We are about to build two 400's. I am confused as to whether to run 5.7 or 6.0 rods. What does it all mean? Also, one machinist friend says to get an Eagle crank and internally balance it. I was thinking of going Scat externally balanced.

Even extremely prejudiced opinions are appreciated.

Thanks,

Jim

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1975 Camaro
1973 Trans Am 455, 4-spd
1971 Firebird

5.7 rods are just fine. I'd opt for the Scat crank and rods.

Rod lenght really depens on what the engine will be used for. If it's just a weekend toy 5.7" will be good, but if you have to buy rods and pistons anyway and price diff. aint too much, you might as well go to a 6" rod.

The longer rod lenght will load the thrust side of the cyl bores less. Also it gives a better rod/stroke ratio, and causes the piston to dwell at TDC longer. Longer rods can also help fight detonation.

I tend to go with the thinkings of the late, great Smokey... "use the longest damn rod that will fit in the block"


As far as the brand of crank... IMO Stay away from Eagle. Both Eagle and Scat are offshore made cranks, but theres a diff in the two. Eagle finish machines the cranks offshore. Scat ships the cranks back to the USA and finish machines them in CA.

Every Eagle crank I have seen has needed work done to em, just to be with in spec., and it's really sad when you pay $150-400 for a crank then have to have a machine shop polish it (if your lucky) or turn it.

Now Eagle Rods seems to be one of the better brands of cheaper priced rods.

I like internally balanced engines myself just for the simple fact of damper and flexplate replacements.

Definitely use the Scat stuff. Eagle's QA is horrible.

On the 383 engines that we have built for the street we have used all Scat 4340 Cranks And the Scat 6 inch rods with 7/16 bolts and by going with the long rods you can go with a internally balanced crankshaft. And we have been using the SRP pistons as have always stayed away from the Hyper pistons as there seems to be a lot more issues with them over the forged cause when its all said and done its still a CAST PISTON THATS VERY BRITTLE.

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WWW.CNCBLOCKSNORTHEAST.COM (http://WWW.CNCBLOCKSNORTHEAST.COM)
IS A DIVISION OF HINKSON AUTOMOTIVE
RESEARCH & DEVELOPMENT

[This message has been edited by CNC BLOCKS (edited August 16, 2005).]

Use the size you have, Or if you have to buy I would get 6.0s

Like they said, 6" is marginally better than 5.7". If you go with 5.7" you've accomplished 95% or more of what you'll gain, but if there is minimal cost impact, go with the slightly better 6". Whatever you do, try to avoid reusing the original 400 rods.

I'm using 6" in the engine I'm building on my engine stand now. I'm also using SRP pistons, so at least I'm putting my money where my mouth is. When all my machine work was complete and I was talking with my machinist after we loaded up my truck with my block and all my newly balanced parts, my machinist said that they found that Eagle crankshafts often had hourglass shaped journals. If you measured them close to the middle, they'd mike out oversized but towards the sides they'd be a bit small. He said the Scats never had any problems. I've heard of problems with Eagle crankshafts but never problems with Scat (doesn't mean it never happens, I just never found out about any). However, I've heard from the same sources that both Eagle and Scat rods are outstanding.

If you're buying new cranks and rods then go for the 6", you won't be RPM restricted by the external balancing and the resale value of the engine will be greater IMHO. Forged pistons only due to the short compression height.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

<font face="Arial,Verdana" size="2">Originally posted by Rick WI:
5.7 rods are just fine. I'd opt for the Scat crank and rods.

</font>

Heres and extreamly prejudiced opinion!!!!
I'm pulling a Eagle 4340 crank OUT and replacing it with a Scat, yes it will be Scats upper end pro-lightened, scalloped counterweight crank, and you can BET it damn sure will be finish machined to the RIGHT size,, unlike this Eagle POS. My machinist has them in his 1200HP blown alcohol sbc motor drag boat motors and has not has a crank failure YET. The scat Pro crank is only $400 cheaper than the Lunati racer series crank, but the reputation they are gaining makes them one of the best crank buys on the market today. You would have to GIVE me another Eagle crank before I'd use it. Your on the right path Burt, stay away from the eagle cranks.

