[Johnny406]

This month will be the final month of racing my good old and faithful 463. It's been in service for a decade now and still have the original 455 4.21 stroke crank with many many nitrous hits so it's time to create a new powerplant.

With that said, I recently picked up a (barely) used 4.50 stroke forged crankshaft (dyno only) and a new set of 6.700 BBC connecting rods.

I'm going to wait until I pull the 463 out and inspect it hard before I decide weather to use the 455 block or the 428 block. Both blocks of course are 3.25 main as is the 4.50 crank.

The 455 block is a 2-bolt block (4.181 bore with Icon 888 pistons) drilled for 4-bolt and has been bottom filled to stiffen the block. I have purchased a set of factory 4-bolt center caps for it and will have them test fit and hopefully only align honed (fingers crossed).

The 428 block is a factory 4-bolt with a 4.155 finished bore cylinders. The late great Greg Merrick honed it for me years ago to fit the Venolia 428 pistons I bought from him at the time.

Either way, I have work to do. I'd prefer to reuse the 455 block assuming it checks out as it's been zero decked, squared and bottom filled. I can then put off the 428 build and use my 990 forged crank for another application.

I did a search here looking for this info but I really didn't find what I was looking for on what is the best piston to use for a 4.50 stroke factory block build. It looks like the Ross pistons are a little weak in the skirt. Icon does have 4.50 stroke pistons for either application.

Anyone have a recommendation on what piston to use? I will be using my 74cc KRE 292cfm D-port heads. This is a bracket motor, not a street motor.

Thank you,
John

[Geoff]

Did Greg Merrick pass away?

[Johnny406]

Yes he did, about a year ago.

[Mike Davis]

Not sure why there are not many replies. I know most of the Scat over the counter rotating assemblies come with the Icon pistons. I have used these for other applications with good luck and they measure spot on. I believe Paul K has built a few 4.500 engines, hopefully he will chime in.

[AIR RAM]

I'm currently building a similar 455 w/ 4.5 Scat Crank and using 6.7" Scat H-Beam Rods custom 4.19 CP Carrillo pistons with a 40cc dish to be used with my EDL 72cc round port heads which should land me at approximately 9.2:1cr... Will be adding 10-12lbs boost with a TTs'.

I do plan to run both mid and front plates to minimize block flexing.

Its slowing coming together as we speak. The block is filled to the bottom of the freeze plugs and currently getting the 4-bolt splayed mains installed. Ive chosen to replace the center 3 mains + the front main and running the longer dowels.

SPEED SAFE, NICK

[Mike Davis]

Originally Posted by AIR RAM

I'm currently building a similar 455 w/ 4.5 Scat Crank and using 6.7" Scat H-Beam Rods custom 4.19 CP Carrillo pistons with a 40cc dish to be used with my EDL 72cc round port heads which should land me at approximately 9.2:1cr... Will be adding 10-12lbs boost with a TTs'.

I do plan to run both mid and front plates to minimize block flexing.

Its slowing coming together as we speak. The block is filled to the bottom of the freeze plugs and currently getting the 4-bolt splayed mains installed. Ive chosen to replace the center 3 mains + the front main and running the longer dowels.

SPEED SAFE, NICK

Did you have those coated or were they already done?

[Singleton]

I have a pump gas 495 in my street car. 4.185 x 4.5, with 6.7 Molnar rods, and off the shelf Autotec pistons, part number 1000583.

The piston is designed for a 4.25 stroke and 6.8 rods, but works perfectly with a 4.5 stroke and a 6.7 rod. Pin height is 1.275, so 1.275 + 6.7 + 2.25 = 10.225 deck height.

Not sure how well they would handle nitrous.

http://racetecpistons.com/pages/autotec.php

[Johnny406]

Thank you, that is very helpful. How expensive are those pistons if I may ask?

[AIR RAM]

Originally Posted by Mike Davis

Did you have those coated or were they already done?

