[/QUOTE] Yep On the 397 subject, If I was bent set on having the cubes and was willing to do all that work to make it happen, you could rest assure that I would be looking at modifying a 15 or 16 degree Dart head to fit. Our shop does stuff like that. Paul
How big does the wrist pin need to be? How do you determine that? Are engines with smaller wrist pins generally known for wearing them out, breaking, or bending them? Have you ever seen a bent wrist pin? How many have you seen that have been worn to the point of having slop in them? Not many I'd imagine, and when you did it was probably a weed eater. I've worked a good bit with motorcycle engines so maybe my perspective has been warped by that experience, but it's not until you get up to the very largest motorcycle engines that you ever see a 3/4" wrist pin. Or a Harley, whichever comes first. Even they don't use real big ones IIRC, and that's a pretty whopping big piston. Bigger and heavier I'd wager than the ones in my Buick. And motorcycle engines these days don't even get close to redline at 7K. Then too, it isn't the combustion pressures that put pressure on the piston, anywhere near as much as the piston speed. That is the limiting factor you always hear discussed any time piston strength comes up. Forged vs cast, it's piston speed primarily. Sure, resistance to erosion and detonation, but if the tune is right it is piston speed. That's the thing that kills pistons. The skirts break off, the crown comes loose, a crack starts at the root of one of the ring lands, but it's because the speed tore the pieces from each other, not because they were slammed more tightly together by the combustion pressures. All you need to realize this is to divide the torque (or horsepower) by the number of pistons and then by the rpms. 800hp becomes 100 and then 0.014hp per power stroke. That's less than two HUNDREDTHS of a horsepower. No way that is going to have any noticeable effect on the chunk of aluminum in the cylinder bore, but the reversal in momentum at 7K certainly will. You can almost completely disregard combustion loading though unless you are working with top fuel dragsters, and as I understand it, even there it is a much lesser concern than the possibility of hydrolocking a piston because the unliquified fuel quantity was too much for the available compression space. Then consider strength of materials. Obviously the aluminum of the piston is weaker than the steel of the wrist pin, but not all steels are equal either, and if you have ever worked with tool steels you are very aware that it is orders of magnitude stronger than the more common steels. It does not flex and it does not bend. It may shatter but the force needed to do that is many times more than what is needed to deform the lesser steels so if you develop enough pressure to shatter tool steel the lesser materials would have long since failed. This does allow the use of thinner sections while still maintaining higher overall strength, in this case meaning a lighter part. The cost is higher of course. Do I trust Venolia to select a wrist pin which will work in the intended application? Well, Yeah, I do. They've been doing it since before I was born and I'm over 50. They knew all the parameters and this was their recommendation. It appears to me they went for the lightest, strongest part that would fit in the available space. I do not doubt that standard FHF wrist pins would work, but these are both stronger AND lighter, which means less internal stress on the engine. And less internal stress means the rods will hold up better and the engine will last longer. In this case, Nick, I think the change was exactly the sort of outside-the-box thinking you were suggesting. Sorry if it happened before you came along, or if it doesn't meet your guidelines, but you can't make a suggestion like that and then expect people to follow the rules. Jim
That above what was originally said? I asked why somebody would run that style pin in that application is all? What good is a lightweight part" INSIDE OUR ENGINE ,IF IT NDS UP LYING OUTSIDE IT AT SOME POINT?" Im trying to understand where that became some type of personal attack towards you,Venoilias pin choice,etc?/?????/ Instead of apparantly gettting your feelings hurt you could have just explained what you did below oh and you could have omitted tha last sentence as well Because id assume someone over 50 yrs old ,would be mature/patient enough and have enough life experience to know not everyone will always agree with you and your ideas But hey thats cool,and likei said before Good Luck Im not sure why you have this hard on for me,and quite frankly i could care less When this htread originally began,i asked another simple question regarding the apparant lack of multiple hard running SB Buicks You then went on this tangent about me supposdedly hating the SBB Buick and what not? WHY? I never once belittled the engine,just its lack of progress at times ,which unless you designed for/ built,where was the vested interest?Where/when was your name brought up? And you are correct,i did say certain things pertaining to different thoughts for different problems So does that mean that i now have to agree with every new idea a person comes up ,with because its different,regardless of wether or not i think its sound? :sleep: Or because a company trying to sell me parts said so? Wow,just Wow
