Just picked up the block and crank from the machine shop for the first ever engine I'm going to assemble myself. A BBC. I've been super anal about keeping it oiled up so it doesn't start to rust. It came home shrink wrapped, and I soaked the cylinders in WD-40 as soon as I unwrapped it. I noticed there's some marking and specs in the cylinders that looks like rust. Is this what it is?! Will it be OK to go forward or should I hone? Thanks guys, from this engine building newbie. Sent from my iPhone using The H.A.M.B. mobile app
See if you can take a .10 cut if you are satisfied at the power level or get down with some horsepower and go .30 to .40 over and rock. The main implication is you will need new pistons and rings anyway. If a honing will get you to where you want to be, it will only cost you a new set of rings and remain stock.
Just came back from the machine shop where it was bored .030. Already have the pistons and rings for .030. Sent from my iPhone using The H.A.M.B. mobile app
It may be just the pics/angle. But what I see is a block that was bored too large and very lightly finish honed with a too rough hone stone. See the pitting/rough/tearing surface in the lower part of the bores. This from the rough boring bar cutter. Way too coarse of a hone pattern. The finished bores should be almost a mirror finish for new modern rings.. I bore and hone blocks on a regular basis. Kwik-Way bore bar and CV 616 hone. I usually use a "cork" stone for final finish on modern/performance stuff. Leaves a dark mirror finish.
Well damn. This makes some sense. The bores feel pretty rough. Wondering if i can run a fine hone in it to save the 30 over.... Sent from my iPhone using The H.A.M.B. mobile app
Only if you have a ridged professional hone. From the looks of these pics. It would take about .002-.003" more removed with a medium stone then a light brush with fine stone. But then your pistons are going to be that much more loose in the bores. Ok for some forgings but a cast piston won't survive. Bore needs to go to .040" with corresponding pistons/rings. Machine shops error. Poor work.
Right on, thanks for the help. I'm going to bring it to a different machine shop. After waiting 8 months for this one that's not right, I'm going to cut my losses with that guy. Sent from my iPhone using The H.A.M.B. mobile app
Actually just double checked the bore as-is. Almost seems like they didn't actually finish the hone. All 8 are right around 4.270. One is at 4.275. Sent from my iPhone using The H.A.M.B. mobile app
X 2 on the hone, looks like the wrong grit for sure. Match your grit spec. to type of rings Iron, Moly and another that slips the mind or it will smoke like Hell and the rings won't take to the Cylinder.
Take the block back to the machine shop WITH the pistons so they can finish the cylinders out to match each piston. I'm not sure if you took just the block to the machine shop and told them to bore it .030 over? If so,then that's asking for problems. Each piston is usually different in size slightly and needs to have each cylinder sized for a specific piston. The shop also needs to know the type of rings you'll be running. There are far too many variables to just bore it .030 over.
Haha....I did bring them the pistons AND told them I'd be using moly rings. Just a bad machine shop. Sent from my iPhone using The H.A.M.B. mobile app
Looks like a poor job at best. Measuring both the top and bottom of the bore, you may be able to hone to the proper clearance at a reliable shop. The only reason to go back to the original shop is for a refund. Pete
Wow, the easiest engine on planet earth to build, to make big HP/TQ, and it still hurts when I see one mullered up. If your measuring is correct you'll be ok to get it final honed. What pistons? TRW/Speed Pro, likely all 8 are exactly the same size. 2 sets for me, all 8 within .0002 of each other. No, not an extra zero, .0002. Check em out, save yourself some time and get a handle on what you have. Ever hear about grooved mains? Run away screaming if you get told to do that. Spun bearings are the 1st fail on BBC first-timers. You want .0023-.0025. They're big parts in there and need some room for oil and exapnsion. Too tight they'll spin a bearing on your 1st full zoot pass, too loose they'll spin later which still sucks. What rods? 3/8 rods will live to about 6500 but perhaps not a steady diet of that without lots of work. 7/16 "dimple rods" will net 7500 or more depending on the stroke. 4" likes 7500 but I went through at 7800 in good air many a night and never hurt a thing. In all fairness I also had a non-twist Chevy race crank and spent a lot of time on balance and build specs. Can you tell I'm a BBC fan? Keep us informed, good luck with it.
UPDATE: Took the block to a different machine shop, someone I trust. This guy did a set of heads for me awhile ago. (If you're wondering why I didn't go to him in the first place, I took the heads to him AFTER the first shop was falling on their face). Anyway....he confirmed what you all said on here. The bore was done way too large and barely honed at all. He checked the bore and found that they're all actually a bit bigger than 4.280, about .003 to .005 larger. He suggested I go back to the original shop and show them the issue, which I did. It was met with quite a bit of resistance. The first thing I had to do was argue with the guy about what the bore diameter SHOULD be. At 30 over, 4.280. He insisted it was 4.550. Red flag, anyone? Then a guy came out to check bore diameter. He used what I believe was an inside mike and checked the pin with a dial caliper. He insisted the bores were EXACTLY 4.280 and the other machinist (who used a dial bore gauge) set it up wrong. They then said that they could ball hone the cylinders to clean them up without taking off any more material. I was tired of arguing, frustrated, and had to get back to work. I left the block there so they can try the ball hone and check bore diameter again -- where they will either see that they were wrong or try and con me into thinking it's fine. Either way, I'm not sure what my next move is here.
oh yeah....and the guy kept telling his employee that I was there because I "didn't like the crosshatching". Can't you see the left over marks from the boring?!?
Well I WAS using a set of Icon Forged. Rods are Eagle forged 4.00 that the mfr says are good for 7500. Looks like the pistons won't be usable once the bores are cleaned up. See above for my update....I'm frustrated to say the least. I don't want to give up on it, but it's quickly becoming something I paid a lot for that isn't what I wanted....
If you build very many engines you will run into this type of work and machinists. If you find a shop that does a good job in a reasonable amount of time become his best friend.Nothing worse than a bad job and everyone denies responsibility. Best of luck.
You are really asking for trouble. A ball hone will only disguise the problem. The bores will still not be correct. The walls won't be straight or the correct finish. I use ball hones on cast iron re-ring jobs specifically because of the "hiding" factor. They leave a good finish, A worn/imperfect cylinder will "look" like new to the eye,but the flawed base is still there. Plus, most shops only keep a "medium" grit ball hone around. NOT the ticket for a new fresh bore with performance pistons/rings..
Ask them for a standard bore block for yours and go back to the other machinist and have him fit your pistons for you.
Forged pistons in a BBC like a lot of room. I ran my TRWs at .008 piston to wall. The trick is to warm it up good, but I was also at 14:1 and ran file fit gapless rings. A street engine wouldn't like more than .005. I don't know that I'd have left it there. I have this "once a fuck-up always a fuck-up" rule. Ball hones are a Sat night fix-my-sled/dirt bike cylinder move. At best a re-ring for a tired old farm implement or a truck at the end of it's life anyways. Maybe you could exchange your new pistons for .060 over and give it to the other guy. 468 is one of those "magic" engine sizes that seems to work really well and worth the effort. No worry what so ever about overheat issues or thin walls. That's a worry once you're +.100 or more. The engine is worth the fight, best of luck to ya.
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