Todays topic building a new M IV big block. Have been looking at cranks and stroker kits. I am at altitude so I always run extra compression for the thin air.

1st question, do you like Eagle or Scat cranks better? Why?

2nd question, stock 427 or 454 or stroker kit? Worth the extra money?

Car is a street car so no drags or auto cross. I already have a good 4 bolt block.

Thanks in advance.

 

I built a 502 , used a scat 1/4 stroker, had the rotating assemby ballanced, no weight added, perfect balance.. 1/4 stroke added 31 cubes. Keep in mind, you will have to buy matching rods and pistons if you go 1/4 stroke

 

SCAT better than Eagle. Callies better than all for "budget" cranks. Callies import line is Compstar and machined on same stuff as Calles main line but different forging than regular Callies. Howards also makes good ones. Callies use to do their machining also...not sure now.

If buying a crank, I can't see any reason not to go to a 4.25" version. It will rev as fast as you ever want to and will pull those mountains with ease.

JIM

 

Thanks, I am leaning toward 4.25 stroke, 6.385 rod, and +.030.

 

Thanks, I have heads that are angle milled so piston dome is iffy, so I need more stroke to get compression up with a flat top piston. I have a friend that likes the Manley cranks but I appreciate the info on Comp star, I did not know that.

 

My machinist told me to go with stock 6223 over brand new Eagle....he had way too many issues. While i was in his shop he had a pallet full of Callies cranks waiting.....guess that answers the question.
Stock forged crank is perfect. I would stick with 427 just for the numbers...around here 454s are like seagulls.

 

been a while but wasn't at one time,
Eagle was the leader in quality cranks?
damn memory.

 

I know of a NOS LS6 crank for sale that I learned is 2nd generation. Apparently GM repopped the LS6 in the late 70s early 80’s as a crate over the counter item. From what I know the early cranks had the last 4 numbers cast in front counterweight. Late cranks had the full number on the rear counterweight. Also the front counter weight is smaller on the later crank.
I have read of oiling problems with the cross drilled main oiling system at higher rpm’s and crank flex from the smaller counter weight.
The big problem is the guys that have these think they are gold. Asking price is much or more than a CompStar or Manley and these are lightened and gun drilled rod throws.
Thanks for the response. R Rogers

 

Crank it up!

 

The 1036a6 Forged Steel 427 crank used in the L-71/L-88/ZL-1 is the strongest crank GM ever manufactured then and now.........you can run 9's in a 3800lb. car and it will keep coming back for more. The key is the short stroke still puts the rod and main journal centerline closer together and it intersects along the forgings length.....a little nerd FYI for you.
That said.....I am now using Scat after using Eagle for 15 years......just a better product all around. Main gripe about Eagle is that the journals tend to run fat and need an "X" one over bearing.......about 60% of the time......They should just sell the MF rotating kits with X bearings.......
The last four Scat cranks I used were all on the money except for the 385ci one piece seal engine which was tight on the mains but I attribute it to the line hone being on the tight side.
I urge you to look at the new series of Mahle pistons.....running a 1.5mm/1.5mm/3mm ring pack.....seal up tight and you can turn the short block on a stand with one finger...(to be fair, I have big Canadian lumberjack fingers LOL).....the 3 408ci Windsor engines I did had Scat cranks and they were beautiful to look at.....looked like money.......
I started using pre-balanced assemblies during the pandemic when nobody would balance **** and had local issues with numbnut ******** here.....I have built 6 pre-balanced engines since 2021 and they all are smooth as silk......more nerd FYI.
Either company makes a real nice budget rod.......and they all are profiled now with shorter bolts for stroke clearance if you need it.....both companies had a separate part number for these stroke rods that were just notched with a hog mill.
Callies has a nice product but it is the same product for more money.....the Dragonslayer cranks are just as good as a Scat.....
I am going to go "crank up" Judas Priest now.....

