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Discussion Starter · #1 ·
I'm halfway through a stroker build and hit a snag. Halfway meaning the block has been tanked,cylinders bored .030,mains align bored and honed and the head mating surfaces have been milled to zero deck height.I tapped and plugged the oil return holes in the oil galley and installed screens in the four corner return holes.I got an Eagle 4340 balanced rotating assembly with 6in h-beam rods and JE -5cc forged pistons with gapless rings. I ground the pan rail and bottom of the cylinders to provide .050 clearance where needed to clear the rods. Now I'm ready to set the high quench 64cc aluminum heads on, order my cam and start putting my valve train together right? Wrong. I called Compcams to order the hyd.roller of my choosing(236/[email protected] and.520/[email protected] with110*lobe sep).I had all the info the tech ask for and felt pretty knowledgable until he ask if I needed a small base circle cam. BAM! All the sudden I felt like Barney Rubble. I know alot of people run a "small base circle" to avoid rod bolt contact but I have added another element to this monstrosity. I'm retrofitting the hyd.roller in a 4bolt 010 NONROLLER block using an OEM spider hold-down and "dog bones" with the GM short roller lifters.(Mostly because I was told it wouldn't work)I've done alot of research and found several people have done this on the 350 configuration using standard base circle cams.I'm afraid to order a high dollar custom grind cam that is either A) too big to clear the rods, or B) so small that the lifters drop out of the dog bones and/or oil passage.When I purchased the rotating assembly,I was told that the rods are profiled for "most stroker applications". It's been balanced already so as far as I'm concerned, grinding on the rods is out. Has anyone out there run the 6in Eagle H-beam rods in a 383 stroker application without a small base circle cam successfully? What is the standard base circle of a smallblock cam? I know alot of headache could be spared by using retrofit roller lifters but I've heard horror stories about link bars failing and I want to build something not many have.I've e-mailed Eagle twice on the clearance issue and still haven't heard back from them. Any opinions or experiences?
 

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Is this one of those balanced kits that came from the manufacturer that way or have you already taken it to a machine shop and have them do it? While I have never purchased one of those pre-balanced kits there have been many accounts from other members of this board saying their kits were still out of balance. It still wouldn't hurt to take everything to the machine shop and have them verify that everything is balanced properly.

Remember that those kits are mass produced and that means more room for error. It never hurts to check.
 

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The last 2 rotators that we checked for for customers the rods were not even taken out of the plastic sealed wraps and the pistons box still had the seal on the top and not broken. I would imagine they are just going off an average bob weight and balancing them all to the same bob weight.

And they say they are ready to assemble NOT as they big and small end of the rods were on the tight side and the pin bores in the pistons were tight as well. When the customer called and told of the problems we found they said it was up to the engine builder to check the clearances and make the adjustments. HMMMMMMMMMMMM
 

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Discussion Starter · #5 ·
thanx for the input thus far.In regards to the comments by CNC BLOCKS N/E, When I got my rotating assembly back from the machine shop, there was only one rod removed from the sealed plastic.Likewise with the pistons and pins.I know that is how it was balanced at their shop, however, upon assembly I borrowed a digital scale from a friend and weighed each component and cataloged its weight.Then assemled each rod/piston combination and paired two on each throw to match the projected weight on the included balance sheet. The results were surprisingly close on the total recipricating weight projected.I dont know all the dimensions of balancing and I know its near impossible to have a truely "balanced" assembly but I hate to undo all the time spent in my basement with a few minutes on the die grinder.In the end if that is what need be done, so be it.I was just hoping someone else used this rod configuration without a smallbased circle cam. Not every block is the same.When the mains were line-bored I could have lost a few thousands.Just looking for a solid starting point before ordering the cam.Thanx again for the posts.
 

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CNC BLOCKS N/E said:
The last 2 rotators that we checked for for customers the rods were not even taken out of the plastic sealed wraps and the pistons box still had the seal on the top and not broken. I would imagine they are just going off an average bob weight and balancing them all to the same bob weight.

And they say they are ready to assemble NOT as they big and small end of the rods were on the tight side and the pin bores in the pistons were tight as well. When the customer called and told of the problems we found they said it was up to the engine builder to check the clearances and make the adjustments. HMMMMMMMMMMMM
I tell my customers when they order a "balanced rotating assembly" that what they are getting is a good starting point. Then I tell them that they will probably need to get the rods resized, the balance job checked and corrected, the crank possibly will need to be turned, maybe an undersized harmonic balancer, etc.

They always seem skeptical until I show them how far out-of-spec some of these items are.

Then their eyebrows go up and down.........

tom
 

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383mudlust said:
thanx for the input thus far.In regards to the comments by CNC BLOCKS N/E, When I got my rotating assembly back from the machine shop, there was only one rod removed from the sealed plastic.Likewise with the pistons and pins.I know that is how it was balanced at their shop, however, upon assembly I borrowed a digital scale from a friend and weighed each component and cataloged its weight.Then assemled each rod/piston combination and paired two on each throw to match the projected weight on the included balance sheet. The results were surprisingly close on the total recipricating weight projected.I dont know all the dimensions of balancing and I know its near impossible to have a truely "balanced" assembly but I hate to undo all the time spent in my basement with a few minutes on the die grinder.In the end if that is what need be done, so be it.I was just hoping someone else used this rod configuration without a smallbased circle cam. Not every block is the same.When the mains were line-bored I could have lost a few thousands.Just looking for a solid starting point before ordering the cam.Thanx again for the posts.
I was talking about the rotators that are bought out of the magazines as those ones tend to need some work to bring them in to where they are suppose to be.

