I have a question about the 5xx577 blocks. Full disclosure; I have the (gasp) 5xx577 block for my 462 stroker motor. However, i am not sure which one 568577 or 500577. It is an XF block. 1977. I will know casting # in a few days.
OK, got that out of the way. As for my usage: I never planned on drag racing car. My friend who build it knows this. I love speed but it has never been about a time slip for me. I am a torque addict. Everything I have ever had (toy wise) has been a torque monster. It is only natural I wanted a firebird 400 .

I digress, To my point and for further discussion/debate from people who are smarter than me:

My research has left me with nothing but what appears to be 'folklore'. Internet cowboys who repeat what they have read and frankly there is very little out there on these blocks to substantiate the 'weak' claims. I don't say that in a sense of it isn't true but how weak when compare to say a chevy 350 2 bolt main or a sbc 400 are we talking. YES! it is weaker than it sibling (various other years of 400) but lets define weak.

For discussions sake:

http://www.pontiacstreetperformance.com/psp/racerGM.html this is a 1976 ... (brace yourselves) a 76 400 pushing some serious numbers and a drag race car at that. ?????

also: H.P.P. page 66 Rocky specifies the one year, 75 400 block,and its casting #500557 to avoid. Does this mean the 568577 will survive abuse?

Thoughts?

I built a 577 1977 400 block few months ago. Yes there's less material in the mains but as long as your not winding it up 6500-7000 rpm I think it will be fine. But if it bothers you pick up a 68-74 block and stick with factory cranks.
There is a lot of folklore and mythology on the Internet about breaking parts and so on. Personally never seen it.

Thanks Bigchief. I do plan on limiting RPM to about 5400-5500 for dyno runs coming up and probably 5000 for my street use. I think I will be around 400whp. A note: when we opened the motor it had burnt and cracked pistons (forged). Machinist said block showed very little wear. So someone beat the snot out of it with nitrous or something in short order after a build. Block held up pretty well.

Probably in hindsight I would have tried to pick another block if I would have gotten wind of this detail before. Then I would have been in the camp of believers that repeatedly warn people of the 557's are 'terrible' without knowing it to be true or not.

However, its at this point, I have to ride this bull, but I do get the sense feel the misinformation is causing people to sign off the 557 blocks too quickly. The community could use more 'facts' on builds and failures with these blocks.

When building for power, most guys want the strongest parts available within budget.
Yes the 557's are the thinnest castings with least amount of nickel in the iron(adds strength).
Does that make'n bad? No, just there's stronger blocks out there.
But even they can be broken at 700 hp.

-557's are good up to 600HP

How many of us run 600HP?

By the way, I have one available if anyone is in need...

The later blocks have lower nickle content as well.

If I were going to build a 600 HP motor with 8-10k invested in rods and pistons, I'd opt for an early standard bore 400 of any code, including a Catalina or Lemons. 67-69 GTO or Firebird block and crank $800. Same year Cat, Lemans or GP? $300-400. Same block, just not a desirable correct "code".

It's piece of mind, insurance and assurance of my investment of machining and parts.

So just to close the loop on this: car is a 557 block with about 1400 miles driven so far.

315 rwhp (5000rpm) and 370 ftlbs (3800rpm)

car runs awesome on street. slight ping at WOT --- a work in progress

Sounds like a decent runner. Drive it like you stole it. Watch out for that pinging. Maybe try backing off the timing a bit. See if that helps.

thanks.

I hear ya. total timing is back to 30 degrees right now. (No vacuum advance) I feel like that is pretty 'retarded' already. Shouldn't it be mid 30's?

I have an 800cfm carb on it. Butler was pretty adamant I would need an 850. Maybe they were right.

I have an 800 cfm carb on my 464 ci, it's large enough.
I have my timing at 29 max. I got best power and torque on the dyno at 29. I also blocked off the vacuum advance as I was getting light detonation at part throttle pulls, none at WOT. I welded the low side advance slots in the distributor to keep the timing from going below 18 at idle. That gives me a cooler idle and have plenty of advance from idle to 3200 rpm.

Hey, Bluebird, you mention having best results at 29 deg. of timing...what heads and cam on that motor ? Frank.

KRE D port heads.
Hydraulic roller cam, 230/236, 112 deg. LSA

well, this is interesting. Maybe I will back off the timing a little more based on the feedback and see what we get.

