sbc 400 help
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
sbc 400 help
I am currently rebuilding a 400 sbc to a 406 and was looking at the options I have and the one big think that confuses me is the rod length some kits offer 5.7in rods which are closest to the factory size but most include a 6in rod. Now I've heard that the 6in rods can cause a clearance issue with certain cams and would like to hear how did you guys rebuild yours and what cam specs did you use also if clearance was ever an issue.
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
434 SBC with 6 inch rods in my 9-car. I have put together a lot of SBCs myself, but my last two engines I had my engine builder put together my short blocks, [not cheap but in my opinion worth every dollar]. Using a small base circle cam. As far as cam specs go, match your cam to your heads. My cam was a custom grind from Cam Motion to match my Dart heads. For the right cam call a couple of cam grinders they will ask all the right questions about your goals with the car, about the car and your engine build. I run solid roller cams, most folks use hydraulic roller for street and track use. T
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
434 SBC with 6 inch rods in my 9-car. I have put together a lot of SBCs myself, but my last two engines I had my engine builder put together my short blocks, [not cheap but in my opinion worth every dollar]. Using a small base circle cam. As far as cam specs go, match your cam to your heads. My cam was a custom grind from Cam Motion to match my Dart heads. For the right cam call a couple of cam grinders they will ask all the right questions about your goals with the car, about the car and your engine build. I run solid roller cams, most folks use hydraulic roller for street and track use. T
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
It has nothing to do with the rod length. The beam and crank end of the rod cause clearance problems. With the cam
you want the biggest base circle on the cam that will work I have two roller cam motors with. .950 base circle
you want the biggest base circle on the cam that will work I have two roller cam motors with. .950 base circle
Dr. Detroit
Joined: Mar 2012
Posts: 10,093
Likes: 4,019
From: New Braunfels Texas
I built my 406 with a flat tappet cam and 5.700 Eagle SIR rods......they are profiled like the SCAT rods for clearance. As far as the 5.700 vs. 6.000 debate.......a lot of us are not running sustained high RPM under load so it is unnecessary to me......
If building a max effort deal.....yes...the 6.00 rod is standard issue.
A 406 with a 5.700 rod has a very similar rod ratio as a 6.00 rod 434.........keep that in mind.
Have fun
Jebby
If building a max effort deal.....yes...the 6.00 rod is standard issue.
A 406 with a 5.700 rod has a very similar rod ratio as a 6.00 rod 434.........keep that in mind.
Have fun
Jebby
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
If you use "stroker" rods, they have more clearance to the cam lobes and to the block skirts; also I-beam rods generally have more clearance than the H-beam rods. Cam wise, greater overlap (the lower lobe separation numbers) will have reduced cam clearance than wider lsa's. In any event, the engine builder must check this. My last 406 used a standard base circle roller cam and cleared fine with the SCAT Pro-Series I-beam rods.
More considerations about rod length... 5.7" rods generally require a non-neutral harmonic balancer and a non-neutral balance flywheel or flex plate. On the other hand, 6.0" rods in crankshaft kits often combine to permit neutral balance damper and flywheel/flexplate.
More considerations about rod length... 5.7" rods generally require a non-neutral harmonic balancer and a non-neutral balance flywheel or flex plate. On the other hand, 6.0" rods in crankshaft kits often combine to permit neutral balance damper and flywheel/flexplate.
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6" rods allow for a lighter piston...which is good. Remember...the stock 400 used 5.565" rods originally.
If you can get rods to clear with better profiling...try not to do the reduced base circle deal. I did a 400 using a Dart block and had no issues with regular cam profile.
JIM
If you can get rods to clear with better profiling...try not to do the reduced base circle deal. I did a 400 using a Dart block and had no issues with regular cam profile.
JIM
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
6" rods allow for a lighter piston...which is good. Remember...the stock 400 used 5.565" rods originally.
If you can get rods to clear with better profiling...try not to do the reduced base circle deal. I did a 400 using a Dart block and had no issues with regular cam profile.
JIM
If you can get rods to clear with better profiling...try not to do the reduced base circle deal. I did a 400 using a Dart block and had no issues with regular cam profile.
JIM
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Joined: Jan 2000
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From: Corsicana, Tx
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You can get the rods that are already shaped correctly...but in reality it's only small amount of grinding.
JIM
JIM