:gp: Thats a great post Jim,I never needed to break down HP that far,so I never thought of doing it,very,very cool! (math is fun!!) And yes,you are correct,those pins will break long before they bend,unless of coarse they get white hot(and if they get that hot the aluminum piston will of failed long before that),which I don't see that being an issue with the 1.82:1 rod ratio that you'll have.(how far are the rods going to go back and forth,what about 1/8 of an inch with that rod ratio,lol,probably a little more than that,but not much,so not much friction there) What is a "thin" wall considered on a wrist pin? I would guess around .125" - .188" which would be plenty of tensile strenght with a heat treated tool steel.750" X 2.00" wrist pin in applications up to 1,000+ HP. Have to remember that around 80% of the pin will be supported by the piston pin hole,and the rod hole,so that doesn't leave much room for the pin to bend. The piston pin holes would have to bend with the pin(if the pin was bendable)and that would mean the whole piston would have to bend,and if that happened,there would be worse problems to worry about. Like I've said before,if Nascar can run a .748" X 1.800" X .150" thin walled tool steal light weight wrist pin in an R07 Nascar engine @ 8,000+ continous RPM,then Jim shouldn't have any issues at all cruising around at 2,000 RPM with an occassional 6,500 RPM blast now and again.:Brow: Derek ---------- Post added at 06:33 PM ---------- Previous post was at 05:51 PM ---------- Yep On the 397 subject, If I was bent set on having the cubes and was willing to do all that work to make it happen, you could rest assure that I would be looking at modifying a 15 or 16 degree Dart head to fit. Our shop does stuff like that. Paul[/QUOTE] Interesting,how would you(I'm assuming you're talking about sbc 15 or 16 degree Dart heads) use heads with a 4.400" bore spacing on a block with 4.240" bore spacing?:eek2: Now that would be a great thread to start.:TU:
I was looking at the 15 or 16 degree heads because the combustion chambers can be as low as 40cc It would involve working with the raw bare casting. If you remove .240" from the center of the head, the SBB bore centers would be offset .080" with respect to the center of the combustion chambers List of problems include: Relocation of the 2 center exhaust ports .120" from original position in the casting Changing head bolt pattern from the 5 bolt SBC to the 4 bolt SBB Pushrod locations? It might be easier with the LS head since it has a 4 bolt pattern and symmetrical port locations. A lot of time would be spent just doing feasibility research. This is why you start with the raw castings. After all of the modifications the heads would have to be heat treated back to T6 Then they would go to HRD racing heads to be finished. Just think, at 397 cu in if you could get 2 hp per cu. in. Paul
Hmmm... Guess I'd better not mention a certain someone's name in a post ever again. He seems to be a mite touchy. I don't see a personal attack in there anywhere myself, just an explanation that it seems to me was asked for. But apparently I just don't know how to obey the rules. Never was my strong suit, and probably isn't going to change much. If that's somehow offensive I doubt there's a whole lot I can do about it. I don't think I've ever asked anyone here to agree with me, but I'll darned sure explain myself when questioned and you can be sure the reasons are going to be well considered. If that doesn't sit well all I can say is go do your own homework and make your own decisions, but don't expect me to go along with what you say just because you said it either, because unless I have reasons to agree it ain't gonna happen. I'm sure I measured the thickness of those wrist pins at some point but I don't recall the thickness. I'd just about bet it was under 1/8" though. What I do have is the weight which I can look at tomorrow. The difference between that and a standard SBB wrist pin is quite dramatic. I've also seen the formula to determine piston speed and inertial stresses and although I don't remember the formula what I do recall is that the stresses go up exponentially, so that it's something like double the speed quadruples the stress. So as you can see, removing a small amount of weight reduces a lot of stress as the speed goes up. Another factor resulting from the long rods is that it changes the profile of the acceleration curve of the pistons. http://www.epi-eng.com/piston_engine_technology/piston_motion_basics.htm The longer rod has a gentler acceleration curve, lower peak acceleration, and less vibration, all of which are better for all of the internal components. It also moves peak acceleration further down towards the 90 degree point, making the intake stroke less abrupt and changing the dynamics of intake induction. An interesting tidbit from the above link is that F-1 engines, despite their very short stroke, use a very long rod/stroke ratio, something on the order of 2.5:1, which is not to say that's the ideal or even particularly good for a street engine, but it is interesting to note that despite the intense need for compactness and light weight the designers felt the need to reduce the secondary piston acceleration was more important. And for those who didn't read the link, the secondary acceleration is the result of the rod moving to the side and back twice each revolution and it means that the acceleration rate at the bottom of the stroke gets all kind of weird, setting up a secondary vibration, while the acceleration rate at the top has a significantly higher peak. And these are the two places where "bad things" happen. But all of this also means that the wrist pin is under less stress with a longer rod. The exact amount can be calculated but somewhere in the ballpark of 5% is quite likely, and in a rod, 5% is a LOT. And with the lessening of secondary acceleration forces the engine will run smoother and be more tolerant of higher speed operation. Jim
It all SOUNDS good,unless your wallet had ears(LOL)but I think if I did all that I would opt for a 3.99" stroke with a 4" bore to yield 401 cid,it just sounds more Buick.:Brow: Using the LS heads,a 340 might line up the pushrods closer? I really doubt anyone would do this though,it would be easier to make billet heads,and probably way cheaper.
