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#41
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So does your 557 block actually have roll pins vs solid dowels? Lots used solid dowels also.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#42
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As far as I'm aware, all W72 557-based engines had rolled dowel pins. That's pretty much just W72 engines used in '77 models (like mine). Pontiac did this because those engines were tuned to rev higher and make more power than the regular L78 400. All L78 557-based engines always used solid dowel pins. They went back to solid dowel pins in W72 988XX-based engines for '78/'79 engines because those had the full web casting. But even disregarding that, if any 557 block used solid dowel pins and careful inspection shows no signs of stress or cracking in the main webs (or anywhere else), then it's a good candidate for the dowel pin fix and can be used for a higher power build without concern.
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#43
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The 557 block my RA IV heads are on are solid maybe why it has lasted being hammered on.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#44
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I have heard it is not unusual to find the spring roll pins in the lower hp 400’s too. I have never heard an explanation for it, I originally thought it was only the 77 W72 that only had the spring type dowel. Doesn’t appear to be completely the case. Could be when they brought back the heavier block for the w72 cars PMD had some carry over 557’s blocks with the springs pins that made their way to the lower performance 400’s. Either way there seems to be some other 557 400s that did not have solid dowels. If you do an internet search all the failed main webbing 557 pictures have dowels. It is hard to even find a good late 75 early-early 76 block (early production 557) that doesn’t have at least a small crack at the dowel, cracks even seem to show up on a 2 bbl 400s in that era.
Just my opinion, but with stock main bolts and either type of indexing pin, properly fitted, with a stock 3.75” crank and stock internals 350-400 HP is a good place to stop on the later blocks. With ARP studs, which have much more clamping force, and proper dowels, preferably 5/16” dia to make sure alignment is true, and lighter 3.75 or 4” rotating assembly, I would go up to 500HP. No girdle needed. I think I could also make a pretty strong argument that the 4” stroke with the BBC RJ’s with the same heads, induction, ect is as good or better than the 3.75 rotating assemblies. The pistons on the 4” are a little lighter and shorter, roughly 25 grams, and the bigger cid holds the rpms back some. The girdle I did is more designed to help the 4.21 and 4.25” combos for 450-600HP when used in the later blocks. I am not certain which is better yet for those combos, the solid dowels or the spring type. At least at first here, we are doing one of each. The girdle adds another level of indexing, especially when it bolts to the pan rails. An example of that is Ford Windsor’s do not have any cap indexing, they often use a Halo girdle to help index the mains more, and help control main cap fretting. The pan rail supports add another level to the control. Girdles are common on Olds and Buicks too. We do them on higher hp BB mopars, I have a pulling tractor with a full girdle and dry sump. They do make a difference for helping locate internal’s and limit the direction of the internal forces on the block. To a point anyway, once you get to a certain point on power things start to move again and it is back to square one. The 557’s I have had apart so far have had a lot of nickel in the blocks, and seemed to be good iron. Maybe not quite as good as the early versions, but still pretty good. I just had a SBC thru here that I had to pin a hole where they ground thru and hit a water jacket, grinding on the bores for rod clearance making a stroker. Very soft iron in that SBC. I port quite a few heads, you can tell right away when they are short on nickel, the carbide burr eats thru it butter. Last edited by Jay S; 01-04-2022 at 08:30 AM. |
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#45
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557 block economics
What were the costs of the switch to the 557 block?
How much money was saved upon the production costs per unit? And how much extra were paid out on the warranty claims? Might it have been better to just have continued with the earlier 400 block? Quote:
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1970 Lucerne Blue Firebird Trans Am, deluxe blue interior. Original Ram Air III, M-21, 3.73. Being built as a 4" stroke "434" with SR 614 Ram Air IV heads 1972+ Lucerne Blue 4-door hardtop "what if" T-41 Le Mans Sport GT/Grand Am concepts. Equipped with future 3" journal "455 HO"/"what if" prototype "SD 455". What if GM had continued production of the 1970-72 GM A body somewhere in the southern hemisphere? |
#46
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Dude... it was literally 47 years ago. I got over it already.
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#47
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The minute weight savings at the expense of durability was another bonehead move by GM engineering and the bean counters. Their thought was that those engine were strangled by emission controls and barely put out 200 hp, that the lightened block was "good enough". For a easily driven grandpa sedan, maybe. For a Formula or Trans Am, not really.
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1976 LeMans B09 Freeway Enforcer, 455/M40 Smokey 1977 Trans Am, 400/M21 Black/Gold Bandit. 44K actual miles 2017 Sierra SLT 1500 Z71 4X4 2019 Canyon SLT Crew 4X4 |
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