Checking Rod to Cam Clearance

[Captainfab]

We're finally getting around to assembling my son's 406 with 5.7 Scat rods. We have discovered that we have a clearance issue with #6 rod with the cam. How in the heck do you get in there to measure the clearances to be sure there is at least .060? Do you have to do it with only one piston and rod in the block at a time?

Any tips or advice is appreciated.

[Sinister]

I read somewhere that you put some modeling clay on the rod, turn the motor, measure modeling clay.

[Captainfab]

Thanks for the reply Sinister

I had thought about that, but I'm not sure how well the clay will stay on the rod through the rotation. Might have to try it unless someone has a better idea.

[Marv D]

A standard ACCO paper clip (the small ones) are about 0.035" They are bendable, small and CHEAP. (the large ones are roughly 0.055-0.065) They work great for clearancing rotating assemblies. Most of the pro's will say use 0.030 - 0.050" , most of the on line writeups use 0.050", I have used 0.030" for a decade of stroker builds and never once had an issue that more clearance would have helped. IMO 0.050" is a 'comfort factor' and 0.030 should be considered a absolute minimum (leaves room for bearing damage and still not contact).

As a BTW, I use Cloyes Hex-adjust timing sets and advance the cam 4 degrees (further than what I plan to run it at) and retard the cam 4-6 degrees and recheck clearances EVERYWHERE and grind as necessary. At very least you must degree the cam before you do the clearancing. Real PITA I know,, assemble, check, dis-assemble, clearance, wash everything up, re-assemble, check, dis-assemble, clearance again, wash everything up,, re-assemble....
Hey,, if it was easy everybody would be doing it! Be persistant, bend a paper clip as necessary and make it slip between the components and you'll have a motor that will survive a long time (and know you have done it right!)

[68 C-10 KID]

That real odd to see a ROD smack into the cam on that combo.
I would look into getting another set of 6" Makes the 400 run hard.
Ive seen Rod bolts smack into the bottom oil pan rail.
Marv is always spot on w/ his info.

[Captainfab]

Thanks for the replies guys.

Marv, I've heard of using the paper clips, but I just don't see how a guy can get it down to where it is needed. Or do you do just one rod on the journal at a time so the others aren't in the way?

I'm really beginning to wish I hadn't had this assembly balanced already. Looks like it will need to be balanced again......just got over confident.

Originally Posted by Marv D

A standard ACCO paper clip (the small ones) are about 0.035" They are bendable, small and CHEAP. (the large ones are roughly 0.055-0.065) They work great for clearancing rotating assemblies. Most of the pro's will say use 0.030 - 0.050" , most of the on line writeups use 0.050", I have used 0.030" for a decade of stroker builds and never once had an issue that more clearance would have helped. IMO 0.050" is a 'comfort factor' and 0.030 should be considered a absolute minimum (leaves room for bearing damage and still not contact).

As a BTW, I use Cloyes Hex-adjust timing sets and advance the cam 4 degrees (further than what I plan to run it at) and retard the cam 4-6 degrees and recheck clearances EVERYWHERE and grind as necessary. At very least you must degree the cam before you do the clearancing. Real PITA I know,, assemble, check, dis-assemble, clearance, wash everything up, re-assemble, check, dis-assemble, clearance again, wash everything up,, re-assemble....
Hey,, if it was easy everybody would be doing it! Be persistant, bend a paper clip as necessary and make it slip between the components and you'll have a motor that will survive a long time (and know you have done it right!)

Originally Posted by 68 C-10 KID

That real odd to see a ROD smack into the cam on that combo.
I would look into getting another set of 6" Makes the 400 run hard.
Ive seen Rod bolts smack into the bottom oil pan rail.
Marv is always spot on w/ his info.

[Marv D]

I do one journal at a time,,, set the rods/pistons for those holes aside all cleaned up ready for rings and final assembly. A set of hemostats holding the paper clip works OK, but your right,, the tight places are a PITA. A flashlight, small mirror, and lots of patients are mandatory.

Like the C-10 kid said,, you must have a boatload of lobe and a full size base circle to be smacking rod bolt shoulders,, but the old saying goes... "If your not whacking on something for clearance, your not trying hard enough".

Oh, a btw,,, a gram is roughly about the volume of steel of a 1/4 x 20 nut. If your having to whack a BYNCH off every rod, then sure, rebalance. But if your just touching up a few shoulders,, Don't get too crazy over it. Most machine shops will say they balance to the nearest 1/2 gram. Take that assembly to another shop down the street and they will tell you it is off x number of grams, take it to another and they will come up with yet another weight. Every shop estimates the weight of the volume of oil in the big end of the rod, the parasitic oil that ropes around the crank,,, etc. Although it is an exact equation, it's full of assumptions and interpretations. Unless you start taking many grams off the assembly,, it's maybe not such a big deal. At least IMO its not.

[Captainfab]

Thanks very much for the help Marv

I kind of thought we might have to do one journal at a time, but I've not had to do this before. I Just wanted to be sure there wasn't an easier way to do it. But like you said if it was easy everyone would be doing it.

The cam's not really that big IMO......just .520/.540 We went with the Scat 5.7 "stroker rods" so I was hoping for no interference, but oh well that's part of building a performance engine.

That's encouraging about the weight issue. I don't think we'll have to take very much off, so we might be good to go.