400 SBC

[gsta86]

So I had bought this 72 Blazer last year. Had some engine troubles 6mos afterwards, pretty sure it had to do w/ oil pressure. Who knows. Took it in to a engine shop here in SD that I was referred to by a trans shop I've used. The whole time I thought it had a 350 in it, because that's what the seller told me. Mechanic pulls it, tells me I have a 400. Bad news is that the previous builder, over bored it. So the mech claims. I brought home the now short block. He's still building me a 350.

1: he said you can't bore a 400 more than ..030 over. Everywhere I read on forum searches,this sounds like BS. Opinions?

I plan on taking to another place and have them clean it and check it all out as well and provide measurements on paper. I see people talking about boring it out all they upward of .060 over. My hopes are really that my block is good, and I can start a very slow 400 rebuild

Opinions

 

[66nova]

BS if it's a good block. Our last 3 motors (between mine and my dads car) have been 0.040 over 400 blocks. Two of them ran for 4 seasons spraying 150-200 shot of nitrous.

Now all that being said, the block has to be good and the build needs to be right. Horsepower and use come into play too.

Both the motors I referred to above ran in 9 second street/strip cars.

 

[PenguinLTZ]

Get away from the 400. 350 blocks are the way to go.

Use that 400 crank and have the crank journals cut to the 350 size.

Now you have a 383.

400 blocks are junk. Been there, done that.

 

[PenguinLTZ]

LOL the doc and I will have to agree to disagree on this one

 

[gsta86]

Well from what I hear the 400s are great torque producing engines. Keeping in mind this would be for a blazer. It doesn't need to be anything close to high performance. Dependability and capable of moving the beast. As it stands now the blazer is going to have a 350, but if this block checks out GTG, than eventually it'll replace the 350

 

[gsta86]

The mechanic also said the crank was trashed also. Again, I'm nowhere close to being even a novice. But I always question peoples intentions when it ends up I have something I never new I had.

 

[PenguinLTZ]

Well from what I hear the 400s are great torque producing engines. Keeping in mind this would be for a blazer. It doesn't need to be anything close to high performance. Dependability and capable of moving the beast. As it stands now the blazer is going to have a 350, but if this block checks out GTG, than eventually it'll replace the 350

One of my experiences with the 400 was in my Blazer. Overheating, gas guzzling POS.

I bored it .030 when I rebuilt it, and got it hot again. Cracked the head and the cylinder this time. The blocks are siamezed, and can't take the heat.

I went with the 350 block after that, and had a 383 stroker engine. Now THAT is torque. The 400 was nothing in comparison.

The doc knows his stuff, and I can only tell you of my many wasted dollars on the SBC platform.

The stories are long about learning the hard way

 

[66nova]

LOL the doc and I will have to agree to disagree on this one

I should probably expand on my previous response. I don't think we are in total disagreement.

Every motor we have built since 1998 has been 400 based (406,406, 408, 408, 421,422, 427, 434) that's just ours.

Cooling is a big deal. We have always ran big radiators and we have never had issues with cooling.

I would never go to 0.060 on a stock 400 block. I wouldn't go over 0.040. The walls are getting pretty thin at that point. We have cracked cylinder walls, but we also hammer on them really hard.

Good 400 blocks are coming harder and harder to find. That brings me back to what Scott mentioned. A 383 is the smallest sbc I would invest money in. I like big cubic in small blocks. Great combos out there.

 

[PenguinLTZ]

The first 400 I built back in the 80s (before stroker engines really became mainstream) lasted quite a while, I just couldn't get that thing to twist higher engine speeds like I wanted, and I eventually overheated it as well, and then threw a rod

One thing I learned the hard way was the goddamn external balancing issues on the flexplates

I built a marine 350 solid lifter beast for my last offroad Blazer, that had such a violent vibration at around 2800 that I pulled it, and yanked every last bolt.

An old engine machinist who was missing most of his fingers walked into our shop, and was helping the old man with some heads on our Cummins truck engines, and overheard my dilemma. He asked me to yank the flexplate off the front of my TH400. He whacked the balance weight off with a ballpeen and told me to put that fWONkin' engine back together I was 18 years old

 

[Alljackedup408]

Old man knew! Haha