speeder Posted March 12, 2003 Share Posted March 12, 2003 My stroker project is about to get off the ground and would like to get some input as to the advisability of boring to 90mm. for a 3.2 liter. I'm using the Turbo block- I know the 89 mm bore is widely used and proven - I'm just greedy I guess. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted March 12, 2003 Share Posted March 12, 2003 Well, rick, I had one block crack between the #5 and #6 cylinder wall, then had 3 other F54 blocks sonic tested before finally finding one that the 89mm bore would marginally work on. I would recommend 88mm bore. I was greedy too Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 12, 2003 Share Posted March 12, 2003 It might depend on your expected HP and RPM levels, more cubes is sure nice but at the expense of possibly nuking the block, not worth it to me. Shops that do BIG bore buildups, usually hand pick the blocks based on sonic testing etc, so you would definately have no choice but to go that route if you are not looking for a dice roll. This will tell you wether your block is a candidate or not. Maybe you could also consider block filler to help strengthen it. Quote Link to comment Share on other sites More sharing options...
speeder Posted March 12, 2003 Author Share Posted March 12, 2003 I'm looking for maximum reliability as well as best potential for big power. Like all of us, I want it all! Data I've been getting lately suggests that those last couple .1 liters are hard to achieve. I really don't want to be changing blocks in my new engine - Looks as if the 88mm bore for a 3028cc displacement is the leading candidate for me- I still plan to get all of my F54 blocks sonically tested and use the best one. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 12, 2003 Share Posted March 12, 2003 Do an offset grind on the LD28 crank, and get a couple more mm on that. Of course your journals will get smaller - could turn into a weak link, and I don't know how you could resize the rods... Just random thoughts - can't get more bore, go for more stroke Quote Link to comment Share on other sites More sharing options...
jgkurz Posted March 18, 2003 Share Posted March 18, 2003 Rick, When I was building my stroker I did some research on maximum bore size. If I was not turbocharged I felt 89mm would be acceptable with proper sonic testing. I decided on a bore of 87.5mm, which gave me exactly 3.0 liters. As I understand it, high boost pressure causes thin cylinder walls to flex creating problems with ring sealing and oil control. The sacrifice of 100cc was worth it in my mind. Best of luck. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 18, 2003 Share Posted March 18, 2003 Exactly, the higher the RPM and the more power delivered, and your going to strain the block which will cause ring wear and possible failure, at best though it will just not last as long. Each .1L is about 6 cubes, not worth it! I never understood why 454 guys went straight for 468 and so on, just not worth it. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 18, 2003 Share Posted March 18, 2003 Agreed - the extra FEW lb-ft or HP that a mm or two of overbore will give you is not worth worrying about. When I had my 400 block done, I was looking for .020" oversize pistons, instead of the .030", incase I ever wanted to bore it again. Especially in a turbo app, I'd be looking for maximum bore stiffness with thick walls, and just turn up the boost. I'd just do a stock or one-size over bore and do the deisel crank. JMO. Quote Link to comment Share on other sites More sharing options...
speeder Posted March 19, 2003 Author Share Posted March 19, 2003 This is all good input - Just what I was fishing for with this post. Thanks! I have just sent my LD28 crank out to be worked, have a set of 133mm race -prepped rods, and continue to think about pistons. In a previous search of the archives, seems to me that I remember that James 240Z Turbo went for the smaller bore also, in consideration of cylinder wall strength. Pretty sure 88 or 87.5 mm bore it will be, with boost being the equalizer. Don't you just hate how long the process of getting parts, then machine work takes? When I have time for a longer post, I'll entertain you with the story about how I destroyed 2 engines. Makes my choice of an avatar appropriate. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 19, 2003 Share Posted March 19, 2003 I know the addiction of wanting more, especially when dealing with a small engine, but that is exactly the magic of boost - "free horsepower!" Alot of the V8 guys that go turbo will run a 355 or 383 instead of going for the ultra big 402/422 etc, because it just isn't needed, but what IS needed is extra block integrity. With more horsepower your also going to get more bearing wear and more side load on those walls anyway, so may as well make up for it with boost and retain what strength you can Myself if I were to upgrade the cam I would likewise aim at maybe a 6200 RPM shift point tops, call me a sissy but again, make up for it with power but keep the revs down, just makes me feel more comfortable. Quote Link to comment Share on other sites More sharing options...
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