Crankshaft questions
03-03-2011, 12:19 PM
#1
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Crankshaft questions What's everyone's opinions on the following crankshafts? I've seen alot of people make negative comments about Eagle cast 3.75" cranks, but I haven't seen any specific reasons why or failure reports.
1. Eagle cast 3.75"
2. Scat cast 3.75" for 5.7" rods (external balance)
3. Scat cast 3.75" for 6" rods (internal balance)
4. Eagle Forged 3.75"
The application would be NO nitrous, 400 - 450 rwhp, forged pistons, Scat 4340 I-beam rods with capscrews. About 6,500 rpm limit.
I know the Forged crank is the best option, but is it really needed at this level? The factory cast cranks hold up fine at this power level. Are aftermarket cast cranks that poor quality? Are Scat cranks better than Eagle? I haven't read any complaints about there cast 383 cranks.
1. Eagle cast 3.75"
2. Scat cast 3.75" for 5.7" rods (external balance)
3. Scat cast 3.75" for 6" rods (internal balance)
4. Eagle Forged 3.75"
The application would be NO nitrous, 400 - 450 rwhp, forged pistons, Scat 4340 I-beam rods with capscrews. About 6,500 rpm limit.
I know the Forged crank is the best option, but is it really needed at this level? The factory cast cranks hold up fine at this power level. Are aftermarket cast cranks that poor quality? Are Scat cranks better than Eagle? I haven't read any complaints about there cast 383 cranks.
03-03-2011, 12:34 PM
#2
What's everyone's opinions on the following crankshafts? I've seen alot of people make negative comments about Eagle cast 3.75" cranks, but I haven't seen any specific reasons why or failure reports.
1. Eagle cast 3.75"
2. Scat cast 3.75" for 5.7" rods (external balance)
3. Scat cast 3.75" for 6" rods (internal balance)
4. Eagle Forged 3.75"
The application would be NO nitrous, 400 - 450 rwhp, forged pistons, Scat 4340 I-beam rods with capscrews. About 6,500 rpm limit.
I know the Forged crank is the best option, but is it really needed at this level? The factory cast cranks hold up fine at this power level. Are aftermarket cast cranks that poor quality? Are Scat cranks better than Eagle? I haven't read any complaints about there cast 383 cranks.
1. Eagle cast 3.75"
2. Scat cast 3.75" for 5.7" rods (external balance)
3. Scat cast 3.75" for 6" rods (internal balance)
4. Eagle Forged 3.75"
The application would be NO nitrous, 400 - 450 rwhp, forged pistons, Scat 4340 I-beam rods with capscrews. About 6,500 rpm limit.
I know the Forged crank is the best option, but is it really needed at this level? The factory cast cranks hold up fine at this power level. Are aftermarket cast cranks that poor quality? Are Scat cranks better than Eagle? I haven't read any complaints about there cast 383 cranks.
03-03-2011, 01:03 PM
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I was really leaning towards #3. I know that there isn't a whole lot of money from one to the other, but it all adds up & I'm really comparing the cost towards sticking with the stock crank with just upgraded rods/pistons. Not just cast 383 vs forged 383 cranks.
03-03-2011, 01:06 PM
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I would be more particular about which pistons I ran... at that level any of those cranks would do fine. Def get the 6" rod crank.
Also if your only gonna spin it to 6500 and only 450 rwhp a good hypr-eu piston would do fine.
Also if your only gonna spin it to 6500 and only 450 rwhp a good hypr-eu piston would do fine.
03-03-2011, 01:17 PM
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If your going for 400-450 HP I would just stick with the stock crank. They have been proven to handle a lot more than that. Just saying its not necessary to buy a new crank unless you just want one
03-03-2011, 01:38 PM
#7
if you want to go stroker that cast scat crank should hold up just fine at your power level........if you stay stock the stock crank wwill hold quite a bit.......I've never seen one break yet.....and stay away from hyperutectic pistons.......they're garbage
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03-03-2011, 01:51 PM
#8
I am running a cast eagle 383 kit with no problems. key is to not go ape **** on rpm and power imo. also invest in a quality tune.
mine revs to about 6-6100rpm and made about 380rwhp through a stalled auto. cam has decent duration but LSA and lift is pretty mild.
mine revs to about 6-6100rpm and made about 380rwhp through a stalled auto. cam has decent duration but LSA and lift is pretty mild.
