big block installation?

[pcwillsie]

i was just wondering what problems ou gys ran into when installing big blocks in your 4x4 blazers. I would like to know be prepared before i dive in. thanx

[1969k10stepside]

Hei/firewall clearance,valve cover/firewall clearance, just to name a few...

[Long Roof]

The engine and tranny are positioned closer to the firewall for clearance of the front axle. This makes it a real PITA to fit the big blocks. The factory never offered a big block in 4x4 trucks from 67-72. Some people beat in the firewall for clearance and some people have done body lifts. All trucks are a little different because some people have installed the big blocks without modification but I think you would have to get real lucky for that. If you have a suspension lift you could look into moving the engine and tranny forward on the frame a few inches but that would probably require drive shaft work. Hope this info helps.

Aaron

[mister.freeze]

The Fox had a 454 before I bought it, and still has the badges. The firewall is intact, but it looks like the motor mounts were moved aft. There's a crosspiece connecting them under the pan and the whole assy looks moved. My stroker is sitting on those mounts now, and the distributor and valve covers are close but not touching. Once upon a time I had HEI and it cleared too. I've got almost a foot of clearence between the radiator and harmonic balancer. Let me know if you want pix and I'll see what I can do.

[vtblazer]

Originally Posted by mister.freeze

I've got almost a foot of clearence between the radiator and harmonic balancer.

What about to the water pump pulley? Fan?

Factory shroud measures in at 9"s off the rad.

[mister.freeze]

I'm running electric fans on the radiator, and no shroud. I just measured 9 inches radiator to pulley.

[Classic Bowties]

Originally Posted by pcwillsie

i was just wondering what problems ou gys ran into when installing big blocks in your 4x4 blazers. I would like to know be prepared before i dive in. thanx

pcwillis: Here is my 72 K/5 with a 468 BBC / SM465 / NP205 installed with NO firewall distributor or valve cover clearance issues. I am a huge fan of the big block in this vintage of 4wd truck or blazer but whatever you do, take your time and DO NOT BEAT in your firewall for clearance reasons, it is unnecessary and only looks cheesy on a nicely built rig. I moved the motor, trans/transfer x-members forward 2-1/8th inches from the stock small block 4 speed location and I am running a accel hei with a super coil sticking of the top of dist. with NO clearance problems. A few other needed mods were the manual trans clutch linkage needed worked out along with a custom/modified tall trans hump cover installed and both drivelines needed corrected due to moving everything forward. As for the parts in front of the motor, they were all pilfered from a factory original 71 2wd 3/4 ton with the 402 BBC. Parts needed from the donor 71 were all the original BBC (short water pump only) brackets and pulleys for the power steering w/remote fill reservoir, the aternator and the air conditioning pump. I also used the original 71 2wd Big Block fan shroud and clutch fan and both fit the front of motor to radiator and core support distance nicely. I feel everything came together great and it almost looks like it could have came this way from GM, this has been a super reliable setup that has been beat on for four summers with absolutely zero problems encountered (except for broken axles & u-joints ). Lmk if you have any other 4wd BBC conversion questions, Cb

[Jtrux]

Originally Posted by Classic Bowties

pcwillis: Here is my 72 K/5 with a 468 BBC / SM465 / NP205 installed with NO firewall distributor or valve cover clearance issues. I am a huge fan of the big block in this vintage of 4wd truck or blazer but whatever you do, take your time and DO NOT BEAT in your firewall for clearance reasons, it is unnecessary and only looks cheesy on a nicely built rig. I moved the motor, trans/transfer x-members forward 2-1/8th inches from the stock small block 4 speed location and I am running a accel hei with a super coil sticking of the top of dist. with NO clearance problems. A few other needed mods were the manual trans clutch linkage needed worked out along with a custom/modified tall trans hump cover installed and both drivelines needed corrected due to moving everything forward. As for the parts in front of the motor, they were all pilfered from a factory original 71 2wd 3/4 ton with the 402 BBC. Parts needed from the donor 71 were all the original BBC (short water pump only) brackets and pulleys for the power steering w/remote fill reservoir, the aternator and the air conditioning pump. I also used the original 71 2wd Big Block fan shroud and clutch fan and both fit the front of motor to radiator and core support distance nicely. I feel everything came together great and it almost looks like it could have came this way from GM, this has been a super reliable setup that has been beat on for four summers with absolutely zero problems encountered (except for broken axles & u-joints ). Lmk if you have any other 4wd BBC conversion questions, Cb

You're right, it looks factory, nice job.

[jaros44sr]

Nice work, CB!! Saw some pics of your truck on the dunes awhile back, truly amazed at the quality rebuild.

Just wondering, got lotsa go but what about the whoa! Is that a 1/2 ton brake system on the right of your engine? Just curious, because the 3/4 ton brake mod. is my next move. Got all the parts...BTW, did I say I liked your truck!!!

[Long Roof]

The other day an idea came to me. What if someone was to swap a 700 auto tranny in place of a 350? I know that the 700 is longer but by how much. This swap would move the BB closer to the radiator and would not require any driveshaft changes. Just thinking out load.

Aaron

[CrewDawg]

I do like the set up. I have a 700r4 built and ready to be installed. Just waiting on the engine. I have had my truck since 2002 and stopped driving it in 2003 due to a wiring/ oil problem. Since then I have replaced both rockers, Lt and RT floor boards and numerous other things. The trucks and work yall do on this site is great and gives me great ideas. I hope mine turns out like some on this site.