400 sbc build questions
Thread Starter
Moderator
Joined: Jun 1999
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From: Dove Mountain Arizona
400 sbc build questions
I'm a C2 guy but am building up a 400 sbc engine. .030 makes it a 406. The question I have is would you use 5.7" or 6" rods? Looking for streetable 425-450hp with 500+ torque on pump gas and the benefits of either length rod. Thanks
Team Owner
Joined: Oct 2004
Posts: 23,831
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From: Springfield MO
St. Jude Donor '07
I've decided to go with 6.00" rods. There was a thread on rod length and 400 SBCs here a few months back, it might be in the archives already.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
The 6 inch rods will put the piston pin up in the oil ring land. This will require a spacer for the oil ring. Not a big deal. I went with 5.7 rodsin my stroker buildup. The guy who machined my block also builds race engines and said the 5.7s will produce the pretty much same HP. He likes the 5.7 rods so that is what I went with. I'm not afraid to take it to 7000 rpm ad have done so many times. I don't think you will go wrong with either one, just get a good quality rod. I think that is most important.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
If I had to choose between the 5.7 rod and 6.00 rod piston
with an oil ring support believe I would just go 5.7. But JE
and probably others have a piston using .043 rings instead of
the more regular 5/16 that uses a 6.00 rod and no oil ring support,
the thinner rings and probably pushed closer together makes it
work. thinner rings would mean less friction and they claim 70
percent of friction in an engine is caused by the rings. The new
LS/1 ZO6 uses thinner milimeter rings, my guess to create less
friction make the engine more efficient for both power and fuel
consumtion. original 50s 3.00 stroke small block had a 1.90
rod ratio, chevy never built a taller deck block took cheap way out
kept stroking enigine no new block. late model LS1 has taller 9.20
block 6.125 rods around a 3.90 stroke, took chevy long enough to
start doing it right. My guess is the original designers designing in a
1.90 rod ratio had it right. Just my 02 5.7 rod will work.
with an oil ring support believe I would just go 5.7. But JE
and probably others have a piston using .043 rings instead of
the more regular 5/16 that uses a 6.00 rod and no oil ring support,
the thinner rings and probably pushed closer together makes it
work. thinner rings would mean less friction and they claim 70
percent of friction in an engine is caused by the rings. The new
LS/1 ZO6 uses thinner milimeter rings, my guess to create less
friction make the engine more efficient for both power and fuel
consumtion. original 50s 3.00 stroke small block had a 1.90
rod ratio, chevy never built a taller deck block took cheap way out
kept stroking enigine no new block. late model LS1 has taller 9.20
block 6.125 rods around a 3.90 stroke, took chevy long enough to
start doing it right. My guess is the original designers designing in a
1.90 rod ratio had it right. Just my 02 5.7 rod will work.
Intermediate
Joined: Apr 2007
Posts: 38
Likes: 0
From: Baltimore MD
The longer the rod, the less side loads on the piston and the slower the piston speed. The only time a short rod is preferred would be on a really heavy nitrous engine.
Former Vendor
Joined: Nov 2005
Posts: 683
Likes: 1
From: Mounds View Minnesota
I used 5.875" rods in my 434, 6" rods were way too long for a 4" stroke!
But realy, unless you are circle track racing and running at high RPM and need every last ounce of performance I don't think it matters at all
But realy, unless you are circle track racing and running at high RPM and need every last ounce of performance I don't think it matters at all
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Your best practice is to buy the pistons and rods as a set. That way you know that they work together.
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Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
Drifting
Joined: Jan 2004
Posts: 1,991
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From: Piscataway NJ
Just something to check on these 400 blocks. I read a post earlier that some of the 400's were not drilled or tapped for the power steering pump bracket at the front of the blocks. It's an easy fix if you are at the building stage. Then after you drop it in and find out later
Instructor
Joined: Jun 2005
Posts: 236
Likes: 0
From: Cedar Rapids Iowa
Will be picking up my motor this week (406). I used 6" rods to keep the pressure off the side walls. From researching it out, its a toss up between the 5.7 and 6. Anyway looking forward to the new power over the 355. As long as the weather permits.
Thread Starter
Moderator
Joined: Jun 1999
Posts: 7,117
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From: Dove Mountain Arizona
Most higher end rod manufactures list HP rating for their I beam and H beam rods. Generally the gram weight of a rod is a give away as to its potential. lighter Oliver forged I beams @ 540 grams might top out at 500 max hp. Where 680 gram H beam forgings might exceed 850
Your best practice is to buy the pistons and rods as a set. That way you know that they work together.
Your best practice is to buy the pistons and rods as a set. That way you know that they work together.
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Just something to check on these 400 blocks. I read a post earlier that some of the 400's were not drilled or tapped for the power steering pump bracket at the front of the blocks. It's an easy fix if you are at the building stage. Then after you drop it in and find out later
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
I'm confused, shouldn't I be able to order any 400 ci engine piston for a 5.7" rod? I was going to use the ones with the teflon coating on the skirts, can't remember the manf right now, they have a lighting bolt on the side. Got them in my 355 now and they've been perfect.
