.927 pins..... WHY??

[GLHSKEN]

Why would you want to run them? The primary reason they were first introduced is because the ONLY piston supplier who made forged pistons for td's was JE. They are a SB chevy supplier and they were what they could offer.

To go to a .927 pin, you have to make the "small" end of the rod smaller. Since this end of the rod is under the most stress after ignition, "downstroke", does this make any sense to anyone. I've never seen a .901 pin fail due to hp levels.

Not only that, you are making the piston weaker as well.. larger hole means less mass between the piston and oil control ring.


Anyone have a good solid reason for me?

[Anonymous_User]

The only thing I could think of is if you already have a good set of rods sized for them.

Larger pin - more weight
Larger pin - more friction
Larger pin - less rod

[GLHSKEN]

LOL... that was exactly my thinking. Even then... I'd rather get a different set of rods.

[Clay]

the only "reason" to do it is its a common size. In bigger engines, moving to a .927 pin is actually moving down in size/weight/friction/etc.

It just happens that for us, our stock pins are smaller than the "chevy standard" eveyone wants to use.

[glhs875]

I agree, I don't think .927 pins are needed or should even be wanted. When I bought my pistons I steered away from that size.

[8valves]

The only thing I could think of is if you already have a good set of rods sized for them.

Larger pin - more weight
Larger pin - more friction
Larger pin - less rod

In regards to weight, who knows for sure that the added mass of the larger pin outdoes the mass lost from machining the rod and piston fr the larger pin?

AM

[turbovanman²]

I didn't realize that the pistons I bought had that size pin and had to have my rods redone. I can honestly say I notice no difference in revability etc. These are JE pistons and the pin is tapered so I would believe that the weight of the pin would be the same as the stock pin or less.

[Directconnection]

To go to a .927 pin, you have to make the "small" end of the rod smaller. Since this end of the rod is under the most stress after ignition, "downstroke", does this make any sense to anyone. I've never seen a .901 pin fail due to hp levels.

Not only that, you are making the piston weaker as well.. larger hole means less mass between the piston and oil control ring.


Anyone have a good solid reason for me?


You typoed "have to make the "small" end of the rod smaller" You meant...larger as in the small end diameter. 927 is a common size for the sbc, so I am sure it keeps costs down as it's made from stock that they already have. Also, the larger pin diameter sounds attractive to people as it has more surface area to distribute to load and more stable as well. The downsides are weight, smaller small end material on the rod, and a larger diameter sometimes, ok... does increase friction. The race sbc engines here use a Honda diameter big end to keep the friction down as a larger diamter bearing has more surface area which = more friction, heat, and chances of failure while limiting revs. That's why the 455 is not good to rev over 5,000 rpms due to the surface feet per minute of the bearings/journals as they reportedly have a large diameter.

Don't worry about the pin bore in the piston interfering with the oil control rings. Here at work, I see some crazy sbc race pistons all the time where that ring interferes with the pin hole as they use a special bottom support ring just for the 3 oil control rings. What does the venolia use for a pin? I know it's larger than what the JE pins are (which would definately be overkill).

[MiniMopar]

Didn't Ed Peters say something (for what it's worth) about pin flexing at high HP levels? I think you have to go with Wiseco pistons to get the .901" pin, which is certainly not a bad thing.

I am running the Venolias with the .927" pin in my 87 CSX. I did not have the (new T2) rods resized, but had the bushings honed-out. I didn't know at the time (1998) that they were brass dipped and the machinist showed me that one of the bushings had steel peeking through. Being naive (first engine rebuild ever), I just ran with it. Along with that mistake , I had the pistons made to fit the stock bores and just re-ringed it. I calculated the gap wrong and ended up with double what I wanted. I also tossed the new T2 rods in with new bearings on the old crank.

Been running this way ever since...over 35k on it now...LOL. Just lucky I guess. It sounds like a diesel when cold, but quiets down when hot. It's proven itself to be a tough little motor.

[Warren Stramer]

Good question Ken, The ONLY benefit with a larger pin is the added rigidity. BUT, it is really a non issue if the pin material is high quality. I would rather have a smaller dia. pin than a thinner rod pin boss. Ive been running weisco's for five seasons with .866 pins! Nascar uses these for 500mile races, should be good for our motors. I just tore my engine down for inspection after 5 seasons and over 250 passes....Pins and pistons are perfect with .866 pins.
If I was starting from scratch and money wasn't an issue, I would use aftermarket rods with larger pin boss and then go with larger pins.....Maybe.
Also, the trend is away from super thin wall pins in stock and super stock classes, too much flex.

[Clay]

Good question Ken, The ONLY benefit with a larger pin is the added rigidity. BUT, it is really a non issue if the pin material is high quality. I would rather have a smaller dia. pin than a thinner rod pin boss. Ive been running weisco's for five seasons with .866 pins! Nascar uses these for 500mile races, should be good for our motors. I just tore my engine down for inspection after 5 seasons and over 250 passes....Pins and pistons are perfect with .866 pins.
If I was starting from scratch and money wasn't an issue, I would use aftermarket rods with larger pin boss and then go with larger pins.....Maybe.
Also, the trend is away from super thin wall pins in stock and super stock classes, too much flex.