( for comparisons sake) I have #62 heads and XE284 comp cam (240/246 and 110 LSA)

That 29 degrees number was just what I have the best power and torque with on the dyno. Every combo is different what is good for mine may not be good for yours. On the dyno we usually tune for max power, which is good if you run the car at max power, mostly race, but most of us use our cars for purposes other than race. You also have to consider what your lower rpm and cruise rpm will be like with a lower setting. When I first installed and ran mine I set the timing to 29 total, that only gave me 8-9 initial. My car ran roughly and hot at idle with the low advance. I didn't know at the time my vacuum advance wasn't working. After repairing the vacuum advance I got a smoother and cooler idle but a slight ping on partial throttle pulls, especially up hill. At WOT it was fine as the vacuum advance goes to zero with the throttle plates wide open but I was getting too much advance in some instances. I had the timing curve I wanted but needed to lose the advance at part throttle yet still have more advance at idle and low rpm. That's why I welded the slots on the low advance side instead of stopping the advance on the high side. I still get the curve I want up to 3200-3400 when the mechanical is all in. The joys [pain] of having a modified engine. Normally one would set the initial from 10-14 and the mechanical to 32-36, with the vacuum operating one would have around fifty at cruise for a nice cool and economical run.

Is your 400 stroked and bored to 463 cid now or is that a planned build?
Your 62 heads will have a small chamber, 72-75 cc, it may not be the timing that is giving you the detonation but the compression. A lot of factors to consider when facing detonation, grade and quality of fuel, quench, heat dissipation, static and dynamic compression ratio, timing, driving style, weight, gearing, cooling, etc.
You say you want high torque from your engine. That's a rather large camshaft, good for high rpm horsepower but you'd most likely get more torque at lower rpm with a smaller cam. I don't know how the 62s flow but you'd have to flow fairly well to use that cam.

yes build complete...I hear ya. I am just trouble shooting.



heads are 74cc and yes still working a lot of this out. Been a long process and not done yet. working on a low fuel pressure issue now when hot



When I say a lot of torque I meant it is what I believe makes a good driver not necessarily looking for a diesel truck. I was blinded by what I had at beginning of build and a desire to keep a nice car fairly stock..hence cast iron heads and the old holley street dominator intake. She is a good driver. I had a buddy wanting to sell me a well built LS1. I guess I just like spending money. :-(

Keep working at it, you'll have the runner you want. I've been at mine forever it seems but getting close.

update: I confirmed the timing was a little higher than 30 (more like 33/34) total. I set it to 18 and 31 total. Went one step cooler on plugs. Seemed to appreciate the change. I have a tank of about 15% cam2 right now. I will drive with this and once I run out of cam2 I will see what she does. Hopefully, I am on the way to no WOT Ping.

update: So she still pinged at WOT in the 3000-3500Rpm range. timing was backed off to 12 initial and 28 total. Good driveablity w/ 10 city and 12 mpg Hwy but stomp on her and she starts to ping in that range and would get rich (9:1 afr) and eventually stumble. I kept backing off secondary jets (116 to 107) and went through all sorts of combos of metering springs and rods on my edelbrock AVS 800cfm. Nothing seemed to help. I adjusted the air flap on the secondaries (thinking it might be opening too slow). No help.

Finally, called company X to discuss the possibility I needed an 850 cfm since that is what the butler guys said it would need, but I was hesitant since I had a good 750cfm which 'should' work. company x said, "OH NO, you need no more than a 750. So conflicted again about spending money on yet another carb, I turn to a friend that had just removed a mighty demon from his 540ci chevy and coincidentally it is the same set up he has on his 428 FGF (bored to 440). So I, being in between this two builds give it a try.

Put it on, fired it up, and it ran better immediately. Took it for a drive and ping seems to be gone. No loss of driveabliity at low speeds and pulls harder/smoother at WOT. AFR is maybe a hint rich. My vacuum is around 7 at idle so I changed the power valve from a 6.5 to a 3.5 this morning. I will fire it up tomorrow and see how she does.

