hey guys,

I'm building a 505(4.35x4.25) with the scat 9000 series 4.250 stroke crank (part # 9-454-4250-6135). I'm looking to find out what the target bob weight is for this crank since I've heard they turn down the counterweights a bit to work with 6.135 rods. I emailed Scat and never got a reply.

What I'm using is a set of 4340 6.135" rods which weigh 792 grams. I'm stuck with this rod length because I bought them before I decided to go stroker. My pistons are ross items that weigh 650.5 grams. I'm hoping that I won't have to use heavy metal to balance this motor. What do you 496 guys think?

Thanks,
Chris

Chris,
I think you will be ok with the 454 damper & flywheel.
I don't recall the target bobweight of the crank but if you email me I will look it up for you tomorrow.

===edit=========
Did one about 4 years ago I just looked at & it took Tungsten with a 2430 bobweight.
The Pistons were 836 w/ pins & stock rods were 830
It was the 4130 crank

Chris,
I have found that the best way to get an answer from Scat is to call them. Personally, nothing bothers me more than companies that have an e-mail address but dont answer it :mad: I would rather they just not show it.

Thanks, Mike and Bill.

Since you guys do this all the time....whats the typical weight for a BBC ring package and rod bearing?

Originally posted by Chris Hill:
Thanks, Mike and Bill.

Since you guys do this all the time....whats the typical weight for a BBC ring package and rod bearing? I sent you the approx counterweight for the crank
It's 2150-2200
It will normally take some Tungsten with stock weight type parts.

1/16th rings about 54 gms
5/64ths rings abot 63 gms
std inserts about 50.5 gms

While you are talking about balancing guys if you don't mind. Does it matter much if you use a file fit ring set for balancing weight calculation before they are filed? I have to assume this happens quite a bit?

Doug,
The amount of material removed during the file-fit operation is negligable. The rings can be weighed either before or after the filing operation.

Do some of you guys add a fixed amount for oil as well?

Guys,thanks for the info..printed out and saved..I'll be building a 496 myself shortly and will be using a 4.25 Scat crank and stock 6.135 rods

Originally posted by Epistuff:
Do some of you guys add a fixed amount for oil as well? =
I use 5 gms.
Some use more, some none. Educated guess at best ;)

Just as a ref note here...I built a 505 like that, but had +250 rods. BOB was 2254g. Piston 535g rod 814g. With the +250 rod and crank weights, I was able to go internal balance with no heavy metal.Cola 4340 +250 crank (http://bellsouthpwp.net/p/c/pcs0snq/505/cola%20crank.JPG)

Hi Paul,
That is the main reason why I like a longer rod in a stroker engine.
You can usually get a crank that has enough counterweight to balance it internally without a huge hassle.
A 5.85-6" rod for the 3.75 & up sb & a 6.385" rod for a 4.250" stroke rat just makes life easier in the balance department ;)
As for the purported performance benefits of the longer rod,,,,,,, probably the most over analyzed part of an engine combo :D
Just my opinion of course

Hey Mike, Been busy racing and on the BTE sponsored BB. More race stuff over there. I come back here now and than to add my 2 cent. Has the perma-frost melted in N Cal yet? lol Hey, I've really gotten deep into oil stuff this year. Ran Vavoline VR-1 20W-50 and now running Schaeffers Micron Moly 40W race oil. Kind of determined to find the optimum Dino oil for my 555. I'm having Oil Testing done on Virgin and Used oil to understand what's happening. It's pretty interesting stuff. Ever here of Terry Dyson? I like you footer... he hee he lol! :D
Hey check out the points race below....my track MMP (http://www.morosomotorsportspark.com/dsweeklyres.html#ET)

That 505 really has a +400 rod in it. Not sure why I said +250. +400 rod with Gas ported Weisco slugs this is a short deck 505 (http://bellsouthpwp.net/p/c/pcs0snq/505/pist%20rod.JPG)
Anyway I have no idea on the performance side of rod ratio deal, but know for sure that longer rod = less cylinder loads = graemlins/thumbsup.gif I think a 6.535" is about as long a rod as I have ever put in a std short deck with a 4.25 arm. Anything more and I'd have to get a very trick piston.

Originally posted by Wolfplace:

As for the purported performance benefits of the longer rod,,,,,,, probably the most over analyzed part of an engine combo :D
Just my opinion of course Rod length is definately a factor in building power. There are two examples that came to mind when I read this post. 1st, The longer rod keeps the piston at the top of the cylinder longer during each stroke, which allows cylinder pressures to rise higher on the end of the compression and beginning of the power strokes before the piston starts moving back down the bore, this means the air/fuel mixture has that much more time to burn and create energy in the same amount of time. 2nd, and I'm taking this from a book next to me, a longer rod will give you a better rod ratio. Increasing the rod ratio reduces rod angularity, which reduces the side loading of the piston against the cylinder wall thrust surfaces, ie less friction and more freed up power. graemlins/thumbsup.gif

Originally posted by three85stroker:
</font><blockquote>quote:</font><hr />Originally posted by Wolfplace:

As for the purported performance benefits of the longer rod,,,,,,, probably the most over analyzed part of an engine combo :D
Just my opinion of course Rod length is definately a factor in building power. There are two examples that came to mind when I read this post. 1st, The longer rod keeps the piston at the top of the cylinder longer during each stroke, which allows cylinder pressures to rise higher on the end of the compression and beginning of the power strokes before the piston starts moving back down the bore, this means the air/fuel mixture has that much more time to burn and create energy in the same amount of time. 2nd, and I'm taking this from a book next to me, a longer rod will give you a better rod ratio. Increasing the rod ratio reduces rod angularity, which reduces the side loading of the piston against the cylinder wall thrust surfaces, ie less friction and more freed up power. graemlins/thumbsup.gif </font>[/QUOTE]And for those who are confused...
The first quote is by a professional engine builder.

The second is from a shipping manager who is reading from a book, probably marketed by someone who profits from aftermarket parts sales...

As Mike stated,
The most over analyzed part of an engine build up.

385stroker,
Have you ever actually looked at the time of dwell at TDC with a longer rod, as expressed mathematically per degree of crank rotation?

Or how about an engine dyno test on the same engine with only a rod length/pin height change?

Thanks Jakeshoe graemlins/waving.gif

I've posted this before but here it is again.

I'll probably catch all kinds of flack for this but here's my opinion.
Rod length is one of the most over rated, over discussed parts of engine building.
I favor a rod long enough in strokers to be able to clear the needed counter weight as it normally makes balancing eaiser. If the rod is too short you can't get enough counterweight on the crank to balance it.
If you were to take the crank angles differences between say a 5.7 & 6" rod & overlaid them on a graph you probablly wouldn't be able to differentiate between the two lines on the graph!
Hell, if you took a 5" & 6" rod you would be hard pressed to see the difference :D

In a longer rod engine the piston dwells longer around TDC & less around BDC which can be argued both ways.
If it is moving away from TDC slower it isn't putting as much power into turning the crank but it gives the charge more time to build pressure.

Ok, if it's a "short" rod it is moving away from TDC faster it will put more power into turning the crank sooner. :confused:
My basic opinion of rod length is if you don't have a good reason to change it that actually makes sense,,,, leave it alone.

This was summed up real good at the Superflow Advanced Engine Technology Conference this year in a round table disscusion with some of the very best minds in the business of engine design in NASCAR.

This ain't a direct quote but it went something like this:
You decide on a stroke, design a piston to fit your needs, measure the deck height of the block & then make something to hook them together ;)
That was pretty much the consensus on the importance of rod length in overall engine design.

