If there is already a thread on the stock connecting rods for 455 Buick's, please someone defer me to that thread. If there isn't one then I have a few questions for you guy's that already done modified stock rods. I know Buick tried a funky way of balancing the connecting rods, here is my questions now! Is there any value in blending those balance pads in the connecting rods? Smooth them in like there ment for heavy duty! I know by reading in here that, I must look for casting misalignment and cracks but, where do you balance this connecting rods besides the sides of them? I'm asking these questions in regards of my hunt for 750 horsepower goal! Balancing and strength is a major part in producing high horsepower . I know I should have them X-ray'ed if possible! Has anyone thaught of having stock rods Nitrided after you done all your modifications? I know its surface hardening but, it all adds up! Yes it comes at a cost but, horsepower comes at a price , no matter which way you go! If I feel that Buick stock rods are not up to task, I will be going to the Sportsman Rods then. Gary M.
Hi Gary, Regarding the balancing, what you want to do is smooth and lighten the rods, removing any casting flash and sharp angles to reduce the chances of a crack developing from those points. Most of the balancing pad can be removed, and match balance the rods to each other within a gram. Be sure to remove roughly the same amount of material on the big and small end of each rod so that each rod will have the same bob weight. Focus on smoothing the rough areas and removing the extra weight at the big end vs. trying to actually remove too much material. Same with the pistons, match them all up by removing weight somewhere that will not harm the piston. The machine shop will have to take the rods, pistons, and piston rings, weigh them, and then determine the bob weights and then balance the crank based on those weights. Contrary to popular belief the rods and pistons are not actually used to balance the crank, they just use those weights to connect onto the crank and then spin in and find out if it is balanced.... From there weight is either added or removed from the counterweights of the crank. In an internally balanced engine all of the balancing is done in the crank. IN an externally balanced engine (stock 455) the flexplate and harmonic balancer also help make up for the lack of internal balance inside the engine. Obviously an internally balanced engine is preferred over an externally balanced engine, and the only downside to internal is the cost.... So with an internally balanced engine the balancers and flexplate cost a little extra however if you need SFI rated parts for your racing class anyways it is not really an issue. With what you are talking about, I strongly suggest an internal balance.... The factory balanced engines are far from optimum for anything over 4500 RPM even at low HP.... Here is some info from a Buick 350 pioneer who ended up finding the limits of the stock 350 rods even with lots of work done to them. Rods, for stock runner the 68-72 are fine but the 73-81 rods last although BEWARE of oddball engines with non correct rods for the date....ARP bolts are available for the late model rods. This combo is safe until about 500 HP or really high RPM, above that step up to the Custom. OR spend BIG time and cash on the stockers which is not really worth the time and effort in my opinion. If you go that route read this: "The rods should be cap screw style. They should be polished along the side-beams to a mirror finish, including, if not especially where the rod broaches at the point where it meets the crank. Have them sonic tested and magnafluxed and checked for size and straightness before you start. Grind all casting flash and all rough edges smooth. DO NOT remove any material from the bearing radius, or you could open up too much end play. Grind the balancing pads down as much as possible [leave a little], and THEN have them rebuilt. Big end re-sized, small end bronze bushed for floating pins [only if your TRW slugs accept floating pins]. After you get them back, your still not done. Now it's time to match balance them. You can do this at home. GET THEM PERFECT, and matched to the pistons!!! You can also have them: Ion nitrated Hard chromed Directionally magnatized Chryogenically relaxed ..... The list goes on, just pick what looks best to you, and what your budget allows, and have it done"
All that said, jump into a set of aftermarket rods and you will never have to mess with them.... You have enough of a challenge ahead of you with the iron heads and your HP goals.
Sean Buick76, what makes you think it can't be done? Just think now, Stage 1 Automotive made 700 hp. with cast iron heads and they weren't. aftermarket nor Stage 2 factory heads! Matter of fact Ron did it with a cam that TA Performance Products sells, now just think, a custom ground cam can pick up 50+ horsepower easily ! I have done enough engines to realize what is needed to make that power level. I'm worried about the connecting rods now not the cylinder heads! Its been proven you can get 700 horsepower out of factory cast iron heads. There is no secrets that won't be unturned if my engine makes it, I promise to display what was done and where to get at. Sincere Gary M.
Yeah it's been done, and I bet a at a big cost too. Not only money, but time and effort. Gary you seem to be "heading to the moon before getting in the shuttle" Dreams are a great inspiration to get **** done, but the difference between the dream and making it reality is what makes the man. I have said this to you before Gary, get it done, then come and brag about it, not before. I persued my goal with my Buick engine, and thankfully **** worked out for me after jumping through some pretty major hurdles, let alone building a TA455 motor down here, miles away from any Buick specialist. Cheers
Gary The main problem with the stock rods is They are too short for your application!!! As JW pointed out, even after you deck the block simply for cleanup, the piston pin height is still around 2.00" for zero deck clearance using the stock rods. A piston with a 2.00" CD is heavy. If you are going to restrict the engine displacement to 455 cu inches the engine will need high rpm to make 750 hp. In this case the piston will need to be very light and having the piston CD around 1.400" will allow the piston to be much lighter. That puts the rod length at 7.2" I recommend going with aluminum. Aluminum rods offer cushioning that is important for the stock Buick block as well as the bearings. Paul
Paul, what about Billet pistons? Would that be light enough? I want to stick with stock Rods if possible! I know I'm gambling hard here but, I want to try..... Gary M.
