Would you.... 402?
 

I might have the opportunity to get my hands on a 402 out of a 1-ton camper, if my dad ever gets his hands on this particular donor truck, and if he's feeling generous (he usually is ;) ).

The question is: Would you go from a 350 to a 402 in your Blazer?

I'm afraid of decreasing fuel mileage. I'm also afraid of bolting it to a TH350, though the motor would come bolted to a TH400. Perhaps I'd just need to find the right tail-housing to bolt up to TH400 to my transfer case?

Any disadvantages?

Where would I get mount brackets for a big block into a 4x4?

Re: Would you.... 402?
 

I have a 454 in my Blazer (installed from the PO) and it rubs the firewall fairly tight. So firewall clearance is an issue. Also the turbo 400 is not going to work without getting a turbo 400 specific adapter and 205 transfer case. If you can find one they are usually expensive . You could always go with a turbo 400 adapter/208 transfer case combo from a newer GM, but then you would need to change your drive line ends. So in other words, you can do it, but it is not just a simple conversion.

Re: Would you.... 402?
 

If your blazer is a 4wd, installing a big block is not just a simple bolt it, not even close.

There were no big block 4x4's made during the production run of these trucks. (not a stock option)

Do a search, you'll find tons of good reading, you could also check over on CK5, piles more reading to be had there.

It's done all the time and it's certainly a valid install, just don't go into it blind...read-read-read. ;)

Re: Would you.... 402?
 

I had a 402 in a 1972 gmc and it got 6mpg with the wind blowing in the right direction. I would stay with a small block. You can go with a cam or supercharger and fuel injection for the wild side and get better gas mileage than the big block. I had problems finding parts for the 402/396 at my local auto parts store, everything have to be ordered.

Re: Would you.... 402?
 

If you were going through all the trouble to swap in a bb, I would step up to a 454. I originally went from a 350 to a 400. Went from 10mpg with a dead 350, to 9mpg with 400 and had WAY more power. Well worth losing the 1mpg. Now I'm moving up to a 454. (For some reason you just can't have enough power). I know of a couple of other guys who got into the teens for mpg with 454s. I'm going for as much low end torque as I can to maximize milage. Ported peanut ports, tri-y headers, as much compression as possible, etc. IMO a 402 isn't a big enough bb to justify the work involved. But I would still snag the 402...just because!

Re: Would you.... 402?
 

I have a 396 bbc in my 72, gas mileage not sure of but the big block tucked in under the hood looks kinda neat IMO.

7D7N

Re: Would you.... 402?
 

Theres no replacement for displacement!

Re: Would you.... 402?
 

Okay, i did a bunch of reading on ck5 about putting the bbc into a blazer. It looks like there are a myriad of options as far as front crossmember, mount perches, and mounts all of which put the motor in a slightly different position. it also looks like most people with automatic transmission are just bolting the bbc up to their 350-205 combo.

What I've got at my disposal is a complete 2wd 72 1-ton. One question would be: do the 2wd bbc mount perches bolt to the 4wd blazer crossmember? If so how would the engine placement be?

Either way it seems that the main areas of concern are firewall clearance for the valve covers and for the distributor. i am hesitant to dent or cut up my prestine firewall, but the bbc sure is enticing. It is unclear to me how to oil pan fitment works out. but it sounds like it varies depending on pan type, perch type and crossmember type.

Overall it really doesn't seem to be that complicated of an installation. is there something else that I have overlooked?

What is the weight difference between a fully dressed bbc with a/c and a fully dressed sbc with a/c?

Re: Would you.... 402?
 

putting a 406sbc in my 72 burb (2wd, 3/4 ton, 3 on the tree). i have the engine, i like BIG stroker small blocks and i can keep my stock ram horn exhaust manifolds to save some money. my dad bought the engine a few years back to use in his 84 burb for trailer towing....the guy was putting in a 402. yeah, big blocks make good power, but it seemed like the marginal increase in power was not worth the swap hassle, the extra weight and decrease in cubic inches.

a 383 is a great alternative to a 350, especially in a truck as most of the extra displacment is in the crank, not in bigger pistons.....they often get better mileage than a 350, actually. there is also a company that makes wide bottom 472's based on the old school chevy small block. big pistons and a super stroker crank long enough to satisfy anyone who needs serious torque for pulling big trailers or racing. i think you need to find a way to add an overdrive to your truck!