[CNC BLOCKS NE]

Originally Posted by k-star

Before this turns into another 2 vs 4 bolt wizzing match lets all take a deep breath...

It's all application driven. Carl spends alot of time with the dirt track roundy-round guys. They spin engines 5000 rpms off the turns and 8500 plus at the end of the straght-a-way. He gets to see what happens to blocks in the high demands of those applications.

Engines that are used for drag racing are a different deal,,as well as street engines. I have had some disagreements on this issue in the past with Carl. I am thinking ( with out putting words into his mouth) he is only trying to give the guy the best case for his build.

I personally have use many studded 2 bolt applications in 400+ hp street strip 350 engines with zero cap issues, but anything can break. I had one customer split a .030 350 4 bolt block in one cylinder due to detonation. 6 or 8 bolts in the mains would not have saved the engine...It just broke another week link.

It is always better to do what works then what you can get away with. If your good at setting up the tune and pay attention to whats happening inside the engine then at that power level and a street engine the 2 bolt is fine....IMO... a 4 bolt would be added insurance.


Keith

I have seen 400 horse 2 bolt mains work using a 3.480 stroke crank, Now factor in a 3.750 and thing change with that much stroke and 400 plus horse power we have seen caps move on 2 bolt blocks.

We build more circle track engines for sure but we build some street and strip stuff as well.

We are noted to build depenable engines that seem to be trouble free.

[baddbob]

CNC, is there a reason why nobody seems to dowel the maincaps to keep them from moving? I know Smokey Unick mentioned this in one of his writings. Many of the aftermarket rods have dowels for alignment and with straps or a girdle I think it might be a cheaper alternative than billet caps?

[k-star]

The problem with installing the dowels is all the time you would get into the perfect alignment and sizing to make them worth while.


I can agree somewhat, Carl on the longer stroke cranks and the loads they impose. I have seen blocks with cap walk but, none of them seam to have a real big effect on the bearings... what have you seen as far as cap walk and bearing issues on the 400 hp ish street engine???? I have a hard time getting these typ of engines back into the shop for maintenance. It's the old it's not broke don't fix it syndrome.


Keith

[machine shop tom]

A lot of the blocks I see are 350s (two and four-bolt) that have been subject to detonaton, so the ability of the owner to tune his engine comes to play here, also. The difference between installing splayed caps on the roller block (two-bolt) and retrofitting the older block (four-bolt) for a roller set-up is probably a wash, with the splayed caps block getting my preference. A 2 bolt block with studded mains and TIGHT registers is probably good for 450 HP or so, but the tune comes into question again. I like to err on the side of safety, but a two-bolt block will hold up to most street use as long as it's not too radical and is tuned properly. The added stroke of a 383 is certainly something to add to the equation and a 4 bolt would probably be the choice.

But all the engines I have built for myself latley have been four-bolts. But then againg I have a lot laying around to pick from.......

tom

[CNC BLOCKS NE]

Originally Posted by baddbob

CNC, is there a reason why nobody seems to dowel the maincaps to keep them from moving? I know Smokey Unick mentioned this in one of his writings. Many of the aftermarket rods have dowels for alignment and with straps or a girdle I think it might be a cheaper alternative than billet caps?

People have a misunderstanding about doweled caps as the dowel are just for alignment only and not for keeping the caps from moving as we build some blower engines with aluminum blocks and those caps still walk and they are doweled.

The SBC has a weak webbing to begin with and drilling or machining extra hole in the main cap area makes for weaker link.

The problem with the GM 2 bolt cap is there is not much surface area where the cap sets in the register. Now if the 2 bolt 350 blocks were as wide as the 400 2 bolt register then you could put some power to them.

[barnym17]

Guy's I gotta agree with carl, I have ran 2 bolts at pretty insane power levels of up to 550hp.BUT! This was in claimer dirt track applications where we knew it was a grenade with the pin pulled going in.Some lasted some didn't.On any thing I wanted to last a 4bolt would definitely be preferable and if pushing past 500 real hp I would say splayed mains are a very wise choice.I'm no machinist but build my own engines and get to pay when they go boom.We usually say it is not a matter of if it will blow but when will it blow. But when your racing in a class where $500.00 will take your engine and you want to win you do what you gotta do.

[Mustangsaly]

Originally Posted by machine shop tom

A lot of the blocks I see are 350s (two and four-bolt) that have been subject to detonaton, so the ability of the owner to tune his engine comes to play here, also. The difference between installing splayed caps on the roller block (two-bolt) and retrofitting the older block (four-bolt) for a roller set-up is probably a wash, with the splayed caps block getting my preference. A 2 bolt block with studded mains and TIGHT registers is probably good for 450 HP or so, but the tune comes into question again. I like to err on the side of safety, but a two-bolt block will hold up to most street use as long as it's not too radical and is tuned properly. The added stroke of a 383 is certainly something to add to the equation and a 4 bolt would probably be the choice.

But all the engines I have built for myself latley have been four-bolts. But then againg I have a lot laying around to pick from.......

tom

theres some good info on this board, but tom your about my age, and you say and explain things in a way that makes a lot of sense to me. you a asset to this board.

[6426yy]

I just wanted to chime in on this discussion be cause I've got the opposite problem. I have a 2 bolt 010 block that is fresh from the machine shop and a 4 bolt roller block that is somewhat fresh. You can still see the cross hatch pattern in the bores! But the heads that were on it were cracked and I haven't had the block checked yet.

I'll be ordering my stroker kit next week. I've already purchased a Crower solid roller and cut away lifters. P/N 00426 .570/.584 with duration at .050 250/252. I plan on running my SR torquers (I bought them before I bought this car) and running my old Offy dual quad tunnel ram with 390's. I plan on using the 4 bolt block if it checks out.

[Cousin_Joe]

Again, thanks to everybody for the input. I think I'll likely just play it safe (and cost friendly) and use the 4-bolt with a hydraulic flat tappet setup, and be extra careful breaking it in.

[CNC BLOCKS NE]

Originally Posted by Cousin_Joe

Again, thanks to everybody for the input. I think I'll likely just play it safe (and cost friendly) and use the 4-bolt with a hydraulic flat tappet setup, and be extra careful breaking it in.

Good cam core and lifters and lube there should not be any problems!!