[CNC BLOCKS N/E]

This block came in the engine shop today and the customer wanted to know why the bearings were tore up and once I pointed out that the center caps were flexing and pinching the bearings that why the copper was showing on the sides of the bearings and the crank was in bad shape and needs to be turned as well.

Notice the registers and how they are fretted and the metal transfer from cap to block as this was a 400 horse 2 barrel circle track engine and this engine was balanced and the pistons show no signs of detonatoin.

This guy read in a magazine that 2 bolt blocks were good for 450 horse and now he has a little different opinion on this. I told him thats why a 2 bolt 400 block have wider center main caps as this helps keep the cap more stable in the register.

Now we will put center splayed caps on this block and I am sure next year the bearing won't look like this.

 

[Junkyard Dawg]

What was it that the late Smokey Yunick said about a 2 bolt being good to 600 hp?

 

[BB_Mike]

Horse power alone isn't the only problem. Horse power over time, that's the problem.

How many miles/races did that 2-bolt block have on it? Whas this dirt-track racing? they turn some high RPMS when those tires get spinning and Cole Trickle decides to drop the hammer.

 

[CNC BLOCKS N/E]

What was it that the late Smokey Yunick said about a 2 bolt being good to 600 hp?

Ya for how long ?????????????

 

[gspan1830]

Those caps don't look like they fit the block, They're too small to fit snuggly into the block.

 

[Whittaker]

CNC,

I'm glad you posted that. I find all this very interesting and keeps us informed way more than some rag of a magazine.

Thanks

 

[CNC BLOCKS N/E]

Those caps don't look like they fit the block, They're too small to fit snuggly into the block.

They are the original caps they no longer fit the registers as they are very sloppy and thi only ones that fit are the front and rear and this engie run at a 1/2 mile pavement track.

 

[jbird]

My 468 mains bearings looked very similar to that at every rebuild. The caps were not nearly that bad though. It was a studded 2-bolt and made over 600HP(maybe as much as 650). The caps walked around a little, but not as much as that one. I never had any problem with it except the bearings always had copper showing on opposite sides like those in the picture. The crank was always fine.

 

[Daren71]

Carl, two quick amateur questions, are splayed caps the ones that the block is machined to fit 4 bolt, and how would a person know that the engine has experienced this type of failure? Was there a rod knock, or was this engine to be torn down for a new season rebuild? Thanks, Daren

 

[BillsCamino]

Carl,
Another question...were the main caps bolted or studded?
BTW, good info!! Thanks for taking the time to share this.

 

[jbird]

Carl, two quick amateur questions, are splayed caps the ones that the block is machined to fit 4 bolt, and how would a person know that the engine has experienced this type of failure? Was there a rod knock, or was this engine to be torn down for a new season rebuild? Thanks, Daren

Not trying to answer for Carl, but in my case I never noticed any kind of failure or problem, just noticed the bearings when I would freshen it up.

 

[30-A rider]

Very interesting. I am no pro at this but correct me if I am wrong. From what I have been reading, that 2 bolt main block would have been OK and lasted much longer if it wasnt in the application of continued high RPMs. If a 2 bolt main 400 hp motor was lefts say in a street strip car that wasnt seeing high rpms all the time it would have been a diferent story? No? Am I wrong for thinking this?

 

[CNC BLOCKS N/E]

Carl, two quick amateur questions, are splayed caps the ones that the block is machined to fit 4 bolt, and how would a person know that the engine has experienced this type of failure? Was there a rod knock, or was this engine to be torn down for a new season rebuild? Thanks, Daren

They did not know this till it was taken apart for a refreshen and it was noticed one thing to remember this ran every weekend on a 1/2 mile pavement track and to dupicate this on the street or drag racing would take years The rod bearings did not look as bad as the mains did.

We machine the registers 7.500 wide for splayed caps and th otter bolt holes are at a 10 degree angle.

Here is a pic of a block all done with splayed caps.

 

[Eric68]

Very interesting. I am no pro at this but correct me if I am wrong. From what I have been reading, that 2 bolt main block would have been OK and lasted much longer if it wasnt in the application of continued high RPMs. If a 2 bolt main 400 hp motor was lefts say in a street strip car that wasnt seeing high rpms all the time it would have been a diferent story? No? Am I wrong for thinking this?

You are exactly right Usage is probably a bigger factor than HP.

I just went through a street-strip 327 (2 bolt LJ mains) with a 142 blower for a friend that is a fair bit over 400 HP. It goes mid-11's in a 3600 lb (with big driver) 69 Camaro. It looked fine and went back together. The difference is that this car gets a lot of lower RPM street miles with occassional 1/4 mile blasts.

 

[Daren71]

Carl, thanks for the info, Daren :thumbsup:

 

[CNC BLOCKS N/E]

Carl,
Another question...were the main caps bolted or studded?
BTW, good info!! Thanks for taking the time to share this.

This block used studs as the Canton pan they used required studs to hold the windage tray in place and we have seen this on both studs and bolts as there is not enough cap register to keep the caps stable.

 

[MarkM]

What was it that the late Smokey Yunick said about a 2 bolt being good to 600 hp?

Being a big Smokey fan, I've never heard him make such a statement. I may be wrong, but I'd need that quote sited.

 

[BB68]

Carl, thanks for taking the time to post this.

 

[383Malibu]

...this ran every weekend on a 1/2 mile pavement track and to dupicate this on the street or drag racing would take years...

I hope everyone read this as closely as you did the opening topic. My point is that how the motor is built, maintained and used are all significant players in this kind of scenario. For example, the 383 in our Malibu is a stock 4-bolt block, makes about 660 hp, gets launched at 6600 - 7000 rpm and shifted at 8000 - 8200 rpm and has looked fine at every freshen-up. Although I have to admit that I keep wondering how long it will last. :clonk:

 

[69 Ratt Vette]

I hope everyone read this as closely as you did the opening topic. My point is that how the motor is built, maintained and used are all significant players in this kind of scenario. For example, the 383 in our Malibu is a stock 4-bolt block, makes about 660 hp, gets launched at 6600 - 7000 rpm and shifted at 8000 - 8200 rpm and has looked fine at every freshen-up. Although I have to admit that I keep wondering how long it will last. :clonk:

Big, big, differance when comparing the stresses of a circle track motor to a drag race motor. One circle track race is equal to more than a season of drag racing as far as rpms and stress goes.