[Tinindian81]

Hi. I have a similar situation. I have a 577 cast block. My dream setup in my T/A is the stated 400 block. I'm after more torque than horsepower. but would like both. So. I plan on stroking the 400. aftermarket heads. Scat 4.5 stroke rotating kit. Overbore not sure yet? .030 .060? 411 rear end gears. With a 6 speed manual transmission. I'm after off the line performance with HI way drivability. This project is totally a manual trans setup. I'm not going to be drag racing it. But, I want the power when it's there. 5000 seems to be the limit on Pontiac motors. Any input will be greatly appreciated! Thanks!

[b-man]

Originally Posted by Tinindian81

Hi. I have a similar situation. I have a 577 cast block. My dream setup in my T/A is the stated 400 block. I'm after more torque than horsepower. but would like both. So. I plan on stroking the 400. aftermarket heads. Scat 4.5 stroke rotating kit. Overbore not sure yet? .030 .060? 411 rear end gears. With a 6 speed manual transmission. I'm after off the line performance with HI way drivability. This project is totally a manual trans setup. I'm not going to be drag racing it. But, I want the power when it's there. 5000 seems to be the limit on Pontiac motors. Any input will be greatly appreciated! Thanks!

I can’t think of a worse block to start a 4.5” stroker build with.

A strong lower block structure is required for that long stroke which the 557 block does not possess.

Find another 400 block.

[Jay S]

Originally Posted by b-man

I can’t think of a worse block to start a 4.5” stroker build with.

A strong lower block structure is required for that long stroke which the 557 block does not possess.

Find another 400 block.

X2..with b-man…The 4.5” crank will push the main saddle’s out of the late block. Find an earlier block.

“5000 seems to be the limit on Pontiac motors”…..

?For doing what?

[Dragncar]

Originally Posted by Tinindian81

Hi. I have a similar situation. I have a 577 cast block. My dream setup in my T/A is the stated 400 block. I'm after more torque than horsepower. but would like both. So. I plan on stroking the 400. aftermarket heads. Scat 4.5 stroke rotating kit. Overbore not sure yet? .030 .060? 411 rear end gears. With a 6 speed manual transmission. I'm after off the line performance with HI way drivability. This project is totally a manual trans setup. I'm not going to be drag racing it. But, I want the power when it's there. 5000 seems to be the limit on Pontiac motors. Any input will be greatly appreciated! Thanks!

Everything about this, needs another direction. 557 blocks are not only useless for a engine like this they are dangerous. If, you build a stroked out to 4.5" block with big ported round port heads there is no need for 4.11 gears on the street. Even with a overdrive trans.
And 5000 RPM is not the limit on a Pontiac engine. I have seen 450 HP 557 block engines with 3.75 cranks rip the mains out.
I think you are better off with earlier block and 4.25 crank.
Myself, 6 speed, street car, 400 with 4" crank or a 455 with 428 crank.
Folks seem to love them.

[77 TRASHCAN]

Jay, I will likely "re" build one of my 557 stock 400 engines. Using mostly ALL stock parts. I have 2 557's in my "too big" parts inventory(!) One is my TA 400. I had to drive it some, with the#7 "exhaust lobe in failure mode. It's been on a stand since 1992, untouched.

Second was in my (late Pontiac buddies) 78 Catalina, that he special ordered.

My initial plan will to thoroughly clean the block, then have it checked for cracks,
Then de-burrr the whole block. The main focus will be on chamfered the oil holes in the air saddles and the dowel alignment holes in saddles, also.

Pretty much a stock build, with many details....

[Steve Shively]

I have a 557 shortblock I want rid of if you want...

[Jay S]

Originally Posted by 77 TRASHCAN

Jay, I will likely "re" build one of my 557 stock 400 engines. Using mostly ALL stock parts. I have 2 557's in my "too big" parts inventory(!) One is my TA 400. I had to drive it some, with the#7 "exhaust lobe in failure mode. It's been on a stand since 1992, untouched.

Second was in my (late Pontiac buddies) 78 Catalina, that he special ordered.

My initial plan will to thoroughly clean the block, then have it checked for cracks,
Then de-burrr the whole block. The main focus will be on chamfered the oil holes in the air saddles and the dowel alignment holes in saddles, also.

Pretty much a stock build, with many details....

Jeff have you had the main caps off both your engines? Do they both have dowel pins to index the mains?

I am still of the opinion that above 350HP do main studs on these 557 engines, with dowels or roll pins.

You know me, I’d love to see the number matching engine back in the T/A.

