350 Pistons

OK so lets use the "better" forged piston, 73 cap screw rods, get the comp up to 9.8 (in the middle), use the stock, or the GS equivalent or just slightly larger cam (my take), stay with the bought convertor and I agree with the 308 gear. Get a Q-Jet or 650 Holley double pumper (my pick), with the TA DP intake. Might as well get a posi while ur at it because it will burn one wheelie peeelies to the ground. This will keep you at stock or just above that and will have good idle and power off the line that a small to stock cam does. Shift at 5400 and you will be good to go. There's my take, short and sweet!

I think we have driven the stock motor so long that we want to race it more and not keep it stock anymore. Gary loves his stock stuff and I am more on the race side but kept the advice on the stock side.

In the end it boils down to what you want and how you want to be driving it.

I have owned my car for almost 40 years now so I have worked it a few different ways and I know Gary has been playing with Buicks ever since I... for a long time. Yer lucky I cleaned that up, lol


and don't forget to read the link Larry posted.

 

While Derek's abusive post was a bit harsh and over-exaggerated, I'm not going to digress into an argument and ruin the thread. I'll let him have his say and maybe he can find closure in that somehow.

There's a place for most everything. You don't need forged for stock stuff; HOWEVER... if you wanted to play with nitrous with a bone stock engine (these engines love the juice at any level of build), then I'd say you're much safer going forged, even for a stocker. There's videos on Youtube of a guy going mid 12's with a low comp stock 350, using 3.73 gearing and a 150 shot. Pretty impressive I'd say.

The low comp cast pistons don't need all that extra machine work to get to 8:1 static. It takes .005-.015 to clean up most deck and head surfaces, so that's .010-.030 right there just for cleanup on deck and heads, and won't cost extra (over what you'd need for those forged slugs) that you'd need to do with ANY build to get the surfaces trued. Most of the cost is the setup and initial grinding, with extra material removed costing more, but not THAT much more.

Sitting .070 below deck with 58cc heads puts those low comp cast pistons at 8:1 static. You'd probably end up with somewhere between there and 8.5:1 with just the cleanup work (less than .030 total removed).

The 340p pistons would be closer to 9.5-9.75 with some mild decking/cleanup, which is a safe zone (on premium 91-93 octane fuel @ sea level) for cams hovering around the 70-75* intake valve closing point. The Melling sbc-5 and Federal Mogul cs647 OEM replica (GS) cams fall within this range.

I can't say I'd recommend using nitrous with cast pistons. If you want to go that path, you best be using forged pistons if you want your engine to hold up for any length of time. Cast pistons can take quite a bit of abuse with a stock-moderate engine, but once you start adding this and changing that, it's a good idea to have a sturdier bottom end.

It's not for everyone. Everyone has his/her own budget to work with and own desires/goals. We're just here to help them along, and I want to make sure people know more than just the hot-rodder's viewpoint.

For an everyday cruiser/daily driver type car, premium fuel can get expensive. Premium here ranges from 50c to 60c more per gallon than regular, and with gas sitting at about 2 bucks a gallon (currently), that's quite an increase in price percentage wise.

Also consider that in order to safely run regular pump gas, compression needs to be miserably low (from a performance viewpoint), since you have to add in a buffer zone for detonation if all you ever plan on using is regular. Consider too that even with this, the Buick 350 produces some nice low-mid range grunt and would make an excellent utility engine in this condition.

Please remember that anything I suggest doesn't necessarily mean that I feel that it is the only way to go, but that it is just another option to consider.

Options are always good.


Gary

 

Good discussion...

Back to the very start of this thread I question if NEW pistons are really even needed???

If the piston skirts are excessively worn then so are the cylinder walls in most cases.... If not boring the block then just a quick hone, file fit rings, and run it with the factory pistons.

 

The skirts are definitely worn.
The OP is not sure which pistons to get based on a slight misunderstanding of the bigger picture, which is necessary to look at because the OP's question is not entirely valid due to incomplete information and the lack of understanding of the tech behind it...

