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custom connecting rods may soon be avaible ............
https://slantsix.org/forum/viewtopic.php?t=26519		 Page 3 of 12
Author:  slantzilla [ Sun Jan 13, 2008 9:08 am ]
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The 7.1 rod for the big block Mopars with the Chevy rod juarnal is not far off from working as is. This would make for a nice piston package also.



Jess
Regarding the big block Mopar rod, not only is the offset of the rod beam wrong, the width of the big end is too narrow. Being too narrow will allow the rod to slide around on the crank. This extra side clearance will also cause the rod to run off center in the bore which will upset ring seal plus side load the rod, potentially causing rod failure.
I've seen the cranks set up for Chevy style rods. All they do is grind the center of the journal so that it becomes narrow and has shoulders to keep the rods centered. Works for Honda size ends too.
Author:  k1tom [ Sun Jan 13, 2008 4:06 pm ]
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Quote:
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The 7.1 rod for the big block Mopars with the Chevy rod juarnal is not far off from working as is. This would make for a nice piston package also.



Jess
Regarding the big block Mopar rod, not only is the offset of the rod beam wrong, the width of the big end is too narrow. Being too narrow will allow the rod to slide around on the crank. This extra side clearance will also cause the rod to run off center in the bore which will upset ring seal plus side load the rod, potentially causing rod failure.
I've seen the cranks set up for Chevy style rods. All they do is grind the center of the journal so that it becomes narrow and has shoulders to keep the rods centered. Works for Honda size ends too.
Can you grind the crank to big block Chevy size? Yes. But since the Slant 6 rod pin is 2.1865" in diameter and the Big block Chevy is 2.200", you cannot grind the crank and put material back on. You can however, weld the crank (read add more cost) then grind (add more cost again), and make it work. If you do this, you either end up with a rod journal that is too wide and the rods float around on the rod pin or, if you weld it then grind it narrow, you end up with the rod beam not running in the center of the bore. This will allow the piston to rock in the bore on the power stroke upsetting the ring seal and causing a loss of power. There is also a couple of things that may have been missed here. First off, the stock big block chevy rod is 6.135" center to center so you are into custom rods before you start regardless of if you are using stock big block chevy diameters or Honda size. Can it work. Yes but it is a half a** way of making it happen. Making the rods correct will not only save money because the crank does not have to be re-ground, the rods them selves will be less expensive than custom big block Chevy rods. Combine that with a power gain from the rods being lighter and running in the center of the bore to improve ring seal before you make your decision.
Author:  runvs_826 [ Sun Jan 13, 2008 7:37 pm ]
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Well...acutally...not to stir the pot... but...
I had contemplated after trying to get billet rods made and having that fall through trying to use a more common rod and mayeb doing a little more maching. The closest one was the 440 rod that was common and could get in I - H Beam as needed. However, like somene had metioned the v8 rods are narrower than the six cylinder stuff. So the next spark of insanity came to me when I was reading about crank grinding and such in a book about engine blueprinting. It talked about how bore and stroke was only limited to finding matching parts (a little exagerrated), or by welding/regrinding the crank. The book even emphasised that a good crank shop could move your stroke up to 5/8in, but suggested no more than 1/2. I double crossed this with Doug's article and quickly saw something about stroking the crank 4.5ish so I knew they weren't off their rockers.
I than talked to a shop about welding the crank, destroking it, and making the diameter fitting a 440 rod. They said no problems, than I threw them a fast ball. I said that the a second cut would put a "collar" on the journal to make it hold the thinner diameter. So one cut would be to that of the normal 440 rods diameter and width, and than a second cut would clean up the weld to make a nice well... collar. They seemed perplexed but confident that it could be done, than they asked why a slant six? Cause a v8 wouldn't be this much of a challenge.
So I don't know what's the best course. Honestly, the price will probably brake even, and these are engineered to fit. So... I personally can't wait to see pictures of the prototype k1tom, and will probably be a customer sometime in the future.
Author:  gmader [ Sun Jan 13, 2008 7:44 pm ]
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Hi K1 Tom,

I just learned more about K1 via Mopar Action's last issue. I am glad you are taking an interest in us, but I gotta ask. Why are you interested in our little old slant engine? We love it, but we are self admittedly a small group.

Thanks,

Greg
Author:  k1tom [ Sun Jan 13, 2008 8:34 pm ]
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Hi K1 Tom,

I just learned more about K1 via Mopar Action's last issue. I am glad you are taking an interest in us, but I gotta ask. Why are you interested in our little old slant engine? We love it, but we are self admittedly a small group.

Thanks,

Greg
There are a lot of manufacturers out there that would be interested if there were a few hundred sets of rods to be built. We build the high volume items like the small block Chevy too but we also pay attention to the small markets. We have made a pretty good name for ourselves by making rods for 392 Hemi's, turbo charged Buick V6's, 426 small block Chryslers (yes, 426 SMALL block. Check the stroker kits at: www.hughesengines.com/ ) and a few other small and / or custom markets. While it is more work to make parts for small markets, we have carved out a nice business by building a lot of special rods. I have been designing rods for near 27 years, so coming up with new rods, is not a problem and is some cases like this, it is fun. Anybody can make a Chevy rod. If some of the Slant 6 people are interested in rods, that is great. I am happy to help and I am very interested in seeing performance gains where ever they are found.
Author:  ceej [ Sun Jan 13, 2008 8:41 pm ]
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Up till I scored some 198 rods I was looking at Flat head ford aftermarket rods.
The crank would have to be welded up to allow for the narrower big end, then cut 60 under for the correct std bearing for the aftermarket inserts. For a performance build, just the ticket.
It gives a true 7" rod.
Given similar crank work, the 7.1" Mopar rods.. Could work with even a light stroker build. I don't think I'd have room with my +5/16' stroke build.
What's the weight of the rod your thinking of Tom?