Alot of this depends on wall thickness though. You can make a lighter pin with thinner walls and a bigger OD more rigid than a small pin with thick walls.

[Warren Stramer]

One more thing, The highest loads and stress on the rod small end is not during the ignition or power stroke as these are compressive forces, rather the highest stress on the entire rod is when the piston/rod is crowning TDC between the exhaust and intake event. This is the point in the cycle when there are tensil streching loads. at that point the piston is being whipped at high speed with no opposing force to counter the rapid change in piston direction and velocity. That is why piston speed must be kept to a reasonable rate.

[BadAssPerformance]

I was thinking the same thing... a rod is WAY stronger in compression.

[Chris W]

Great topic Ken! To combat the customer's response, "But my rods are already machined for .927 pins." TU now offers larger bushings which will allow you to go back to a .901 wrist pin. We will add these to our website as soon as we are able to. Please contact us directly if you are interested in these rod bushings

Chris-TU

[GLHSKEN]

SEE IT WAS A GOOD question!!!! I learned something;)

[turbovanman²]

One more thing, The highest loads and stress on the rod small end is not during the ignition or power stroke as these are compressive forces, rather the highest stress on the entire rod is when the piston/rod is crowning TDC between the exhaust and intake event. This is the point in the cycle when there are tensil streching loads. at that point the piston is being whipped at high speed with no opposing force to counter the rapid change in piston direction and velocity. That is why piston speed must be kept to a reasonable rate.


I also heard that and thats when the rod breaks or the rod bolts let go, especially if you float the valves or rev to 6000 RPM and push the clutch in, :eek:

[crazy1eye]

JE's come with a .912" pin, Venolia's have the .927" pin.

[GLHSKEN]

LOL... You are right.

[86Shelby]

Hmmm, my TIII JEs have .900 tapered pins... They were built at least 3 years ago; probably close to 4 by now. Makes me wonder if they were as custom as the machine shop said they were when Supercrackerbox and I started asking about the engine at the machine shop.

I'll be using every bit of that meat on the small end while rapping this thing to 7k.:nod:

[GLHS0658]

I like the .927 pin because you can get a lightweight pin cheaper...because it is a popular size.
I'm not running a T2 rod but wouldn't hesitate to hone one out for a .927 pin.

Has anyone had a failure from the pin end being honed larger and therefore less rod material?

Mike

[turbovanman²]

I like the .927 pin because you can get a lightweight pin cheaper...because it is a popular size.
I'm not running a T2 rod but wouldn't hesitate to hone one out for a .927 pin.

Has anyone had a failure from the pin end being honed larger and therefore less rod material?

Mike

Not yet, :eyebrows:

[My96z]

I got my wisecos in the larger pin size cause thats all Chris could get to me at the time. Since its been together, I have beaten the bricks off my 2.5 and have no problems. I dont think its a issue, get whats in stock.

Go Wisecos!!

Jeff

[MiniMopar]

Yeah, I think it probably doesn't matter enough to warrent going one way or the other. If you have stock rods, just stick with the stock pin size. That's what I plan to do if I ever get a chance to redo the CSX motor (correctly).

[WVRampage]

so the only differents is .027 thats not realy that much when you half it do to it being in the center of a bore,so .013 and we all have our cranks turned .010 and no ill effects so I think the difference is small enough that is shouldnt cause most of us any problem.

[gasketmaster]

One more thing, The highest loads and stress on the rod small end is not during the ignition or power stroke as these are compressive forces, rather the highest stress on the entire rod is when the piston/rod is crowning TDC between the exhaust and intake event. This is the point in the cycle when there are tensil streching loads. at that point the piston is being whipped at high speed with no opposing force to counter the rapid change in piston direction and velocity. That is why piston speed must be kept to a reasonable rate.

While this is true..............connecting rods in turbocharged engines don't feel the pull as much as they do in N/A engines due to exhaust back pressure and intake boost pressure that keeps some cylinder pressure in the cylinder during overlap in turbocharged engines ;)

Jack Sparks from Carrillo told me that connecting rods in turbocharged engines are on vacation :D

[gasketmaster]

Why would you want to run them? The primary reason they were first introduced is because the ONLY piston supplier who made forged pistons for td's was JE. They are a SB chevy supplier and they were what they could offer.

To go to a .927 pin, you have to make the "small" end of the rod smaller. Since this end of the rod is under the most stress after ignition, "downstroke", does this make any sense to anyone. I've never seen a .901 pin fail due to hp levels.

Not only that, you are making the piston weaker as well.. larger hole means less mass between the piston and oil control ring.


Anyone have a good solid reason for me?