8.5 or 10:1 pistons don't really measure that way, due to many variables.
The shop's suggestion towards the compression ratio needed itself is very subjective, due to many variables of a running engine's octane needs.
Stock replacement pistons are theoretically fine, but there have been known issues with the foreign made versions of US brands.
(This itself has vast search info on the 'Net)
A hotrodder or more accurately, a machinist mindset shows that with a little forethought, an engine with twice the quality or performance potential could be had for little more than the cost of a stock rebuild.
Some suggest that Buicks were darn good from the factory and need little, if any improvement.
There is definite concerns that even if a factory 'type' piston and related parts were used, that the finished product would not necessarily duplicate a true example of a factory engine and it's merits...which raises up the bigger picture questions.
People are fairly touchy about others' opinions as to how they would go about approaching a build of this nature, and differ in opinion with what we think the OP is really asking (based on the conflicted original post).
This is also an issue because of the forum's past history of different opinions.

I guess the OP needs to either be more clear about what they are trying to accomplish or start over with the project's goals in order to utilize the forum's vast knowledge pool.

 

Tony brings up an excellent point: the quality of parts made today (whether they're USA made or not) may not exactly meet or exceed what was available from the factory back when these engines were poured and assembled.
As with all mass produced items, there will always be the potential for defects no matter where the aluminum was melted down and poured. Reducing the chances for this would be a wise consideration no matter what the goals were.
I don't think anyone could dispute the fact that forged pistons are a better choice for maximizing durability and abuse potential over any cast piston, no matter where it was manufactured.

The trick is using the right grade of aluminum. I think as long as you're sitting at or close to cast silicon content (around 12.5% for eutectic saturation) for expansion coefficient, then there would be little reason to use cast pistons at all, ever again, no matter what you were building--especially when the price is right.

If, however, the cast pistons are indeed shown to meet or exceed Original Manufactured Equipment (OEM) (which the manufacturers of Sealed Power pistons claim is true), then is it really necessary to kill a rabbit with a Knigstiger Wunderwaffe? It's always a good idea to *over*engineer anything--up to a point. You wouldn't want to use a 4" thick piece of steel as the handle for a pocket knife.

This is obvious hyperbole, but gets the point across I think. If it could be shown that OEM replica parts are indeed worthy only of the trash can, then we could move on to a more productive path toward reconciliation between leaving 'well enough' alone or if it should be merely used as a solid foundation upon which to build the ultimate street machine.

Even the OEM replica camshafts have been shown to exceed the quality, precision, and engineering intent of the (actual) original equipment with today's improved hardening techniques for mated surfaces.

It's not for everyone, but shouldn't be dismissed either as an unworthy option.

Everything has its place. There is no 'magic bullet' for every application--or is there? I think it's all in our minds. Psychologically satisfying numbers are what gives our brains the anchors they need to remain stable within a society defined by imaginary borders. A few of us aren't so easily molded though...

Thanks Tony. I was wondering if you'd show up here on this thread.


Gary

 

I was thinking that the original poster might be a bit overwhelmed by the responses, and might not be aware of what lies beneath that first layer of onion.
"Are you sure you want to look inside door #3? ........No, I just want an engine"

 

Good idea Sean, a good set of used factory 1970 "high compression" pistons with composite gaskets should get right around 9:1. Can probably get them still on the rods for less $$ than a set of new pistons. If the bores don't have excessive wear this is probably the most budget friendly option to use.

What I hate about "stock" style replacement pistons especially for a sbb 350 engine is that they are typically "destroked". The destroked stock style replacement pistons have a .020" shorter compression distance assuming the deck height is actually what the factory advertised them to be and not the .030" to .080" + taller most sbb 350 blocks actually are. The stock replacement "builder" pistons assume that the deck will be machined that extra .020" and the same steel shim factory type gasket will be used(which are getting harder and harder to get) So running one of the "stock" type replacement pistons with a composite gasket that will be at least twice the thickness than what the factory ran will be WAY down on compression. Take a "8.5:1" replacement piston for example, to get to an actual 8.5:1 the deck will actually have to be milled at least .030" PLUS the extra .020" to get to an actual 8.5:1 the piston is rated for assuming you can find the factory steel shim type head gasket, if not an extra .020" more would need to be removed from the block to use the composite head gasket to get to an actual 8.5:1. Even the "stock" style replacement pistons rated @ 10:1 are destroked .020", which would be closer to 9:1 than 10:1, especially with a composite head gasket. To make it easier for you here is a site with a compression calculator you can use to figure out where the deck needs to be;

http://www.wallaceracing.com/cr_test2.php

Deck height - compression distance - rod length(sbb 35 is 6.385") - half the stroke( sbb 350 stroke is 3.850" divide by 2) = how far in or out of the hole the piston will be.(a negative will be above the deck)

