Scat or Eagle: Any comments one what is a better crank and rod?

Ok Im getting ready to a LT1 355 and im just trying to see anybody have any bad expierences with either?

Scat Standard weight Steel crank vs eagle esp forged 4340 nittrided steel crank.



Scat 4340 H beam vs eagle H beams 4340

Also I have heard some people say that they have seen I beams take more then a H beam?

Im a mild headed and cam with all the bolt ons and with a 175 shot running a 10.83@125 I was planning on putting a direct port on it and squeezing a 200 through it with a stand alone and hoping to creep the singel digits. So I just want some strong internals for this.

I think you need better parts. I'd suggest a Callies "Dragonslayer" crank and Lunati Pro-Mod or Oliver forged rods. Won't be much more expensive and will be more likely to hold up. Of the parts you mentioned I'd prefer the Scat crank, just because I have no experience with Eagle cranks. The are good I beam and H beam rods, I wouldn't pick them on that basis.

Rich Krause

If I'm not mistaken, I believe the H-beams are stronger on compression and the I-beams are stronger in tension.
Assuming they are metallugically identical.

There is a lot of debates about H and I's not going there.

Eagle makes a good budget rod for the money and usually they measure out dead nuts to what they are supposed to measure out at. Pile on the good rod bolts and you have yourself a great budget rod. No real experience with the Scat H's but they should be in about the same boat. I have had Scat I's need some touching up on teh hone to get the fitment right. A good Eagle, Scat H beam or a Howards Rod with ARP2000 or L19 rod bolts (or equivalent) is probably going to hold what you need, but you should check the parts every time you rebuild for stretch, runout and they should also be magnafluxed.

IMHO Scat makes one hell of a crankshaft. Most likely you don't need more crank than that for what you are doing here. So I have to disagree with Rich on that one. Just my personal opinion. I just don't think you are getting more crankshaft for the extra money you spend on a SBC Forging going with a Dragonslayer over a Scat 4340. If you want to stay 100% american then hey spend the extra $100., but both cranks are going to hold 1000hp pretty easy. Cranks get eaten up from high duty cycle setups. Meaning if they see high RPM all day long then they are more likely to break vs a low RPM or low cycle life motor.

On top of that Scat now has the 7000 series cranks. They are awesome for engine builders like me because they give you custom crank specs at a forged crank price, so you can have whatever combination you want in a crankshaft and it's almost a off the shelf item. For $300 more a crank that saves a ton of money on having a crank offset ground, ground down and then re-heatreated and nitrited. Needless to say I'm very happy with Scat for coming up with that.

Eagle's cranks have a bad reputation from years ago. Tolerances are not exact and the crank throws are not 100% indexed correctly. Not sure if they have corrected that all yet though.

Remember some of these aftermarket parts are way over designed for what we use them for. A lot of them are rated for 750hp @ 8000rpm, that's a huge difference from 750hp @ 6500rpm. RPM and piston/pin weight is what kills rods for the most part. Some guys have huge cylinder pressure that puts a lot of compression loads on the rods, but that's not the main killer in what you are talking about here. If you had $1200 you could easily get a set of 500g rods for your setup that would hold your power just fine all day long.

Bret

OK Compression wise I will be only running about 11.5-12.0 I am running a Nitrous cam and am basically looking for a decent cruizer but a killer on the gun!! I want to be able to bump it up to 250 if I can. What would you reccomend?

Bret knows more about engine parts than I do, so listen to him! Maybe I am letting my "all-American" bias cloud my judgement! Ditto wrt the good rod bolts. They will add to the cost but are a good investment. I think the ARP2000 would be plenty good, the L19 probably isn't warranted for anything any of us are building. The ARP2000 bolts are in the range of ~$50/set over standard 8740 bolts. I just bought a set of Oliver billet rods and passed on the L19 bolts, they were ~$300 more than the ARP2000. But if Bret feels different, listen to him! In fact, if he says so I will ante up for the L19.

8740 chrome-moly ~190,00psi tensile strength
ARP2000 ~220,000psi
L19 230-260,000psi
ARP3.5 ~270,000psi

Rich Krause

Is tis a good kit?
http://cgi.aol.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33620&item=2450165120
Also, what compression do you'll recomend for a street car?

Originally posted by 94TA_LT1
Is tis a good kit?
http://cgi.aol.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33620&item=2450165120
Also, what compression do you'll recomend for a street car?

Seems to be decent parts, but the description is sketchy. Are wrist pins included? Rings? Locks? You will also need bearings. What specific model are the parts? They (especially the pistons) may or may not be suitable for what you have in mind (boost, nitrous, very high revs, etc.). Is the crank a 1-piece or 2-piece seal? What is the compression height of the pistons? Etc.

