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Old 11-03-2008, 06:48 PM
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rod clearance

Hey guys I was wundering how much clearancing I will need to run vortec 5.7 rods In my 406.

I don't plan on running a cam much bigger than a comp 280 magnum. Infact that may be the exact cam I run cuz I already have it.

If I put ARP rod bolts in them will they be OK or still need grinding??

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Old 11-04-2008, 07:53 AM
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stupid question or what????

Hey guys I've had 24 views on this thread but no replies. Do you just not know or is it just a stupid question?????

Any help would be nice so I can continue plannin my build
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Old 11-04-2008, 07:56 AM
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rods

If you are asking about rod bolt to cam lobe???

.050" is a good number.


Keith
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Old 11-04-2008, 07:59 AM
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Quote:
Originally Posted by eatonde
Hey guys I was wundering how much clearancing I will need to run vortec 5.7 rods In my 406.

I don't plan on running a cam much bigger than a comp 280 magnum. Infact that may be the exact cam I run cuz I already have it.

If I put ARP rod bolts in them will they be OK or still need grinding??
The ARP bolts are very close in size to a factory bolt so that will make little to no difference.
You do know that you'll need to have the big end resized after installing the ARP's though right?
They don't just drop in loosely, they'll need to be pressed in, which will make the rods funny shapes. Best to drop them off at a shop and have them press them in and resize for you, it'll save you headaches too.
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Old 11-05-2008, 05:16 PM
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050"

You said this is a good number?? Meaning??? I should shoot for that much clearance or what??

The 280 cam has 280 lift, I need to know if it'll clear a 5.7 rod or not ???
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Old 11-05-2008, 06:29 PM
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You won`t know until you do a mock up assembly. If you don`t know what this is, it`s a assembly to where you assemble the engine and check clearences and which parts will and will not fit without grinding. I think it won`t matter what cam you were to use, it`s still not likely to clear, however there have been some rare cases where they didn`t. What K star meant is what he said. .050 between the rod and cam lobe. Many use a small base circle cam which can eliminate grinding altogether as some don`t wish to grind anywhere as it`s very easy to grind off too much and you can`t put back what`s ground off. Do the mock up assembly and get ready to assemble it, get all the clearences right, strip it back down, clean it all to he**, then reassemble it so it can go raise he**.
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Old 11-06-2008, 05:03 AM
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Clearance

Quote:
Originally Posted by eatonde
You said this is a good number?? Meaning??? I should shoot for that much clearance or what??

The 280 cam has 280 lift, I need to know if it'll clear a 5.7 rod or not ???

.050" is a minimum. The only way to know for sure is to check it. This is one of those deals where you cannot find out by asking on the internet if it will work. You need to physically check the clearance.


Keith
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Old 11-07-2008, 05:28 PM
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clearance

well I just took my block /crank/rods/ heads and everything to the machine shop. I asked him about the clearance issue, and He said exactly what I was thinking.
He said that the rods are exactly the same as thet short ones except they are just longer and take the side load off the cylinders. He said there's no reason they should change unless you change the stroke. This is a machine shop thats been in bussiness since 1932. He said he's put 5.7 rids in 400's all the time and never had to clearance them.
HOWEVER, He said he would check it anyway and if they do need it He'll do it for free for being wrong.
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Old 11-07-2008, 05:49 PM
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Quote:
Originally Posted by eatonde
well I just took my block /crank/rods/ heads and everything to the machine shop. I asked him about the clearance issue, and He said exactly what I was thinking.
He said that the rods are exactly the same as thet short ones except they are just longer and take the side load off the cylinders. He said there's no reason they should change unless you change the stroke. This is a machine shop thats been in bussiness since 1932. He said he's put 5.7 rids in 400's all the time and never had to clearance them.
HOWEVER, He said he would check it anyway and if they do need it He'll do it for free for being wrong.
OK, that's why people have gone thru the expense and trouble of designing and making SBC blocks that move the cam further up from the crank and why a similar effort was put into a smaller diameter core camshaft. Or why GM went to a short rod with even shorter bolt bosses for the 400. I think you need a machinist that knows something about engines made since 1932. The chances of you sticking a 5.7 inch, powdered metal, Vortec rod on a a 3-3/4 inch stroke crank, stuffed into a stock SBC block and expect it to clear a high lift cam has odds somewhere between zero and a really large negative number.

Bogie
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Old 11-08-2008, 09:08 PM
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oh well

either way if thats the case, He told me he'll do it for free. and I was always under the assumption that the purpose of a small base cam and the blocks with the raised cam location like rodeck, were for whend you go to a 4" stroke to a 434 or something. I'm no pro, just repeating what I was told.... Don't shoot the messenger. These guys know a lot more than me, but so do you so, who knows. I don't plan on going ofer .500 lift anyway so not sure if thats gonna be a factor
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Old 11-08-2008, 10:47 PM
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It's all about mock up...........it's just the best way to go about things like this.....
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Old 11-09-2008, 01:44 PM
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Quote:
Originally Posted by eatonde
either way if thats the case, He told me he'll do it for free. and I was always under the assumption that the purpose of a small base cam and the blocks with the raised cam location like rodeck, were for whend you go to a 4" stroke to a 434 or something. I'm no pro, just repeating what I was told.... Don't shoot the messenger. These guys know a lot more than me, but so do you so, who knows. I don't plan on going ofer .500 lift anyway so not sure if thats gonna be a factor
I'd say at least in my experience that around 80 percent of 3-3/4 inch stroker small blocks using 5.7 or 6 inch rods have clearance problems between the cam and the rod. It doesn't happen on everything just 2 or 3 lobes, but in the interest of balance I clearance all the rods.

I prefer to use the cap screw design rod rather than the bolt and nut type. When you have to remove material from the bolt and nut type rod, it's right at the bolt head and its boss, both of which are highly loaded and usually feature fracture prone rectangular shapes. With a cap screw design, the bolt is flipped around so it's head is on the cap side and the nut is eliminated; replaced with a screw thread machined in the upper shank of the rod. In this design, if clearancing is required, your removing material from an area that is now the lighter loaded base end of the threads. There is an added benefit from the shape as this area of the cap screw rod is rounded and smooth, compared to the bolt and nut design, so stress and strain in the area cannot fine rectangular shapes in which to concentrate. Plus, the rounded shape of the blending surfaces is often enough to provide the needed clearance without additional material removal.

I will say in defense of the bolt and nut design, that I've seen some really cobbled up clearance jobs that hold together under extreme conditions, but for me it's one of those things that eats away on the back of my mind. I find it hard to push the machine to its limits when known or imagined weak spots are floating around in there, brings out the chopper pilot syndrome in me. That of "chopper pilots being brooding, introverts, anticipators of trouble", thank you Harry Reasoner for that.

Bogie
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