The above is why I mentioned having your machine shop measure the ACTUAL deck height before you buy pistons and have them give you a quote for how much the deck milling will be to get to the compression you want with the cheap pistons. It would seem a previous poster is in denial about machining costs and how much extra the deck heights usually are on a sbb 350 from the factory, "hot rodding" or not machining cost are real and do add up. :shock:

The 4032 pistons I posted a link to are NOT the best choice for a nitrous piston, I would recommend a 2618 forged more of a race style piston for nitrous. The 4032 pistons will handle up to a 175 shot IIRC and about 5 PSI of boost but anything more than that, an upgrade to the 2618 material would be a better choice.



Derek

 

Quite true, but as we all know these threads seldom if ever end up being a 'yes' or 'no' type answering system. Dynamic and layered for sure!

I think it's nice this way, as long as the OP gets the information needed, the rest can be used for posterity or reference. The real problem with this though is that so much information can get buried underneath the other layers, so some digging may be in order which may overwhelm and frustrate some readers. Such is the reality of so much information--as long as it's actually information and not bickering.

However, I think the same questions and answers can be given over and over instead of having the website simply reading like a book (but can then appear to read like a broken record!). This is the beauty of sticky threads--and having semi-live conversations with the on-board techs.

 

The cams are still made here in my home state of MI, of coarse the quality is going to be as good or better than they were back in the day. The pistons are a different story. Look at UNDERDOG's India import pistons that looked like they were cracked before they were installed for example. Plus how they are destroked as mentioned in my previous post.

Back to calm discussioning, welcome back Gary!


Derek

 

Hey Derek, they make it that way so it gives more room for machine work--which is usually needed to do the job properly and so won't make the final compression ratio too high for today's gasolines. You're going to need to take some off to true up the surfaces because of block shift/warp/'settling' after decades worth of heat cycles.

If you just take it apart, re-ring/re-hone/re-bearing and put it all back together, your odds of success are much better this way with the same original parts being placed back in their original resting places.

But then it can also be like disturbing the rest of some ancient Egyptian tomb with a mummy that springs up and slaps a curse on yo arse and sucks your wallet dry. lol


Gary

 

Steve used hypers though.

 

Doesn't matter, when the hypers were made here they never had that problem unless guys were using lots of nitrous without the extra ring gap required to run nitrous with a hypereutectic piston on the top ring.

I have USA made speed pro hypers in my 383 and have lead footed that engine as hard if not harder than Steve has with his, with the only difference being mine is still in service still taking a beating. About 5 to 15 QM passes a week for 2 spring, summer and autumns until the track closed weather permitting on Friday night's King of Street bracket racing @ Milan Dragway. Plus I am running those with 9.8:1 compression with a very mild cam so the dynamic is way up there! And I only use pump gas usually straight mid grade, top off the tank with premium when it goes to the track. Have even ran it with 87 mixed in before and it is still taking the abuse, trying to kill it so I can build something different.

Now how bad are the India made cast pistons vs the hypers? I wouldn't want to be the guinea pig with my engine. Plus "stock" replacement pistons suck how they destroked them .020" even when they were made here!! Of coarse they would be fine with 6.5:1 to 7.5:1 they would actually be if proper corrective machining is skipped, but how crappy would an engine run like that? How disappointed would someone be, and mostly how bad of a rep would an engine get when they run like that? An engine like that probably wouldn't get very much aftermarket support at all with a reputation like that until the "hot rodders" figured out how crappy the actual compression ratio really is and corrects it. Then many, many years later an aftermarket aluminum S/P intake comes out for that engine and supposedly performance aluminum heads are on the way. To bad the "stock" replacement pistons were so crappy by destroking them and the unobtainium factory type head gaskets are, plus the Fel-Pro composite head gasket hype because they claim that machining could be skipped on an already higher than spec deck height and they would still seal. Well not hard to seal 6.5:1 compression that the engine is now from using the "stock" type replacements, skipping the deck correction machining and using thicker head gaskets!!! o No:

The factory pistons weren't that bad, plus they had .020" more compression distance than the "stock" replacement type pistons. Taking the deck down to the factory spec, using the steel shim factory type head gaskets with factory pistons(not factory replacement pistons, the actual original from the factory pistons) would result in a decent runner.