Jebby

 

Good information and thanks for the tip on the Mahle pistons.
Everything I read says use the 6.385 rod and I seem to remember reading once either Grumpy or Reher said always put the longest rod possible in it.
I have a set of like new L88 TRW pistons but can’t find any aftermarket 3.76 cranks. Most used ones I find are all used up. I would love a 427 as this engine is going in a 66 390 car but may have to go bigger and just lie.

 

Just to throw another angle at it. Eagle has a 454 stroker kit with a 4” stroke and 6.535” rods, giving you a rod ratio of 1.63.

From a standard kit, this is the closest I have found to the “ideal” 1.75 rod ratio.

 

I'll take cubes over an "ideal" rod ratio any day.

The Dragonslayer cranks are actually the same piece of steel as the high end mega $$ Callies. The fancier ones just have more features and lightening done. They are from a completely different Japanese forging last time I heard whereas the Compstars are a Chinese forging.

My crank guy (used to be part of Porsche race team building their engines) told me the over the counter GM cranks almost always had runout to the high side and needed straightening out of the box or just set it up real loose to give it some room.

SCAT has been making cranks/rods for the OEM's special projects/crate motors for years....Ford, GM and Mopar.


Mahle does make some nice pistons.

JIM

 

You are right....I got the Compstar and Dragonslayer confused.......
I agree on the whole rod ratio thing.......after seeing 347 Fords spin 6500rpm day after day and run 50,000 miles with a 5.090 long rod.....I called BS on all of it unless you are class racing.
I also would go a shorter rod if it will pull the oil ring land out of the pin boss and not need an oil rail support......but a lot of combos that is impossible..(like a 434ci small block).

I want to add that I used Icon pistons in the three 408 Windsors and I have nothing bad to say about them......hard to screw **** up on a CNC machine unless you have mixed batches.

Jebby

 

As bad as those 347's look with the ring through the pin boss they don't seem to have any trouble with them surprisingly , I just got a set of Icon 2618 forged two valve relief flat top forged pistons with the modern ring package for my white 80 L82 and it looks like a nice product

 

Ok, let’s look at this at this angle. Longer rods are known to make more power. If you have your engine already torn apart and it doesn’t cost any more to put longer rods in it, why wouldn’t you get the longer rods??

Yes, one piston set is a flat top and the other is domed, but I wanted to get a manufacturer apples to apples comparison.

 

Unless you are spinning this to 7000rpm and making like 800hp.....the H-Beam rod is overkill.....they are also heavy.....which can sometime make balancing difficult.....
The I-beam rod is much less expensive and very formidable.......

Jebby

 

Yep..there CAN be some power there...but one of my big interests is in the reduction in piston weight with a long rod....I like RPM. I've run pistons with the pin in the oil land forever with no issues.

There's a tuning and dynamic component also. Short rods can help a high compression pump gas engine by getting the piston away from TDC quicker and dropping cylinder pressure a little faster...as well as it can help with a large intake port to get it flowing quicker.

Engine Masters tested it also.
Engine Masters: 5, Episode 1 - Rod Ratio Examined | MotorTrend


Interesting dyno session with a ricer motor.


JIM

 

Just a quick update.
1st, thanks to all for the information and advice, greatly appreciated.
2nd, I had to stop and take a step back and check myself. Being an avid racer and engine builder I always appreciate the latest high tech and trick pieces. Chasing tenths of a second make this an art form.
Now, having said that, I had to remind myself this is a street engine in a street car, that will probably never see the far side of 6000 rpm, maybe only 5500 if I use a dual plane intake. As such I decided that GM performance parts would probably meet my needs. Also being on a budget helped define the parts to be used...............because I got a screaming deal on a NOS GM LS6 crankshaft, never used in the box. Also to go along with it, a set of 7/16 GM LS6 dimple rods. I now have a GM std bore LS6 block, std forged crankshaft, and good dimple rods for less than $1000. So I think that is a pretty good start.
Will post some pictures tomorrow.
Thanks to all.

 

You've got the makings of a killer "last forever" combo. Keep us up to date!

JIM