It's unfortunate, but the 198 rods I got were reconditioned by somebody that didn't do a very good job. I've got another set coming that will be done right.

CJ
Author:  sandy in BC [ Sun Jan 13, 2008 8:55 pm ]
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Tom,

I admire your business approach to small markets.
Author:  Dart270 [ Mon Jan 14, 2008 6:24 am ]
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Tom,

I also very much appreciate your interest.

I agree it is far easier to just make a custom rod with correct big end rather than go through finding a good shop that will custom grind a crank and reconditioning a set of hard-to-find 198 rods.

Lou
Author:  k1tom [ Mon Jan 14, 2008 6:55 am ]
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Quote:
Up till I scored some 198 rods I was looking at Flat head ford aftermarket rods.
The crank would have to be welded up to allow for the narrower big end, then cut 60 under for the correct std bearing for the aftermarket inserts. For a performance build, just the ticket.
It gives a true 7" rod.
Given similar crank work, the 7.1" Mopar rods.. Could work with even a light stroker build. I don't think I'd have room with my +5/16' stroke build.
What's the weight of the rod your thinking of Tom?

It's unfortunate, but the 198 rods I got were reconditioned by somebody that didn't do a very good job. I've got another set coming that will be done right.

CJ
At this point, it is a little hard to put a weight on the rod. I am waiting for the sample rod to arrive. Once it does, I will take some measurement from it and it will then be time to decide what length etc. will be used. I will then look at the loads the rod must handle and design the rod based on all of this information. Of course, I will keep it as light as possible.
Author:  66aCUDA [ Mon Jan 14, 2008 7:58 am ]
Post subject:  New Race Rods
K1tom
I too am actively shopping for full race rods. After getting 5 198 rods and not wanting to spend another 200 for a unknown set of 6 more Ill be looking at your rods very close.
Thanks
Frank
Author:  AnotherSix [ Mon Jan 14, 2008 8:59 am ]
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Thanks you to everyone putting out the effort to make this happen.

I am very interested in a set of these rods as well. I have been looking for some 198 rods up to this point, but would rather have a set of these.


I would hope for a rod that is a direct fit and can use later off the shelf pistons. Custom pistons are always an option anyway for anyone that wants or needs to go that route. An option to press fit the pins might make this easier for off the shelf pistons, is that possible? Really, I would use floating or pressed for our engine but do not know of an off the shelf piston for a 7" rod that is machined for the clips. Any solid options out there?
Author:  Doc [ Mon Jan 14, 2008 9:15 am ]
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The Sil-vo-lite 1291H has the machined grooves for floating pin clips.
The trouble with this piston is that it is not forged.
http://kb-silvolite.com/spistons.php?ac ... ls&S_id=30
DD
Author:  440_Magnum [ Mon Jan 14, 2008 9:45 am ]
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We had some major problems with what I call piston slap. What had happen is my uncles "buddy" put the short block together and I had assembled the heads. Upon fireing up the engine we learned he didn't pay attention to the valve reliefs and the intake valve hit the piston.
FYI, that's technically not "piston slap." Piston slap is the unwanted noise caused by the piston switching over from pressing on one cylinder wall to pressing on the other cylinder wall as the crank passes through TDC. Piston slap sounds very much like the sound a diesel engine makes normally. Factory pistons have the connecting rod pin placed ever-so-slightly off center in order to reduce the sound, and also pistons are ground slightly oval to reduce it ("cam-ground" pistons). Short skirt pistons also make more piston slap noise than long skirt pistons because they rock side-to-side more, and hypereutectic pistons make more than cast pistons because they don't expand as much in the bore. Forged pistons make a lot of piston slap when cold, but expand significantly so they don't make the noise when hot.

Chevy/GM new car buyers raised a HUGE stink about the Gen-III smallblock GM engine having a lot of piston slap when GM went to hypereutectic pistons at the factory. There were threats of class-action, nasty GM-smearing websites set up talking about 'being afraid to take the truck on a long trip,' etc., but the truth of the matter is that piston slap is HARMLESS. It may sound God-awful to the uneducated ear, but there's really no damage agoing on in there. In fact, if I built a hypereutectic-piston engine that didn't piston slap at least a little when cold, I'd worry that the slugs might get *too* tight when the engine is pushed really hard. Its always a balancing act between having the pistons tight enough in the bores to be quiet and loose enough to never bind, and the balance is much narrower with pistons that don't expand much.
Author:  SlantSixDan [ Mon Jan 14, 2008 9:52 am ]
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Listen to what 440_Magnum says about piston slap. He knows what he's talking about.
Author:  Doc [ Mon Jan 14, 2008 10:05 am ]
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All the "long rod" Slants I have built using hyper. pistons get more piston clearance (.003 to .004) and also get lot's of top ring gap. (.020 to .024)

These engine do make more piston noise when first started cold, it goes away after the first few minutes of operation. The cold piston noise also seems to lessen as the engine gets more miles on it, or I just get use to it. :? :wink:
DD
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