Taking the jump to a 396
10-04-2013, 06:01 PM
#1
Taking the jump to a 396 So, I come to the boards as always for advice...
I'm scooping up a 4.1" crank tomorrow. 4340 Eagle. I'm trying to piece in my head how to get a true 396, but I'll settle for a 393/5.
I'm aware of the consumption issues, but technology has come a ways as well. I'm thinking Brian Nutter at Wiseco has a few tricks up his sleeves.
Still looking around for some good 6.125 rods.
**I think**
I've seen this 393 eagle kit advertised different places, and while the crank is the same 4.1" in the description, the rod sizes are listed different. Some say a 6.2 rod, some say a 6.125.
What will each do, and how will displacement be affected?
Also, block will be sonic checked and completely gone over. All options are on the table. 3.903, 905, 908. I'm aware of a single person going 3.915, but I'm more leaning towards 3.905
Thanks gents.
I'm scooping up a 4.1" crank tomorrow. 4340 Eagle. I'm trying to piece in my head how to get a true 396, but I'll settle for a 393/5.
I'm aware of the consumption issues, but technology has come a ways as well. I'm thinking Brian Nutter at Wiseco has a few tricks up his sleeves.
Still looking around for some good 6.125 rods.
**I think**
I've seen this 393 eagle kit advertised different places, and while the crank is the same 4.1" in the description, the rod sizes are listed different. Some say a 6.2 rod, some say a 6.125.
What will each do, and how will displacement be affected?
Also, block will be sonic checked and completely gone over. All options are on the table. 3.903, 905, 908. I'm aware of a single person going 3.915, but I'm more leaning towards 3.905
Thanks gents.
Last edited by dr_whigham; 10-04-2013 at 07:53 PM.
10-04-2013, 06:31 PM
#2
Erik Koenig has some custom pistons he uses for the long stroke stuff. I think him and Brian came up with the design to minimize the rocking at BDC. Everything is moved up higher in the piston, so I think he uses a 6.20" rod with it. Email Erik and he can get you lined out with a set.
10-04-2013, 06:32 PM
#3
Erik Koenig has some custom pistons he uses for the long stroke stuff. I think him and Brian came up with the design to minimize the rocking at BDC. Everything is moved up higher in the piston, so I think he uses a 6.20" rod with it. Email Erik and he can get you lined out with a set.
10-05-2013, 07:24 AM
#4
I've seen this 393 eagle kit advertised different places, and while the crank is the same 4.1" in the description, the rod sizes are listed different. Some say a 6.2 rod, some say a 6.125.
What will each do, and how will displacement be affected?
Also, block will be sonic checked and completely gone over. All options are on the table. 3.903, 905, 908. I'm aware of a single person going 3.915, but I'm more leaning towards 3.905
Thanks gents.
What will each do, and how will displacement be affected?
Also, block will be sonic checked and completely gone over. All options are on the table. 3.903, 905, 908. I'm aware of a single person going 3.915, but I'm more leaning towards 3.905
Thanks gents.
Did you have a few adult beverages before posting that?
Bore and stroke are all that effect displacement.
Since pistons are the hard part, let the piston guy tell you what rod length he wants you to use.
10-05-2013, 07:51 AM
#5
No, I'm stuck offshore on a drill ship riding out tropical storm Karen.
Sorry. I was curios if the rod size would affect it at all, or if there were any pros and cons between the two.
Anyways, bought the crank, so it's a done deal.
Sorry. I was curios if the rod size would affect it at all, or if there were any pros and cons between the two.
Anyways, bought the crank, so it's a done deal.
10-05-2013, 10:02 AM
#7
6.125"/4.1"=1.4939"...rod to stroke ratio...piston comp. height of 1.065"
6.200"/4.1"=1.5122"... " " " " ... " " " " 0.990"
Since the ratio improves only by 1.2% I'd opt for the slightly taller piston to
add bore stability, less rocking, ring flutter, oil & compression blowby, blah,
blah, blah....perhaps either a Wiseco or Mahle with the skirt coating to help
with friction and I wouldn't rev this thing much past 6500 as the big ends of
the rods will be traveling 1.49" more distance each revolution (13.45 ft/sec)
.....thats a ****-TON of additional piston speed as well. What block are you
planning on using ???? New LS 3 blocks are only around $1450 bucks and
your new crank in a 4.070" bore would only be 4 hundred and twenty seven
inches of dare I say rectangle headed NASTY !!!!!........
6.200"/4.1"=1.5122"... " " " " ... " " " " 0.990"
Since the ratio improves only by 1.2% I'd opt for the slightly taller piston to
add bore stability, less rocking, ring flutter, oil & compression blowby, blah,
blah, blah....perhaps either a Wiseco or Mahle with the skirt coating to help
with friction and I wouldn't rev this thing much past 6500 as the big ends of
the rods will be traveling 1.49" more distance each revolution (13.45 ft/sec)
.....thats a ****-TON of additional piston speed as well. What block are you
planning on using ???? New LS 3 blocks are only around $1450 bucks and
your new crank in a 4.070" bore would only be 4 hundred and twenty seven
inches of dare I say rectangle headed NASTY !!!!!........
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10-05-2013, 10:17 AM
#8
6.125"/4.1"=1.4939"...rod to stroke ratio...piston comp. height of 1.065"
6.200"/4.1"=1.5122"... " " " " ... " " " " 0.990"
Since the ratio improves only by 1.2% I'd opt for the slightly taller piston to
add bore stability, less rocking, ring flutter, oil & compression blowby, blah,
blah, blah....perhaps either a Wiseco or Mahle with the skirt coating to help
with friction and I wouldn't rev this thing much past 6500 as the big ends of
the rods will be traveling 1.49" more distance each revolution (13.45 ft/sec)
.....thats a ****-TON of additional piston speed as well. What block are you
planning on using ???? New LS 3 blocks are only around $1450 bucks and
your new crank in a 4.070" bore would only be 4 hundred and twenty seven
inches of dare I say rectangle headed NASTY !!!!!........
