cutlassefi

Hi Guys,

I'd like your feedback to gauge the amount of interest in a possible new piston from a major American manufacturer for stock stroke '68-'80 350's. Here is the initial design being considered;

1.625 Comp Distance
D shaped cup, approx. 10cc
Full floating
Coated skirts
.984 pin size
VERY Modern ring pack, VERY modern
Multiple oversizes to be offered
4032 material
Valve reliefs?
Est. $600.00-$650.00 for pistons, rings, pins, and lock rings.

Let me know what you think. The 10cc dish would equate to about a 9.0:1 compression ratio with a 68cc 5, 6, or 7a head.
Is there are a market for these? Would you consider them instead of the archaic and heavy Speed Pros?

Thanks!!!

coppercutlass

I think a 6cc would get the best of both worlds like the factory small dish . You can get 10 to 1 or 9 to 1 depending on some of the controlable variables. Thats a hell of a price for everything as well .

cutlassefi

Thank you for the feedback Copper.
However there is one thing I forgot to mention. I'm trying to get this done by being able to kill multiple birds with one stone. That is, being able to use these pistons for 400E's as well, and maybe even 425's. There are so few options there as well I thought a 10cc dish gives the best of all worlds. Compression can be upped on a small block by simply cutting the heads. While on a 400E or 425 it'll give mid to upper 9's. Very streetable for any combination.

Just trying to get someone to offer something for the "forgotten" engines as well without having to make it just for that.

By the way, the manufacturer would be Mahle. Their new ring pack is a notch above the rest and they make a great, lightweight, strong piston.
Keep your fingers crossed. At this time there is genuine interest in this project. We'll see.

Fun71

I initially agreed with Copper but after reading your explanation for the 10cc dish I changed my mind and I agree with you. I would absolutely love to have a set for a 425 build. That would likely require larger than a 4.125" piston.

cutlassefi

Thanks Kenneth.
Right now I'm proposing bore sizes of 4.09, 4.100 and 4.155. Piston sizes are always dictated by available ring packs. The new Hemis have a std bore of 4.090. That makes it that much simpler and easier to sell to the guys at Mahle.

coppercutlass

I did not even think about the 400's and 425's but the versatility would probably better from a sales point of view so that's a no brainer.

OldSoldier

What's the advantage of a 4032 piston over a 2618 piston? Just tighter clearances when the engine is cold? I've got a crazy idea for my 350 that involves some small boost, do you think a 4032 with a tight ring pack would be better than a currently available alternative in a <10 psi environment?

I think your idea of a 10 cc dish is a good one.

Magna86

If you can make it happen and they are within price of others like Probe then they should sell well. The only issue would be will the manufacturer keep making them even though sales won't be like Ford/Chevy numbers.

Fun71

Good reasoning on the 4.090" size (available rings and not far off from a .030 over 350 @ 4.087), but why a 4.100 size? It's only .010 larger than the 4.090.

cutlassefi

Again, they are or will be making a 4.100 Hemi piston so that'll ride along with that. It also gives us some room in case someone already bored and ran their block at 4.087 and 4.090 won't do the trick.

A 4032 offers better scuff resistance than a 2618 and yes takes less clearance. But it will still handle light amounts of boost or nitrous, just not the all out stuff better suited for the 2618.

captjim

Not trying to be negative, but in my experience dealing with the Olds community, most guys are not spending that kind of money (even though it is worth it) for pistons on a 9 to 1 street engine. A high end engine, perhaps. A guy willing to spend that $ will probably opt for a stroker with better rods. JMHO

cutlassefi

I wouldn't argue that but take a few things into consideration.

One, these pistons will fit other Olds that have no good piston options, unless you go custom. Just an example, Smitty gets $1200-$1500 for a set of custom Diamond pistons.

Two, someday the Speed Pros will be even harder to get.

Three, these are still cheaper than going the stroker route or a custom piston, and their ring pack will undoubtedly make more power than any other aftermarket piston out there for a small block. Apples to apples I'll bet these make 10-20hp more than any other currently available small block piston.

coppercutlass

Imo the price is very fair. Total seal rings are 120 ish so the pistons still fall into the range where to be honest an extra hundred bucks will go a long way. Specially for a company like mahle . I'm one cheap bastard but if I had to build an engine from scratch., all new components I would opt for a nice piston. Our olds can use all the new technology they can get

Fun71

That is a very good point that I hadn't thought of.

61reoldsman

Mark, what connecting rod would you use with this piston , for guys not wanting to use a standard Olds 6" 350 rod ?

steverw

And what better connecting rod could be available for the 400 E block, the pistons sound very reasonable, and a good upgrade for the E block crowd.

cutlassefi

Stock rods, until someone makes a quality aftermarket piece.
Otherwise you need to go the SBC route for rods and pistons.

cutlassefi

Rocket Racing sells a Scat 7.00" H beam with the correct pin size.
K1 was supposed to have one as well but so far nothing.

olds 307 and 403

Probe's are supposedly in short supply right now, these Mahle's would be inline with those and CP's through BTR. Problem with the CP replacement is your block must be standard bore with minimal wear. I wish someone would step up and make factory replacement rods, even Olds Rocket Parts rods are out of stock.

captjim

I did not realize that custom pistons had become so expensive. Nor that Speed Pros will become hard to get. If Speed Pros and Probes are unobtainable, then certainly a quality, similarly priced unit should sell. There won't be any other choice.

