I know the accepted method to strenghten the cast iron 455 block is to add a TA girdle. The V6 turbo builders use billet main caps to gain some strength for added insurance in moderate performance applications. Now I've learned that Pro-Gram Engineering makes SAE 1045 main caps for the three center caps for BBB engines. These have three times the tensile strength (90,500) verses grey cast iron at 30,000. I'm building a 470ci BBB for the street that should be limited to 6,000 rpm at about 600 HP, maybe a hair more. Does anyone reading this have any experience with these caps? Are they a good intermediate block strengthener before going to the heavy girdles?
I'm surprised no one has replied. The problem with the stock block is not the main caps but the main webs. The webs under the main caps are very thin and even 4 bolt caps will not help. The full girdle (If installed properly) applies a substantial clamping force on the main caps which helps the main webs from cracking.
This one belonged to a board member. If I remember correctly it had a halo girdle that held both broken webs in place until the autopsy. The oil pressure drops to nothing which is a clue to a broken block and time to shut down. We had a similar deal on a Dart aluminum SBF block where oil pressure disappeared half way down the track. Cracked all 3 center webs. Switched to the Dart cast iron block and had no further problems.
The main webs are the weak link in the bottom end of the block. Adding stronger main caps wont get you much, if anything, as far as durability. The bottom end is only as strong as it's foundation, and the only way to strengthen the bottom end of the stock block is to reinforce that foundation with a block girdle.
OK, do you think a halo girdle and studs without the "full girdle" would help this situation better than just studs? By tying all the main together with a halo girdle seems like it would be good enough for an extra at least 100 HP over what a stock block with studs would handle? What do you think Chris? Derek
Chris I definitely agree, in the case of the BBB. I should have saved that for later in the thread, as I have a feeling you will be discussing the weak links found as you go up in power and rpm/bobweight increments. This could be a good thread to help folks plan their BBB builds, as well as serve as a lesson in good building practices in general.
I see where a pin in each side of the caps or some say a dowel pin would come in and work. How ? Simple, drill holes in either block or caps first then install pins, align the cap with block and install either studs or bolts, this will mark your predetermined nexted holes needed to be drilled. That would stop a lot of the cap movement. You could also use a hallow spacer like most aftermart rods use and do the same thing.. Still, the block is gonna move around no matter what. Now on the bobweight, there is two different ways of balancing, one is for high rpm and the other is for nothing over 6000 rpm. If you know somebody in the electronics area, see if they have a ocilliscope ( spelled wrong sorry) , this has always helped the machine shop I worked in. Sincere Gary M.
A stock block with correctly installed main studs, index ground caps and properly line honed is plenty strong for most applications. Sure, a full girdle is the ultimate for a stock block, but if the rpm is not real high, would not be a necessity. The halo girdle is an excellent compromise. Light connecting rods would help the cause. Molnar or Oliver rods are excellent for this application. Of course, a perfectly balanced rotating assembly and quality damper help too. Controlling the crankshaft's double amplitude bend and twist cycles is important. if you decide to just use stock caps and studs, the stud installation is paramount to the housing bore being consistent when the cap is removed and installed. It must not bind in the cap when everything is in place. ARP bolts are a fine alternative, but don't give as much thread engagement as a stud and do not have the same yield strength. A good, accurate line hone job is paramount. Unless you are building a total stock grocery getter, not indexing the caps and line honing the mains would be the pinnacle of foolishness on a performance engine. I wouldn't even risk it on a stock build at that. I start every block machining job with line honing the mains, no exceptions. Every critical operation after that is machined off that datum line, decks, bores, transmission dowels, lifter bores... After years of heat cycles, compounded with the factory machining that was not perfect, running a stock main bore would result in bearings that look like they have shadows and wear spots all over, after some run time. Even if the bores did mic up ok, they would all most likely be out of alignment with one another. It would be ugly and I don't know anyone who would do it, so it's sort of a mute point.
I have to agree with you on that statement. When a customer came in wanting anything past 475 hp we consulted with them on the problems of factory cast iron and it didn't matter what make it was! The machine shop I worked at always opted for locating pins or locating sleeves , this assured us that the mains never moved again during a running engine. From that point on I always have done this on all my engines and I have seen 1200+ hp small block Chevys that have been treated to this! Controling flex is something Buicks are plagued with and we have to try and stop it, even at 500+ hp. a good balance on the crank and a good balanced flywheel and a darn good harmonic balancer is the only ticket to stop flex. Now, what did the connecting rod bearings look like? There is where I can tell if it wasn't detonating or if it was! Sincerely Gary M.
Gary, a good balance of the assembly and having high quality parts at each end of the crankshaft is all well and good and always helps durability, but all that stuff being in good shape and top notch is no "ticket" to preventing flexure of the block. It's going to happen as cylinder pressure rises which is the goal of higher than stock builds. Devon
I don't remember who's block this was or what shop did the work. I'm also not sure if this block failed early or lasted many racing seasons before failure. I do remember that it only had a halo girdle that at least kept the bottom end from spilling out on to the track.
Buickstage1, I thought the samething in a big block chevy our shop did. He is what was involved, 1970's 427 HIPO block non four bolt. Factory steel crank, big bolt connecting rods ( not the dimple rods ) beamed, polished, and ARP bolts installed. The crank was nitraded. The pistons was Ross 14.7:1 compression pistons, a comp cams .675 solid lift roller cam. The cylinder heads was new cnc ported Dart Pro 1's with a Team G intake and a 1250 Dominator Holley. After having it broke in on the dyno we did the necessary stuff to let it rip! After beatin on it for a half hour we noticed a lower end knock. We took this engine down to Sterling Performance in milford, mi. Now remind you this is where ATI had there test done for their balancers. They suggested we take it apart and see what's wrong with it, the results was the caps were moving around and they were held down with ARP bolts! We dided not have one bit of detonation, had every type of sensors imaginable hook to it! I. understand Buicks are pleagued with a weak block but the crank is only nodular iron and I had a steel crank! Paul, mentioned that having the best components does help and sometimes that's not enough! I still would like to see the connecting rod bearings, because if there was any flex in the crank or block it still will show on them too. Please measure your main bolts before and after installation and keep a record of them. This is your number one problem solver in engine failure . Our bolts did stretch do to main cap movement ! I understand Buick has a weak main web area and TA has done the best they can do to stop it but, the weakest link is below the maind not above them and for that reason we are basically screwed unless we go aftermarket block. I'm always studing engine failures, they always have a story to tell and sometimes its not the one you wanna here! Sincerely Gary M.
Paul, I understand your point and that's why its impairative to have eventhing possible to stop the flex that includes the block and main girdles installed. Then sometimes that's not enough. I know I go over bored on things but from what I learned from other engines, I rather be safe. then sorry.
Gary, a BBC steel crank with 2.75" main journals will flex MUCH more than a BBB 3.25" main nodular iron crank, Chris gave you that info. already. The advantage of a steel crank is that it WILL flex more than a cast crank that would break if it flexed as much as a steel crank can, steel cranks needs heat treating because they are super soft without it. The BBB nodular iron crank having such huge mains was to control block harmonics and flex. Because of the huge mains and made from the superior cast material a BBB block will fail long before one of those cranks. Why do you think an aftermarket steel crank isn't made for a BBB? That's right, no need for one because even with a block girdle the block still breaks before the crank. FYI Derek
