3.8 supercharged piston with 350 rod Some things to consider when using a 3.8 V-6 supercharge piston with the 350 rod. According to the information I have, the late Buick V-6’s use a small .9054 diameter pin . Typically, the wall thickness on a pin bushing is about .0625. This means that a bushing is needed with approximately a 1.030 OD. .9054 + .125 (.0625 x 2 ) = 1.030. The small end of the 350 rod would have to be oversized .090. 1.030 - .940 ( 350 pin ) = .090. This is more than double the amount of material than what was removed for the pressed Olds piston pin ( .980 - .940 = .040 ). Will this weaken the 350 rod too much? I can’t make a determination because I don’t have a 350 rod to check so I don’t know how thick the wall is on the critical top half of the pin hole. If, for example, the thinnest section of the wall is .300, this would be a 15% reduction in cross sectional area with a corresponding 15% reduction in strength. At low RPM this would not likely be a problem, but at high RPM the tension loads on the connecting rod go up exponentially. I do know that there wasn’t a lot of extra material on the 300 rod. From a durability stand point, the small .9054 dia. pin may be a problem in higher H.P. applications, especially with a lot of N20 or boost. This supercharge piston has a nice short skirt with modern 1.5 mm top rings, but it is a Hypereutectic with coated skirts, just like the Olds piston, so there is no strength advantage and to insist so is purely an opinion with no data to back it up. One thing is for sure, the Olds has a stronger pin with considerably more bearing surface area. Also, there is nothing trick about the top of the piston, a standard round 2.870 x .167 dish with no valve notches. 8 of these pistons will cost about $175.00 more than 8 Olds pistons and the cost to oversize and bush the rods ( including the cost of the bushings ) is significantly more than just over- sizing the rods for a larger Olds pressed pin. If it cost $300 to $400 more and is worth next to nothing in terms of power, is it better or worth the extra expense? This is money that could go towards a good set of ported heads or maybe a roller cam and those up-grades will for sure turn you on. One last point, it is pure speculation to say a particular combination or piston design is better than another especially when the one that is claimed to be better has not been built, let alone seen any dyno time, and the one that is said to be not as good has been built, made numerous pulls on the dyno and performed very well.
Some clarification: <B><?xml:namespace prefix = o ns = "urn:schemas-microsoft-comWhen Karl and I came to this forum, our original intent was to shed some light on how and why we built the Buick 349 stroker motor and make a reasonable attempt to answer your questions. There was some confusion and disagreement about the path we took and after we shed some light, several people expressed their appreciation for our efforts and the results we got. As we have previously stated, this motor was never intended for anything but the street. If Hot Rod had not become interested, it would have been a 300 H.P. mild street motor with the emphasis on low end torque. I did not know what problems I would need to overcome when starting out, how much money it would take or whether or not everything would go together right or what the power potential was. Believe me when I say, it took a lot of effort both mentally and physically. There were times when we couldn’t see any light at the end of the tunnel. I had the short block finally together with a mild Isky cam and then Marlan Davis became interested after Joe told him what I was doing. The stress level and work load escalated significantly after Hot Rod said they would like to do an article but the motor has to make at least 350 H.P. Based on the displacement and compression ratio, the new cam spec’s, the head flow and port limiting area data and a few other calculations, I felt the motor would peak between 5500 and 5800 RPM and make as much as 375 H.P. and the torque would be close to 400 lb.s . But as you can see it exceeded my expiations. The biggest surprise was the torque output and the extra wide powerband. There is a 2000 RPM spread between peak torque and peak H.P., something I never expected, especially with the tight lobe centers There is something in the combination, I have some ideas as to what it could be, but all I can say for certain is it worked better than expected and the wide powerband will make for a great street motor. I don’t claim that this is the best and only way to do this motor and if someone comes up with a better way I won’t hesitate to use their ideas or give credit where credit is due. But my definition of better is: the same or maybe a little more power for less money or a lot more power for the same money and, proven on the dyno. Also, to gain 15 H.P. at the peak, at the expense of 25 lb. ft. down low, is not “ better” for a lot people. What you should take away from all this is that this build shows you what is possible and the results you can expect if you build yours the same way. We at least deserve credit for paving the way. Some combinations work better than others and it is not always clear exactly what made the difference. This is why even the most experienced engine builders, like Joe Sherman, still rely on dynos and flow-benches to sort out different combinations. This is something you should consider when picking an engine builder or asking for advice. We like Buicks and are working on a Buick specific web site and will offer parts and engine services including head work. In the interim, if you want to talk to me please send me a personal message on this site with your phone number or email address and I will contact you. Thanks for your interest Dave <o></o>
Well I'm sorry to say this thread really took a turn for the worse. Dave had to waste a lot of time defending his decisions about how he went about building an engine that just about nobody has experience building, let alone a high performance version of. What is that all about? Karl financed and Dave built this engine and really pulled it off nicely and that is the main point: THEY ACTUALLY BUILT THE ENGINE. The coverage in HOT ROD just about sends it through the roof. If Joe Sherman gets into building Buick engines that would be great because it would give us Buick lovers another outlet. Nothing wrong with doing some bench racing. I've done plenty of theoretical engine building in my many years of working on Buicks, which I'm sure is in the top 10% of years of all the people on this site. Lively give and take is good but to just keep hammering away at the same, and in this version of this engine, insignificant points. If you couldn't infer from the article that he was talking about the classic Buick engines then you have pretty low comprehension skills. I'm sure I'm not the only one who's been at a show or track and had to put up with "Bench Racers" who will shoulda', coulda', woulda' you to death. If I was a suspicious guy I'd think it was a shop up the street trying to take business away from the Sherman shop. I'd say the best thing for somebody/anybody to do is start a new thread called "Best Ever 300 CID Theoretical Engine Build". If all the theory was actually put into practice and an engine was ACTUALLY built I'd bet if you applied to get in the PHR Engine Masters they let you compete in a minute.
