Riceburner Posted May 13, 2015 Posted May 13, 2015 Does anyone know the minimum recommended cylinder wall thickness for an over bored block? I've had one of my spare F54 blocks sonic checked and the figures are 3-4mm, it currently has stock 86mm bores. Quote
Administrators gav240z Posted May 13, 2015 Administrators Posted May 13, 2015 I'll check when I get home but Steve Wilkins wrote down some figures for my F54 block, he stopped after Cylinder #3 because he said it wasn't good for overbore past 1mm. Quote
Riceburner Posted May 13, 2015 Author Posted May 13, 2015 I'll check when I get home but Steve Wilkins wrote down some figures for my F54 block, he stopped after Cylinder #3 because he said it wasn't good for overbore past 1mm. Thanks Gav! 160thou. Is that prior to doing the over bore Lurchos? Quote
zed74 Posted May 13, 2015 Posted May 13, 2015 Does anyone know the minimum recommended cylinder wall thickness for an over bored block? I've had one of my spare F54 blocks sonic checked and the figures are 3-4mm, it currently has stock 86mm bores. FYI You will find me bored thickness "on average" in a N42 block... F54 perferred - but just so your aware... Quote
Administrators gav240z Posted May 13, 2015 Administrators Posted May 13, 2015 I don't know what the unit of measurement is, the writing in the top right says "Small area at bottom of bore 3.0". You can see cylinder 2 had a smaller area at the bottom of 2.7. Quote
Riceburner Posted May 13, 2015 Author Posted May 13, 2015 FYI You will find me bored thickness "on average" in a N42 block... F54 perferred - but just so your aware... I thought N42 was the better block for big over bores as per this quote I found on Classiczcars "Carl, I think you have got this N42 and F54 block internals thing the wrong way round.... The N42 block casting ( the earlier of the two ) had more 'meat' between the bores than the F54 block casting that followed it. The F54 block casting had 'siamesed' cooling passages between the bores - ie less 'meat' - which actually makes it less stiff than the N42 casting. When going for maximum bore on an L28 block, the N42 has often been chosen because the extra material in the block casting leaves greater wall thickness, which helps to keep bores round in use. In contrast, the F54 block has often been chosen because people misunderstand what 'siamesed cooling passages' means. They think that they are "stronger", when in fact they simply have better cooling properties. The F54 has less internal structure than the N42. And amongst tuners in Japan, the earliest N42 block castings were always reputed to have 'better' metallurgy than the later F54s" I don't know what the unit of measurement is, the writing in the top right says "Small area at bottom of bore 3.0". You can see cylinder 2 had a smaller area at the bottom of 2.7. Seems to be a trend with the F54 blocks, mine too was ok on the sides of the cylinders but the wall thickness between 2-3 and 3-4 were too thin for my purpose. Quote
C.A.R. Posted May 13, 2015 Posted May 13, 2015 (edited) Gareth, you need a minimum of 120thou bore wall thickness AFTER boring to your desired size.'Correctly' sonic testing the block before boring to pinpoint the thinnest part of the bore, is the only way to determine where you can bore & how big you can go.Check out this photo of a L28 block that Les milled the top off:(Don't despair - that block had a dirty great big crack running along the deck between the stud holes. It was only ever going to be scrap).It's standard 86mm bore N42 block & if you look closely you can see how much core shift it has in the bore walls.After going through & sonic testing 10's of L28 N42 & F54 blocks for customer stroker builds, Les has found no difference between the two types of block castings in relation to bore thickness's.'Most' L28 blocks can safely be bored to 88.5mm (some like Gav's can't), a very small number can go to 89mm, and I've only seen two that can tolerate a 90mm bore safely (Owen's and the US L34).It's just all pot luck - you can can't tell until the block is acid bathed & sonic tested. Edited October 26, 2015 by Lurch ™ Quote
PZG302 Posted May 13, 2015 Posted May 13, 2015 My old "caterpillar" motor, because the block waqs painted yellow, that I had in my first Zed, and was carried over to my green zed for a while, was a N42 block that also handled a 90mm bore, but after a couple of seasons of racing, at refresh time it was throw it out as the bores were starting to get oval and couldn't be used. Oh how I miss the days of picking up L28 blocks for nothing...... Quote
