I6 position vs v8?

[71Rat]

how far back does the I-6 towers move a smc back vs the standard v8 towers in the stock position? and are they different towers or the same towers moved into different holes in the frame?

thanks everyone

[Robznob11]

pretty sure i6 towers are taller. as far as i know ther are 3 types of towers all different i6 sb and bb.

[Aarons72s]

I have seen a small block mounted on the I6 frame mounts. The engine was almost pend against the fire wall. Not sure if there were distributor clearance issues. So if the question is can you mount V8 on the I6 mounts then I am pretty sure is yes. There has to be someone on here that has done it. I only wish I knew where this truck was then I would look for you. Hope this helps.

[special-K]

Without knowing the differences in the I6,SB,and BB towers I have put a SB in an I6 truck,SB in BB,and visa versa.But,I don`t like the V8 back into the firewall.So,I always move the towers forward(about 2 1/2")when swapping a V8 into an I6 truck.I can have a driveshaft built longer for under $100,done deal.

[crazy longhorn]

Its a 3 1/2" setback, mounting the sb on I 6 towers. if you measure the diff in boltholes on the top of frame, you will measure exactly 2 1/2" center to center on the holes........but, due to the shape of the stands(the 6 stands kick rearward & the sb stands kick foward), you add 1" to the mix As far as height, I have not seen a measureable difference either way. The hei dist will fit in most cases......but is very tight to the firewall. L

[69-350]

Originally Posted by Aarons72s

Not sure if there were distributor clearance issues.

Yes, it is VERY tight. My 69 is an original I6 truck with a 350 stuffed in there. With a points distributor and wires on there, you've got a little space to work with, enough to turn the distributor all the way around. But, with an HEI in there, you barely have enough room to get it in there, and you barely have enough room for wires. With an HEI with wires on it, you can't turn it more than a little ways, before a plug wire will hit the firewall. Too tight, that's why I got a new frame from my buddy that was a V8 position truck already.

[Robznob11]

well there is actually a certan degree of tilt back the motor is suppost to have to keep pinion angle in check and altohugh it may woork ok for a stock engine i would not run any hot rod like that. how ever moveing the engine back helps you weight ratio

[crazy longhorn]

It sure doesnt hurt to check driveline angles, but sliding the eng back wont hurt em(from what I have seen anyway). L

[71Rat]

i have a built sbc in the truck now in the stock location, i was just trying to get more weight transfer by moving the engine back. Would the stock SB towers fit in the I6 location?.. also i am not to worried about dist. clearance, the engine has a msd pro billit dist on it so its about the size of a points... and if need be i will notch the firewall.

thanks everyone for the input

[crazy longhorn]

You need I 6 /250 stands for a bolt /drop in, & the smaller cap dist is a good fit.... L

[TDs6t9]

I have done that. Dizzy alittle cose in the back(stock). Ram horn headers are great. Clutch linkage kinda tight but no binding. I used the stock mounts from the I6. Just need a little longer fan shroud. Everything else was just about bolt in. Maybe a 2 degree slant back but nothing that would hurt as far as oilling goes.

[71Rat]

nice, at least it fits without many problems, i have headers, an auto and electric fans so a few things less to worry about..... im just tossing ideas around not sure if im going to do it or just build another truck..... but thanks everyone for your help!

[jacobs]

Originally Posted by 71Rat

how far back does the I-6 towers move a smc back vs the standard v8 towers in the stock position? and are they different towers or the same towers moved into different holes in the frame?

thanks everyone

That's exactly where the sbc IS mounted in the 4x4's.

[Truckstr]

Sorry for the late reply. I've been away from here too long. I'll try to do better.

I have a small block w/ TH350 auto installed in the I6 position in my '67. I also have a stock '72 that came from the factory with a 350 SB. I installed the SB in the '67 that way because I wanted the better weight distribution front-to-rear. It also lowers the center of gravity a bit to help cornering. (Can you tell I'm a "hotrodder"? hehehe) I can only speak of the I6 and SB V8 mounts and not of the BB V8 mounts. I have no experience with the BB mounts. I'll leave the BB V8 mounts to others.

Now, how to do set the SB V8 engine back in the frame with the least pain. Take the stock I6 frame-to-motor brackets, just like the ones for the SB V8, are left (L) and right (R) specific. I recently sandblasted an extra set of I6 brackets that I had laying around and found that they are even stamped L and R. All you have to do to set the SB back is swap the I6 brackets side to side and install them in the rear most holes that are already in the frame. Move the trans crossmember back a corresponding amount too and you're basically done (I don't think I had to drill there either - I can't remember). That's it! No drilling. No cussing trying to line everything up.

I installed a Pertronix "Flame Thrower" HEI distributor in as well - same diameter as the stock unit. Yeah, it's a little tight with the firewall, but it does NOT interfere. The wires attach to the cap in their normal manner and route just fine - headers and all (incidently, I use headers designed for use in a '68-'72 Chevelle. They fit great!). The only problem that you're going to have with this "set back" install is with the column shifter rod. I had to do a little fabricating on it. It's nothing that anyone with a little mechanical ability - and a welder - shouldn't be able to do. Since then, I've changed over to a Hurst floor shifter, so that's not even a problem if you go with one of those. Other than that, I went to a one-piece driveshaft, rather than monkey with the factory two-piece assembly.

As far as driveline angles, yes, ideally the axis of the engine/transmission should be parallel with the axis of the pinion gear - not in line with, mind you, but PARALLEL! It should be checked with the truck sitting at ride height. If your truck sits too low, just put a set of jack stands under the rear diff. and check the angle of the pinion gear (use the face of the yoke) relative to the transmission (I use an old slip yoke). It's a simple calculation. Like I say, ideally the two axes should be parallel, but they will likely be off by a little bit (I really need to write this stuff down instead of committing it to memory ). The higher the power you're putting through the driveline, the closer they need to be to perfect. Use wedge shims from a NASCAR-type supply house if you want to "get it right". The angle difference between the two axes is the wedge angle that you need. They install between the U-bolts and the truck arms.

That's it! Have fun.

P.S. jacobs, I wasn't aware that the 4x4s used this set up. Whodathunkit. I "discovered" this setback install when I had too much time on my hands and all the right parts sitting there with an open engine bay. It gives tons more room in front of the engine, especially since I went to an electric fan. I love the setup. It's just a little customization that sets my truck apart from most.