If you EVER have aspirations of making your 400 a 434 go with a 6" rod NOW so you don't have to replace them later. I don't think it's even possible to use a 5.7" rod in a 4" stroke sbc. So with a 6" rod now you would be saving the possibility of having to change rods 'of' you ever wanted to go for broke with your little mousemotor.

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Proud member of the "bright side"
Track toy (http://www.small-block-chevy.com/nova.htm) 9.94 @ 133 n/a Small Block (and we aint done yet!)
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ET X708
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Weekend Grocery getter (http://www.small-block-chevy.com/md_toy.htm) 12.3's through the mufflers on DOT's, in street trim

Marv,

Thanks for the info. If I use the 6" rods and my bore is .030 over, will that make 434?

Where do you think is the best place to get the Scat cranks and rods?

I really appreciate your advice and will go the 6" route as both engines need cranks anyway. By the way, is you engine internally balanced?

Thanks,

Jim,

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1975 Camaro
1973 Trans Am 455, 4-spd
1971 Firebird

<font face="Arial,Verdana" size="2">Originally posted by Burt:
Marv,

Thanks for the info. If I use the 6" rods and my bore is .030 over, will that make 434?

Where do you think is the best place to get the Scat cranks and rods?

I really appreciate your advice and will go the 6" route as both engines need cranks anyway. By the way, is you engine internally balanced?

Thanks,

Jim,

</font>

The bore is the bore, and the stroke is the strroke, changing rods don't do nothing to cubic inches.
To make your motor a 434 you will need to short fill the block, clearance it for a 4" stroke, get a 4" stroke crank, get pistons with a 1" compression height for the 6" rod 4" stroke combination (434), run a small base circle cam and fight through all the rest of the stroker crap. By the time you spend $3-4k on a short block your not going to scrimp and external balance. The thing is when your done the big inch small block makes KILLER FREEKING TORQUE (http://www.small-block-chevy.com/UPNUP2.JPG).

Parts are parts,, I'm running 6" Lunati ProMod rods and the few places that sell them all get about the same price my machinist sells them for. Same with Scat,, I think Speed-o-motive or Flatlander.com probably offer a few buck price advantage, but remember your buying a box of parts (and especially if you pick Speed-o-motive), not a finished combination. You would be MUCH wiser to deal with a local trustworthy, reputable machine shop and bite the bullet for sales tax and the slight markup.

Marv, as I read between the lines......yes your correct, the Eagle stuff sucks D*ck.

NOW, given that when I did my build and didn't want to spend $8000 on mallory to balance I ended up external balancing my engine.

Bearing issues....NADA. RPM issues, ya all come see how fast it revs to 7500. Maybe in 100,000 miles I'll see some affect but then again by 100,000 miles I suspect something else may crop up between the fenders of the Camaro.

On a basic 400 build that's not all out I think it's smart to put in:
A) What works (Scat)
B) What will fit with limited issues

As for your lightweight crank Marv, we use those in the top end circle track motors and they are very nice pieces. You will like that crank.

Please excuse my ignorance, but I don't fully understand the internal/external balance issue.
I'm used to Pontiacs and 283-327 chevys.

Just a little confused. A complete and utterly boring thesis on the subject would be good.

Thanks,

Jim

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1975 Camaro
1972 Camaro (Son's car)
1973 Trans Am 455, 4-spd
1971 Firebird

[This message has been edited by Burt (edited August 17, 2005).]

No thesis here, just the condensed version:
It's all about the counterweights in the crank. Internal balancing requres a harmonic balancer and flywheel / flexplate that is perfectly, neutral balanced. To bring the assembly in balance the counterweights are drilled or chucked up in a lathe to remove weight,, or a plug of dense, heavy metal is added to balance the assembly. For external balancing the harmonic balancer and flywheel / flexplate is built 'out of balance' partially compenaste , then the crank requires less 'adjustment' to the counterweights.