To sum up, crappy .020" destroked "stock" replacement pistons, .030" to .080" + extra deck height vs factory spec, thicker composite gaskets that claimed the deck machining could be skipped = virtuously no after market support for 35 years!!!

Yeah I love those "stock" replacement pistons, NOT!!!


Derek

 

You're exaggerating again, Derek. lol

Just because you had luck with yours and Steve didn't with his doesn't give rock solid proof on anything. There's many stories out there where some have good luck with them, while others do not. Is it because of where they were made? (a legit question--maybe we can zero in on a potential cause instead of assuming)

It does matter when you hyper saturate the aluminum with silicon because depending on the method, you could have strong and weak spots within a hyper saturated unit creating weak spots prone to failure under certain duress scenarios that may or may not present themselves, depending on how the engine is being (ab)used.

Others tried to make hypers without much success until the Germans figured out how to do it properly (this is based on memory, so forgive if it's not 100% spot on). Would this mean that we shouldn't buy hyper pistons made by anyone outside of Deutschland?

I wouldn't want to use pistons that may get damaged just by popping them out of the frickin mold or get micro cracks from the frequencies emitted by the machining process (hypers).

Normal eutectic pistons are more forgiving than hyper-eutectic pistons to abuse.

Of course, the forged units will hold up to just about everything you can dish out, other than melting them down.

I disagree with your assertion that anything other than forged pistons are garbage and everything should use forged aluminum.

The 340p have a better CH than the low comp variants, close to the factory CH, so compression on those wouldn't be so bad (eliminating half your rant).

Anyone using the low comp variants probably wouldn't be as interested in performance in the first place, eliminating the other half of your rant. lol

If a specific product is so poor in quality that it cannot perform its intended duty, it wouldn't last very long on the market.

If you plan on subjecting harsher conditions to the product for which it was not intended and expect miraculous results and survival, then you're not being realistic with your assertions and would only be setting yourself up for disappointment. Maybe you'll get lucky...maybe you won't.

I assemble thousands of aluminum parts every day where I work now that come from India (and elsewhere). Some have too much silicon and are so brittle they crumble/snap/crack under the slightest load, while most assemble just fine (depending on whether or not the silicon saturation is uniform). During the quality control process you eliminate the defective units while the product is still in the assembly process so that the final product isn't shipped to the customer as a ticking time bomb waiting to fail after so many hours of use.

These parts are not pistons, but the casting process is very similar and hyper saturated aluminum is too risky--you never know what you'll end up with.

Sorry for the tangent.


Gary

 

In the bold above, they would be concerned that the thing didn't run like POS dog that couldn't get out of its own way though. Add your "stock" low compression destroked replacement pistons to a late model sbb 350 block and only do a minimum cleanup on the deck and use a set of Fel-Pro blue gaskets and the poor bastard will run worse than the tire old engine it use to be! Don't believe me, then run it through the compression calculator with an extra .060" more deck height and see what you get. That's the point I'm trying to get across your closed mind. If they made cast pistons that you could order with any deck height you needed I would recommend them, but alas they don't. The pistons I posted the link for are NOT an all out performance piston, one of the points you aren't realizing. They can't make a customizable cast piston so they make them out of 4032 to keep cost down while bringing durability up. I seen you post in a body repair post and like all the body and paint guys I know, they just can't wrap there head around engine building, I guess you're not an exception to that rule even though your really good with the cam math. Me being a machinist makes me not that good with body work so I guess it works both ways. o No:

In blue, if you actually read all of my posts in this thread you would of seen the one where I said I would use a factory piston, not the crap "stock" replacement piston. Not all pistons I recommend are forged, but unfortunately the sbb 350 doesn't have any decent cast pistons to recommend without a ton of extra machining costs.