I dont have enough knowledge or experience to question the parts used in the build. i simply stated that for the average guy the motor is not cost effective. still cool to see a buick engine that is seldom done (even by buick guys)
yes, i dont get the comotion either.. this is a great build and a similar one was done up one before.. http://www.britishv8.org/Articles/MonsterMotor.htm so no one should dare make these two guys unwelcome its a buick build in a mag!! one that could go in seans book too lol
I think Karl and Dyno Dave did a great job on the research, planning and the actual build of this engine. And it's not just talk, it actually happened. I'm super impressed with the tenacity that was obviously required. I do mostly SBC and lots of Buick 455s, but it's a 300 that got me into Buicks many decades ago. I'm planning a 300 project of my own, so I really appreciate the input. Thanks Karl and Dyno Dave. And thanks Mike, for starting the thread.
<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <wunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> Mike, Thanks for shedding some light on the point of this project. It is also nice to have someone appreciate the difference between an engine build that has proved its worth on a dyno and flow bench, not Bench Racers theoretical dream motors. One other point that is being missed, all car magazine budget builds do not include labor. They are written with the intention that you supply the labor. They are pointing out what a person with automotive knowledge can do. This motor is a example of what can be done with original iron parts and old school know how. KAM
Glad you like the motor. It is getting close to running in the car. I will keep you posted on how it runs. Thanks, KAM
Dave, I hope you guys don't feel unappreciated. I for one think what you've done is just great. People will always disagree on the finer points but I don't see that as a problem, most of the guys wouldn't be here if they just wanted a copy cat car or motor. I've been stalled out from the cold weather and probably won't really get rolling again for another month or so, and even then I've made so many changes to the car that it's not likely to run before mid summer. Anxious as I may be to see how it performs I'm just going to have to wait. But it's a moderately serious effort this time around. Numbers won't matter to me at all but driving most definitely will. I'm pretty well assured that power will be adequate. So anyway, thanks from me and on behalf of any who share my opinion, as I think you guys have brought a benefit here. The rod/piston of the stroker 300 is the knottiest part of the problem and any solution helps move the cause along. We're a long way from perfect, but we're closer. JB
It unfortunately won't be me. Since I joined this site and have been learning about these older SBBs, I have found out (among other things) how to tell a 300 from a 340 (yes, I now know it is quite easy, silly easy actually but what can I say? I've never had one of these before. I did have a 71 Skylark with a 4 BBL 350 though). Anyways, here is my situation: I bought a 70 Jeep Wagoneer that came from the factory with a Buick 350 but when I got it it had a kind of tired 300 in it. Or so I thought. Since it was only a 2 BBL, I just assumed it was a 300 cause I didn't know there was a 2 BBL 340. But there was and this is one of them! So long story semi-short, I don't have a 300 to build! My plan was to throw a 455 in the Jeep and then build the 300 and throw it in an Apollo. But now that it is a 340 I don't have a 300 core to build. Still gonna put a 455 in the Jeep though. There is no reason not to. It will be just a week-end rig anyway and I already have a good 73 455 for it. Someone will build my 300 combo though. It's too good not to build! Regards, Eric
Wonderful. I don't see anything there about 200,000 mile street engines. Now look at all of the OEMs who's engines have rod ratios that exceed even the 1.66 rod ratio of my combo. The OEM's engineers know a few things too about engines and about longevity. Don't take somebody having a different opinion and wanting to build their engine differently than yours personally. I'm not a threat to your dreams of having an income stream from this. Regards, Eric
I did point out in one of my earlier posts that my combo is still a short rod engine. Just not as short as your combo. Your combo's ratio is too short. If that is true, then why do most all of the OEMs have rod ratios that exceed even my combo's 1.66 ratio? Again, even Chevy LS based engines have longer ratios now than the old SBC 350s did and are even longer than my combo's ratio is too. 100,000 miles is nothing by today's standards. I want a 200,000 mile engine! That might be one of the reasons why rod ratios are getting longer! I'll bet fuel economy improvements from decreased friction are another. Even you admit that the reduced rod angularity of the 350 rod would probably reduce cylinder wear, so why not build it that way? What possible reason is there to build a 300 using your combo when, As we have already seen, it is just as easy if not easier to build it with a 340/350 rod and a series II 3800 piston? It's even still a short rod engine for crying out load! Why are we even having this discussion? Ego? I'm just presenting an alternative for folks to explore. Why are you so threatened by folks having an alternative? I've also pointed out many other advantages of my combo over yours that have nothing to do with rod ratio. Why not build my combo so you can take advantage of those advantages too? Regards, Eric