Hey Mike, Not to be a pain, but what about the reliability aspects of a longer rod ratio engine. Seems as the angle is relaxed, the side force (vector) on the cylinder wall and piston would be less and result in less ware. If I have that wrong, I'd like to get the right answer... thanks in advance
:D

Originally posted by pcs0snq:
Hey Mike, Been busy racing and on the BTE sponsored BB. More race stuff over there. I come back here now and than to add my 2 cent. Has the perma-frost melted in N Cal yet? lol Hey, I've really gotten deep into oil stuff this year. Ran Vavoline VR-1 20W-50 and now running Schaeffers Micron Moly 40W race oil. Kind of determined to find the optimum Dino oil for my 555. I'm having Oil Testing done on Virgin and Used oil to understand what's happening. It's pretty interesting stuff. Ever here of Terry Dyson? I like you footer... he hee he lol! :D
Hey check out the points race below....my track MMP (http://www.morosomotorsportspark.com/dsweeklyres.html#ET)

That 505 really has a +400 rod in it. Not sure why I said +250. +400 rod with Gas ported Weisco slugs this is a short deck 505 (http://bellsouthpwp.net/p/c/pcs0snq/505/pist%20rod.JPG)
Anyway I have no idea on the performance side of rod ratio deal, but know for sure that longer rod = less cylinder loads = graemlins/thumbsup.gif I think a 6.535" is about as long a rod as I have ever put in a std short deck with a 4.25 arm. Anything more and I'd have to get a very trick piston. =
Hey Paul,
Looks like you been busy, good deal on the points chase graemlins/thumbsup.gif
Yeah, it's thawed out LOL
Spent the day thrashing the crap out of a late model 2bbl on the dyno. Nothin hangin out yet so I guess I'll have to try again next week. Playin around with some different intake stuff & headers.
Email me the results on the oil, always interested in oil stuff
Don't know Terry Dyson??

Man these posts sure can take a left turn,, hope Chris got all his questions answered tongue.gif

Originally posted by pcs0snq:
Hey Mike, Not to be a pain, but what about the reliability aspects of a longer rod ratio engine. Seems as the angle is relaxed, the side force (vector) on the cylinder wall and piston would be less and result in less ware. If I have that wrong, I'd like to get the right answer... thanks in advance
:D You type too damn fast :D
If you draw up the differences in the angles we are talking about they are very small but yes in a long rod engine there is going to be less cylinder wall pressure.
Question is how much?? When you got nothin else to do look at the differences per degree & you will probably quit worrying about it but for the sake of argument I would stay with the longer rod for your deal if I were doing it.
As long as the cam timing is right I highly doubt you will see any difference in power though.

Something more for you to ponder :D ,, you can run more cam by a couple of degrees or so with a short rod & will end up with the same or less reversion because of the longer dwell time difference at BDC & can end up with more HP in some combinations. :confused:

So,how bad is it from a reliablity standpoint have a 496 stroker with stock 6.135 rods?

Originally posted by mr 4 speed:
So,how bad is it from a reliablity standpoint have a 496 stroker with stock 6.135 rods? =
If I were building one I would recommend the 6.385 rod & 6.385 crank but in regards to reliability, it's not really an issue.

At least in my opinion ;)

Mike,is it kinda like having a 400 SBC with stock length rods?

Originally posted by mr 4 speed:
Mike,is it kinda like having a 400 SBC with stock length rods? =
Sorta except a 400 has a better rod stroke ratio than a stock rod 4.25 stroke rat.
A 400 is 1.48 & the rat is 1.44.
A 6.385 rod is slightly better than a 400 with a stock rod at 1.5
So much for people who tell you a stock rod 400 is terrible & cannot be made to run because of rod length.
If this is the case I guess you are in real trouble along with a lot of others out there :D

BTW, with all this posting about rod length my preference is toward as long a rod as practical but it's not a primary consideration to me ;)

Back in the days when Buddy Morrison and I built dozens of small-block Modified motors, we earnestly believed that an engine needed a 1.9:1 rod/stroke ratio. Today every Pro Stock team uses blocks with super-short deck heights, and we couldn't care less about the rod ratio. A short deck height improves the alignment between the intake manifold runners and the cylinder head intake ports, and helps to stabilize the valvetrain. These are much more important considerations than the rod-to-stroke ratio. There's no magic - a rod's function is to connect the piston to the crankshaft. Period.
-- David Reher

I gotta feeling we just heard from the MAN!!!

