I have a 454 block that was just bored .30 and decked. I just bought a brand new set of 6.135(std) Scat H-beam rods and when I showed them to my neighbor he told me that he has a ext. balance 4.25 scat crankshaft still in the box (he inhereited it from his brother)
My question is can I used a 4.25 stroke crank with standard length connecting rods? I know very little about stroking an engine..My initial feeling is "No, this wont work" but maybe you guys could give me some more definate feedback.
Thanks guys

You could use the 4.25" crank with your 6.135" rods BUT an easier approach, and one I would recommend, is to use 6.385" rods. Balancing and pistons choices are much simplier that way.
Sell/trade the 6.135" rods...the longer ones are nearly the same price.

I agree with Bill, use the longer rods.

Ok, I'm going to try to sell my rods or see if I can exchange them for 6.385 ones.
BUT...if I can't get longer rods and I do end up using the std length ones, what problems/disadvantages will I encounter and can I still use my KB207 pistons?
I'm starting to wonder if it's even worth my time to stroke it

It's always worth the effort...more cubes is a good thing. ;)
But, your KB207 pistons won't work with a 4.25" crank. Too much compression height...with a 6.385" rod and a 4.25" crank, they'll hang out the bore 3/8"! :eek:
I used these Manley rods in my 540...awesome product!
Near the bottom of the page...
http://www.sallee-chevrolet.com/sales.html

The crank will have to be cam cut and then balanced with Heavi-Metal to be able to run the stock rods with the correct stock rod length, but 1/4" stroked compression height!

I did this after NOT hearing Lunati tell me to run 1/4" longer rods!! I used my stock truck rods I had rebuilt with good bolts and such and then had to have them set the crank up like I just said..

Back then, it was a wash on costs b/c there were fewer less costly stroker rods to pick from like there are now..

pdq67

sapper,
Do you know what crank you have?
I am a dealer for Scat & there are quite a few different cranks in the 4.250 stroke.
Most of the ext balance ones WILL work with the 6.135 rod without cutting the crank.
Just putting in 6.385 rods with the ext crank will not help balance that much.
One of the main reasons for going to the 6.385 rod is so they can put larger counterweights on the crank which makes balancing easier.
In fact if you use the long rod with the right crank & pistons it will internal balance usually without adding any tungsten (heavy metal)
Each crank/rod combo uses a different piston as the compression height will differ.

Yup :D I sure do have the PN# 9-454-4250-6135, the box says "454, 4.25 stroke, 6.135 rod, 2 pce seal"
My rods are SCAT H-beam PN# 2-454-6135-2200 and my pistons are KB207 .250 pop up with 1.655 compression ht.

I think that I'm supposed to use the std. length rod with this crank because thats what it says on the box...at first I thought it was just a misprint graemlins/clonk.gif
If those pistons aren't useable, can anyone recommend a piston that will work? I would like ~10:1 CR with 118cc heads and I don't plan on using any NO2 or blower so cast or preferably Hyper please. Thanks guys

That's the 9000 series cast crank designed for stock length rods. You can always use the longer rod with a crank designed for stock length rods but you can't go the other way as the difference is the counterweights which are larger in diameter on the long rod crank
Again, you need to use the correct piston for the stroke & rod length.
Fed Mog has a nice coated hyper piston for the stroker but I don't have the book in front of me.
If someone hasn't posted the number by this evening I will try to have it for you.
You may have to add Tungsten with these pistons as they are pretty heavy.
The H beam scat rods are actually about 25-50 grams lighter then the stock ones.
The last one I did with these pistons & stock GM rods came in about 2450 bobweight which is pretty heavy. As I recall I had to add Tungsten to balance.

The piston is H603CP, 23cc dome,
advertisied 10.1 @ 119cc @ .015 deck
Just for info, this piston weighs about 840 w/ pin vs an SRP which weighs about 750.

Right on! Thanks for the help graemlins/beers.gif Time to start saving for the pistons

Mike,

Would you recommend the Scat 4130 forged crank (4.25" stroke) in an application where the rpm's would stay under 6500 and maybe a small shot of nitrous (125-150hp)?

I know this may be difficult to do but if you had to put an HP rating on a crank, how much would the 4130 be rated for? How about the 4340?

I seem to recall my bobweight is about 2346 or so with 9.5 ROSS's and stock truck rods..

pdq67

Originally posted by 71454Chevelle:
Mike,

Would you recommend the Scat 4130 forged crank (4.25" stroke) in an application where the rpm's would stay under 6500 and maybe a small shot of nitrous (125-150hp)?

I know this may be difficult to do but if you had to put an HP rating on a crank, how much would the 4130 be rated for? How about the 4340? If you keep the rpm down you could probably use the cast crank if you wanted.
I had a customer use a cast crank in a 383 alcohol modified & it lasted three seasons to about 7200 before he finally broke it :eek:
Not the way I would do it but kind of tells you what you can get away with.
The 4130 is a good deal but it is my understanding one of the major drawbacks to 4130 besides not being as strong is it doesn't take hardening as well as 4340. Plus the difference is price is only about $70 for the 6.385 rod ones.
I don't know how much HP they will take but I know of quite a few 700hp give or take engines that have been running for quite a while & of one that is about 850 est. & runs a 200-400 shot on top with Scat crank & H beam rods. It's a 540 BTW.

PDQ,
That's real close with forged pistons, I did one a few years ago for a propane deal with Fed Mog hypers & stock rods & it was about 2425.
For comparison, another with SRP' & H beam 6.385 rods was 2225.