> since that supercharged engine has a lower compression ratio, we can be sure > that there is a decent sized dish on it which will help keep our compression > ratio from being too high with our increased displacement. The Silvolite catalog list a 2.87" diameter recess 0.167" deep for the Buick 3800 supercharged pistons. They also note the pistons are for floating pin. The 307 piston dish is deeper at 0.270" but the diameter isn't listed as it's a D-shape. > This will also effect pricing, with the Olds piston getting the raw end of > the deal (if it isn't already.) For a set of eight at Summit Racing, the price for the Olds pistons is $205.95 versus $393.85 for the Buick V6. Be aware the Buick pistons use metric rings. In some applications, those can be significantly more expensive but that typically depends upon how common the ring the thickness and bore size combination are. > Plus we already know that the piston top's shape and valve notches are > gonna be right The Silvolite Buick 3800 supercharged pistons do not have valve notches. > I'm sure the series II piston has a dish that is just as good if not > better since it is a more modern design The piston dish pictured in the Silvolite catalog for all the Series II pistons is a simple circular dish, same as they've used in the Buick 215 pistons since the 1960's. The Olds is D-shaped with an angled floor. > I'll bet the dish's CCs will wind up being about the same as the 307 Olds > piston's dish is so the compression will wind up being about the same too You might want to call Silvolite on that. The Olds dish is considerably deeper but from the illustration in the catalog appears to be angled so the cc's may be similar. > the port work and flow bench work make this motor a poor choice when > looking at cost vs hp made. even if the labor rate were only 50.00 > per hour you would have 5000.00 in head work alone,( i'd love to find > a professional head porter who only charges 50.00 per hour) I'm not sure what the context of that statement in the article is but I just dropped a set of Buick 300 aluminum heads at the head porter ported who did my previous set. His Stage III port job is $1050 and gave me 200 CFM intake and 153 CFM exhaust with 1.775" intake and 1.5" exhaust valves. > I believe you meant to say that induction limited engines tend to > respond to longer ratios. Yes, that was a typo on my end. > You mean "lazy" low velocity port engines. It's much better to have a high > flow, high velocity port that doesn't need to be crutched with a shorter > rod. Like long and short, low and high are relative terms. For a given combination, there's an ideal port cross-sectional area. In a high performance build, the Buick 215's and 300's are generally port area limited. Too high a velocity makes it difficult to make to turns in the intake tract and flow can separate over the short side radius. > If there ever was an engine that was/is induction limited and could > benefit from a longer rod ratio for the reason stated above, the 300/340 > is it. Do you have an idea of how much power improvement you think you'll see with the rod length increase? Even on 2 barrel induction rule classes, the effect isn't large. > I would love to ask ole Jon what his rule of thumb is for engines that are > gonna be abused on the streets for 200,000 miles. I have one of those engines built to Jon's rule of thumb with 220,000 miles on the thin wall block, rods and pistons. Works just fine. > There is no doubt that that supercharged Buick piston is designed and built > to take more abuse than that 307 Olds piston is. That is likely the case with the OEM pistons. It may not be the case with Silvolites. If you look at the Silvolite catalog, you'll see the same caveat including "Not intended for racing applications". Both are hypereuctic alloy with optional coated skirts. It might be worth a call to Silvolite to see if there's any difference in the specific alloy or construction. > When you add in the other benefits of longer rods and then you factor in > the fact that it doesn't cost us any more to build this engine as a longer > rod engine, it makes the choice a no brainer. Agreed, as long as it doesn't compromise something else potentially more important. Cost, compression ratio, rod strength, machine labor, etc. can all be deciding factors. My point is to not get too hung up on any single design factor. > I think Karl and Dyno Dave did a great job on the research, planning and the > actual build of this engine. Yes. Thanks guys for taking the time the post and putting up with the trolls. Dan Jones