Glad he dropped in..

pdq67

Originally posted by pdq67:
I gotta feeling we just heard from the MAN!!!

Glad he dropped in..

pdq67 ???Glad who dropped in?? I believe that was Jason supplying a quote from David Reher. Appologies if I am incorrect.

Originally posted by DragRacer:
</font><blockquote>quote:</font><hr />Back in the days when Buddy Morrison and I built dozens of small-block Modified motors, we earnestly believed that an engine needed a 1.9:1 rod/stroke ratio. Today every Pro Stock team uses blocks with super-short deck heights, and we couldn't care less about the rod ratio. A short deck height improves the alignment between the intake manifold runners and the cylinder head intake ports, and helps to stabilize the valvetrain. These are much more important considerations than the rod-to-stroke ratio. There's no magic - a rod's function is to connect the piston to the crankshaft. Period.
-- David Reher </font>[/QUOTE]=
Thanks for the quote Jason graemlins/thumbsup.gif
Guess I will have to agree with Mr Reher as I believe that is what I have been trying to convey in the last 5 or so posts :D

Mike, if you were to build an 'inexpensive' 4.25 rat using a standard GenIV block, what reciprocating parts would you buy. We're talking sub 5500 rpms here. 90% street. ( all I have is an old L88 crate block - 1972 , and some old 049 heads.)

Manley rods seem overkill. I could use cheap GM 3/8s, but after rebuilding them , they ain't so cheap. Plus, if I could keep it internally balanced, it'd use the same flywheel etc.

Anyway, customer comes to you and wants to build a 496 to look and sound like a 1967 325hp 396. Non max effort deal, what would you recommend?

The rod length is a much debated thing. Jon Kaase who could have used any length rod he wanted in winning the Engine Masters challenge picked one that was 2" longer than the stroke and Reher-Morrison's David Reher said it also didn't really make much difference so as Wolfy said the counter weight clearance is the main plus of the long rod.

You are right, I am wrong..

Jason just posted what the Man said and I am glad he did..

My bad...

pdq67

Originally posted by 427L88:
Mike, if you were to build an 'inexpensive' 4.25 rat using a standard GenIV block, what reciprocating parts would you buy. We're talking sub 5500 rpms here. 90% street. ( all I have is an old L88 crate block - 1972 , and some old 049 heads.)

Manley rods seem overkill. I could use cheap GM 3/8s, but after rebuilding them , they ain't so cheap. Plus, if I could keep it internally balanced, it'd use the same flywheel etc.

Anyway, customer comes to you and wants to build a 496 to look and sound like a 1967 325hp 396. Non max effort deal, what would you recommend? =
Std weight Scat 6.385 forged crank, Scat H beam or I beam cap screw rods, SRP pistons.
Reason for the forged crank is you can internally balance it without adding Tungsten.
The 6.385 H beam rod is lighter than the stock GM 6.135 rod by about 30-40 grams & the SRP pistons are pretty light.
I'd need to check on the capscrew I beam weight as I don't remember it offhand but if it is light enough it is a real nice piece for the money.

If you used the cast crank you would need to add tungsten which gets pretty expensive quick & you end up spending damn near as much as buying the forged crank smile.gif
Of course with the cast crank I get to charge you more labor for all the balancing work so I make more :D

If you didn't mind using the 454 damper the cast crank & Fed Mog Hypers along with the I beam rod would be cheaper. It may take a little Tungsten to balance but the price of the parts would be quite a bit less.

For the "396 stealth deal" I think the first option is what I would do.

Thank you Sir!

Hey Wolfy, It might be worth looking into the pricing on the Wiesco Pistons as they appear to be quite a bit lighter than the SRPs and from what a friend of mine said that used to build pro stock motorcycle engines the quality is very good.

Wolfy, that's funny. An old expression of my dad's " Cool your jets Wolfie" . I have no idea where that immigrant got that one!