Big Block Question

[chastain90]

I am considering a big block in my 72 blazer. After researching I believe I will move the engine mounts forward 1 1/2 inches according to what everyone says to avoid the firewall clearance problem. My question is, I have a SM465 4 speed and wonder what will have to be done as far as clutch linkage placement? Will I have to modify anything else for this to work besides the cross members and driveshaft being lenthened?
Thanks for any help

[Yukon Jack]

If you move the engine forward the linkage will definitely be effected. Your front driveshaft may need to be shortened. It's angle will become a little steeper too.

[chastain90]

In that case would it be better to just do the firewall clearance?

[colgad]

Originally Posted by chastain90

In that case would it be better to just do the firewall clearance?

I believe the bellhousing mounts are effected also.

I would work on the firewall if there are clearance issues. I had at one time a stock 71 with a 402 and didn't have any clearance issues

[kehstr]

you will probably just be better off to buy an nv 4500, sm465 don't hold up to big blocks very well, telling you from experience

[cleszkie]

Originally Posted by kehstr

you will probably just be better off to buy an nv 4500, sm465 don't hold up to big blocks very well, telling you from experience

I gotta admit, that is the first time I've ever heard someone say the SM465 won't handle a big block. If an SM 465 won't do,then neither should the NV 4500, as it is basically an SM 465 with an overdrive. What kind of horsepower/torque were you making when you took your SM 465 out?

[kehstr]

they actually aren't even close to the same. The nv4500 up to about 1998 when the nv5600 came was the strongest manual trans. The nv4500 has gears that hold up to a lot more. The input shaft is the thing that normally goes on the sm465, and when they go, everything on the trans goes. The input shaft on an nv4500 is larger, i couldn't tell you how much larger, but i do know that they are larger. My motor could have been able to hold up to it, but i saw one that went when it just have 450 horsepower and about 370 foot pounds. I was planning on running a little bit more when i was building mine, and i decided that it wasn't worth the hassle, so bought an nv4500 to not have to deal with it

[kwmech]

I guess GM messed up when they put a 465 behind a 427 then put it in a 2 ton truck

[kehstr]

yeah those 465 didn't hold up for very long at all. Unless someone at one point put some 5.13 or lower gears in it, then the trans at least lasted a little while, but still weren't very strong

[kwmech]

That's called sarcasm. I've got a 465 in my 3/4 ton that I work a lot and a 465 in my 1 ton wrecker, never had a problem with either one, AND I rebuild quite a few with different mainshafts and such and never seen a major problem except in the early ones where the countershaft just had a snap ring holding 3rd gear in place, all it takes is a solid spacer, done

[chastain90]

So can anyone tell me what has to be done exactly on the big block swap with the 4 speed? I would like to see what has to be done to the linkage from someone who has done it

[Lieferson]

put a 2" body lift on there if you want some extra clearance. it may just fit in there though, same trucks but they are all different. best bet is trial and error. might get lucky.. just my .02

[1rippen6]

I went from a small block to a big block years ago the only thing I remember having an issue with was the distributor to firewall clearance but I was running a 350 turbo. I never moved the crossmember and if I remember right I just removed the motor mounts from the SB and bolted them to the BB.

[chastain90]

Thanks but even with the body lift wont the clutch linkage have to move?

['63GENIII]

Originally Posted by kwmech

That's called sarcasm. I've got a 465 in my 3/4 ton that I work a lot and a 465 in my 1 ton wrecker, never had a problem with either one, AND I rebuild quite a few with different mainshafts and such and never seen a major problem except in the early ones where the countershaft just had a snap ring holding 3rd gear in place, all it takes is a solid spacer, done

The comments about the 465 really made me do a double take for a minute. TBH, I really like my 4500 over the 465 for drivability, but IMO, the 465 is a stronger trans in stock form. My 4500 has made a few "noises" that I never had with the 465. Mainly bearing noise and the occasional "Halloween noise" as my son calls it. I drive that trans as if it would cost 2 - 3k to rebuild. On the other hand, the 465 always seemed to get abused and I didn't give it a second thought.
If I really wanted a 5 spd that could withstand power / abuse like a 465, Id look for a NP540 or a Clark 5.

[chastain90]

After further thought I may stay with the 465 if I can move the engine forward and make my clutch linkage work.

[SleepyK5]

I went with nv4500 with hydraulic clutch setup works great. I'm pushing 575HP and 550 torque through mine. Hope my 12" holds up!

[kehstr]

if the 12 bolt does go, an easy thing to do, is to put a 6 lug 14 bolt out of a 88-98 Chevy or gmc pickup, I've seen them hold up to lots more torque, and tons of abuse, and are still working