Administrators gav240z Posted May 13, 2015 Administrators Posted May 13, 2015 Oh how I miss the days of picking up L28 blocks for nothing...... Yeah, I still remember going down to pick-a-part in Kilsyth and seeing 240k coupe's, old skyline's with L-bangers, 280zx's, rx3 coupe's etc.. Even back then I felt that the RX3's and 240k coupe's didn't belong in there and always thought it was a shame. Now when I see cars in wrecking yards I can't help but think they all look too modern. But it's just me who's got older . Quote
dat2kman Posted May 13, 2015 Posted May 13, 2015 SSS Automotive/Graham Wilkins, in md 1980's would go through around 20 four clylinder blcks on Sonic, before finding a good one to turn it into a 2.4 litre with offsett welded/ground crank and boring. The pile of L20B blcks at one stage was a bit big! Quote
Riceburner Posted May 14, 2015 Author Posted May 14, 2015 Oh oh, this doesn't sound promising. I already have the 89mm pistons and finding a block good enough sounds like it's going to be quite the task. I have two un tested N42 blocks, one is the engine currently running in the car :'( I will not go smaller than 89!! Lol. I guess sleeving the block is way too expensive? Quote
Administrators gav240z Posted May 14, 2015 Administrators Posted May 14, 2015 That's why I haven't bought pistons yet... Quote
Administrators gav240z Posted May 14, 2015 Administrators Posted May 14, 2015 Sonic first Pistons second,,,, always,,, I'm sure Gareth is saying... Quote
Riceburner Posted May 14, 2015 Author Posted May 14, 2015 I had read that before but I dismissed it. I know there's bugger all difference but for me this is my ultimate engine build (on a budget) and I would've always felt if it wasn't 89 it wasn't quite right. I had initially asked for 88's but I changed my mind because of that very reason. So, anyone got a block suitable for 89 bore laying around? Lol Quote
Cozza Posted May 14, 2015 Posted May 14, 2015 I guess sleeving the block is way too expensive? Any idea on the cost of sonic testing? It might be cheaper to bite the bullet and sleeve what you have rather than sonic testing a bunch of blocks. Especially if you have to buy the blocks to start with. Would I be wrong in assuming sleeves have good metallurgy and are very hard wearing, giving longer life? What's your goal with this one Gareth, LD28 crank. Isn't hindsight a wonderful thing. Cheers Mick Quote
Riceburner Posted May 14, 2015 Author Posted May 14, 2015 Mick, I have 2 more N42 blocks to check, one is my current running engine so needs to be removed and stripped if required. Not sure on the sonic test price, I didn't ask when I dropped the F54 off. I have a knife edged LD28 crank, 139.5mm rods (500gm), 89mm pistons (288gm) with 27mm pin height. P90 PMC head with 42cc chambers 10.7:1. It'll be a longer rod stroker. I'll wait to find a block to fit the 89's, anything less won't do. Sleeving is an option I will investigate. Quote
Cozza Posted May 14, 2015 Posted May 14, 2015 Cool, sounds like it should be a bit of a weapon. Hope one of your blocks will suit. Keep us posted as to Sonic and sleeve pricing. Quote
pauly_adams Posted May 14, 2015 Posted May 14, 2015 you could always part with your pistons gareth, they would go nicely in my engine Quote
dat2kman Posted May 14, 2015 Posted May 14, 2015 CDC thickwall sleeves, fitted to a machined bottom step ( to stop tyem being pulled down further) and no T tops, have a higher graphite content in the sleeve, and thus offer less friction to affect the rings, will give higher horsepower output, compared to regular block cast iron. Sleeves do come with some disadvantages, and do need to be o-ring sealed, and fully supported by block bore, but they are a viable alternative. There may he a few stripped blcks laying around, yet to be soniced, it can get to be a bit of a costly exercise to purchase, then sonic. What about the dea of the intending seller have the blck(s) sonced, and the buyer pays half the test cost? If a blck comes up as acceptable to go to 89 mm then buyer pays other half f sonic test, and gives the seller $$$ for that block? Quote
C.A.R. Posted July 11, 2015 Posted July 11, 2015 OK whats with you lot & the sudden fascination with L28 blocks that will go to 89mm? ? ? Can anyone tell be why an 89mm bore is superior to an 88mm or 88.5mm bore? Quote
Administrators gav240z Posted July 11, 2015 Administrators Posted July 11, 2015 I don't care.. I'm happy if I got to 88 or 88.5 89mm would just be a bonus. Quote
dat2kman Posted July 11, 2015 Posted July 11, 2015 Maybe it's just so they can use the 91mm MLS Nismo head gaskets! You watch, they'll be chasing sonic tests for 90-91mm bores now,,,,,,,, Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.