[gtofreek]

We worked out a deal with CP pistons on some stroker pistons for the 350 block. Here's what we have planned:

These pistons will be made from the same 2618 material as the high end custom pistons are made from. T

Because of the small bore of 3.875", they will be made from the LS Chevy engine piston forgings. These are box forgings by nature and are very strong. Here are some features:

1. They will come in .030" and .060" oversize or 3.905" and 3.935".

2. They will have a .990" pin[BB Chevy] with a .150" thick wall by 2.25" long. This will be a stout pin. Even thicker .180" walled pins will be available.

3. They will have double pin oilers.

4. They will have an awesome ring package with them. 1.5 mm top, 1.5 mm second, and a 3 mm oil ring. The top ring will be a steel gas nitrite ring that will be good for N/A, nitrous, blower, or turbo applications. Second ring will be a Napier ring for the ultimate in oil control. No concern with the 3mm oil ring since it has the Napier second ring.

5. They will be a flat top design with 2 valve reliefs. A multitude of compression ratios can be made with the various Pontiac heads out there. Anywhere from 7:1-13:1 can be made.

6. They will have a CP groove on the top ring groove. This groove helps to evenly distribute the combustion pressures behind the ring when the piston rocks at TDC.

7. Very lightweight, yet very strong forging.

8. Will be built for a 6.8" long BB Chevy rod which is readily available. This will still allow for plenty of room for the rings so they are not too close to the top.

9. Made for a 4" stroke. Will make either 383 CID in .030" over, or 389 CID in .060" over.

10. Made from 2618 aluminum alloy for ultimate strength.

These will sell for somewhere around $675 per set with rings and pins. This is a smoking deal. If these were customs, they would be around $1100-$1200 with rings and pins. In order to get these made at this price, we need to order at least 5 sets at a time.

If anyone is interested in a set of these, contact me and let me know, and when we get 5 orders, we will get them made. They will be proprietary, so they won't be available directly from CP.

Small bore/long stroke engines make good street engines because the smaller bore is less likely to detonate than a big bore, making them better for pump gas while still maintaining a compression ratio that makes good power. The long stroke will make a great torque curve. Plus, the smaller engines are better suited for the factory iron heads, so good power can be made without the expense of aluminum heads. Iron heads are very restrictive on big engines and aluminum heads are much more necessary for them .

I will post a pic of one of CP's box forging for an LS Chevy engine. This will be a good representation of what these piston's underside will look like.

Feel free to cal either myself or Jeff at 520-294-5758 if you have any questions.

[gtofreek]

Here are some pics of CP's box forging.

[nytrainer]

I am more of a body/paint guy than an engine guy but I have been toying with the idea of stroking the 350 in one of my cars for additional TQ/HP rather than swapping engines (source of many debates I know). Would you explain a bit more what machining to existing crank, deck, piston wall clearance and BBC rods would be needed to use these pistons. What additional parts? I assume using the stock 350 (4") crank you get the additional C.I.'s from the longer 6.8"/special piston combo?
I understand the alternative would be a stroker crank w/special rods and standard pistons? So aside from the cost difference of stroke crank vs. stroke pistons what pros/cons would there be with stroker pistons versus crank (other than the obvious strength of these forgings). Would you still go with the stroke piston route if you wanted to add a forged crank?
Thanks

[72LuxuryLeMansLa.]

Originally Posted by nytrainer

I am more of a body/paint guy than an engine guy but I have been toying with the idea of stroking the 350 in one of my cars for additional TQ/HP rather than swapping engines (source of many debates I know). Would you explain a bit more what machining to existing crank, deck, piston wall clearance and BBC rods would be needed to use these pistons. What additional parts? I assume using the stock 350 (4") crank you get the additional C.I.'s from the longer 6.8"/special piston combo?
I understand the alternative would be a stroker crank w/special rods and standard pistons? So aside from the cost difference of stroke crank vs. stroke pistons what pros/cons would there be with stroker pistons versus crank (other than the obvious strength of these forgings). Would you still go with the stroke piston route if you wanted to add a forged crank?
Thanks

The stock 350 crank is a 3" main with a 3.75" stroke. The 3" main 4" stroke crank is a stroker crank. The addition of .25" to the stroke along with the over bore of the cylinder nets the additional cubes. A stroker piston is just a piston that has had the pin height moved in order to accommodate the additional stroke and or rod length.

Karl

[nytrainer]

Ahhh. Thanks Karl. Well that makes my question moot (and plain dumb) now. I was thinking the stock stroke was 4".

[HWYSTR455]

A long rod 4" stroke will rev to the moon too...

Subscribing.

I may choose to do a 383 for an upcoming project in the spring....

.

[72LuxuryLeMansLa.]

Originally Posted by nytrainer

Ahhh. Thanks Karl. Well that makes my question moot (and plain dumb) now. I was thinking the stock stroke was 4".

There is nothing dumb about learning something.

Karl

[PunchT37]

Originally Posted by gtofreek

Small bore/long stroke engines make good street engines because the smaller bore is less likely to detonate than a big bore, making them better for pump gas while still maintaining a compression ratio that makes good power. The long stroke will make a great torque curve. Plus, the smaller engines are better suited for the factory iron heads, so good power can be made without the expense of aluminum heads. Iron heads are very restrictive on big engines and aluminum heads are much more necessary for them .

Agreed. How good does the 5.4L Ford engine run? 3.55 bore, [smaller than a P350], 4.165 stroke,[longer than a P350]. I know it`s a modern OHC engine but, talking about just bore and stroke?

Stock cast Pontiac heads are good "small block" heads vs the "big block" heads of Ford and Chevy.