I chose to have CP Carrillo coat them for me. The heads are also going to be ceramic coated both the combustion chambers and exhaust ports. The idea is to keep the heat in the exhaust as well as keep the heat out of the intake charge.... I do feel that due to the intake air speed traveling through the head to the cylinder, the actual heat transfer to the intake air must be minuscule... I dont believe the heat in the head is able to heat the intake charge much... I have to assume it will be less after being coated so I am considering ceramic coating the intake runners as well. if there is an area that can be improved on I intend to improve it... I intend this to be a daily driver and can see myself putting 5,000 to 6,000 miles a year on the car easily... So I'm trying to build for that.

I would imagine Tom V has traveled down this road of coatings at one time or another... I'm curious on his thoughts.

SPEED SAFE, NICK

[AIR RAM]

Originally Posted by Johnny406

Thank you, that is very helpful. How expensive are those pistons if I may ask?

My total cost for Scat 4.5" Stroker Crank, Scat 6.700" H-Beams w/ARP2000 bolts, and Carrillo Dished 2618 Forged Power adder pistons w/ Steel Nitride Rings was $2,589.60...

Ceramic coatings on the pistons where an additional $200.00.
Race balance was an additional $300.00

There where a bunch of odds and ends that brought the total spent on this engine build to 3,974.00... After the machine shop work it will be an additional 1,200.00 and then Knolton Thunder Racing is doing my heads with 2.19 S.S. Intake / 1.77 inconel Exhaust valves. They are ported to flow 345cfms. Obviously the ceramic coatings will bump the price up some more.... I expect the head work to run about $1,400.00 ball park.

Im about to purchase the Stainless Steel modular Turbo headers today or tomorrow... going to look into having those coated as well... Hell coat everything! LOL



SPEED SAFE, NICK

[PAUL K]

We generally stay away from building 4.5" stroke, stock block bracket engines. The additional stroke is hard on the mains and cylinder walls. It also beats up the pistons and makes it harder to seal the rings. They don't offer a bunch more power over a well built 4.25 stroke bracket engine.
If you're going to do it I'd recommend filling the block to the water pump holes and using billet caps on at least the front four and if it's in the budget the number 5. Splayed caps are better than straight. The longer the rod the better.
IMO your 290 cfm d-ports will choke a big CID shortblock and keep you from making any kind of big power. The additional stroke will add quite a bit of torque down low but will be limited at higher rpms. If everything in the combination is optimized now you would need to tighten the current converter, back off on the rear gear and reprofile the cam. A least that's how we do it, take advantage of the additional torque and let the engine work at lower rpm's.

I PM'd you a price on the Auto-tec pistons

[shaker455]

Hey Johnny,
I know you already have a 4-bolt block but I would recommend a 2-bolt block that is not drilled for 4-bolt so you can run splayed caps.
Done it on a few motors here and the caps reach out to the pan rail.
Also, Lenny Caverly built a 488 with 4.5 crank & custom Diamond pistons for his Gasser.

[chiefbigb]

Listen to Paul or get a aftermarket block

[AIR RAM]

Originally Posted by PAUL K

We generally stay away from building 4.5" stroke, stock block bracket engines. The additional stroke is hard on the mains and cylinder walls. It also beats up the pistons and makes it harder to seal the rings. They don't offer a bunch more power over a well built 4.25 stroke bracket engine.
If you're going to do it I'd recommend filling the block to the water pump holes and using billet caps on at least the front four and if it's in the budget the number 5. Splayed caps are better than straight. The longer the rod the better.
IMO your 290 cfm d-ports will choke a big CID shortblock and keep you from making any kind of big power. The additional stroke will add quite a bit of torque down low but will be limited at higher rpms. If everything in the combination is optimized now you would need to tighten the current converter, back off on the rear gear and reprofile the cam. A least that's how we do it, take advantage of the additional torque and let the engine work at lower rpm's.

I PM'd you a price on the Auto-tec pistons

I could not find where anyone could say when the front and rear mains are necessary. Everywhere I have looked says only to do the center 3.

With that said, I have gone with the first 4 however I have been told the rear is fine... Would have changed it if it where recommended... but nobody did.