Rick, I know this is probably archiac thinking, but my only problem with external balancing is that funky @$$ spinning mass hanging off BOTH ends of the crank. We fight so hard to make things so true and perfect,, then hang some out of balance blob out there past the end of the crank snout. It just doesn't set well with me. Now I've never personally broke a crank snout, and have not seen one break the snout off (except with a fluidDamper). SO justifies or not,,, to me external balancing a upper end motor is like giving a beautiful girl a butch hair cut! It just don't set well.

Yeah, I know. It's especially bothersome when you install the flexplate incorrectly. Then it really sucks.

BUT, sometimes it's just not practical to internal balance. I'd have maybe thought different if I was going to build a motor for long distance endurance racing but to put put down the road and blast a few 1/4 to 1/2 mile runs it didn't seem to be necessary.

I found my best prices on Scat 6" rods and Scat crank on eBay too, from an outfit named racers outlet or something like that in Iowa.

Have you had your blocks sonic tested to make sure you've got nice thick cylinder walls? Some blocks are great, while some are downright scary due to core shift. Liners aren't always a bad thing tho.

Burt,
I've found the best deal for Scat and Pro-Tru's (Forged Pistons) by Wiseco from:

www.midwestmotorsportsinc.com (http://www.midwestmotorsportsinc.com)

800-262-5033

They have a lot of stuff on ebay at killer prices too.... Their user name is midwestmotorsports, I think...

Go with the 6" cap screw rod and get an internal balanced 6" crank and you'll be set....

OK,

I'm starting to figure this out. Will get a Scat crank, internally balanced, with 6" rods. What about balancers, flexplates, etc?

Thanks,

Jim

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1975 Camaro
1972 Camaro (Son's car)
1973 Trans Am 455, 4-spd
1971 Firebird

Balancers and flexplates will be the same as any ol 350 chev, both neutral balance.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

I'll just chip shot this one in ... this is a popular topic. Somebody once posted a real good reason to go 6" rod in the form of a picture of a piston for a 5.7" rod, beside a piston for a 6" rod. The piston for the 6 weighs a good 100 plus grams less and the longer rod only adds 20 or so so the net gain is always a lighter, less stressed assembly.

Camertom,

Why would you do anything else than a 6" rod, given what you said, and what I have been absorbing during all of this?

I am going with 6" rods and internally-balanced crank in both of the 400's we are building. The cool thing here is that we can do anything we want without restrictions or monetary contraints. I am actually considering buying a crate 572 for another of the cars we have just for fun. But the idea of making mucho HP out of a small block is very appealing to me.

We have a shop full of 400-455 Poniac engines which will be built for the various Pontiacs we have. But the Chevys are becoming more and more interesting to me. Maybe it's because when I was a kid, I had a '55 street chevy 510 that could pull wheelies and ran in the low 12's when I was in High School (1962-1964). I am trying to play catch-up, as I have been out of it for about 35 years (got into Porsches, Mercedes, and BMW's and lost site of the reality of HP and seat-of-the-pants torque!).

I want to thank everyone who has contributed to this thread. It has been very informative to me and will certainly help in our decisions. It is really great that there are all of these people out there who will take the time out of their busy lives to share their knowledge with the rest of us. What a great group of people!

Thank you very much,

Jim

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1975 Camaro
1972 Camaro (Son's car)
1973 Trans Am 455, 4-spd
1971 Firebird

[This message has been edited by Burt (edited August 20, 2005).]

Burt I am using a Scat crank and 6" rod combo with Probe forged pistons in my 406. Funny you should mention your return to hi-perf. I'm in much the same situation, hot rodding 30 years ago, then working as an engine machist for 12 years, changing into sales and management and now returning to the pursuit just a few years ago. This is a great board for support. My set up is a mix of old tried and true ideas from the 60-70s and every new idea posted here and worth stealing;-) There are lots of new ideas these days woth using!

Bring a almost dead thread back to life....
Is it normal to have cam to rod clearance issues on a 400 sb when using 6" rods?
A local racer with a SBC406 told me this afternoon that he used the same combination I'm looking at(Scat crank & rods) in his 406, had to go to a small base circle cam & still had to grind some of the rods to clear.

I thought this only happened in 350 blocks when using a stroker crank.