Good to see ya`ll started out with a piston for the 350 block vs. the others. There`s more out there now than the others. Plus, it`s a later block vs. the 326/389.

[gtofreek]

Thanks Karl, for answering nytrainers question.

[gtofreek]

Originally Posted by PunchT37

Agreed. How good does the 5.4L Ford engine run? 3.55 bore, [smaller than a P350], 4.165 stroke,[longer than a P350]. I know it`s a modern OHC engine but, talking about just bore and stroke?

Stock cast Pontiac heads are good "small block" heads vs the "big block" heads of Ford and Chevy.

Good to see ya`ll started out with a piston for the 350 block vs. the others. There`s more out there now than the others. Plus, it`s a later block vs. the 326/389.

Yes, and some of those engines are 9.85:1 compression stock, with small cams too!

[gtofreek]

Originally Posted by HWYSTR455

A long rod 4" stroke will rev to the moon too...

Subscribing.

I may choose to do a 383 for an upcoming project in the spring....

.

I like your thinking!

[PONTIAC LARRY]

Now the value is gonna go up on the blocks I scrapped or gave away cheap , Seriously man, I like the sound of this build alot though. Really great for the guy with all original VIN matching 350 Firebird or LeMans Tempest etc.. to get them something torquey, 68 #17 heads on 68 350 block but the advertised 9.2"1 would go up to about 9.75 I suppose... nice

[Matt Meaney]

thanks, for taking the initiative to come out with these great new parts. the 350 has great potential and these will help realize this.

ok, where do you get a 4" stroke crank now?

[gtofreek]

There are several places that sell them. We can sell them, as well as most any Pontiac vendor. Tomahawk Performance Products will be up and running again soon, they will have them.

Just need to get 5 sets sold so we can get started on them!

[Squidward]

OK, now ya got my attention. What would be the build benefits of something like this (350 stroker to 4", 6.8 BBC rods)? I'm hearing great torque, rev capability, and some other stuff. I thought that the small bore/short stroke nature of the 350P was its biggest limitation? And now the stroke gets bumped out even more? What manner of witchcraft could this be?

Seriously, tho, it sounds like a kinda sexy build, but what pros/cons are we talking about? The weird factor intrigues me.

[PONTIAC LARRY]

Say you have only a crappy "557" 400 block and then you have a earlier sturdy 350...mmm.. which one gets the 4" crank.... now that choice is easier

[gtofreek]

Originally Posted by Squidward

OK, now ya got my attention. What would be the build benefits of something like this (350 stroker to 4", 6.8 BBC rods)? I'm hearing great torque, rev capability, and some other stuff. I thought that the small bore/short stroke nature of the 350P was its biggest limitation? And now the stroke gets bumped out even more? What manner of witchcraft could this be?

Seriously, tho, it sounds like a kinda sexy build, but what pros/cons are we talking about? The weird factor intrigues me.

Think of it as a small bore 428. The 4" stroke will make more torque than the 3 3/4" stroke. The added stroke gets you up close to 400 inch's.

Iron heads won't be so deficient as they would be on the larger engines so a nice stout engine can be built without having to buy expensive aluminum heads.

If someone wanted to put aluminum heads on, they could and it would be that much better.

Larger bores are more likely to detonate.

As far as cons go, I'm not really seeing any. The 6.8" rods will give a 1.7:1 rod/stroke ratio which is good.

350 blocks are in abundance[at least in my back yard ]

Think how cool it would be to tell your buddy you just toasted his Chevy with a 350 Pontiac! He doesn't have to know it has a stroker crank in it.

[torqjunki]

Got the original 52,000 mile 350 from my '71 Bird. Thinking about a stroker with o-ringed block and these nice pistons with some self-induced grinding on the heads. Top it off with a Luhn performance supercharger kit with A/C. Whatcha' think?

[gtofreek]

The other thing is, once Tomahawk Performance Products is back up and running completely, we would like to start working with them[since they are only a couple hours away, it makes it real easy and convenient] on bringing complete rotating assemblies to market that would truly be ready to bolt in. These kits would be fully qualified for the following:

We[Koerner Racing Engines] will balance each crank to within 1 gram or less of the assemblies bobweight. I will be doing this personally unless I'm on vacation or something[which rarely happens] in which case Jeff Koerner will do it.

The big end of the rods will be checked for size, roundness, and taper/bellmouth, and trued up as needed. We hold our tolerances to .0001".

The pin bushings will be honed to proper clearance[most rods come with minimal clearance and the end user usually needs to take them to a machine shop and spend money getting them honed for proper clearance].

We will figure out bearing clearances so the proper bearings will be supplied. Each bearing shell will be checked with a micrometer to verify their thickness. Also, race bearings will be furnished with cranks with large filet radius. In other words, no cheap passenger car bearings where race bearings are needed. We see a lot of kits where they supply the cheapest parts they can get whether they correct for the application or not, just so they can sell the kit cheap. Then the end user has to spend extra $'s getting the correct bearing, rings, etc., or to have the machine shop open up the clearances.

Pistons will be checked for proper pin clearance.

Crank will be micro polished and cleaned, as well as oil holes brushed out. Oil holes will be chamfered better if needed.

Each assembly will be furnished with a spec sheet showing what everything checked out at. We don't believe in generic kits. Each kit will be Specific to itself.

These will be very high quality kits at a reasonable price as well as many options for different applications.

[gtofreek]

Originally Posted by torqjunki

Got the original 52,000 mile 350 from my '71 Bird. Thinking about a stroker with o-ringed block and these nice pistons with some self-induced grinding on the heads. Top it off with a Luhn performance supercharger kit with A/C. Whatcha' think?

Sounds bitchin' to me!