[Jay S]

Originally Posted by Steve Shively

I have a 557 shortblock I want rid of if you want...

That would be great. I”ll PM you.

[Tinindian81]

Yeah. I'm Thinking the same. I got the block for free. probably why? Even though my 81 came with the Chevy 305. I want to keep it Pontiac. Been thinking about the Chevy 454. SB 383 stroker. This is why I joined this group. To get input from all angles! thank you!

[Jay S]

Originally Posted by Tinindian81

Yeah. I'm Thinking the same. I got the block for free. probably why? Even though my 81 came with the Chevy 305. I want to keep it Pontiac. Been thinking about the Chevy 454. SB 383 stroker. This is why I joined this group. To get input from all angles! thank you!

Look for a 455 or stroke a earlier 400. If you want tq and HP, SBC 383 would not measure up well on tq compared to a big stroke Pontiac.

[77 TRASHCAN]

Originally Posted by Jay S

Jeff have you had the main caps off both your engines? Do they both have dowel pins to index the mains?

I am still of the opinion that above 350HP do main studs on these 557 engines, with dowels or roll pins.

You know me, I’d love to see the number matching engine back in the T/A.

Both engines have been on stands for years, just as removed. I used to think I could build one good " hot rod" engine out of the two. Withe the knowledge we all have. I will possibly build them to a stockist standard.
My thoughts are of tearing down the 78 Catalina 400, to see what I have. I am unsure of my buddies maintenance doings?
I took extreme maintenance measures with my 400. I was was unhappy to find that flattening cam lobe on it, way back. I bought a set of standard forges pistons for it, here. Of course, many measurements will be in line, to see if that's possible.

I'm really curious to see what the 78 cam looks like. I sold auto parts in an independent auto parts store from 1985 to 1998. I probably sold 6 Pontiac cams in that time. They were all purchased to improve power, and all went into TA's. I saw 3 or 4 of the h e old cams. They ALL had lobes that were at least starting to go down. The cams I sold were either the 260H or the 268H Higj Energy type cams, The XE stuff was not happening at this time. All the customers loved their new cams!!!

I'd like to zero deck the 78 block, mill the 6X-8 heads. Do some mild porting on the heads and intake. My idea with this stockist 400 is to keep port velocity up.
I PM'd Dave at SD Performance, years ago. He had zero reservations about using the last of the Pontiac EGR iron intakes. Of course it will be conservative grinding on it to. I have some intake grinding thoughts that I have not seen on any other Pontiacs, at least, here.
I hope to use 5/16 pushrods with stamped 1.65 rockers. 90's.
Of course, this all thoughts, for now. Even if this engine idea only improves a stock low compression, a little bit, it WILL perform good enough, for a while. I rebuilt the 2.41 position rear end in 2001. I'd like to drive it in its stockist form, for a while, at least. The car ranso very well. The first 50-60,000 miles. I'd like to deal that again, before I build a fire breathing 456 into it

After reading here, A LOT, it seems like keeping roll pins in 557 blocks, may be the wiser way to go? What do you think?

The roll pins have some give, possibly allowing the block and/ or the main caps to flex just a fuzz, without snapping a chunk out of the block. All the photos here, of broken 557 blocks, the dowel pin and oil holes in the main saddles look untouched. Nothing touched. ShRp edges all around those orifices...

[Jay S]

If the engine survived this long with dowels I would guess it should be ok on a reasonably stock build. Every once and a while, due to poor alignment, you will see a broken main cap at the dowel hole on the older blocks. On the later blocks, if the dowel alignment wasn’t perfect instead of breaking the cap at the dowel hole, they start a crack at the dowel hole on the block. The late blocks are not very forgiving on dowel alignment.

The roll pins used in 557 blocks are not strong enough to start a crack, but they don’t index the caps all that well, they tend to spin main bearings. Those engines really need the extra clamping force of main studs.

It seems either cap index method was used on those blocks for the 77 and later years. Every broken block I have seen were broken thru the dowel holes. The crack started there, then continues to grow until the entire bulkhead breaks out. The more power is put to it, the quicker the crack grows. There are quite a few 557s out there that already have a crack started at the dowel, it good idea to have the block magnifluxed at those dowels before you get very far into them.

The best solution for the indexing seems to be reaming/honing the dowels to 5/16” and using longer dowels that engage more with the caps, it seems to make the caps share more of the stress, with less leverage on the block. The dowel then has full contact the entire depth from the bottom of the drilled hole in the block to the top of the cap.

[Tinindian81]

Thank you! 455 is my favorite Pontiac motor! Makes total sense!