Crank counterweights hit Pistons in 327 build! - Team Camaro Tech
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post #1 of 30 (permalink) Old Jan 16th, 07, 05:45 PM Thread Starter
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Crank counterweights hit Pistons in 327 build!

My Crank is hitting my # 3,4,5,6 pistons. I called my shop and told them about the problem. They are going to call me tommorow. I have an Eagle 3.25" stroke forged crank, Eagle 5.7" rods and Speed Pro forged 327 pistons.

Anybody else had something like this happen? I figured since I was going with a stock stroke I would have no problems and this came as a big surprise.
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post #2 of 30 (permalink) Old Jan 16th, 07, 08:09 PM
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Re: Crank counterweights hit Pistons in 327 build!

5.7" long rods regardless. They have the wrong pistons in it!!

OR, OR!!

The crank isn't cut to a 327 dia. counterweight dia......................

End of conversation!!

Double check this big-time, imho!!

pdq67
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post #3 of 30 (permalink) Old Jan 16th, 07, 08:23 PM
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Re: Crank counterweights hit Pistons in 327 build!

sure you didn't get a 350 crank on accident?

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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post #4 of 30 (permalink) Old Jan 17th, 07, 01:31 AM
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Re: Crank counterweights hit Pistons in 327 build!

Or that the 327 crank didn't call for a 6.0" rod?
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post #5 of 30 (permalink) Old Jan 17th, 07, 03:33 AM
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Re: Crank counterweights hit Pistons in 327 build!

Make sure they gave you the right crank. There are two depending on the year. May have the small one with a large block. I believe it was 1967 was the year when it was changed to the larger journal like a 350 crank. I believe that the smaller had more weight inside and called for a smaller ballancer on the front of the block. I think they cut the bottom of the block to accomidate the extra weight. Anyway its worth check first.
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post #6 of 30 (permalink) Old Jan 17th, 07, 04:44 AM
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Re: Crank counterweights hit Pistons in 327 build!

Quote:
Originally Posted by cambird68 View Post
Make sure they gave you the right crank. There are two depending on the year.
It's an Eagle crank and according to their catalog they offer one (1) 3.25" stroke crank for the early SBC's. It requires 5.7" or longer rods. Maybe the piston skirts are long. If it was me I'd use a 6.125" rod and a 1.25" or 1.26" CH piston depending on how much deck you've got.
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post #7 of 30 (permalink) Old Jan 17th, 07, 04:53 AM
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Re: Crank counterweights hit Pistons in 327 build!

Quote:
Originally Posted by pdq67 View Post
5.7" long rods regardless. They have the wrong pistons in it!!

OR, OR!!

The crank isn't cut to a 327 dia. counterweight dia......................

End of conversation!!

Double check this big-time, imho!!

pdq67
What pdq67 says.
Been there myself.
In my case a Stroked 384.6 CID, I was origionally using Wiseco ProTru pistons. Switched to SRP pistons and problem was solved. The Crank counter weights were hitting the bottom of the piston boss area on the Wiseco pistons.

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post #8 of 30 (permalink) Old Jan 17th, 07, 06:02 AM
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Re: Crank counterweights hit Pistons in 327 build!

I have used those pistons on a awful lot of motors. Do the pistons come up to the correct heigth in the block? Have no clue about the crank having too big of counterweigths I haven't played with that brand but anything can happen.
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post #9 of 30 (permalink) Old Jan 17th, 07, 09:49 AM Thread Starter
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Re: Crank counterweights hit Pistons in 327 build!

I have measured everything and the stroke is indeed 3.25 and correct. I think the counterweights were just designed to go with something with a little shorter area under the pins as that is where it hits. How much can be taken off the piston under the pin? We are talking on the order of less than .125" most likely. The other alternative is to take about that much off the backside of the two crank counterweights that are causing the problem if that would even be possible. The issue is that the shape of the two inner counterweights tapers out (gets longer) as you go to the backside of the weight.
From what my shop says the pistons can't have material removed from there since it would weaken it too much. Now to call Eagle and see what they say.
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post #10 of 30 (permalink) Old Jan 17th, 07, 10:20 AM Thread Starter
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Re: Crank counterweights hit Pistons in 327 build!

Eagle says to grind off the offending area until I get .060 clearance. I popped in one of my old pistons/ rods and it just barely clears. The piston (TRW forged flat top) has less material in that area than the new ones.

I am going to have my machine shop take the material off on their lathe since I want it done cleanly, then rebalance. Unfortunately they are on a 8 week backlog. I have plenty to do to get the car on the road though so will concentrate on getting the rest done now.

Guess it juse shows you can't trust these parts to fit even for stock configurations.
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post #11 of 30 (permalink) Old Jan 17th, 07, 02:03 PM Thread Starter
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Re: Crank counterweights hit Pistons in 327 build!

I have pictures of the problem and the two piston types, if anyone is interested I can email them. I just want this to be a warning to other builders so they can expect that there could be an issue of parts compatibility.
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post #12 of 30 (permalink) Old Jan 17th, 07, 04:02 PM
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Re: Crank counterweights hit Pistons in 327 build!

Quote:
Originally Posted by forttusken View Post
I have pictures of the problem and the two piston types, if anyone is interested I can email them. I just want this to be a warning to other builders so they can expect that there could be an issue of parts compatibility.
Hmmm, sounds like more of a problem with Eagle's parts.

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post #13 of 30 (permalink) Old Jan 17th, 07, 05:01 PM
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Re: Crank counterweights hit Pistons in 327 build!

You really need to have a competent Machinist cam-cut your cranks counterweights and then rebalance it AND I will bet a 6-pack to a donut hole that you will need to add heavi-metal after doing so..

It went right over the top of my head when Lunati's Salesman told me to use at least 1/4" longer rods in my 496 b/c I had a good set of truck rods i wanted to use.

And sure enough, I had this problem and if I would have listened to the guy, my big motor would have stock balanced fine after welding up some counterweight holes!!

CAM-CUT here b/c you most definately will need heavi-metal if you cut their complete diameters down by just chucking it up centered!!!

I ended up having Lunati's fixing my f--up and rebalancing it w/ h-m and in the end everything was fine!!

pdq67
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post #14 of 30 (permalink) Old Jan 17th, 07, 05:46 PM
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Cool Re: Crank counterweights hit Pistons in 327 build!

I agree with Paul (pdq67) in that you will probably have to rebalance the crank anyway, but rather than putting money into heavy metal at $50 bucks a slug, I'd invest that money in a new set of pistons with smaller skirts and less reciprocating weight (like I said a rebalance will be in order anyway). And while your buying new pistons now would be a great time to invest in some longer than stock 5.7" rods; 6.0" is a good start, but I'd go still longer with a 327 (let piston availability and cost be your deciding factor).


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post #15 of 30 (permalink) Old Jan 17th, 07, 06:03 PM
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Re: Crank counterweights hit Pistons in 327 build!

Don't mess with the pistons do the chamfer thing and rebalance or send the crank back.,you should not half to ,common stuff stock stroke ,I know I had to chamfer cut the web of my block to get my 6.0 rods to work,as this motor has been together for a couple yrs, so I beleave was close tolerance wise on a couple pistons .050 or so counterwight to pistons,good luck bud , Happy Motoring
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