I never said anything about stroking... I just listed the rods and pistons that are proven to work well and are nice and strong.
Just want to put my 2 cents in and join the party. The cam will determine the compression ratio but it will be around 10:1 for street use and pump gas. With a 58 cc head and 3.830" bore, a flat top piston with 4 cc valve reliefs will sit around .060" in the bore. Considering the open chamber head and a .060" piston to deck, the flame front will have to travel clear to the cylinder walls to combust all the fuel charge. IMO it would be better to have a Spherical dish piston set at zero deck where most of the fuel charge is available at the piston center and away from the cylinder wall. The other problem with piston travel falling short of the cylinder top is more of the piston skirt travels beyond the bottom of the cylinder. I'm expecting a set of custom Spherical dish pistons (for a Ford 300 six) tomorrow from RaceTec. I went with a .500" longer rod to shorten up the piston skirt (For the same reason) and reduce piston weight. Paul
By the sounds of it you have a really good plan! Is this 68 engine the one in the car? If so I suggest you find another engine to build. He sounds like he wants to do it right the first time, which sounds smart to me... It is tough to put a $ budget on these type of things as you know... Sounds like he is going to build it as he can afford it and it should end up really nice.
Most engines do. I should have worded that differently. I prefer not to run the piston skirt out the bottom of the bore any further than needed. If there is a choice between in the hole or zero deck, I'd rather do zero deck. Thanks for helping me clarify. Jeff indicated he didn't want to compromise so it would follow that he would want a more efficient combustion process and less piston wear. I talked with Randy Gillis who was with the Spherical dish development program when he worked at JE. (Randy is with RaceTec now) They found power improvements with a spherical dish over the inverted dome using the same test engine and same compression ratio between piston types. Piston swaps where made more than once just to check on repeatability of the test results. There was also less skirt scuffing with the Spherical. I've also had the same conversation with the crew at CP Pistons and Diamond pistons. Diamond is going as far as balancing the piston about its center point. Al Dicksen (HRD Racing Heads) does our aluminum heads and he says the spherical dish was worth 30 HP over inverted dome back when he was doing heads for Nascar Paul
As usual Paul makes very good points. My thinking behind running the flat top pistons is that he could run the piston at about 30 or 40 thou in the hole and have about 10.5:1 compression. With that compression and a nice roller cam the dynamic compression could be fine for pump gas. There is no other combo of pistons and rods that I can suggest would be a bolt in type deal without any fancy machine work, stroking, or customizing of the piston. As already designed the Ross pistons with job number 115793 could be duplicated and would work well with the Eagle rods after some slight work is done to the rods. This saves about $400 off of my piston and rod setup. I do agree that in general it is a little better to have a longer rod and a shorter piston you make a good point about that too. Ironically enough I have a set of Rods here that I bought from Jeff Pye of all people LOL... They are custom rods that will work well in a 350 if some custom pistons are used. They are $1100 rods that Jeff got cheep and then sold to me. Using these rods with a set of diamond pistons like mine however with a shorter compression height to make up for the longer than stock rod would work out ideal I think and better than the flat top. Diamond could make the same pistons and I show here but with a different compression height. As paul says a dish is a better match for the open combustion chamber design of the 350 however either will work great I am sure. This is what Paul suggests for a piston: The above piston sitting at zero deck with a head that is milled to about 53 CC would be about 10:1 compression and could be as high as 10.5:1 compression with lots of milling on the heads. In my Turbo engine it will be just a hair under 9:1 compression with the pistons 60 thou in the hole. The rods I show pics of above are going into another engine I am building, which has another set of diamond pistons, and that engine is getting the block girdle and big time boost.... Otherwise I would sell you back the rods Jeff...
Sean It doesn't look like there is very much offset between the beam and the big end of the rods looking at those pictures. How much offset is there in the stock 350 rods? Paul
Price is not a factor...I want the best for my own sanity. When I fire it up I don't want any regrets so I'm gonna give it 110% and leave it all out on the field so to speak! The other limitations are listed in prior posts...everything else is in the realm of possibilities. ---------- Post added at 11:02 AM ---------- Previous post was at 11:00 AM ---------- Bare cast iron sitting in my garage ready to load up and haul to the machine shop. ---------- Post added at 11:14 AM ---------- Previous post was at 11:02 AM ---------- @ Sean...Those rods are pretty heavy if I remember correctly. Nice...that you would be able to use them for a future project. I would hope to get the lightest rods possible for my build to lighten the load and increase the overall life of the lower end. I want it to rotate free and easy and decrease the gravitational effect as much as possible. To me...the lighter that rotating assembly is...the better. That's what I mean when I say I want to have no regrets. I want to drive that car and not think of anything I could've done better!
Yes no need for those heavy duty rods in a naturally aspirated build.... My good engine with the hershe rods is 200 grams per cylinder lighter than stock. Paul I'm not sure about the offset on the rods.
Sean The reason I'm asking is: The aftermarket LS rods come in lengths longer than Buick 350 rods and you can get them in 2.00" journal or Honda journal. The only problem is the LS rods are "On center". If the Buick rods have a small offset and since the LS rod big end is wider than the Buick rod end, the LS rod can possibly be offset by taking different amounts off each side of the big end. Paul
I just measured a '77 sbb 350 rod and it looks like that they are 1/32" offset(.032" or .813mm for the metric system users out there). Not sure where the thicker side goes because the factory chamfers look about the same on both sides and I alreay took the pistons off.ou: Derek
Anyone have an idea as to how I could measure the offset on the stock rods with the piston on the rod? ---------- Post added at 06:58 PM ---------- Previous post was at 06:56 PM ---------- Here is a picture of a Spherical Dish piston that Paul is talking about: http://www.livernoismotorsports.com/products/JE-PISTONS-5.4L-FORD-8.5:1-227125.html I am guessing that the only application that these type of pistons are popular is with an open head chamber design like the Buick 350 however I could be wrong. http://www.livernoismotorsports.com/products/JE-PISTONS-5.4L-FORD-8.5:1-227125.html
If you have a set of calipers and the rods are cap screw rods,you can measure the offset on the threaded holes from the thickness sides of the rod.(measure the difference of where the hole is from the .845" thickness and how off center they are) If they are bolt and nut type rods,the same way but using the depth measuring feature of the calipers. If they are stock rods and numbered,the pistons should have a notch or a dot to indicate that way forward. The cylinder bank that has the odd numbers(1,3,5,7) is the forward bank.So if you measure say number 1 piston and rod assembly,and the thicker side of the bolt hole(or from the bolt) is towards the front then the thicker part will be against the crank. If its toward the back,then it will be against the other rod. I hope I explained this clearly,if not ask again,I'll try again. Derek
Thanks Derek, that makes sense! The offset makes it so that the thicker side of the rod goes against the crank and the thinner side against the other rod. I checked the stocker rods and then my Hershe rods and found they were both the same. I will show a few pics to show why this offset is made into the rod. And the thinner side of the rod which goes against the other rod. They really did a nice job on these rods!
Hey hey! THIS: http://www.livernoismotorsports.com/...A1-227125.html This is what I was talking about in the other thread! Too bad I didn't see this thread until now... Gary
