[10secbird]

I'm thinking of starting a new engine build with a spare 455 4 bolt block I have lying around.

I'm interested in how much cubes I can reliably build into a stock 455 block.

Can you guys tell me what the biggest bore and stroke I can run? I assume if people are running stock blocks they are generally sleeving the entire block if they want to run any bores that are more than .060 over stock bore.

What can you guys tell me about sleeving stock blocks? What are the down sides of sleeving if any? Cooling between center cyldrs or? I would love to build an aftermarket block motor, but that's just not in the cards for me right now.

Also, do you think it would be better to use a small journal block? I have 2 455 blocks, but no small journal blocks. I could probably find someone willing to trade if you think a 400 block is a better block to start with due to the main journal size.

I'm looking forward to building my first aftermarket headed engine with a roller cam and these days, after reading about what all you guys are running, my 462 is feeling kind of wimpy....lol

My 48 heads and flat-tappet cam are due for an upgrade and I'd also like a few more cubes

I can't have a 540 yet, so how big can I get with a stock block.

[10secbird]

Should have mentioned....I will most likely buy a rotating assembly from KRE .... what mods required on a stock block to run a 4.5 stroke crank if it's possible

[mgarblik]

I am not a fan of putting sleeves in a performance iron block except as a way to save a block because of cylinder damage. It is a very intrusive machining operation and adds lots of instability and stress to the already marginal block structure. Also, the cost really becomes a factor if putting in 8 quality sleeves. Around here, properly machining the block with a step at the bottom to accept sleeves would run $800.00-$1000.00 for 8 including the sleeves but not including the bore and torque plate hone of the new sleeves. That would add around $500.00. So with just the sleeve install, you are half way to a quality aftermarket block! Then add a line hone becaused the sleeve install will distort the hell out of the housing bores, add steel caps and you add line bore and hone to the cost. Then add the cost of square decking the block because the sleeves distort the hell out of the deck and by the time you are done, you are right at the cost of an aftermarket block and you have a far inferior piece to work with. Not picking on you in any way, just pointing out the true cost to get a stock block to a big displacement and point out how lucky we are to have the IA II and other aftermarket blocks. We used to go through this whole process with the Grocery Getter in the old days, then go out and hurt the block or break off a lifter bore and we were back to square 1. Once you buy an aftermarket block once, you will never go back. Finally to answer your original question, The largest I would build a stock block is +.060 4.25 stroke, light rotating assembly, 7500-7800 RPM max. Slow opening ramp on the cam to keep the lifter bores in the block.

[BruceWilkie]

What mgarblick said ... However if stayin with factory sono the block... some might allow up to 4.25 bore(dont plan on it but if its safe enough cant hurt) preferably 3" main as it is stronger(except 557 casting). IMO stroke beyond 4.25 in a stock block only ups the stress level...

Core you start with makes a big difference... water jacket corrosion/erosion and core shift indications like offset core plug holes are not good candidates.

If you stay with mechanical flat tappet, lifter bores wont get stressed as the cam cant push the lifter to the side in the way a roller does... You can get pretty good lobes in a solid flat... often as good as a street roller and adding hi ratio rockers further ups the power possibilities.

Block prep makes a huge difference in liklihood of things goin wrong! More you detail the less likely you have problems later... Clean up casting flash leave no sharp edges etc.. Payin someone to do it for you is not cost effective. I was detailing a block once and near done when I found a crack I should have spotted earlier... saved me the expense of finding out the hard way like after machining process or worse yet after an engine failure. The extra time detailing IS extra time seeing things you need to see!

There are strong factory blocks. Prior to 61 and thinwall casting techniques they were pretty beefy...BUT if it aint cheap or free you have to fab a trans adapter that will also allow the use of a bell mount starter. Dependin on year and cooling scheme you chose there are slight deck hole changes that need attention.(I know as my build is based on a 59 block) The 67 2 bolt drilled 400 block is said to be pretty beefy as are early 70's 400 castings(as are late 70's '8XX service replacement castings.) Speacial blocks like RAV and SD455 are beefy and even have the lifter bores secure but finding one would cost a fortune or be like winnin powerball if you just stumble on one cheap.

factory caps... some arent too bad but many a 2 bolt and 4 bolt iron caps have been broke over the years... most are smallish... especially #1...

2 bolt drilled blocks are better than straight drilled 4 bolt... the outer holes are not in the stronger part of the bulkhead and not suitable for splayed 4 bolt caps(which tie the block better and are located into the stronger portion of the webbing). Studded 2 bolt seems to be better than factory 4 bolt and many have done fine at the 600+ hp range.

700 hp seems the limit most are willing to push a stock block and there are some who have gone more than double that limit... but at those elevated levels they know their block WILL crack eventually and adjust their inspection schedule accordingly.

Keep in mind rpm and stroke are very important in the durability of a stock block... HP itself not as much. A well tuned power adder on a 400 that doesnt exceed 6000 rpm could well exceed 800 hp and live quite awhile if it never sees detonation or pre-ignition.

[10secbird]

Thank you guys ... great informative answers. Looks like 4.21 X 4.25 So I guess a 472 is the limit without getting all crazy and still having reasonable reliability. I appreciate all the insight on machining requirements and great info on using old blocks etc.

[Dragncar]

Sd Performance has built several stock block engines with 4.5 arms.
I would have no problem with a 4.35-4.375 stroke if you keep the RPMs reasonable.

[screamingchief]

Block does'nt limit the stroke you can use,so you can go bigger than that with an aftermarket stroker crank,so no 472 cid is not the limit for a stock block.

But yeah it's generally accepted that the stock block bore can often go 4.25" when sonic test results say so,possibly even a bit more but most prefer not to push that limit too hard.

Anyhow,yeah there are 4.250",4.350",4.500",and 4.750" stroker cranks out there for 3" main blocks and 4.250" and 4.500" stroker cranks for the 3.25" main blocks.

So,for a 455 block (3.25" mains):
4.250" bore x 4.250" stroke = 482 cid.
4.250" bore x 4.500" stroke = 511 cid.

And I'm not a fan of sleaving blocks either.

Sonic test to know if the wall thickness is there to go to a given bore size,and be sure to fill the block to support the cylinder walls,and know that you did what you could to try and help it live as long as possible.

As for the mods required for the 4.500" stroker cranks,I believe that's been discussed here in the past,and IIRC it's NBD really.

HTH

Bret P.

[racegto65]

I've been running 2 different 455 blocks for years one is 4.250 x 4.210 and the other is 4.250 x4.250. They are also poured half way up the water pump holes.

[455firebird1969]

A 750 HP stock block will split at the main webbing, shortening its lifespan. The more power, the shorter the life. My last engine made about 600 HP and on the 1087th pass (seven years), it spun a rod bearing. Upon tear-down I found the main webs splitting, so at lower power levels the block life is longer before the mains split. A 4.21 stroke .03 or .035 overbore (462 or 463) can easily make the power in that 750+ range with the right cam and good heads, so it's not like you need the stroke to make the power. Other than offset grinding the crankshaft for 4.25 stroke to use the chevy size bearing, rod and piston combinations that are available, I don't see more than 4.21 or 4.25 needed to make block splitting power.

I considered a larger bore and/or stroke for my new engine build, but in the end I choose to go the offset grind 4,25 stroke route, so I could use a set of Ross pistons I already had. With some head porting and a little more cam, my new build (468) should make close to 700 HP, but there is no way it is going to last seven years like my last engine.

Having said that, it is a compromise when using a stock block, as more power equals shorter lifespan before the block tries to split in two. With a roller cam and aftermarket heads you already have the potential to make block splitting power without a long arm.

[J.C.you]

I would trade or sell the 455 4 bolt to a guy wanting a restro motor. Hand pick and sonic check a 400 block and install splayed caps on the three center journals. I assume this is a race motor, so preferably fill the block halfway up the wp holes. Use a 4.5 crank and the lightest rotating assembly you feel comfortable with. Prefer aluminum rods and spring for some titanium pins. Lifter bore brace and like mjarblik said, keep the opening ramps on the cam in check. A good 400 core will go 4.18 bore easily.

Since you are dealing with Kaufman a stock set of HPs would go nicely with the setup and make 700 hp easily.

[Jim Zeek]

Originally Posted by J.C.you

I would trade or sell the 455 4 bolt to a guy wanting a restro motor. Hand pick and sonic check a 400 block and install splayed caps on the three center journals. I assume this is a race motor, so preferably fill the block halfway up the wp holes. Use a 4.5 crank and the lightest rotating assembly you feel comfortable with. Prefer aluminum rods and spring for some titanium pins. Lifter bore brace and like mjarblik said, keep the opening ramps on the cam in check. A good 400 core will go 4.18 bore easily.

I ran a butler 502 kit in a 400 block. it had straight billet caps on three center journals. billet front cap. mega brace. 4.500 forged crank. 4.210 bore. 6.8 grp rods. ross domed pistons. filled 1/2 way up water pump holes. no problems. shifted at 6500 going thru at 6900

[Donovan]

Why not sell the 455s and buy an aftermarket block? Your requirement to go as large as possible seems to trump looking stealth or original?

There's no reasonable cost argument here. Extra prep work, machining and misc stuff will eat the difference. With a performance aftermarket block you very well may not need to have that extra 455 around taking up space...

Now you are 4.25" bore PLUS, and you get all the additional features that will never come from a stock block. Like compatibility with all GM transmissions, priority oiling, lifter bores that don't break off.

[Dragncar]

I do not think the aftermarket blocks have priority main oiling like a BBC.
Anyone know for sure.

[73 TRANSAM]

No priority oiling for the aftermarket block.

[Tom McQueen]

Fairly simple to add a .250" external hard line to put a pressurized oil source on the front main of the aftermarket block and oil the rotating assembly from both ends.

[BruceWilkie]

Originally Posted by Tom McQueen

Fairly simple to add a .250" external hard line to put a pressurized oil source on the front main of the aftermarket block and oil the rotating assembly from both ends.

http://www.pontiacsafari.com/55/Shop...ubrication.pdf

With a little creative plumbing...

Study the stock oil routing... if you block the 8 lifter bore oil holes on the driver side then create new feeds to those lifter bores from the passenger galley then oil goes to mains first and the lifters would all be fed last!

The stock routing is fine for most apps.

[Donovan]

Originally Posted by BruceWilkie

http://www.pontiacsafari.com/55/Shop...ubrication.pdf

With a little creative plumbing...

Study the stock oil routing... if you block the 8 lifter bore oil holes on the driver side then create new feeds to those lifter bores from the passenger galley then oil goes to mains first and the lifters would all be fed last!

The stock routing is fine for most apps.

Very fun and informative read, thanks Bruce!

[Donovan]

Originally Posted by Dragncar

I do not think the aftermarket blocks have priority main oiling like a BBC.
Anyone know for sure.

Good catch. They say "improved oiling" which I read into.

[Half-Inch Stud]

Originally Posted by Jim Zeek

I ran a butler 502 kit in a 400 block. it had straight billet caps on three center journals. billet front cap. mega brace. 4.500 forged crank. 4.210 bore. 6.8 grp rods. ross domed pistons. filled 1/2 way up water pump holes. no problems. shifted at 6500 going thru at 6900

Jim, I would have more confidence with that in a 455 2- bolt drill block with 3.25" Mains; would you figure as well?

[jm455ho]

Originally Posted by Tom McQueen

Fairly simple to add a .250" external hard line to put a pressurized oil source on the front main of the aftermarket block and oil the rotating assembly from both ends.

Could you please explain how that would be done.
Thanks