03-03-2011, 02:07 PM
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Yes, there are great quality pieces, but out of my budget and if I need that good of a crank at those levels I will just stay with a 355.
I like the stock cranks just fine, I'm just considering adding some cubes while building if the expense isn't that great.
Definately going Forged pistons and 4340 I-beam capscew rods no matter whether it's 3.48" or 3.75" stroke.
Good info. I'm just wanting kind of mild and reliable. I already have most all the parts for my build except for a rotating assembly and a spare block.
Good info. I'm just wanting kind of mild and reliable. I already have most all the parts for my build except for a rotating assembly and a spare block.
03-03-2011, 02:24 PM
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I ran into cut hours at work while doing my build. But my motor is done Ive built a 355 with the Scat forged 6 inch rods and forged Mahle pistons. I stuck with the stock crank with the build. Is 355 what your thinking ?
03-03-2011, 03:06 PM
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Either a 355 with the stock crank, or a 383 with a budget crank since the extra cost would only be about $300 or so. I've already got to buy pistons, rods, and balancing. The difference would mostly be between the cost of the 383 crank and having the stock one turned.
03-03-2011, 03:10 PM
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I got lucky on rods and pistons, I found them NIB from a guy who was doing the same build as me but he changed his mind. Look out in the Classifieds never know what you might find. As the guy said above there is a guy selling a cola crank in there along with a 4 bolt main block
03-03-2011, 03:15 PM
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I got lucky on rods and pistons, I found them NIB from a guy who was doing the same build as me but he changed his mind. Look out in the Classifieds never know what you might find. As the guy said above there is a guy selling a cola crank in there along with a 4 bolt main block
Also that ad lists the pistons as standard bore - 4.125", but LT1's are 4" bore. I don't imagine that his 4 bolt block is one of the few rare siamesed bore LT1 blocks that got released? If so it would be over 2K for just the block.
03-03-2011, 03:37 PM
#15
if you're willing to spend a little extra Ohio crank has forged cranks for a little over $400. ramair95 is running one I believe among others. they're who I'll be going with on my next build.
03-03-2011, 03:45 PM
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the cost won't be much different honestly. my friend ended up buying a cast eagle crank for his old LT1 he was rebuilding because it was actually cheaper than having his stocker turned at a local machine shop.
if you're willing to spend a little extra Ohio crank has forged cranks for a little over $400. ramair95 is running one I believe among others. they're who I'll be going with on my next build.
if you're willing to spend a little extra Ohio crank has forged cranks for a little over $400. ramair95 is running one I believe among others. they're who I'll be going with on my next build.
I've used there parts in BBC's and have friends who run them too. One friend has a 598" from them.
03-03-2011, 06:08 PM
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Ive had bad luck with the cast cranks, the first one an eagle 3.75 inch stroke ate the thrust bearing, and tore up the thrust surface on the crnk beyond repair, almost ruined the block. The second had the snout break off, key is it was N/A. My present crank is doing fine, its the 4340 non-twist Eagle peice, using the same flexplate and converter that was used on the other motor that ate the thrust bearing. Oiling was fine on both motors and the one that ate thrust bearings actually made really good power until I was just no longer comfortable rolling a new thrust bearing in every few months...lol. The clearance finally got too great for my liking there.
My present motor is said crank with Scat pro mod rods (4340 I beams, cap screws) and -11 cc Speed pro lightweight forged pistons, coated, and with the 1/4 inch rings. I had the block "0" decked to make the compression right around 11:1 where i wanted it. I have not had this motor on a Dyno yet but it runs very strong in any gear, and knocks down low 11s over 120 mph without breaking a sweat. Total short block cost (minus cam) was 2300$ with machining.
My present motor is said crank with Scat pro mod rods (4340 I beams, cap screws) and -11 cc Speed pro lightweight forged pistons, coated, and with the 1/4 inch rings. I had the block "0" decked to make the compression right around 11:1 where i wanted it. I have not had this motor on a Dyno yet but it runs very strong in any gear, and knocks down low 11s over 120 mph without breaking a sweat. Total short block cost (minus cam) was 2300$ with machining.