Now, you have to make a decent stock replacement rod...........

1BOSS83

I think that is a reasonable price point. I think a 4-7cc dish would be better for most builds. The modern ring pack is huge. I spent 404.00 on 5.8cc speed pros when I wanted probe 3cc dish [sold me hopes and dreams for 2 months and never delivered on the product.]. The price point of the probes +rings was $600.00 and when I tried to go custom I couldn't get under a 1,000 dollar price point. If the set you are verifying proof of concept on existed I would've ordered no question.

captjim

I agree, that is what I meant by saying it is a bit overkill for a 9 to 1 SBO, which will be pretty mild. Make a piston that will get a guy close to 10 to 1 with a "normal" chamber. With a 10cc dish, that is going to be tough. With the smaller dish you can get the Cr higher but still use it if a lower Cr is desired. JMHO

cutlassefi

Any smaller dish and the compression gets too marginal for the 400E and 425. Trying to kill multiple birds with one stone here. That's our best shot at getting this done.
Just cut the heads .040 or so on small block. Problem solved.

61reoldsman

I found a Mahle Chevy 400 piston at 1.425 CH , 4.125 bore ,-5.0cc flat top , 4032 forged piston and with a 6.125 rod it'd work for a 350 @ 3.5 " stroke -$650.00 (CNC motorsport) , just another option .

captjim

I got you, but you will need a 60 cc chamber to get 10 to 1 out of a stock stroke 355.

cutlassefi

With all due respect, what makes you think everyone that would buy this piston wants 10.0:1 with iron heads? I'll bet most shoot for 9.5-9.75:1. With that you can cut the .040 I mentioned. Remember this piston would be taller than the stockers and Speed Pros.
If we reduce the dish then the 425 guys are pretty much stuck at 10.0:1 no matter what. If that group is ok with that then I'll recommend that instead.

Thanks.

joe_padavano

I'd be interested in these for the early BBO applications, and 10:1 on a 425 does not bother me (especially since FelPro gaskets and real chamber volumes - as opposed to blueprint numbers - likely lower the CR a little anyway).

olds 307 and 403

Honestly, if these came out and Probe and Speed Pro continued making their offerings, we would be set. Now come on I beam drop in rods.

olds 307 and 403

With the big bore size, 68cc chambers, 0 deck and Felpro's, 9.6 to 1. Small bore size, 70cc chamber, rest the same, 9 to 1. 78cc, about what my untouched #8's measured, big bore, rest the same, 8.7 to 1. Not bad street compression. If these actually sold, maybe a flat top in the big bore size?

cutlassefi

Great feedback. That's what I was looking for!
I'll propose an 8cc dish. Should give anywhere from about 9.25:1 on a 350 to upper 9's on a 425. If you all can live with that then that's what I'll push for.
Remember these pistons would most likely be taller than the SP and of course all the cast stuff. That'll help in compression and head gasket choices.

captjim

That seems like a good compromise, you have to make something that appeals to as many customers as possible. For that price with quality rings; no brainer.

cutlassefi

Here's what I'm proposing;

1.625 cd
.980 pin(not sure if that will fly, they don't do that size now, only .984 for Mopars)
8cc valve reliefs
4032 material
Fully Coated
1.0, 1.0, 2.0 all steel ring pack
Full floating
Sizes may only be 4.090 and 4.155 at this point.

I'm filling out all the spec sheets tonight. Hoping for a release date around the PRI.

Keep your fingers crossed boys!!!!

Fun71

I missed that the first time. Is that a typo or are they really going to be .010" taller than factory spec?

cutlassefi

Not sure what factory spec is but the Speed Pros are 1.612 and the Probes are 1.625. Most guys don't cut their decks yet strive for good squish. I would think it would help if you could use a regular gasket and still achieve both. I can propose 1.620 but I wouldn't go any shorter than that.

61reoldsman

If you do the math it works fine , leaves you with .015 in the hole with stock stroke.

Fun71

Doesn't that depend upon the factory piston-to-deck clearance of the particular block (as in the factory deck height)?

61reoldsman

The standard factory deck of a SBO is 9.33 '- 6.0 " rod -1.625 CH of the piston -1.69 (1/2the strokeof 3.385)=.015 below the deck surface .Just the math , and you'd have a pretty good place to adjust compression based on gasket thickness and cylinder head CC .

cutlassefi

Exactly. Add to that you'll probably be reconditioning the rods, that shortens them. Plus I've never seen a crank on anything that had the full stroke. Part of the reason why you find out the advertised comp ratios are sometimes a half of a point off.
I think at either 1.620 or even 1.625 we'll be fine. I'm just tickled my contact told me he'd like to be able to show these at the PRI in December. I think that's awesome.

olds 307 and 403

That is awesome. The Olds 350 was GM's most reliable 350 and has good performance potential. Yes, it doesn't have the torque of a 403 or 455 but also doesn't have their bottom end and over heating issues. Now if a drop in rod comes available from someone other than Mondello's, we will be set.

captjim

Great job! Easier to use a thicker gasket than to deal with a slug down in the hole. This should fill a niche, especially with the Probe pistons being unavailable.