I just built two 6" 400's in the last 3 months.... One was a (roundy round) 408" with the Scat 7/16 capscrew bolts and played it safe and chamfered the rods used a small base. TONS of room. The second one I just finished for my Chevelle and just chamfered the rods and used a standard base Voodoo cam and had more .060" between the rods and cam. I mocked-up the short block and checked 2 and 6 rods and if they clear, all's good.... Do all your grinding before balancing BTW...

So to answer your question, YES rod/ cam clearance needs to be checked and sometimes is a problem.

[This message has been edited by ryork (edited August 23, 2005).]

Greg since the basic crank centerline to cam centerline is the same between the 350 and 400 block you will have the same issues running the same stroke crank. Clearancing the rods isn't an issue allowing you to run most any cam you want without concern. It is a good idea to have the cam in the block once the trial assembly begins to avoid having to take it all apart to grind the rods afterwards. (hint hint)
The nice thing about the capscrew rods such as the scat I beams is you don't even touch the rod bolt when you grind on the rod, basically from the top thread of the rod body down towards the rod cap at roughly a 45 degree angle. Grinding the rod bolt heads with the throughbolt style rods used to worry me but after you do a few you stop worrying.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

(hint hint) Ain't going to work considering I'm going to be beating on the cam while your are building the new shortblock. Hopefully everything can be together to make a few weekend runs this year.

I really want to run this 282S with the 408 combo to start & them maybe swap out to a 280B-8 Comp grind.

Can the clearances be checked(at your shop) with a mock-up cam of some kind?

Not to worry, there will be room. http://www.nastyz28.com/ubb/wink.gif

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

I almost went with 6" rods when building up my 406, but I stuck with the GM 5.7 "X" rods I already had, already cam clearanced, and my KB pistons.
Going with a longer rod does increase the time the piston spends at TDC slightly, and does take more load off of the outside cylinder wall, but it increases the piston speed a whole lot. Also, the piston pin cutout gets into the lower ring land on the piston. I would say if you have the money and want to do it, go for it. Internally balanced would have been nice, easier to track down flywheels and balancers that way... I already had the SCAT ext. balanced crank though.

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'71 RS/SS pile of parts: full roller 406sbc / 9.76:1 w/ E-Tec Al. heads / 750 Competition AFB / 12"/11.1" 4 whl discs / big sway bars / 4 speed 3.23 posi / 81 Z28 & dual snorkel vette Air Induction

Chuck78,

What cam are you using in your '71?

Thanks,

Jim

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1975 Camaro
1972 Camaro (Son's car)
1973 Trans Am 455, 4-spd
1971 Firebird

I read in Dave Vizard book the 6 inch rod will make the engine last longer and the longer rod makes more torque cause its got more leverage on the crank

I would call Scat first and ask them to garentee there crank.
I recieved mine and have built and tore the engine down three times, two different builders. The problem is the Scat crank has 1 1/2 thousands run out on the rear journal. Now Scat is telling me they dont make any mistakes, BS.
A dial indicator shows 1-4 journals at 1/10 thousands run out, however the rear is out 1 1/2. The rear bearing last about 45 min. each built before the engine is full of bearing material.

I would call Scat first and ask them to garentee there crank.
I recieved mine and have built and tore the engine down three times, two different builders. The problem is the Scat crank has 1 1/2 thousands run out on the rear journal. Now Scat is telling me they dont make any mistakes, BS.
A dial indicator shows 1-4 journals at 1/10 thousands run out, however the rear is out 1 1/2. The rear bearing last about 45 min. each built before the engine is full of bearing material.

Welcome to the board, DadNova! You must have been digging when you found this post in the archives judging by the date. Sorry to hear about your bad crank.

I'm glad you brought this up though. This site is very pro-Scat products. I was ready to order my Scat crank & rods before I talked to my machinist. He reported several experiences with Scat similar to yours.

My point here is that NOBODY has 100% perfect quality. Scat's reputation is better than most, but they are not perfect.

Many people here respect their producst; however, we should all be double checking our brand new parts.

...stepping off of soap box now. Carry on.