on a geardriven engine, is it still possible to advance or retard the camshaft 4 degrees? would you just move it over a tooth or what?

my problem is, in my test assembly for my 383 im building, the connecting rod bolt is contacting the cam unfortunately. so i was hoping if i retarded or advanced it, that would cure it?

 

That may work but it's going to throw off all the valve timing A LOT.

The right way is the obvious... get a small base circle cam and/or grind the rod bolt down.

If you grind the rod bolt down, the entire rotating assembly will need to be rebalanced.

 

they are arp bolts that are already pre ground to near nothing.

of coarse, i wouldnt see an issue with retarding the cam. the timing would be off, yes, however that would also help my topend, thats the positive way to look at it. im gonna go out their for fun and see about adjusting the cam a few notches just to see what it does.

ill be sure to post back.

 

If you have an adjustable gear drive, you might be able to get a few degrees out of it, but it still might not be enough. You might have to change the cam or the rods to get enough clearance.

 

these are eagle forged 6" rods, and they are already pressed into the piston.

i tried moving a cam a degree over one way, i believe advanced, and that only made it worse.

 

Probably need a smaller base circle then.

 

dont those need to be custom ordered? i dont want to wait for a custom cam to be ground, not to mention the extra cost.


whats the chances a shop could take care of this problem>?

 

They're not that uncommon. I believe Summit usually has them in stock if you ask for it specifically, the cost should be the same as the normal grind. Even if you had to order it from the manufacturer the lead time for custom grinding is only a couple of days.

 

do these small base circle cams carry part numbers? i checked the comp website and they dont have any listings for this sort of thing.

 

You'll have to call them and ask. It will have the same grind number since the lobes are ground the same, just smaller.

 

is thier disadvantages to a small base circle cam? wouldnt a smaller base create a tighter lobe or something?

 

The "lift" is only the distance from the base of the lobe to the peak of the flank.

About the only disadvantage would be the need for longer pushrods.

 

The lobe is smaller but it's the same shape and profile as the regular grind. Once it's installed you won't be able to tell the difference.

A very large cam on a very small base circle would be weaker than a normal grind, but you're nowhere near the point where you'd have to worry about it.

 

I'm not an expert on balanceing rotating assemblies but going to go out on a limb and say that the small amount of material that needs to be ground off the edge of the top of the rod bolt to clear the cam will not cause a big problem.

Making the bottom end of the rod lighter would move the balance toward a 'overbalance" condition. ( where the counterweights are slightly heavyier than needed). This is not nessessarily a bad thing.

If you bought your engine kit as a "balanced assembly" it will have some +/- tolerence all ready. Maybe more than you think. A gram or two don;t make that much difference.

Further some "balanced rotating assemblys" kits are not actually balanced but are close meaning they will not need mallory metal or too much counterweight cutting.

Haveing to move the cam out of its sweet spot to get clearance, will.

You could have the crank rebalanced after grinding the rods for clearance. Probabily cheaper, certainaily comparable in $$$price$$$ to haveing to buy a new cam and maybe longer pushrods.
The crank would only need to be lightned. No $$$mallory$$$ would be needed to bring it back to balance.
You need to check and clearance the block as well.
This is all part of the joys of building a non stock motor like a 383 or long rod 400. You're supposed to do all the clearanceig and grinding before the rotating assembley is balanced.

But its worth doing it right.

When we did mine we clearanced it for a big big race roller cam, so that anything I would put in the motor downthe road would easily clear the rods.

It' all about planning and details.

 

just for the record, this is my testfit, and I have not had the engine balanced yet.

without the cam, the assembly rotates just fine.

this is my last step. clearing the cam. and its aggrivating me.

 

Well moving the cam is not the way to go. Did you degree in the cam yet?

 

I ended up having to go with h-beam rods to clear my cam and it was a small base circle cam to start with. There was no way to get enough clearance between the rod bolts and the lobes with the i-beams I first bought. This may be the case for you also. Of course, I then had to grind on the oil pan rails to get rod bolt clearance but, given the choice, I'd rather do that than grind on the rod bolts and I now have plenty of clearance all the way around. My $.02

 

i am running H beams.

and as for degreeing, i have not done that yet, but, playing around last night, I had to turn the cam about 45 degrees either way in order for it to clear.

 

I'll go along with that.

A factory balance job can sometimes be within (maybe) 5g or more
I had a smooth running 350. And when it was rebuilt, I got it rebalanced cause I got hyper pistons.
I was really surprised at the amount of material that needed to be removed from the stock rods to get them to within 2g of each other.
If you have to grind .060" off a bolt head to get clearance, it might make the big end of the rod 1/2g lighter.
To put things in perspective, a dime weighs a little over 2g.
The greatest concern when grinding a rod bolt is weakening the head.
But it looks like you have the capscrew bolts so you aren't going to take any material off a bolthead anyhow... Right?
I think your life would be simplified if you just grind the rod and keep the cam you have.

How did you end up with pressed pin H beams though.
I thought all those were floating.
It seems like I remember someone suggesting in one of your other posts, to get floating pins.

 

If they were cap screws it would be the shoulder of the rod hitting the cam, not the bolt. Which rods have you got?

 

I have been told they are eagle forged 6" H rods.

i can tell they are forged, but their really are no markings on them at all, they are not cap screw's. they are bolts or studs whatever u call em.

they are 6" though i measured.

 

I just read the part where you said the engine isn't balanced yet.
If you do have the Eagle H beams, grind the corner of the rod to your heart's content til it clears the cam.
Degree the cam first, of course.
When you take the assy in for balancing, the metal that you removed won't be an issue.
It's too bad the pistons are pressed on tho.
Remember which rods needed clearancing, mark them, and put them back in the holes they came from when you put it all back together.

It sounds like you have Ibeam rods if they don't have cap screws and they're pressed pin.

Are those the rods that came from the motor that you took apart last week?

 

yes, here ill post a picture of the rod as well.


does this help any?

 

That's an I beam.

 

Yeah, those are I beams.
Grinding the bolt head will be nessecary if you don't want to get a small B/C cam.
Do you have any way of knowing how much needs to be ground?
In most cases it's not more than .080" off the corner of a few of the bolts.
If I wasn't busy, I could probabaly find a pic of one that's done right.
Bolt heads can be weakened by grinding, be careful.

 

How much more can be safely taken off those pre-clearanced ARP bolts?

 

thanks for telling me those are I beam rods.

im not sure how much can be ground, i dont think i want to do the grinding, i want to let a shop do it, what do you guys think?

if you can find a pic of a properly ground rod, please post it.

 

Well you can do anything to them that the shop can, but I wouldn't want to do it myself either.

 

You should start a new thread.
I've seen some pics posted here. Maybe the right guy will read it and post.

 

HERES instructions to read over , theres NO subsitute for KNOWING EXACTLY what your doing

http://www.thedirtforum.com/degree.htm

http://www.hotrodder.com/kwkride/degree.html

http://www.454ss.com/whitess/Camshaft.htm

http://www.cranecams.com/?show=article&id=3

but be aware that retarding the cam 4 degrees only tends to move the tq curve about 200rpm higher in the rpm range
(heres a kit that contains most of what youll need to do the job correctly AND a taped instructions on how to do it
part #
CCA-4796 and CCA-4760

http://store.summitracing.com/defaul....asp&x=20&y=10

knowing its installed correctly is FAR SUPERIOR to GUESSING