6.200"/4.1"=1.5122"... " " " " ... " " " " 0.990"
Since the ratio improves only by 1.2% I'd opt for the slightly taller piston to
add bore stability, less rocking, ring flutter, oil & compression blowby, blah,
blah, blah....perhaps either a Wiseco or Mahle with the skirt coating to help
with friction and I wouldn't rev this thing much past 6500 as the big ends of
the rods will be traveling 1.49" more distance each revolution (13.45 ft/sec)
.....thats a ****-TON of additional piston speed as well. What block are you
planning on using ???? New LS 3 blocks are only around $1450 bucks and
your new crank in a 4.070" bore would only be 4 hundred and twenty seven
inches of dare I say rectangle headed NASTY !!!!!........
A 4.070 sonic checked iron 6.0 has crossed my mind, but theres just something about the 396 that has always intrigued me. I had an old 65 Chevelle back in the day with a 71 Chevelle SS 396 motor in it. I was hooked after that.
It'll be going in my LS1. Not an 1168 block like I thought, but literally looks identical. No ridges inside the valley area, all the telltale signs of an 1168 block. So it's definitely one of the newer ones.
This will be paired with a set of Mast 240cc small bore LS3's and either an LS3 intake, or a Mast CNC'd 2 piece with a 4150.
It's not necessarily a number I'm after. I just want something completely opposite spectrum and different.
10-05-2013, 11:47 AM
#9
[QUOTE=dr_whigham;17730935]Decisions decisions.
A 4.070 sonic checked iron 6.0 has crossed my mind, but theres just something about the 396 that has always intrigued me. I had an old 65 Chevelle back in the day with a 71 Chevelle SS 396 motor in it. I was hooked after that./QUOTE]
From the truth and corrections department: the bore size on the 71-72
engines was actually 4.154" instead of 4.094" but GM continued to call them
396s.....this also explains why some pickup trucks had fender badges that
said 400-8 but they could be either the GEN I mouse or the 402 RAT motor.
Ironically the General bored them out .030" to reduce emissions...funny how
they knew about that whole valve shrouding thing over 40 years ago ????
BTW the 65 is still one of my favorite years for Chevy....The A-bodies were
tight, little, and boxy..very sleeperish, The Novas were a stand alone 1 year
only shape, The Vettes got the Mark IV Rat and the only year a 396 was in
them, The Imps had the 1 yr only round tail lights and could also be had w/
the 425hp/396 Vette engine.....even wagons looked cool...sorry to ramble on
A 4.070 sonic checked iron 6.0 has crossed my mind, but theres just something about the 396 that has always intrigued me. I had an old 65 Chevelle back in the day with a 71 Chevelle SS 396 motor in it. I was hooked after that./QUOTE]
From the truth and corrections department: the bore size on the 71-72
engines was actually 4.154" instead of 4.094" but GM continued to call them
396s.....this also explains why some pickup trucks had fender badges that
said 400-8 but they could be either the GEN I mouse or the 402 RAT motor.
Ironically the General bored them out .030" to reduce emissions...funny how
they knew about that whole valve shrouding thing over 40 years ago ????
BTW the 65 is still one of my favorite years for Chevy....The A-bodies were
tight, little, and boxy..very sleeperish, The Novas were a stand alone 1 year
only shape, The Vettes got the Mark IV Rat and the only year a 396 was in
them, The Imps had the 1 yr only round tail lights and could also be had w/
the 425hp/396 Vette engine.....even wagons looked cool...sorry to ramble on
10-05-2013, 03:32 PM
#11
Eagle used to make a 3.900" stroke crank...all you'd have to get is a 4.020" piston for that stroke and the 6.125" rods and its dead on 396ci...plus you still have a little more bore than stroke...not sure how you feel aboug that though. I believe another company makesa 3.900" stroke crank too but I can't remember who.
10-05-2013, 07:36 PM
#12
Eagle used to make a 3.900" stroke crank...all you'd have to get is a 4.020" piston for that stroke and the 6.125" rods and its dead on 396ci...plus you still have a little more bore than stroke...not sure how you feel aboug that though. I believe another company makesa 3.900" stroke crank too but I can't remember who.
I really want this motor topped off with the Mast Small Bore LS3's. I think it'll be a nice punchy combo, with a broad powerband, and flat torque curve.
Custom cam from Ed Curtis, of course...
10-05-2013, 08:25 PM
#13
We have done similar builds in the past and have used 6.3" connecting rods and pistons designed for a 4.1" application. There won't be consumption issues like you have heard about on these boards. If you have someone who is knowledgeable about how it should be designed it will work out fine. Good luck with your build.
10-05-2013, 08:39 PM
#14
We have done similar builds in the past and have used 6.3" connecting rods and pistons designed for a 4.1" application. There won't be consumption issues like you have heard about on these boards. If you have someone who is knowledgeable about how it should be designed it will work out fine. Good luck with your build.
What manufacturers have you guys went with?
10-06-2013, 12:57 PM
#17
Scat is probably the best bang for the buck IMHO. The I beams are like $300, and will be more than enough for what you are putting together, or you can use the H beams, which I've used in a LSA that made over 750whp on a Mustang dyno. They were $400, lol.
10-06-2013, 02:43 PM
#20
It depends how squeezed I am at the end. I'm not putting 1800 into these heads to get them where I want, and I'm pretty set on the Mast small bore LS3's. I'll probably wind up selling them loaded, sell the cam, as well as the Fast 92 with the 42# injectors.