[Glenn Lever]

Ok, we are building a 1,200 HP after market block.

I am currently running a stock cast iron block in an 8.0 index developing around 713 HP.

I am considering running it one more year and wondering if it would stand up to running in the 7.5 index.

The block is a 1970 Ram Air III block.

I carefully looked at the main bearing webbing under cutting when purchasing the block.

The only things left stock in the engine are the block and the four bolt main caps.

Everything else is capable of much more HP.

I do have the valley braces in the block, the block is not hard blocked.

I would need to run at lest 8,000 RPM at the top end.

I can drop about 200 pounds in weight (remove the water pump radiator and coolant, go to a smaller racing battery and a couple of other things). That would gain be about 2 tenths of a second.

I do not want to be on the razors edge of splitting the block.

So the question is how much HP can a stock cast iron block take and still be "safe".

Thanks Glenn

[BADDTA]

Glen that FED is kick a$$! My son and I are going to try and pull 900+ hp out of his 434 this upcoming season. 705 on motor + 200 shot n2o. I have done everything possible to strengthen the 67' 400 block. I'm hoping to get the season out of it and then get an IA aluminum block next fall. I know that doesn't really answer your question. Just letting you know your not the only one thinking about it.

Brian

[PAUL K]

I don't think there is a definitive answer to your question. It looks like you have a light car which will help. If you've been running the same combination in the past and it's holding up, I'd keep going. I have fourteen years on a 700 hp combination that sees a 200 shot of nitrous regularly and it's still going strong. However we're only seeing about 7400 rpm.

[mgarblik]

Glen, we ran about 1100 HP in 455 blocks in the Grocery Getter for years but we did eventually kill 3 of those blocks. Detonation is the killer and shock load from running a stick car probably didn't help either. This was with stock N cranks, 5 billet steel main caps, 3.25" main bearings. We ran 8200 RPM. We never had a catastrophic failure. All three blocks split in the same place. Right through the main oil feed up to the cam bearing. At the HP level you need to run, I would strongly recommend at least 3 billet main caps. I also really like the cushion aluminum rods offer. Don't know what you run. There is a certain risk and a narrower tuning window, stock block vs aftermarket. How many runs are we talking about in a year? We were averaging about 100 or a little more out of a 455 block at 1100 HP.
Call us crazy but we did not fill any of the blocks or use a lifter brace. It's all about everyone having a different opinion. I have never broken a filter bore in a Pontiac. We ran over 1" of lift at the valve. I value straight/round cylinders, better cooling and ring seal above some theoretical strength improvement. But Summit sells allot of concrete, so what do I know?

[BruceWilkie]

Do a search on Vin63 here... He's taken a 406 with cast crank to @8500+ and 19x mph on alky and a blower without the funny car body on chassis. Later went with 3.75" Ohio forging and ran over 200 mph with trap target of 9200 rpm same blower but on nitro. His race weight was near 3000 lbs with body on!

Steel splayed caps and lots of attention to cap fit/movement as well as harmonic control. Conservative tune a BIG factor as well.(tune-up can play havoc with harmonic control)
Dont know what oil system off hand, but at that level in ANY block I wouldnt have much faith in an internal system.

Marty P's old turbo'd 406 was over 1600 hp @ 7800 rpm. IIRC 38 psi. This was early to mid 90's

[mgarblik]

Those two are excellent high water marks to consider for a stock block. I know the quality of your car so I am sure your attention to detail will give you a little margin of safety. Still as you know, an IA II gives you allot more. I was just amazed when we did finally make the change, how much better the cylinders survived a tuning blunder. Where the stock block would be all out of shape and cut-up and require .020" to fix, the same type of mishap with an IA II and .002-.003 clean-up in the hone and it was like new again. Huge difference.

[BruceWilkie]

Originally Posted by mgarblik

Glen, we ran about 1100 HP in 455 blocks in the Grocery Getter for years but we did eventually kill 3 of those blocks. Detonation is the killer and shock load from running a stick car probably didn't help either. This was with stock N cranks, 5 billet steel main caps, 3.25" main bearings. We ran 8200 RPM. We never had a catastrophic failure. All three blocks split in the same place. Right through the main oil feed up to the cam bearing. At the HP level you need to run, I would strongly recommend at least 3 billet main caps. I also really like the cushion aluminum rods offer. Don't know what you run. There is a certain risk and a narrower tuning window, stock block vs aftermarket. How many runs are we talking about in a year? We were averaging about 100 or a little more out of a 455 block at 1100 HP.
Call us crazy but we did not fill any of the blocks or use a lifter brace. It's all about everyone having a different opinion. I have never broken a filter bore in a Pontiac. We ran over 1" of lift at the valve. I value straight/round cylinders, better cooling and ring seal above some theoretical strength improvement. But Summit sells allot of concrete, so what do I know?

