can anyone tell me the width difference at the exhaust ports between the B and RB engine ? on my humpback project, the steering shaft runs between the header tubes, and i need to move the #7 tube for extra starter clearance having a 440 with iron heads used as a mock up engine. as it is possible i may use a 400 based engine, i would like to be sure i move the pipe enough so these pipes can be used with both engines. i don't have access to an engine at this time to get a measurement. the pics give some idea of my space i have to play with. thanks guys !

the RB block deck height is 3/4" higher on each side up/outward at 45 deg angle (give or take a few thousands) so the actual height increase would be less than that amount. & obviously that would be with the same heads/everything else the same (head gaskets etc). I think if you got the part in question (ports?) & measured their width across then you could Google some triangle math to get a dead on number. You might just be able to visualize it. EDIT If you drew a V with the "tips" of the V being the heights of the ports then drew a line across horizontle to connect em & did that math for the hypotenuse (horizontle line length) of that line then added 3/4 onto each "tip" then another horizontle line & calculate/measure it then subtract the first horizontle line from the 2nd one & likely that will the width increase.

if the 45 degree angle is correct the math should be simple. Rise and run on a 45 is the same amount. IE 3/4" up is also 3/4" over.

It 3/4" on 45 degrees so rise and run are both .530 up and out

^^ good info guys

I heard years ago it was 3/4" difference. Just measured a stock headed 71 B block exhaust flange to flange 19,7/8" My E head RB was 20,7/8"

Maybe if both had stock heads it would of been 3/4" instead of 1" difference.

Look at the diagram above. for the hypotenuse extension of 0.750", the lateral length is 0.53". That's one half. The other half is just the same. So the extra width is 1.06 inches.

The heads add the same amount no matter the deck height of the block they're attached to.

So the increase in width is 1.06".

The only fly in the ointment is that the deck height changes by 0.745" so the actual width increase is 1.0536".

R.

The same answer 2 ways:
1. A^2 + B^2 = C^2, either A or B = (C^2/2)^.5 = .530"
2. H * COS 45 = .75 * .707 = .530"

Man you guys make stuff hard.

For 45°, you either multiply, or divide by the square root of 2, depending if you are starting with a leg, or hypotenuse.

The numbers are 1.414, or .707 (inverse of 1.414). And .707 is half of 1.414.

So for the rest of your life, the only number you need to remember when dealing with A 45-45-90° triangle is .707.

you guys are great ! and for some reason, i had roughly 3/4"[.750] in mind to move the pipes ! there is nothing on the passenger side remotely in the way, and as it sits now, the steering shaft clears every thing by a ton [1/2"+]. the starter is around 1/4", so i need to get some extra there [#5 pipe] just because of heat, and if a B block is used, i'll need to move #7 because of the shaft joint. i have tons of chassis clearance to go outward almost 1", so i'll move it as much as i can and that will be perfect for both blocks. thank you guys for the math lesson ! i had forgotten how to deal with triangles, and i don't have a "fourth grader" here to help me out. again, you guys ROCK ! THANK YOU !

So for the rest of your life

unless you're dealing with a V6 or V12 (.500)

should be easy since i have been accused of only being 1/2 [.500] there at times by many people !

(1) it'll get worse (wait & see) (2) that's our job (3) yes we are, (25K die hard Moparters, that's a big brain trust)

BTW: the correct firing interval of a V12 is 60° (720° ÷ 12), but not all V12 use a 60 bank angle. Liberty engines were built with 45° and it didn't work.
The Viper V10 is a 90° bank (inherited from the Magnum) with the firing interval corrected by offsetting the pins 18° to reach 72°.
Some GM V6 are based on either the Buick small block V8 (215, 300, 340, 350) or the SBC V8 and use a 90° bank with (even fire) or without (odd fire) a 30° pin correction.
Most modern V6 use a 60° bank and 60° pin offset.

Or there just might something else in the world that is 45° that this info could be useful. You really need to get out of the garage for a little bit

A major reason for 60° bank angle choice today is FWD's space limitations: the cross-wise engine length is better than L4 by several inches* but the width radiator to firewall is less than a 90° (which would be shorter top to bottom).

Engine lengths (all plus accessory drive)
V6: 3 × bore pitch + 1 rod width (roughly 1")
L4: 4 × bore pitch
V8: 4 × bore pitch + 1 rod width
L5 (Volvo, Audi): 5 × bore pitch
V10: 5 × bore pitch + 1 rod width
L6: 6 × bore pitch
V12: 6 × bore pitch + 1 rod width