Slimfromnz, I rather get my information before building! The reason behind that is, Time isn't nothing to me, money is! I know where to get my stuff done and who to do it. It's getting the Information down patt. I do homework before building!!! Gary M.
Paul's point is that the piston compression height is what makes the piston heavy. Even a custom forged or billet piston will be heavy i the compression height is stock or taller than stock. Ideally a longer than stock rod is used and then a lighter piston will make the rod and piston package lighter... I saved about 100 grams per rod going to an aftemarket forged rod for my 350, and that was a stock spec replacent rod (same length). That was a 800 gram weight savings for a stronger rod, and then the pistons were 120 grams lighter than stock saving a bunch more weight off the assembly....
Stock BBB rods only have balance pads near the big end, not on both ends. So balancing the rod is a more difficult task compared to rods that have both BE and SE pads.
Yes the billet piston is your best bet but not sure if it is enough. Here is what a billet box and strut design looks like. The CD on this piston is just over 1" and the narrow box allows a short piston pin which also reduces weight. If you have the same piston with a 2.00" CD the piston pin will be about .750" lower in the piston and the piston height can increase as much as 1.500" which makes it at least 100 grams heavier but still lighter than stock. The reason the piston height increases twice as much as the CD increase is to keep the piston pin near the center of the piston. If the pin is high in the piston, the top edge of the piston digs into the cylinder wall and if too low the bottom of the piston digs in. The other consideration is to machine the head so the combustion chamber has only 60 cc. This will allow at least a 13.5 compression ratio using a flat top piston. The flat top is the lightest piston configuration and also promotes better flame propagation during combustion. One final thing on pistons. The modern thin piston rings 1/16" and less are only available for the 4.350" piston. The reason is, 4.350" is a Mopar piston size. That's why the aftermarket BBB pistons with 1/16" rings are .038" over or 4.350. Remember that the forces on the connecting rod goes up exponentially with RPM. Double the rpm, quadruple the "G" forces at TDC trying to pull the rod cap off. You might at least consider a billet cap on the stock rod that has a pad for balancing. Would that be Cheating? Paul
I see I'm screwed on using stock rods . I like to thank you for the great information on the stock rods and I am gonna have to run aftermarket rods to achieve my goal. Thank you, you guys. This information will be used greatly . Sincere Gary M.
PMuller, This is what I decided to do on the attempt of making 750 hp on stock block and heads (had to scrap the stock connecting rods idea.) , and stock crank. My block will cleaned of debris, crack checked, and sonic tested. After that, it will be deburred, all edges rounded, including casting flash areas, all oil passage areas modified, and last, it will go in the bead blast tank for an hour. My heads will have the same treatment as of above, valve pocket inlarged to a certain size, and ported. The crank will look like a aftermarket piece after I'm done with it. The balance weights cut down, the connecting rod journals cut down to 2.00", flywheel mating surface will be cut in a star shape to reduce even more weight but it also adds ridged, campfer all oil passages, then it goes in the bead blaster for an hour too! After that it gets ground to size and sent off to be Nitrided. The connecting rods I want to use, be at 7.500", to able to have a piston with 1.120" compression height! The rest I will display as I get them or tell you later. Yes, the connecting rods will be aftermarket but, close to stock weight or a bit more. I would like your input on this so far.. Gary M.
Here is a BBC 7.100" rod that is rated to handle 850 HP that won't break the bank; http://www.ebay.com/itm/H-Beam-7-10...Parts_Accessories&hash=item2a471f3d51&vxp=mtr GL Derek
Before you buy pistons you must finish the heads first because the heads will determine piston top shape including valve pockets. The hopes would be to get the combustion chambers down to 60 cc so high compression can be achieved with flat top pistons. The rods and pistons shouldn't be ordered until the block is line bored and decked so you will know what the deck height is which will determine piston CD and rod length. The block could end up as low as 10.550" What you can do in the mean time is start collecting 455 blocks, cranks and heads. Good cores are getting harder to find. The 455 blocks have core shift. You are looking for cylinder wall that are thick on the thrust side (passenger side) and have at least .100" thickness on the adjacent sides. Below is a sonic test for a 76 block. I also have a 73 block that tested really similar. Notice the core shift favors the major thrust sides of the odd cylinders and the minor thrust sides of the even cylinders. The real problem with this block was the thin areas less than .100" on the adjacent walls on cylinders 4 and 6. I just went through 3 BBB cranks to find 1 good one. One had deep cuts around the main journal and the other had a rod journal that was over heated from a bearing failure which warped the crank. I'm not real comfortable with a 2.00 rod journal. Yes the BBB crank has plenty of main to rod journal overlap but it is cast iron and needs all the help it can get. If bearing speed is a concern then one would be more concerned with the large 3.25 main journal. Removing .250" from the crank pin diameter will make the crank less rigid and if it starts to twist and wind up the main bearing and the already weak main webs will see the stress. Personally I would use a 2.200" pin but if you must a 2.100" minimum. I like margin. Do consider using an aluminum rod not just for it's light weight but also for the cushioning it offers for the sake of the weak main webs. You are going to use a full girdle on the block? Paul
Paul, don't the 494 BBB stroker kits use a 2.00" rod journal that is also offset ground with more stroke with a factory crank? If I remember the rods are 7 something inches as well? Derek
Yes that's correct but I suspect Gary will need to turn his engine many more rpms than those strokers. Obviously the 494 has to have a 2.00 rod journal to get the stroke but my thinking is why remove the material if you don't have to. The crank will be more rigid with a larger journal. It's just my opinion and I'm hoping others will put their comments in also.