Yes. You just need a custom intake. Infact, they will bolt onto a 350. But to run them you would need a hybrid cam and custom intake.
There is the other issue of overcoming the push rod misalignment of using those heads on a sbb 350. And actually on a 340,the 340 factory intake should work? Not 100% positive,but the 64' 300 heads have been used on 215s,so.............?
I havent looked at the pushrod issues, but I dont think it would be unworkable. The stock 340 intake might bolt up, but Im pretty sure the intake ports are different. But If you pay the big $$$ for the T/A-Rover heads, why would you want a stock cast-iron dual-plane intakeo No:
The pushrod misalignment on the 350 block is about 3/8" at the center pushrods, which is not enough to get excited about. Lots of engines have it much worse and it should work just fine. Hardly enough to even see. The cast iron intake will work, in fact the '64 aluminum intake would work if it was wide enough. Guys have used those on the cast iron heads. So it's really down to the cam. But that's no small matter. It has to have the lobes of the 340 and the journals of the 350. The lobe positions are different in the center and the center bearing journals may have a little offset as well. It basically means a custom cam, and it's real questionable whether one could be made from a rough blank of either engine. If so, I'd think the 350 blank would have to be used but with the different firing order it's doubtful there would be enough meat on the lobes. Jim
So that leaves the billet roller option,and a solid grind would be better in this case because offset lifters could help out the push rod situation.
One simple solution: BOOST A stock 350! And if it blows upgrade the rods and pistons then up the boost.... :TU:
Your're starting to sound like the just put a 455 in it guys with your just put some boost in it.:spank: :laugh: :laugh: :bla: Anyway,boost can always be added later after building a strong foundation,and those TA heads would make it even funner to drive after boosting is added,if one would be so inclined. Myself,I perfer NA on a gas engine,I'll leave the turbo on my 7.3L Diesel F-350 4X4 super cab long bed.
Sean We have too much of that around here already and it is a real pain. We hate to see these guys with junkyard engines show up at the track. One oil down on a lane from a blown engine screws the track up for the rest of the day. And now here we are going into the finals without lane choice, so it was costly to us. (yeah I know, why didn't we cut a better light last pass?) One of our customers competitors announced that since they went through 5 engines last year they have another 5 lined up ready to go for this year! What a great strategy! The other thing is; we really want to explore pulling up to any brand X or BBBs that also do not have a power adder and put the hurten on em. Paul
TA 510 cam made as a roller with 410-430 gears, ported heads, a good tight but loose 3500-4000 stall convertor and this is very streetable. close to 400hp at 5900-6200 rpm 380 ft lbs at 4 grand. This is about where it needs to be to rock. how about a solid lifter cam somewhere in this range.
Some reciprocating assembly weights on the long rod 340: piston: 454.6 grams wrist pin: 71.5 teflon buttons: 19.0 rings: 34.6 rod: 159/405.5 insert: 41.6 So the piston end complete is 738.7 grams while the big end is 447.1 grams. If I had realized at the time that the buttons were going to be that heavy I would have insisted on spiralocks which would have dropped about 15 grams off the piston end. The difficulty is that the wrist pins are short and the spiralocks would be deeply recessed. I would like to know how much a typical SBB wrist pin weighs and how these weights compare to a SBB build with more standard length rods if someone has that info. Jim
