? rod hits cam

[Lee Thompson]

Trying to assemble a Stage II short block.
3.600 BMP crank
6.50 Carrilo rods
Roller cam
If I install the cam straight up, ever thing clears
Degreeing in the cam, it looks like it needs to be advanced 4 degrees. When I set it up advanced, # 2 rod hits the lobe on the cam. I only had # 1 & 2 pistons in the block so don/t know about the others, I had heard only one of the front ones will hit
How much clearance do I need ( min. ) between rod and cam.
If I have to grind for clearance, is my balance out the window?

Thanks

 

[Chuck Leeper]

Rods/cam

On the 3.625" I have in my stage 2, w/ a CC roller, the inside rod bolts are shorter than the outers. The rods are milled on that side for added clearance in this situation. I think the balance of the rods will come into question, given the material milled off and the shorter bolts.

This is a common mod for all Busch and ASA engines I've seen, due to the high lifts and duration on the cams they use. [combined w/ the long strokes used.]

I'd be asking CC why the cam is 4* out of spec to begin with. MOST cams are already 4* adv when ground.

Look at the rods still out of the engine and see if they are already milled and fitted w/ the short bolts on 1 side.

HTH,

 

[re-evaluating]

Stroker rods

I have seen a lot of posts lately on rods and clearance issues. I know for a fact Corillo rods and most others build standard and stroker rods and the stroker rods are built to clear the block webbing and cam etc. This is the first thing to ask when considering buying a set of rods in my opinion. Good luck in your search. Dave

 

[SIXBANGIN`]

How does the length of rod come into play with respect to camshaft clearance ?

Would a shorter rod, because of a different rod angle, improve clearances ??

I have the 3.625 motorsport crank for my 4.1 on centre block and haven`t decided what length rods to use yet. What`s better ? It seems that most use 6.5 inch long but I know some are using 6.3

George, in ALBERTA

 

[Chuck Leeper]

ROD LENGTH

George, it's actually the stroke on the crank that contributes to the problem. A shorter rod will change the angle. How much, I don't know. Most I've seen are 6.300 or longer.
Only 3 of the rods will need to be cut and the boss shortened about .125". This applies to the 3.590" or longer cranks. The reduced length is done on all 6 rods so they can be interchangeable, anywhere in the set.

Carrillo can do this when you buy a new set. If they are used, it's easy to see if it's been done.
REMEMBER, if it's done, the bolts are different lengths!! Long bolt in the short side and you are right back into a problem.

HTH,

 

[Lee Thompson]

rods

these are stroker rods

 

[Chuck Leeper]

Rodz

Lee, are they already milled on 1 side?? Can you measure the cam C/L to the crank C/L and compare it to the dim's in the perf. manual?
If these rods AND bolts are already milled, and they still hit the cam, then either the cam is WAAAY off, [AKA the keyway is wrong],
block has had the crank bore raised excessively due to several line bores, or Im outta ideas!!!
How bout it Billy A, Kendall, Ron T., Todd K.???

Back to scratchin my head. [Easy to do, no hair left messin w/ these danged BUICKS!!!]

 

[Lee Thompson]

rods

Yes they are machined with short bolts on the cam side. The block has been line bored. I bought a .005 under Rollmaster chain that fits perfectly. I beleive the crank key way is off 4 degree. Cam is suppose to go in at 110 intake center line.If I put it in straight up, I am at 114, set the crank gear at 4 degree advance,--110. It doesn/t hit at 110. At 108 just touches, at 106 will not go past it. Calld CC. Asked for Tim Cole, but out sick today, got another tech guy who was very nice. He said to put it in at 110 also that that cam was ground on a Chevy grind, hence larger lobes including base circle. Now I don/t know, but I would guess all Buick CC hyd. roller are on a Chevy grind. Does anyone know? The machine shop I will be OK if I don/t have to remove more than 4 grams. I may be out of the woods. Any thought?

 

[Chuck Leeper]

Chevy cam??

Lee, as far as I know, the cams are made using an odd fire blank, thus the removeable ft end pieces. I think at 1 time all cam grinders were getting their blanks from Crane and were, as I said, odd fire blanks.. That may have changed. Not for sure.
Ron T. any ideas??
Did you have the crank checked for index? Is it new? If it's a used NASCAR piece, it may be twisted!!!

I checked the "book" and see the C/L to C/L on the cam and crank is 4.335"

 

[SIXBANGIN`]

Re: ROD LENGTH

Originally posted by Chuck Leeper
George, it's actually the stroke on the crank that contributes to the problem. A shorter rod will change the angle. How much, I don't know. Most I've seen are 6.300 or longer.
Only 3 of the rods will need to be cut and the boss shortened about .125". This applies to the 3.590" or longer cranks. The reduced length is done on all 6 rods so they can be interchangeable, anywhere in the set.

Carrillo can do this when you buy a new set. If they are used, it's easy to see if it's been done.
REMEMBER, if it's done, the bolts are different lengths!! Long bolt in the short side and you are right back into a problem.

HTH,

Chuck, what`s the preferred rod length for the Stage 2 and why ?

Back in the old days and I won`t say how far back ago the old days go, we used to use the longest rod length possible in our small block chevys for piston dwell at TDC

Does the same theory hold true for our Buick Turbo`d 6`s ?

George

 

[Lee Thompson]

Crank

The crank is used. Not sure where it is from. Probably Nascar. One of my bestest friends got it in a package deal. It had a damaged rod journal. I took it to a crank shop. They checked it and turned it .010-.010. I assume it is correct. When they CHECKED it, I know he magnafluxed it. If it was checked for index, I will have to ask. Or is that done when they are turned. Dumbie here on a lot of this technical stuff. Thanks for the replys. If the center line was wrong, the chain wouldn/t fit. It would be loose. Correct

 

[Chuck Leeper]

Crank checkout

Lee, you are right on. When the shop turned the crank, they should have index'd it to do the grinder setup when they ground the rod throws. [If done right. I'd ask!!] At .010 under, there's very little leeway on index correction as it's only .005 on a side!!

If the new chain fits tite @ .005 under, thn the line bore did not upset the distance from the 2 centerlines.

I'd look at another cam, or if that if the cam works on the 110* C/L and that's where the cam card says it goes, then I'd put it in at that location.

Know anyone w/ a CAM DOCTOR??? That will tell you in a heartbeat where all the dimensions on the cam are. Have you talked to Dave Weber?/ I got my cam/kit from him.. NO PROBLEMS!!!

Chuck

 

[odell4o8]

lee. i hope you have the rods figured out, i have the same problem, with my motor that has the bbc rods, not much clearance, with the even fire cam, a lot with the cam for the stage 2 heads, later oc,

 

[Lee Thompson]

am and rods

Learning a little bit at a time!!! Looked at some older billet roller at O C/s Shop today ( both odd fire and even fire ) They had much smaller lobes than my roller. By smaller I mean at the base circle. His had more lift than mine ( mine is .500 intake--.520 exhaust ) his were .600 +. His base circle was ground down to about the same dia. as the main shaft. Mine is at least .200 thicker on the base. I assume that is what CC was saying when they said it was a Chevy cam. Chevy dia. lobes, which would make my lobes roughly .200 taller.
What bothers me is that I have to advance the cam 4 degrees to get 110 intake center. I am positive I have TDC correct ( checked and rechecked more than once ) I put my front cover on and my stock balancer, rotate to TDC on the degree wheel, TDC on the balancer and pointer line up perfectly. Does this tell me my crank keyway is correct? If so I borrowed another chain and gears off OC. Will try them tomorrow to see if the gears are correct. I WILL SOLVE THIS

 

[Chuck Leeper]

CC and such

Lee, the method used to determine the lift when grinding a cam obviously involves the use of the overall hgt of the lobe. Thus, when the cam is ground w/ less lift, then the base circle is "fatter" than a cam w/ more lift. The controlling dimension on all cams is that the overall hgt of the lobe does not exceed the diameter of the cam brg journals.
I am certain that, since the rods were originally designed to be used w/ the cam design OC has, that the rods will have to be shortened a bit more to fit the lower lift you have.

Congrats!! You got it!!! Now back to the machine shop and a session on the mill!!
CU @BG

 

[Lee Thompson]

Rod

Chuck, I understand what you are saying and that makes sense. My theory is that a cam is too big when it won/t go in the block. But my rod is hitting or close to hitting at the very tip of the lobe. Thanks