I remember discussing in another thread about how much extra material the sbb 350 has on its deck and you couldn't wrap your head around that then, in unbelief that there would be that much extra material and questioned the blueprint spec. Now still in that river in Egypt claiming the "stock" replacement pistons are good even if you say you have built a bunch of sbb 350s with them and they run great, I would find that VERY hard to believe. I think you want to believe those cheap pistons would make as good of a runner as your '68 sbb 350 and others old cars you had back in the day because the price tag of the ones I posted the link to sticker shocked you so much you are still blinded of the hidden cost to make the "cheap" pistons run like the engines of yore you use to own. Can the cheap pistons be made to run satisfactory? Well, sure they can but the cost needs to be weighed out vs all the machine work that would need to be done with the "cheap" pistons to make them run right vs getting the superior pistons to start with.

There is absolutely no reason at all to build a "stock" sbb 350 and spend thousands of dollars when a running replacement "stock" engine can be bought fo cheap, usually under a grand for a decent runner. So why in the flock would anyone want to do a "stock" rebuild? This site needs a stock rebuild section where people can recommend where to get the stock rebuild parts. No need for tech in that section because the info to do a "stock" rebuild would be in a chassis manual or Motors manual or a Chilton manual, all the no brainer info is readily available. Even a re-man sbb 350 short block is probably cheaper than doing a "stock" rebuild just trade in your short block core for a brand new used reman, down the road. Same with the heads, even though you will probably get a set of '74 or newer heads for your 1970 cores, but that's ok because you probably got a later model reman engine as well.


Mr. Cam math guy that tells everyone to get their static compression ratio right to run with the fuel they want to use, but to me seems clueless what that takes to get it there. He just tries to claim I'm trying to get people to build a performance engine, when in a thread like this I am just trying to advise to get to the proper compression ratio so he engine doesn't run like a turd.

No offense Gary, you're obviously not a machinist(or is your real name Bullwinkle?:laugh and never have used the parts you're recommending so you really don't know how horribly mis-matched they can be without all the corrective machining to the block. Like I posted before, either get the customizable pistons or pay for the custom block machining to make the "cheap" pistons work right. And make sure you get the Federal Mogul CS-647 stock replacement cam, not that Melling one, or make sure that Melling cam isn't the really crappy one Gary has wrote about before.



Derek

 

My hypers are US made.

Now that I've used the Auto tec pistons in my last 2 350 builds I will never again use a cast piston, hyper or not.

Sure they cost a little more up front. But you can get exactly what you want with NO compromises. They are as quiet as a stock, tight cast piston and should never break. Also much lighter to ease the load on the rods and crank.

 

:gp:

 

Not quoting this to single out anyone...there was a huge problem with quality control and manufacturing learning curve with the overseas subcon transition.
It's a well known problem and much non-Buick info on this subject is out there if you dig for it.
There are plenty of parts on shelves within the automotive aftermarket that have issues waiting to happen.
Many end up on secondary markets.

Products on the market can have very little to do with their merit or validity.
As long as people are willing to buy them, they will survive the marketplace.
Ebay is abound with sellers of rejected castings and 'soft' aftermarket blocks.
It can take 10 years for 'everyone' to know, and by then it can be renamed or sold off differently, elsewhere.
I can cite some stroker BBC short blocks out there that seem to snag a few every year.
Crap parts aren't thrown away, they just go to different markets or are presented differently.
(I'm not knocking foreign production, only isolating known problems)

As far as Buicks are concerned, look at the choices for Nailhead pistons.
Most say they strongly regret the cast offerings, even if they haven't had failure yet. (Not talking about the Nails that began with piston probs here)

Gary, I'm not jumping on the bandwagon with a Lord of the Rings style bashing, but these are very valid concerns.
It's rare to get machinists to actually help you appropriate your $$ for benefits directly to you, rather than giving vague answers that support what goes into their (our) pockets.
Your points are 100% logically sound though.

 

I truly appreciate all the points brought up here and its apparent there are many ways to go with respect to piston selection. I received word this morning that the block will be cut 30 over. In searching many of the choices brought up in this post and based upon economics I believe the 340P Seal Power pistons are the ones I'll be ordering.

 

I believe those Pistons will work for you. Don't forget to do something about the carb problem. Don't want fuel wash to happen again. Mark from Quadrajet power does a great rebuild on qjets. Don't get a rebuild from the parts store. The big carb rebuilders don't try any more since most cars are fuel injection.

 

Actually Mark has the carb already. Thanks