OK, finally, a valid issue to address. We've obviously got to address this. I don't suppose there is enough meat in the piston to safely take the pin bore out .0346" to the stock 300/340/350 pin size is there? I've seen crazier stuff than that in my time. We need to get one of those 3800 S.C. pistons and investigate. I don't want to bore those cast 340/350 rods that much. Hey, I'm not above putting this out there for the other board members to address. Any ideas anyone? This is too good a combo to be felled by this one thing. You know though, I'm not a big fan of cast rods, I've made no secret of that, saying like I did that even the later capscrew 350 SBB rod is still cast and making it clear that I'm not too happy about that. Maybe it really would be worth it to run a set of the many high quality yet relatively inexpensive aftermarket rods for the strength improvement they bring. That would also solve the pin size issue. Then while we are at it go ahead and raid the 3800 S.C. guys' forged piston sources to create a combo that could really take some copiuos amounts of N2O! Just a thought. Still would love to see a solution that would allow us to use the stock 340/350 rods and the stock and/or stockish 3800 S.C. pistons though so we can have a more affordable option. Come on now, you know as well as I do that these small pins have been and are the wave of the future. They are building them to withstand way more abuse than what our stroker 300 engines, even with copious amounts of N2O are going to be able to dish out. The stock 340/350 rods will give out long before those pins will. No data to back it up? Come-on man common sense would dictate that a piston for a supercharged application is gonna have some pretty impressive strength built into it vs.a smog era low performance Olds 307. There was never an Olds 307 that made anything anywhere near anything approaching even decent power. Yes, they are making Hypereutectic pistons for it but far fewer people have actually taxed those pistons like the numbers of people who are taxing those S.C.3800 pistons and you can bet those S.C. pistons are being taxed more severely too. What I said is that the stock 3800 supercharger application is a way more demanding application than ANY Olds 307 application ever dreamed of being. I would invite any doubters of the strength of this piston and/or it's pins to go over to a site dedicated to these 3800 S.C. engines. They are running obscene amounts of boost AND some are even adding N2O on top of the boost. I've chatted with some of these guys at the track. They are pulling some pretty mean numbers with those stock pistons. Yes, they do have their limits, but those 307 pistons do too and I still would submit that the 3800 S.C. piston has had the benefit of trial by fire and a better, broader, more extensive learning curve from the much greater number of people using it and pushing it to it's limits than what the 307 Olds piston was/is seeing. I've addressed this above. There are no valve notches in your Old pistons either. Long engine life turns me on. Fewer trips to the machine shop turns me on. An engine that is gonna live longer is a savings of money, not a waste of it. You machine shop guys are always telling your customers "you get what you pay for". Since we are talking about a 200,000 mile engine here, it is worth it to spend a little more to do it right. Spread that slight cost difference out over the 20 year life of the engine and it amounts to next to nothing. And don't forget those 307 pistons need to be clearanced on the bottom, the 3800 pistons don't. How much $ does that add to the build cost of the build that uses the Olds piston? Don't forget to factor that back in. Many of us do that stuff ourselves, but there are others who will have to pay to have it done. I knew you would play that card at some point. Kinda feels like a personal attack. The bottom line is that my combo is as Buick designed the 340/350, only we are substituting their own way more modern, but thoroughly proven S.C. 3800 piston. Our only other deviation from Buick's design is that we are of course reducing the main diameter like you did. I would love to see how well your engine is doing when it has a 100,000 miles on it. Some friends and I go to the street legal drag days at Fontana all the time. I invite your engine's owner to come out and do some racing with us! Let's see how that puppy holds up! I am out of time. I will address the remaining posts later. Regards, Eric
If you contact Silvolite, they may be willing to open up the pin bores and supply matching pins at a fair cost. It'd be worth checking into. If I read it right you're only talking about 34 thou or so, which is nothing. As far as using those big diameter heavy pins, what is the reasoning on that anyway? As someone who is very familiar with motorcycle engines, I am amazed at the size and weight of those things. Can anyone here tell me that they've ever seen a loose wrist pin on tear down? I never have. Never, ever, on any type of engine. So why do those things need to be so darned massive? I'm sorry, I just don't get it. I used 3/4" diameter thin wall alloy 71.5 gram pins and I think they'll be just fine. That might be overdoing it a little, but tell me how much a stock Buick piston pin weighs. I know it's well over 300 grams. The less weight you have on the end of that rod, the better everything works. Going back to my argument that sometimes a custom piston is worth the extra money, same thing Eric said, over the