Question... when is replacing the rear and front mains on a cast Iron Pontiac Block considered necessary? This seems to be an unspoken topic that I have been unable to find the answer to anywhere... If I need the program rear main I will do it... The block is supposed to get the mains installed this week.

496ci TT (10-12lbs)


Thanks ahead of time.

SPEED SAFE, NICK

[chiefbigb]

There is allot more material in the aftermarket caps and its not cast iron. I believe its clamping force he is going for with that much stroke.

[AIR RAM]

I went ahead and just ordered the rear main... there is way to little information to go on other than inconsistent hearsay... There is not a single written article that I could find that goes into when the front and rear should be considered. I would rather be out a few bucks and have the peace of mind than not and wish I did.

One would think that the sites that sell these mains would add some informational articles as to when all 5 are needed... Yet I could not find a single one.

So now ALL the mains will be replaced with the Program Engineering Splayed center and front + rear mains. The machine shop is on hold waiting for me to bring the rear main into them so they can begin.

SPEED SAFE, NICK

[LiL Jack]

Originally Posted by PAUL K

We generally stay away from building 4.5" stroke, stock block bracket engines. The additional stroke is hard on the mains and cylinder walls. It also beats up the pistons and makes it harder to seal the rings. They don't offer a bunch more power over a well built 4.25 stroke bracket engine.
If you're going to do it I'd recommend filling the block to the water pump holes and using billet caps on at least the front four and if it's in the budget the number 5. Splayed caps are better than straight. The longer the rod the better.
IMO your 290 cfm d-ports will choke a big CID shortblock and keep you from making any kind of big power. The additional stroke will add quite a bit of torque down low but will be limited at higher rpms. If everything in the combination is optimized now you would need to tighten the current converter, back off on the rear gear and reprofile the cam. A least that's how we do it, take advantage of the additional torque and let the engine work at lower rpm's.

I PM'd you a price on the Auto-tec pistons

Some good advice right there.
Found this out the hard way years ago!


I like Ross pistons.

[chiefbigb]

When it's all over you will have 2/3 the money in a stock block you could have used twards a aftermarket one.

[AIR RAM]

Yeah, ever since the aftermarket blocks have come out it seems as though some people say converting a factory block to 4-bolt mains is close to the same cost as an aftermarket block... I wish this was true.

While sound advice for many reasons, I completely disagree with that the cost of prepping a factory block with 4-bolt mains is remotely close to 2/3ds the cost of an aftermarket block... Ill have about $1,700.00 into converting the block to 4-bolt splayed mains... of course if you subtract the 700-800 I would have into normal machine shop prep we are sitting at approximately $900.00 to $1,000.00 over a normal build... that's a far cry from the nearly $4,000.00+ aftermarket iron block to my door (Not even the aluminum one at that) and we haven't even begun to add internal parts to that list.

Here is some math to dispel the cost difference.

Aftermarket IRON block $4,000.00 (Rumored to be $2,666.666 = 2/3 difference)
Convert Cast Iron Pontiac Block - Mains $750.00 + Machine work $1,000.00 = ($1,750.00)

There is a $2,250.00 difference... the point is, the price is not 1/3 away from the holy grail. While I get it, it would be a great idea, the funds just are not there for most. And I would not make that investment into an Iron block... I would want the aluminum block... which is an easy 1,500 more than the Iron block.

With that said, like many others, I'm forced to work with what I have. This is a MPFI and coil on plug ECM controlled engine. My current rotating assembly is lighter weight than the factory 455 set up, I plan to run a boost cam that's in and out by 5,800 - 6,000RPMs... Heads flow 345cfms 2.19/1.77, with 9:1cr and 10lbs of boost it should be close to 750-800hp give or take a few HP. Block is filled to the freeze plugs and will make use of front & mid plates with solid factory mounts to minimize block twisting at the center mounts when under load. Will any of this help it live longer... I HOPE so... only time will tell.

I'll start saving for a $5,000.00 aluminum block and hopefully be ready if this build should go south.


SPEED SAFE, NICK

[chiefbigb]

I have probably done a dozen factory race blocks over the years. I have a good idea what I'm talking about.