Glad I'm not the only one. I cant see where adding a material that has such a vastly different expansion characteristic can do anything but MAYBE give some a warm comfy feeling. Maybe if poured and cured at expected cylinder wall temp???

On the lifter brace...seems a "drop on" fit and glued in place with JB weld(I like the properties) might be safer bet than bolting it in and then tightening...reminds me somewhat of a crude log splitter when you pull it down into valley with bolts. I prefer iron water crossovers. A steel strap across the back of the heads probably cant hurt.

Also like the idea of solid midplate but let front plate have a small amount of cushion. Chassis flex TO the block not THRU it. Bell area is strongest part of block. (IMO there is much merit in original 55-58 mounting scheme and concept only needs a tid of refinement to hold up to high power)

Lastly CHECK the oil feed passages to the cam bearings...

I found two different drill sizes were needed to clean out mud dauber nests in both a 69 400 and a 73 455 block I had.

There is a distinct step down on size as you approach the cam bearing. The bearing itself is the restrictor you dont need a step there. (I suspect the factory used a step bit to drill these.) Consider the step a possible stress riser and make hole a uniform size top to bottom.

My 59 block doesnt have any step BUT had considerable detailing to oil system already done to it when I got it.(work by unknown sometime in 1962)

Not saying its the cause of block cracking...just sayin' it cant be helping.

[92GTA]

Wow, great thread and discussion. Subscribed.

I'm looking to push 750HP + 200hp nitrous on my 461 and I was wondering if I needed to install all the lifter valley braces and block fill to the bottom of the freeze plugs. My 69 XH code 400 block was gone over with a super fine tooth comb by Houston engine when they did the build and it was as solid and as you could ask for and they threw the book at it machining wise.

When I do my new heads and cam it's been bothering me if I should do the lifter valley braces.

[Elarson]

If the lifter bores aren't braced, you have to be cautious of the opening rate of the cam. A radical opening rate puts more side load on the lifters. The Butlers advised us on this and were right on the money.

Eric

[johnta1]

When using roller lifters.

[Glenn Lever]

A little more information.

Fully loaded with me and fluids the dragster weighs 1800 pounds. 7.5 index would mean 190 MPH

I am running aluminum rods.

The engine is bored and stroked to 462 from a 400 (Main bearings are 3 inches) (was originally built for a carburetor and now is blown).

Cam is for a blower so raise rate is slow.

Seems like the responses are saying I can build more HP, just add more fuel and blow it a little harder.

Some shots of the new engine

If I do this the engine will be torn down honed, probably new rods (have 150 runs on it now). I could do billet caps.

BADDTA 705 plus 200 for 905?
PAUL K 700 plus 200?
MGARBLIK I think I talked with you at Bowling Green. Around 50 runs a year

[PAUL K]

PAUL K 700 plus 200?
[/QUOTE]

Just over 700 n/a with an additional 200 hp of nitrous.

[ponjohn]

I am completely confused by the fickle answers.

Not long ago there was a theoretic limit of around 700hp n/a depending on RPM. Much more if turbo'd.

Now everyone is saying 3500hp on nitro for a stock block is good to go.

[Tom Vaught]

Originally Posted by Glenn Lever

Cam is for a blower so raise rate is slow.

Seems like the responses are saying I can build more HP, just add more fuel and blow it a little harder.

Boosting a bit more and less rpm (as well as your raise rate being conservative) all helps in the package surviving and still going faster with the same Pontiac parts.

Tom V.

[charlie66]

I have a 461ci 660 hp +200 shot. No problems.

Soft ramp lob is key for better lifter bore life..

[BADDTA]

Originally Posted by ponjohn

I am completely confused by the fickle answers.

Not long ago there was a theoretic limit of around 700hp n/a depending on RPM. Much more if turbo'd.

Now everyone is saying 3500hp on nitro for a stock block is good to go.

I didn't see one person say that??

Brian

[Elarson]

There is no black and white limit.
700-ish horsepower is safe.
701-1000 is ever-increasing risk
Above 1000 hp the risk goes up exponentially and everything has to be pretty much perfect to survive.
Vin63 took stock blocks farther than anyone else imagined possible. Not for the faint of heart.

So it comes down to each individual's willingness to accept increasing risk.

Eric

[BADDTA]

Well said Eric.

Brian

[slowbird]

Originally Posted by BADDTA

Glen that FED is kick a$$! My son and I are going to try and pull 900+ hp out of his 434 this upcoming season. 705 on motor + 200 shot n2o. I have done everything possible to strengthen the 67' 400 block. I'm hoping to get the season out of it and then get an IA aluminum block next fall. I know that doesn't really answer your question. Just letting you know your not the only one thinking about it.

Brian

Jake have a diaper on the car?

[BADDTA]

It will. That's on the to-do list.

Brian