life of the engine $500 is chicken feed. I have exactly the piston I wanted, in every way and it weighs 454.6 grams (plus 34g rings and 19g teflon button pin locks) and despite being such a light weight assembly, under 580 grams complete, it is specifically designed for the blower application it is used in and should give a long service life. There was no messing around with trying to fit a square peg in a round hole. Bear in mind, less piston weight means a very significant reduction in all stresses particularly as those stresses go up exponentially with engine speed. So there is a lot to be gained by decreasing that weight. It's all well and good to search for a close equivalent in an available mass produced piston, and I hope you guys or someone else does one day find the ideal replacement, but once you start undertaking custom machining operations to make that square peg fit the custom pistons get more and more attractive. There is a good reason why those companies are still in business. I would suggest broadening the field of inquiry and look into more modern engines for candidates, starting with bore size, skirt type, dish volume and pin location. Pin diameter is something you can work with and to some extent bore size is too. Any stock 96mm piston is going to be a .030 overbore and there should be plenty of those out there. That's also the same thing as a 1mm oversize 95mm bore. In all probability they will be better designed, better made and of better materials. With all the different engines that have been on the market in the interim it is unthinkable that a suitable candidate cannot be found, it's just a matter of looking in the right place. JB PS: Don't get too hung up on dish shape. Unless you go over .500 lift and 10:1 compression you'll never even come close to the piston crown. It's there to increase the chamber volume.
i dont want to know your background, but i dont think you ever built a small block buick. do you have any clue on how to build sbb with stock parts and go 7500 rpm and more. i think you should stick to the kohler and briggs and stratton engines. the rest of you wonder why i hate posting on here. :blast: :blast: :blast:
Has anyone mentioned "offset pins", in the formula-yet. Oem manufacturers have used this tool, based rod lengths/strokes, to reduce lateral thrust/wear, reduce "I loads" at TDC. and reduce the potential of ring flutter. Some after market, piston manufacturers provide this option on custom forged pistons. What a refreshing article. It seems a shame to me, that some felt a whizzing contest was needed ,to thank those involved ,for all the hard work. Good Job Gentlemen ! roverman.:TU:
This is all good news but you've got to remember that I'm not gonna be the one to build this engine cause my "300" has turned out to be a 340 so I am gonna be building an engine more like the one that you built. It won't be as cool as the one that you built though. That thing is awesome. And it took some pretty big stones to do that Lexus trans swap too! I don't want to use big heavy pins either but I don't want to weaken the weak stock rods by boring out the small ends either. At least using the stock .940 Buick pin isn't as bad as using the huge stock .980 Olds pin. Like I said before, a third alternative would be welcome and I wouldn't take it personally if someone came up with an even better combo that could be done on a budget and doesn't dip the rod ratio below 1.66 to one. Absolutely agree with you on all of that. That would be the best way to go. You have to admit though that the 3800 S.C. piston is at least a good step in the correct direction and is certainly an improvement over that Olds 307 piston. I only presented it as an option to replace the Olds piston in a budget build, not as a replacement for the better custom piston option. Again, no argument from me. Good valid points there that we should heed. Several guys here seem to want to spend more time and energy badmouthing and attacking me instead of coming up with an even better combo of their own. If they would spend just half of that time and energy working on an alternative, we might have some even better choices to choose from. If they can't come up with some decent alternatives of their own, then it would appear that they aren't as clever as they think they are. Again, I'm not trying to make any money off of anybody here so trust me, I won't be hurt or offended if you all come up with even better combos. I in fact hope you do. Like Jim, I too believe there may very well be even better combos out there. Just don't build that old tech short rod Olds pistoned combo! I don't have the time to waste responding to every negative stupid post against me here. Just go back and read my posts again as most of all your issues have already been addressed in them. Then do as the man Jim Blackwood suggested and come up with an even better combo of your own! We don't have to be "monkey see, monkey do" people here, doing what we read in Hot Rod. That kind of thinking and acting is for Chevy people! Regards, Eric
This is getting ridiculous. A little 300 that does a lot. Great job on this. I just hope that someone showcases the 350 like this. gsjohnny1 has it right. Shut the pie hole. :spank:
