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I really need help on an aluminum BB assembly question

Posted By: 1320Dart

I really need help on an aluminum BB assembly question - 03/20/15 09:35 PM

I have a tall deck KB block. The cam is standard location. But it has been machined for the 54mm cam by KB.
I have a 4.675 crank with 2.2 diameter rod journals.
I know that my 7.1 aluminum rods will not clear the cam. Does anyone know if steel rods will clear without having to modify them? I don't have steel rods to do any mocking up with. I'm hoping that other people have ran into this situation before. Any info is helpful.
Posted By: avenger572

Re: I really need help on an aluminum BB assembly question - 03/20/15 10:29 PM

Im using oliver steel rods with 4.75 stroke callies crank in a kb block standard cam location. . I had remove a small bit off rods for clearance to the cam .

Attached picture 8466120-image.jpg
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/20/15 10:55 PM

Quote:

Im using oliver steel rods with 4.75 stroke callies crank in a kb block standard cam location. . I had remove a small bit off rods for clearance to the cam .



Are you running the 54mm cam as well?
Posted By: avenger572

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:01 PM

Standard cam bearing , and cam base circle is 1.012 " . Cam lobe size will affect clearance .
Posted By: MR_P_BODY

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:09 PM

Quote:

Standard cam bearing , and cam base circle is 1.012 " . Cam lobe size will affect clearance .



The cam journals will effect the clearance.. the lift is
ground down into the base to increase lift from the
journal diameter... if he doesnt get crazy with lift
he can cut the OD of the cam and cut farther into
the base just as long as it doesnt flex with high
spring pressures
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:21 PM

the lift at the lobe will be about .490/.495
Posted By: MR_P_BODY

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:28 PM

Quote:

the lift at the lobe will be about .490/.495



Thats not bad at all... and with a 54mm that would
be easier to grind the OD of the lobe and cut into
the base to get the lift and get you some clearance..
the big 54mm starts with a taller lobe.. once you
get a rod to mock up then you can see if you need
to grind much off the OD
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:36 PM

I don't want to go much farther with this setup if there is going to be a ton of issues.
I may have to abort this big crank and stay with my 4.375 crank instead.
Posted By: MR_P_BODY

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:47 PM

Quote:

I don't want to go much farther with this setup if there is going to be a ton of issues.
I may have to abort this big crank and stay with my 4.375 crank instead.



With the 54mm lobe your taller than the smaller lobe
so your gonna have to cut the OD of the lobe as the
starting point then cut the lift into it on the base..
but the 54mm gives you more meat to start with.. I
dont know how much you would have to cut off the
OD since you dont have a rod... this is a test and
see UNLESS the cam grinder has a bit of knowledge
of this set up... might be time to call a grinder
and this is assuming you would use a chevy rod(more
clearance)
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:51 PM

yes it's a 2.2 rod journal
Posted By: avenger572

Re: I really need help on an aluminum BB assembly question - 03/20/15 11:58 PM

You stated above that the 54 mm is the bearing journal not the lobe right
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/21/15 02:08 AM

Quote:

You stated above that the 54 mm is the bearing journal not the lobe right



Correct
Posted By: Monte_Smith

Re: I really need help on an aluminum BB assembly question - 03/21/15 07:01 AM

You can get the aluminum rods "cam cut", but if that is enough clearance for your crank and cam combo, I don't know. Would just have to mock it up and do some measuring. You can also have the lobes "thinned". We have done some cams for "X" pattern BBC that have the lifters moved. To keep lobes and lifters from crashing, the lobes are only .250 wide. Again, would have to measure to see it that would even matter

Monte
Posted By: Tig

Re: I really need help on an aluminum BB assembly question - 03/21/15 12:09 PM

Quote:

I have a tall deck KB block. The cam is standard location. But it has been machined for the 54mm cam by KB.
I have a 4.675 crank with 2.2 diameter rod journals.
I know that my 7.1 aluminum rods will not clear the cam. Does anyone know if steel rods will clear without having to modify them? I don't have steel rods to do any mocking up with. I'm hoping that other people have ran into this situation before. Any info is helpful.



Wedge or Hemi head?, you will be able to run more lobe lift with a Hemi, Hemi cams clear the rods better with a 4.75 crank.
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/21/15 01:12 PM

Wedge
KB block 4.500 bore.
Standard cam location. Has the larger 54mm cam option.
K1 crank 4.675 with 2.2 rod journals
B1-MC's with Jesel, 1.7 ratio, paired shaft rockers. CNC ported. Flows 445 on the In. and 300 on the Ex.
Will be running carburated alcohol.

Scott over at Koffel's recommends this cam grind;
285 @ .05 In.
300 @ .05 Ex. with a 115 lobe separation.
.490 lobe lift In.
.485 lobe lift Ex.

I also wanted to run the dual swap firing order. 1 8 7 2 6 5 4 3

I dont know if any of this helps
Posted By: dvw

Re: I really need help on an aluminum BB assembly question - 03/21/15 02:22 PM

Quote:

I have a tall deck KB block. The cam is standard location. But it has been machined for the 54mm cam by KB.
I have a 4.675 crank with 2.2 diameter rod journals.
I know that my 7.1 aluminum rods will not clear the cam. Does anyone know if steel rods will clear without having to modify them? I don't have steel rods to do any mocking up with. I'm hoping that other people have ran into this situation before. Any info is helpful.


Which aluminum rods? A BME 396 forging has a smaller outer configuration than a 426 forging.
Doug
Posted By: Jerry Kathe

Re: I really need help on an aluminum BB assembly question - 03/21/15 03:38 PM

I’m guessing that your crank is 4.625?
As a first step, I wouldn't advise cutting the cam BC below or into the cam core, money and effort spent on the 54mm is lost, unless its absolutely a minor amount. Restoring the radius’s to prevent stress risers adjacent to the journals and lobes and the column profile isn't as easy as it sounds.
If conditions allow minor lobe reductions, then OK, but avoid getting into the nominal core diameter.

There are so many variables with these combinations that mocking is the only answer, unless….someone has built the same exact combo right down to every last characteristic such as exact cam grind/core, rod profile, journal diameter, rod length and so on – Take a spent rod and start the clearance process until you get there and then evaluate the practicality of the end result. Personally, I would want to see for myself and have the end result in my hand over taking a forum reply for granted anyway….

Finding a spent 2.2 / 7.100 aluminum rod shouldn't be too difficult – brand won’t matter for mock up, your only looking for dimensional criteria.
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/21/15 04:08 PM

R&R billet Pro-Mod rods.

And no. The crank is in fact a 4.675
Posted By: TS3303

Re: I really need help on an aluminum BB assembly question - 03/21/15 04:17 PM

I have a World block with 55mm cam in std location, 4.625 stroke, 7"+ GRP 5300 series rods, OVER .500 lobe lift and only minor rod clearencing required. Lobes are not cut into the base.
Posted By: 1320Dart

Re: I really need help on an aluminum BB assembly question - 03/21/15 04:43 PM

That's refreshing news!
I have no problem getting steel rods, if it will gain the extra clearance.

It looks like me getting greedy on cubic inch and finding this 4.675 crank has caused me heart burn
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