I'm sure they are overkill for most TDer's but in some applications you need a larger pin for strength :)

I have a buddy that bent a very high dollar set of .927 pins in his Buick V6 in a handful of passes but he's making over 150 hp per cylinder ;)

We put BB Chev (.990 if I remember right) hot rod pins in them now when they are cranking out that kind of power :eyebrows:

[TurboJerry]

I'd run Honda pins if I get pistons made..... They are smaller OD and that size is used in prostock engines.

[GLHSKEN]

Yeah, I think it probably doesn't matter enough to warrent going one way or the other. If you have stock rods, just stick with the stock pin size. That's what I plan to do if I ever get a chance to redo the CSX motor (correctly).


Answer I was looking for... why bother having to get new rods if you don't have to

[BadFastGTC]

Tool steel pin is longer. Material removed from rod is less and you have a bronze bushing. Pretty easy to see the weight differences.





In regards to weight, who knows for sure that the added mass of the larger pin outdoes the mass lost from machining the rod and piston fr the larger pin?

AM

[BadFastGTC]

My JE slugs came with a .905" pin from Lambros.



JE's come with a .912" pin, Venolia's have the .927" pin.

[8valves]

Tool steel pin is longer. Material removed from rod is less and you have a bronze bushing. Pretty easy to see the weight differences.

Thanks for replying. However, material from the piston itself being removed as well for clearance would also have to be added in. Enough to make a difference in the outcome? Not likely, but this is what I was curious about.

About the pro-stock rods... as far as I know they only use the Honda journal sizing for the crank end. I have a piston and rod here, maybe I'll go measure them up later tonight.

AM

[glhs875]

Thanks for replying. However, material from the piston itself being removed as well for clearance would also have to be added in. Enough to make a difference in the outcome? Not likely, but this is what I was curious about.

About the pro-stock rods... as far as I know they only use the Honda journal sizing for the crank end. I have a piston and rod here, maybe I'll go measure them up later tonight.

AM

Steel is heavier than aluminium. So the material removed from the piston would weigh less than the larger pin would.

[talanthalus]

Didn't Ed Peters say something (for what it's worth) about pin flexing at high HP levels? I think you have to go with Wiseco pistons to get the .901" pin, which is certainly not a bad thing.

I am running the Venolias with the .927" pin in my 87 CSX. I did not have the (new T2) rods resized, but had the bushings honed-out. I didn't know at the time (1998) that they were brass dipped and the machinist showed me that one of the bushings had steel peeking through. Being naive (first engine rebuild ever), I just ran with it. Along with that mistake , I had the pistons made to fit the stock bores and just re-ringed it. I calculated the gap wrong and ended up with double what I wanted. I also tossed the new T2 rods in with new bearings on the old crank.

Been running this way ever since...over 35k on it now...LOL. Just lucky I guess. It sounds like a diesel when cold, but quiets down when hot. It's proven itself to be a tough little motor.

I was in the same boat when I started working on my 87 Daytona back in around 97 / 98. I hadn't found any online resources or met anyone online yet, so when I started the modifications, we were strongly encouraged to run forged pistons instead of cast (due to the increased boost and larger turbo). I couldn't find any .030 over forged pistons, so we had Ross make a custom set. They actually recommended going with a Ford .912 pin, so needless to say, after the pistons were done and delivered, the pistons and rods were sent to a shop to have THAT work done.

I have about 7500 miles on that engine and haven't had problems with THAT at least.

Live and learn... hehe... I wish I had the knowledge AND money to do all of that work again now. I could make so much more progress on so much less. hehe

[GLHS0658]

As far as I know Nascar is using Honda Journal size but the pin end is still .927+
Also for weight/strength purposes they are using titanium pins casidium coated

[John B]

My 2.5 Venolia's came with .912" pins that are as light as stock pins.

[MiniMopar]

A lot has changed in the past 8 years. Now we can just go to a vendor and pickup one of three brands of forged pistions. Back then there was just FM and I had already had some problems getting them to send me my stuff (plus I didn't have much money). I got the Venolias custom made for me via Chris, but the only choice was the Chevy pin.

[talanthalus]

A lot has changed in the past 8 years. Now we can just go to a vendor and pickup one of three brands of forged pistions. Back then there was just FM and I had already had some problems getting them to send me my stuff (plus I didn't have much money). I got the Venolias custom made for me via Chris, but the only choice was the Chevy pin.

Yes it has...

...at least here, I have yet to have anyone tell me the mods and work I did way back then is all a bunch of worthless crap... :confused:

[John B]

The internal combustion piston engine is in it's very last stages of development, and it's unlikely that any world shaking discoveries will be made at this point. Still...we try;)

[BadAssPerformance]

There are lots of new IC engine developments but when racing classes are based on rules that use 50 year old technologies it is sometimes difficult for the world to embrace them.

[Directconnection]

I was thinking of a way to word it, but you explained it much better than I would have.

Technolgy limited to CI, valve angles, chamber cc's, pushrods, ohv but not ohc...etc.

[87csx2.4]

I would rather have a smaller dia. pin than a thinner rod pin boss. Ive been running weisco's for five seasons with .866 pins!me too warren 450 to the wheel and no problem's yet 8.8:1 comp.