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neverendingproject

neverendingproject

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I got my block back from the machine shop this weekend (going 383 roller motor) and I test fit cam, crank, and pistons. About four of my rods hit the cam and one of the rods would "click" against the block.

My question is how much minimum clearance is needed for the cam to rod and rod to block?

It would also be nice to have some pics of a rod that has been ground to fit.
Thanks
 
I like .100" clearance.

If you're holding the rod in your hand looking at it as if it were installed in the motor and looking from the front the inside rod bolt should be somewhere about .625" from the inside radius of the rod to the outside of the rod bolt.
 
Clearance the block, just be careful not to enter the water jackets. I'd switch to a smaller base circle cam instead of clearancing the rods if that is an option to you.
 
When I built my 388, I made sure to have at least 0.060" clearance around the rotating assembly. I did not have clearance problems at the camshaft with the H-beam rods and relatively low lift cam (.447/.462).

The H-beam rods did require more grinding at the bottom of the cylinders and oil pan rail than a set of stock rods would have. Make sure you test fit your oil pan before bolting it on. I had to "persuade" mine in a few spots to clear the rods.

Happy building. You'll like that 383! :bow: :D :D :D
 
As they were saying I would use the circle base cam, you should not have a problem with clearance. As for the other I agree with them too on clearancing your block instead of rods, thats what I did. If you can get a 400sbc oil pan or you can tap some dents in your OEM pan but if you dont the rods will rub and sound like you have a rod knocking. That happened to me and it scared me to death I thought I had a rod knocking when I first fired the engine up but found out it was the rod hitting the oil pan DOAH!!! Good luck!!!!!!
 
Im not going to get a small base cam, because they dont make the grind I want in a small base circle.

Also, I dont plan on clearancing the rods for the block, just for the cam, thats what I wanted pictures of. (along with specific clearances)
 
neverendingproject said:
Im not going to get a small base cam, because they dont make the grind I want in a small base circle.

Also, I dont plan on clearancing the rods for the block, just for the cam, thats what I wanted pictures of. (along with specific clearances)
Click to expand...

But you WILL have to clearance the block to clear the rod.
 
You probably already know this then, but try to take the same amount of material off of each rod to keep the rotating assembly in balance.
 
The rods aren't going to be balanced right no matter if you take the same amount of material off of each rod anyways. It's not a simple equal weight function with rods.

I would *think* the proper approach would be to clearance everything as much as it needs, then have the parts balanced. That is of course if you believe balancing is a good idea. (not intending to start anything, just the approach I would take)
 
I dont plan on balancing because its just going in the blazer and it wont see past 4000 rpm. So I dont think it is necessary
 
Clearance tip

An easy way to check for clearance is to use a nylon zip tie as a feeler gauge. If an 1/8 wide by 10 or 12 inch long zip tie slides through then you have enough clearance, oh one other thing... balance that engine.
George
 
People I had talked to said it was okay not to be balanced. I am runinng an aftermarket crank and proper balancer and flexplate. Its gonna suck to get everything balanced as I fit my budget around not balancing.
 
Grinding on Connecting Rods

Balancing connecting rods CAN be done at home, BUT as mentioned earlier there's more to the job than grinding the same amount off each rod. It requires SPECIAL PRECISION TOOLS & a lot of patience.

There are TWO different aspects to rod balancing in addition to gross weight. ROTATING ASSEMBLY balance & RECIPROCATING ASSEMBLY balance. It is not only about TOTAL WEIGHT of the rod, BUT WEIGHT DISTRIBUTION between the big end/small end. High Quality factory balanced connecting rods are precision parts that really should NOT be modified unless you are a VERY EXPERINCED MACHINIST with the proper tools.

Clearancing the engine block can be done at home. I was taught by a machine shop foreman to take a felt tip marker and mark the block. Then use a piece of steel wire as a "feeler gauge" (like safety wire) and grind the block until you can pass the wire easily between the rod and the block. Use your micrometer to measure the safety wire (I use .041 wire) so you know exactly what your clearance will be before you start.
 
Balancing around here is "only" $125. I know it adds cost to a build, but compared to everything else, I don't think that's really expensive.

Pistons, rods, bolts, crank, balancer and flexplate/flywheel are all needed to balance an engine...how many of those have you changed? A stock engine is put together within tolerance (including weight) so even a neutral balance would be possible as all components are known to calculate in. In your setup, you are throwing a crank in balanced by the manufacturer not knowing what weights every other component will be.

Sure the rods will be balanced end to end stock, the pistons will be within X grams of each other as delivered, but if the crank is balanced assuming X grams for rod and piston weight, and your new ones are *actually* Y weight, balance could be very bad.

Most people that don't balance a rebuild re-use the stock rods and crank (at least) from what I've seen.
 
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So far, the only thing I have changed is a little grinding off the rods for cam clearance, and everything is stock other than crank and pistons. (400 Balancer, Scat Crank, 350 flexplate, powdered metal rods, and speedpro pistons) The machinist said it would cost extra for the balance job because he would have to disassemble the rods/pistons.
 
neverendingproject said:
So far, the only thing I have changed is a little grinding off the rods for cam clearance, and everything is stock other than crank and pistons. (400 Balancer, Scat Crank, 350 flexplate, powdered metal rods, and speedpro pistons) The machinist said it would cost extra for the balance job because he would have to disassemble the rods/pistons.
Click to expand...

By thinking you're saving money now by not balancing is only going to cost you much more money and time and frustration once you have it all back together and in and running just to find out you now have to take it all back out and apart to do what should have been done from the start.
 
So far, the only thing I have changed is a little grinding off the rods for cam clearance
Click to expand...
You've changed the balance of the rods by taking material off them. This WILL cause vibration, and the rod bearings are NOT gonna like that.

I got my block back from the machine shop this weekend (going 383 roller motor) and I test fit cam, crank, and pistons. About four of my rods hit the cam and one of the rods would "click" against the block.
Click to expand...
I'm gonna be blunt... your machinist sounds to me like a dumba$$. How the hell could an automotive engine machinist do block work for a 383 without the components that are going in the engine, so that proper clearances could be checked or created?
 
you would be better off having someone who builds motors assemble your bottom end. If something goes wrong and you break a bunch of parts you will be out of alot more money in the long run.
 
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