For some reason people like to under carb Pontiac performance engines
Minimum I would use is a 850

I don't disagree with bigchief, but I've found the opposite, a lot think bigger is better and put large carbs, big camshafts and big honking intakes on their engines thinking they will make monster power as a result. Not always.
While I had mine on the dyno, we took my 800 eps off and installed a 750 holley. I got more horsepower with the 750. I wasn't about to buy a new carb. I had to lean mine by changing needles and jets to get the highest power. It may not have been the rated flow of the carb but it's efficiency, I don't know.
An engine will only pump so much air depending on its volumetric efficiency. Fuel flow in pounds per hour, mass air flow, volume of airflow at standard day, air temp, air density, etc all affect the engine's performance and carb size requirement. There are many formulas to determine volumetric efficiency, mass airflow, PPH of fuel flow, SCFM air flow and on and on. At 100% volumetric efficiency on a standard day my engine should use 671 cfm of air at max power rpm and 644 cfm of air at tax torque rpm. My engine reached it's max power level at 5000 RPM and it's peak torque at 4800 rpm.
SCFM at 100% VE=displacement X rpm/4256=464X5000/3456=671.2964
Now not very many naturally aspirated engines achieve 100% volumetric efficiency although some go slightly above at certain rpm during the dyno runs.
That doesn't mean I should put on a smaller carb, just because a carb is stated to be 800 or 1000 cfm rated doesn't mean one will be using 100% of the carbs rated flow. You have a large carb and only draw what you need but you can't draw what you need if the carb is too small.
I think one has a more efficient system if he or she uses a carb just slightly higher flow rated than the engine requiers.

OK I was thinking more about this as I had my bbqed brisket and beer.
It's rather difficult to determine what one needs for a carb, as every engine, other than a bone stock one, is different in the way it breathes. My heads flow a certain cfm but they have relatively small ports, they get the flow by high velocity, a large port head may flow the same cfm at a lower velocity. Big hole low velocity small hole high velocity, for the same flow. I don't pretend to know much about the different flow characteristics of all the available carbs on the market as it relates to air speed. One can only go by what one has experienced, I know what works for my engine but others who have dealt with more engine combos than I, may have a completely different thought on what cfm is needed in a carb.
Just my thoughts,
I'm not an expert.

My old 406 only had D ports that flowed 209 cfm and 12.75:1 compression the carb that the car ran it's best was a professional built dominator that flowed 930 cfm. I would guess VE over 100%
Current 462 has a 1050 Dominator in my street car with 220 cfm D Ports.

I remember many moons ago my buddy gave me a Holley 850 DP carb. He said there's nothing wrong with it but you have to replace the power valve about every year. I bolted it on in place of my...now come to think of it that was the first 4bbl carb that I used on the 350. So that replaced the original 2bbl. Man, I tell you what, that carb change really woke up that 350. First time I could light the tires from a 5mph roll. I think it ran stronger with that Holley than it did with a new 750 Qjet.

Shows we really don't know what will work best until we try different combos. My d-port heads flow 310 and a 750 works better than an 800.
Not many of us have a box full of carbs to try until we find the one we like, I know I don't.

I had a double pumper on my 68 GTO. High compression, solid lifters, single plane, ran great, got 6 miles to the gallon. Swapped it for a Q-jet and a dual plane, ran great, got 14 MPG.
My 428 in the Firebird gets 14 mpg on this island, I get 22 mpg on the highway at 80mph, but a lot of that is due to the fifth gear, I suspect it would get better mileage with a Q jet.
Don't know but suspect.

Camshaft and carburetor tuning has a lot to do with it. Even with a double pumper your only driving off the primaries till about 1/2 throttle depending what linkage is on the carb.
A professional tuned carb is just as good as EFI.

good discussion here. I have had the car on the road for a little over a year with the edelbrock carbs (750/800). I have used all the carb CFM calculators on the internet and talked to many experts and no one agrees what was going on. It was easy for everyone to blame compression or the POS edelbrock.
So I took it out for a short 5 min run to make sure I got the carb all squared away after this happened.




After that short drive I believe it may come down to the transition circuit. Carb had a 6.5 PV when I received it and for that first drive that resulted in no pinging. With the more appropriate PV (3.5) given my vacuum at idle the car pinged again. Although, much much less than before the Mighty Demon went on the car. For the life of me I don't know how I could have solved it on the edelbrock.. I mean I tried everything except a bigger primary jet. If the mighty demon keeps working out so well we may never know ;-)