As far as CR goes, it depends on the cam you are running as well as the fuel that's available. In general, the bigger the cam (the later the intake valve closes) the higher the static CR you can use. About a year ago there were some informative threads about static and dynamic compression ratio. You may want to do a search and look those up.

Rich Krause

Ok guys heres what I received via email from a shop down south.

I am very interested in the Negative Dome Setup with less compression. Do you think it would be a better setup with the 9.5/1 300 shot(dual stage most likely now), then the other setup with 11.5 with about a 200 shot? The gains he said I would see would be a decent one when sprayed what do you think any comments welcome!! Thanks Guys I appreciate it!!!

I don't agree with the comments on H beams vs I beams. Both are very strong
>rods if made correctly. Some would argue that the I beams can be made a
>little
>lighter due to their design. The Eagle H beams 4340 forged with the
>standrad
>ARP capscrew are good to 675HP beyond that I would recommend going with a
>bolt
>upgrade to the ARP 2000 or L19 capscrew. I have 2 customers making over
>1000HP
>on twin turbo set ups using these rods and the L19 bolts.
>
>For your 355 combo I recommend the following:
>
>Eagle #435334805700 4340 forged crank with 1 piece rear main seal
>$499.00
>Eagle #CRS5700B3D 4340 forged H beam rod
> $325.00
>SRP forged pistons #138081 (11.5/1 compression with your 54cc head)
>$445.00
>
>Total
> $1269.00
>
>FYI I would run lower compression, say 9.5/1 and, use a 250 to 300 shot of
>nitrous. SRP makes a great negative dish piston with a thick crown
>specifically
>for nitrous applications. They are part number 139632 and sell for $495.00

From what Ive been hearing lately after paying attentino to the N2O forum is that nitrous likes compression, so I dont agree with him saying 9.5:1 compression, unless its carbed, dont remember.

If you are running that large of a shot you will need race gas anyway so why not use the most compression available for N/A, above 12 would be best, seen a few people running close to 13 on 94, just requires a little larger cam like Rich said.

When ever I spray I use 110.

hey, how much hp would that kit that i posted above make with a good set of heads and a cam, long tubes,ect.

i use a set up like you want.355 callies billet crank,oliver billet rods
je pistons 11.5.1,i use nitrous have put a 250 shot on it no problems.

scat and eagle both have good stuff and like every thing else each person as there own opinion.

good luck

i was talking about the scat crank from the above link

Well the only part of the rotating assembly that is going to effect HP is the the piston/CR ratio.. cause your power comes from the your induction and exhaust systems (heads,cam,intake/exhaust)

Not entirely true. THe Scat crank is 10 lbs lighter than the stock crank. Well i know the cast Eagle crank is and the scat 9000 is the same weight 49lbs as the eagle. So rotation mass is reduced which will free up some power..
Also if u go lighter pistons and rods that'll help too. Thats 1 reason why people opt SRP or Diamond pistons over Speed Pro which are twice as heavy.

The gains probably wont be much but every little bit counts.

actually. lighter rotating mass wont gain power, but it will let the motor rev faster.

Originally posted by menlatin
actually. lighter rotating mass wont gain power, but it will let the motor rev faster.

Well, no and yes.

If you dyno at steady state rpm steps (no engine acceleration) rotating mass (or part weight) doesn't really effect hp at the flywheel. That's how OEMs rate engines. However, if you measure the flywheel output during engine acceleration, typically 300 rpm/second or 600 rpm/second, there will be less flywheel hp with the heavier parts because some of it is used to spin up the rotating mass. That's the 'no' part.

The 'yes' part is that the engine produced the same "indicated" power, before friction and pumping losses. Of course it's "brake power" or power that actually gets to the flywheel and eventually to the drive wheels that does the job.

Bottom line is that lower weight rotating/reciprocating parts will help increase flywheel (and rearwheel) power whenever the car is accelerating. Some of the very few race engines that run wide open throttle at max power but don't vary rpm much are NASCAR engines at Daytona and Talladega. A couple hundred rpm max. Watch this weekend. Of course they are using very lightweight parts also, but for other reasons, like friction, durability, and the only times they do accelerate: after pit stops and yellow flags.

My $.02

The only SCAT cranks ten pounds lighter are definitely more expensive but they do make some SBC cranks and stroker cranks etc that are even up to 12 pounds lighter. I have a 43 pound 3.750 right now but it's more like a 1000.00 crank and the regular Eagle stuff is half that.

Well... seing these threads make me worry a bit.. I hope my crank doesn't break at 6400rpm and 700rwhp...

I know intimd8 did 775rwhp with his eagle crank no problems... My engine builder found none with my crank though...

we'll see how it holds up... I have eagle forged rods... anyways.. I do hope they hold and if they dont, lunati bottom end...

I always thought the first thing that went where pistons, if you had good pistons and a "street" car you wont likely break it...

I HOPE and I will see ;)