it clears the lobe!! I had to cut away some of the thread though (maybe 3 or 4 pitches) so I am concerned that the "capscrew" will no longer have enough material to forcfully hold the cap on I took some pics and they should be posted below but before looking could you also tell me if the amount of material I took off is minimal enough that I will not require the re-balance, I have included pics of both sides so you can compare how much was actually removed. Thanks for your time and input, I don't knwo what I would do without your guys' help.


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The last pic is of the good side.

Keith.

Any thoughts on the pics??

Looks fine, just the way it should Put'er together and run the snot out of it

On the 383's we have built for the street we use the 6 inch scat rod with 7/16 rod bolts as they are cam clearanced and on the hyd. cams we order them with a 1.130 base circle which gives ample clearance every where have your cam machined on a P-55 core as we have done this for yers with no problems and they would not make small base circle cams if there was going to be a problem.

And your balancing should be fine as that will put you into over balance which is fine.

Heres all your pics opened up.

They look fine. I have done that exact same thing 20 or 25 times and never had a single issue.

The balancing is also ok. Going lighter never seams to hurt anything, as long as it's with-in reason. I doubt if you took 2 grams off of them..

Keith

I had to do mine the same way. Put it together and rock and roll.

that is why we use 5.7 rods in a 383 stroker because they clear the camshaft. If you take the short block into a machine shop they should beable to clearance the rods for you i think it is the number 2 and 7 rods that hit. you will have to have the assembly rebalanced after this. another bad thing about the 6 inch rod is your wrist pin is up in the oil ring and i don't like that, that is another reason i have 5.7 rods in my 383 stroker. good luck man

Not all 6 inch rod pistons have the wrist pin up in the oil ring with the right rods and a 1.130 base circle cam we have had zero issues with clearance.

We just balanced a crank that is going to be a blower application and wanted it to be internally balanced, do to the heavy JE pistons and Lunati Pro Mod rods the crank needed 4 peices of mallory which brought the price of balancing up to almost 700 dollars.

I warned him this would happen.