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Discussion Starter #1
Hi all, I know that the 400 sb takes shorter rods than normal and all, but I am curious if 6 in. rods can be used, or if this will cause the piston to protrude out the top and bottom of the bore? If these don't jive, is there any advice.opinions on stock length vs. a longer, compatible rod? I know there was a similar topic elsewhere, but I didn't think it addressed this issue directly.

Thanks in advance for any info,
BW
 

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stock 400 rods are 5.56, and most people will go w/ a 5.7 (350 type rod) or a 6.0 rod to achieve a better rod/stroke ratio, and reduce sidewall loading of the piston. i went w/ a 5.7 rod in my motor, and you can go w/ a 6.0 rod, but any h.p. gains are small. you have to have a piston designed to utilize whatever rod length you choose, and pistons are readily available for each. my feelings are the 5.7 rod is better than the stock rod, and clearance isnt as big an issue as w/ the 6.0(although you do have to slightly clearance the side of the rod on #1,2,5,6, for clearance of the cam w/ any other than stock length, but no biggie) if you have good stock pistons, just go w/ the stock rod, but if you need pistons, id get a 5.7 or 6.0 rod/piston. hope that helps
 

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Discussion Starter #3
Indeed that does help. I can totally see the reason for needing to allow clearance on longer rods (simple mechanical resoning I suppose), but is there any actual advantage to a longer rod other than less side loading? If not, then what might one expect to see, wear-wise, from a stock rod as opposed to a 5.7" or 6" rod under normal use (daily driver with the odd "show off" moment)? All info is greatly appreciated, as I am rather unfamiliar with this particular theory.
 

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Here's a link to a rod length study with some hard numbers: http://www.aros.net/~rbuck/rick/rodstudy.htm

You'll find very little difference between a 5.565 stock 400 rod and a 5.7 rod in a daily driver. When you're having that 'show-off' moment, just say you've got long rods, who's gonna check?

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1967 Nova coupe daily driver
406, 10:1, 224° cam, Q-jet, 700R4, 3465# w/driver
11.76 @ 116 thru the mufflers
18 mpg on the road
 

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I'd go with the 5.7's. I priced the diff of a 5.7 rodded engine vs. a 6.0. The 6.0 was about $300 higher with machine work and pistons with non-tradidtional rings spacings for the six inchers aren't cheap either.

I wouldn't use the 5.565 inch stockers. They're no good...powder coated stuff...unless you can find a good forged aftermarket rod in that size. Choices would be probably be limited though.

Good luck with your 406!
 

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Discussion Starter #6
Wow, that link was extremely helpful! I guess in a nutshell, it doesn't really matter what rod I use for my apllication, as the differences are so small. I think I will base my purchase on price, quality, and availability in this case. Thank you all very much for the help, my question is answered fully.
 

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I went through the same thing you are. After a bunch of evaluation, I went with the 5.7 Lunati rods. They have a set of 4340 I beams with cap screws ( better clearances than bolts) for 299 USD. A very nice looking forging, tested for 1 million cycles. I have always had good luck with Lunati products.
 

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I've agonized over rods for quite awhile now and actually came to a couple of conclusions. First, while longer rods aren't truly necessary for the average street motor - the cost difference is so small for stepping up to the 5.7" rods that it doesn't make sense not to. The cost for rebuilt rods or new rods is basically the same for either stock 400 rods or the 5.7". Same for pistons set up for either rod. I went with the 5.7" rod and feel like it was a good decision. Going to a 6" rod costs quite a bit more so it probably doesn't make sense for the average guy.

The second conclusion is that it probably would be a very wise decision to invest in new rods. Forged or cast - whatever fits your needs. The Lunati rods mentioned sound like a great set. Maybe the Summit brand forged rods as well and I'm sure there are others. I personally don't see the need to spend $500 or $600 for a set but I'm just the average street guy.

The standard path seems to be rebuilding stock rods unless you're shooting for really serious power. Maybe if you get your own rods rebuilt and you know their history you're fine. But what if they came out of a million mile taxi? Or out of some schmuck's motorhome that overheated back and forth across the country for years? Or a blown up budget racing motor? Who knows what kind of abuse they've been subjected to? Next time around I'm buying new rods if for nothing else but piece of mind. Just my humble opinion.

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Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1
 

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I think that you would have a problem using 6 inch rods in a stock 400 block. You would probably have to notch out the pan rails and grind on the rods or rod bolts not to hit the cam. I think you have been given ideas using the lunati 5.7 street rod.

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SCOTT
69 RS-SS 396 4-SPEED
 

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in addition to what i said earlier, you can plan on some grinding of either a 5.7 or 6.0 rod, especially w/ an h-beam, which IMO is overkill with just about any street or street srtip motor. just extra weight. you really should be ok on the pan rail w/ an i-beam rod, i know i had a mile w/ my 5.7 . the idea of a cap screw rod as mentioned is a darned good one, because you do have more clearance and you aren't touching the rod bolt at all w/ clearancing. another thing i did is ordered a cam w/ a small base circle, but even then when i checked it it was too close for me (about .030") so i touched up the rod a tad bit. you simply must mock any unusual combo up, and check everything. as for cost of a 6.0 rod, for about 100$ more i could have ordered the same rotating assembly w/ 6.0 rod set up, but i dont like the fact that you have to use a rail support ont the oil ring, because the pin is so high up in the piston, also more prone to rock in the bore, i would imagine. the horsepower gains are minimal ,at best. just my .02
oh yeah, another thing, one of my buddies just put his 406 together for the end of last season, it consisted of a stock 400 crank, .010,.010 , stock 5.7 rods w/arp bolts, a solid roller cam, brodix track one heads a vic. jr. and a demon carb, in a 72 nova, 10" tires, ran a 10.90 his first (and only) day out. so, although probably not recomended, stock stuff can take some abuse.

[This message has been edited by 68rs406 (edited 02-28-2002).]
 

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My brother started building a 400 25 years ago. The family came and the 400 went on the back burner. A couple of years ago he got it back out. So with three kids at home this was going to be a budget motor. He honed the rust out of the cylinders and it has .040 ring end gap. Cut about .060 off the top of the factory dish pistons, mached up each piston and flycut each piston for valve clearance, match weighted each piston and rods(I think he used 5.7) stock cast crank,A old set of chevy turbo angle plug heads that he just laped in the valves,an old lunati bracketmaster 285 cam, air gap intake,750 holly. msd box and accell dist. Its in a 71 3400 chevelle with a olds rear with 390 gears. Every thing on this car came from the bargin bin with nothing sent out to the maching shop. It runs 11.70 at 112 with 1.60 sixty foot times. He has about 1,700 in the motor.The 350 turbo in it is the orignal one with 250,000 miles(we're waiting for it to explode). The only part new was a 3,000 stall converter. I know this is getting long but it just shows you what being a little creative and long rods with a good combination can do.
 

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hope im not to late and you are not done i think you got some good advice here on a 400 i have built on my self using the 5.7 rods scat crank dart heads roller cam in 6,s etc the one topic never touched was windage no one makes a windage tray for a 400 but the diamond stripper can be modified for the 400 main bolts also moroso trap door pan and most importantly milodon main stud kit to properly space the tray away from crank also a 400 uses a special oil pump rod not a 350 rod and if you are concerned about cam clearance have your cam choice ground on a small base circle. my 406 winds to 7000 with ease never smokes and is a lot of fun need any help give me a yell [email protected]
 
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