4 Bolt Block

Ok, let me explain my situation. My brother gave me a 350 that originally came out of an older vette. I was thinking it was a 4 bolt main block. Well, to make a long story short, we loaded it up in my truck, brought it home and put it on a stand but when I flipped it over and pulled the oil pan off I realized it was a 2 bolt block (not what I wanted). So heres my question....which vehicles did Chevy put the 4 bolt blocks in? My uncle has an old 3/4 ton, I'm guessing late 70's, chevy truck at his house and said I can have the 350 thats in it. It would be pretty easy to just drive over and pull the pan and see if its a 4 bolt but he lives about 70 miles from me and I dont really wanna ask him to pull the pan for me....that would be asking a little too much since he said I can have the motor. What do you guys think? Could this truck possibly be housing the 4 bolt block that I'm looking for? He says its the original motor. Any feedback would be appriciated. Thanks, HRS10


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I would guess that if it's an original motor in the 3/4 ton it would be a 4 bolt. I'm know ex-purt, but I think Chevy put 4 bolts in all their truck. I pulled an engine out of a '78 Blazer to rebuild and put in my T-Bucket and it was a 4 bolt. I think it's the passenger car line that's a hit or miss on the engine. Although I would think that if it's a high performance car it would be a 4 bolt. My money would be in the truck and the price it right.

The truck probly has the 4 bolt, but if you relly want a strong botome end go ahead and use the 2 bolt, but order 4 bolt splayed caps for it and have it linbored. Jeggs carriers them.

[ May 19, 2002: Message edited by: jeff of nc ]

[ May 19, 2002: Message edited by: jeff of nc ]</p>

Jeff...how is it that makeing a 2 bolt into a 4 bolt better. Are the caps from jeggs stronger or something? Thanks, HRS10

What he is talking about in a factory 4 bolt, the 2 outer bolts are parallel to the inner bolts-both going straight up and down. When you take a 2 bolt and make it into a 4 bolt you use aftermarket maincaps that have the 2 outer bolts splayed. What that means is the outer bolts are at an angle (angled towards the center). It is stronger than a factory 4 bolt but I think factory 4 bolts are plenty strong for street use.

ok, time for my 2cents. the splayed bolt system is definately the strongest setup, however, unless this engine is going to see some very sevier and extreme punishment on a regular basis there is really no need for a 4bolt block. 4bolt blocks were put in pickups and suv's because of thier semi-commercial use (hard regular punishment) however, if this engine is only going to see daily street driving and mild street racing then a 2bolt block is plenty strong, but then again if you can get the engine from the pickup free, then that would be the least expensive route (and it is most certainly a 4bolt) but then its your project and my 2cents have fun and good luck

Not all trucks had 4 bolt mains. Only way to know for sure is to pull the pan.

However...every engine I have seen with the 8" harmonic damper has been 4 bolt. Of course, there could have been exceptions, and someone could have swapped dampers....

Again, teh only way to be 100% sure is to...pull the pan.

Yes, the conversion main caps are made from a higher grade of material usually and yes, the splayed setup is better.

However, 2 bolt block is great for up to 6000 rpm, maybe more. Use the 2 bolt

the 2 bolt block will take upwards of 500 hp. as is. but if uou realy want to stick it to it, the option of mashining the 2 bolt into a 4 bolt is way stronger than an oem 4 bolt because the splayed bolts do not run into the flimpsy webbing like the 4 bolts do. they are put in at an angle and so run into the metal beween the cylinders and thus are much better at takeing the loads since the bolts ar emore paralell to the load sthan the oem 4 bolt ones are

I'll start this buy saying I am by no means a enngine expert,altho I put SBC in all my cars for 30 yrs. I was of the opinion that if the last 4 digits on the blk read 0010 it was a 4 bolt main........I also would like to know if there are exceptions to this......Don

I would think that it is a 4 bolt block because it is a heavy duty truck if it was a half ton it might be a 2 bolt but since the truck is a 3/4 ton chances are that it is a 4 bolt. I like the qoute you put at the end all throttle and no bottle i agree.

Don is correct the best block you can find is a 010 block..also there is no really reason for a street driven car to have 4 bolt mains.We have raced the 2 bolt main blocks in circle track racin all nite 4500-7200 rpm with no failures. If you come off the ground and hit hard you might break a cap. Again the strongest is the 2 bolt block with splayed caps. The best one you can do would be a small journal 327 with splayed caps. less reseprocating weight,lighter factory rods all the good stuff.Maybe why a lot of old 331 smallblocks will out run a 350 4 bolter LOL Use what you have ..unless your spending 10 grand on the motor or have it on kill with a bottle nobody is gonna know if its a 2 bolt or 4 bolt.

No, 3970010 does not mean that it has 4 bolt mains. It could have two or four. I have some of each.

Being in a 3/4 ton truck does not mean it is a 4 bolt either. Having 4 bolts means it has 4 bolts. That's the only way you can be sure. Period. There are other clues, but to be sure, you must check it. The factory did some stupid stuff, so you never can be sure, and then you have to possibity of swaps that could have taken place over the years.

I didn't expect to get this many responses but I'm glad I did because I think I may have learned a thing or two. Many thanks to all that contributed. HRS10

What about getting the casting numbers off the front passengers side of the deck surface and checking them out at mortec.com?
Just a thought.

well if i were you i would drive over there and get the 350 ,if hes going to give it to you then 70 miles is not that far and you could get it all done within a day.its always good to have a spare engine lying around anyway . i agree with reddwarf ,i have three 3970010 350 blocks and they are all 2 bolt ...two of them had factory 2 barrel carb and manifold 3rd one was a bare block.