Sorry if I misled you.
 

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CNC BLOCKS N/E said:
I was talking about the rotators that are bought out of the magazines as those ones tend to need some work to bring them in to where they are suppose to be.

Sorry if I misled you.
I see the same conditions (out-of-spec, etc.) in the kits I get direct from Scat, Eagle, etc.

tom
 

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383mud,
Nobody can really answer your question on if the rods will clear the cam, the only way to know is to measure. All the 383's I have built never needed a small base circle cam. The first one I built using stock 400 rods needed a lot of grinding on the rods. I have built a couple using 6" H-beam rods and they provided the most clearance by far. My current 388 has 6" h-beam rods and a standard base circle, no issues. Every block is a little different, some guys don't have to do any clearancing on the block, some have a lot of clearancing to do. If I had to bet I would say that you will be fine with a standard base circle. The few guys I know that had to go small base circle were all monster solid roller cams.

If you stick your rotating assembly in you can get an idea of the cam clearance by looking through the cam tunnel but, that is not an exact science.

Royce
 

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hey man an easy way to see if it'll clear is to see if anyone you know has a cam similar to what you want to run and set it in place and measure how much clearance you have. if you don't think you have enough with what ever cam your mocking up with then get the smaller one.
 

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Did you say the crank and rods were in with pistons and ready for heads?

I find it a serious pain in the back side to do it that way. Not to mention I don't like buying and installing part's as I'm ready for em for reason like this. hard to mock up stuff for assembly when you don't even know what you have yet.

I preferr to have everything sitting in front of me and a quiet place without distractions, girls included. Keeps my head in so I don't forget stuff.
 

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johnsongrass1 said:
How are ya install the cam with a crank in the way?
Cams get installed everyday that slip into the holes with the entire assembly in place. It would be a beatch to change a 383 cam if we had to disassemble an engine to change a cam.

Depending on the specifics, most 383s only need 2 rods trimmed about .050.

A couple grams makes NO difference at all.

(think overbalance, 1% = about 64 grams)
 

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I'm using "stroker" rods in my 383. They are i-beam Lunatis. I used a standard base circle, and have no clearance problems to the cam lobes. Please understand, I am not an automotive machinist, so I may be mistaken here, but sometimes I think the machinist guys assume we know more than we actually do. So, I'll try to explain how I THINK this thing works.

The big end of the rod gets built into the "rotating" part of the balancing science, I believe. Reciprocating parts (pistons, rings, pins, small ends, etc) tend to get matched very, very closely. In part because this isn't too difficult to do. But the big ends, and the bearings, and the oil film value (1 or 2 grams) get used to establish the bob weight. The rotating mass (with bob weights in place) is run on the balancing machine. Drilling (or heavy-metal addition) is done to bring the rotating mass in close to a blanced condition. While you may hear about balancing to "half a gram" or so, I don't think rotating assemblies are often that close. Reciprocating yes, rotating no. Hence, I don't think it makes much difference if you knok off a couple of grams of rod weight to achieve the clearance you need. Which, personally, I don't think you'll need to knock off anyway. I'd buy the cam.

If I'm off base on any of this, I hope one of the machinist guys will set me (and maybe some more of us) straight.

Pat
 

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Discussion Starter · #16 ·
thanx again for all the input guys.I think alot of uncertainty has been cleared up. Especially from the posts of camaroman7d. Investigating this build I have been getting alot of unfounded information from people along the way that haven't been directly involved in a 383 build and try to solicate opinions based on what they have heard or read. Dont get me wrong I apreciate any input I get, but its great to hear directly from someone that someone has had a success on one motor let alone several and from others that do this for a living that aren't out to sell their products or services. This group has given me more insight to this stage of my build than any other sources I have explored. Its great to get unbiased opinions from machinists and fellow rodders willing to pass along alittle help. I'm glad I joined and hope that at some point in the future I can shed some light on someones project as well as you guys have here. I'm going to order the cam as previously decribed and grind if needed. This is my first engine of this caliber, so to speak and as you may have noticed I'm a bit of a freak when it comes to details(weighing each component and so forth) but when I was big into reloading the golden rule was "consistancy equals accuracy". With this project I've been seeing it the other way-"accuracy equals conistancy".
 

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When we have time in the shops we have built some stroker engines for some of our customers and we have a hyd. cam that works very well and we have it ground on a 1.130 base circle and we have been using the Scat 6 inch rods with the 7/16 bolts and this combo has plenty of cam to rod clearance.

To belt sand off the corners of the rods will not affect the balancing to where it has to be rebalanced as I worked with the great Smokey Yunick on a project and he described balancing as an IMPERFECT SCIENCE and I think he is 100% right.

Good luck with your build, Carl
 

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CNC BLOCKS N/E said:
When we have time in the shops we have built some stroker engines for some of our customers and we have a hyd. cam that works very well and we have it ground on a 1.130 base circle and we have been using the Scat 6 inch rods with the 7/16 bolts and this combo has plenty of cam to rod clearance.

To belt sand off the corners of the rods will not affect the balancing to where it has to be rebalanced as I worked with the great Smokey Yunick on a project and he described balancing as an IMPERFECT SCIENCE and I think he is 100% right.

Good luck with your build, Carl
Smoky was between 95 and 105 percent right, give or take a little......

tom
 
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