Alfa Romeo Forums banner

1 - 20 of 27 Posts

·
Premium Member
Joined
·
176 Posts
Discussion Starter #1
All,
I've had Ross pistons make me a set of .020 over pistons to fit a 750 1300 veloce motor. My local machine shop did the bore/hone work. I supplied the liners installed in the block with metal hold downs on all 10 studs. I'm not so happy with the results. The bore at the top (not at the very top) between the four liners varies by .0019". The taper varies from .0011 to .0015 and worst ovality is .0015 with the other three under .001"
These used liners all started out with near new specs.
What bore/hone tolerances should I expect?

Thanks,
Jim
 

·
Premium Member
Joined
·
740 Posts
I think honing is the answer

Hi Jim

I'm very interested in this issue as I'm going to be doing something similar myself soon. Check out this thread

http://www.alfabb.com/bb/forums/engine-repair-diagnostics-rebuilding/157953-overboring-stock-2-0-liners-vs-new-complete-set-up.html

As you have found out machining these liners for oversize pistons is quite a trick.

http://www.alfabb.com/bb/forums/engine-repair-diagnostics-rebuilding/304857-liner-trueness-out-torque-plate.html#post5330865

In post two of this thread Gordon Raymond states

"...A great deal depends on the sharpness of the boring bar and depths of cut. Due to liner distortion by boring, I only use honeing as a method of opening up Alfa and Ferrari liner bores. The boring bar will displace or compress metal under the cutting edge resulting in a less than ideal finished surface with included stresses. The honing method avoids all this completely.
So generally, yes, bored Alfa liners will be distorted. ''


I gather from this that the better way to proceed is to hone the liner, starting first with aggressive stones, then moving to finer stones and then finally the traditional drill based or brush type hone.

Do a search using the terms Boring & honing in this forum and a number of interesting threads come up.

Please keep us informed as to how all this shakes out.

Bye
 

·
Super Moderator
Joined
·
11,215 Posts
Find a shop with a Sunnin honing machine. This is most often used by motorcycle and light aircraft engine builders. This machine hones liners to specific dimensions. It is computer operated. Whatever dimensions one dials in, is what you get.
This is the best method I've found for dimensional uniformity with wet or dry liners. Best part is it creates NO machining stresses.
From my personal experiences.
 

·
Premium Member
Joined
·
13,071 Posts
I don't claim to be an expert on this but I had a set of 2L liners bored to 85 mm and they were perfect. They were done in Pensacola using a jig belonging to Richard Jemison. I believe that the key was to have the liners torqued down during boring exactly as they in the motor with the head torqued down.
 

·
Registered
Joined
·
4,136 Posts
Jim, I don't know of anyone in town with the Sunnin hone setup Gordon is talking about (although given the size of our town you'd think that somebody would have it). I'm not sure if Robert Rodgers in Dallas has a Sunnin hone or whether he uses a torque-plate but I know he can bore/hone liners that are true. It might be just as easy to send the pistons and liners to the shop in Ill. that Gordon uses.
 

·
Premium Member
Joined
·
176 Posts
Discussion Starter #7
Thanks all,
If I find a machine shop with a Sunnen engine hone, can I expect tolerances to be held to new specs i.e. .0005?
What specs should I be happy with?

Jim
 

·
Super Moderator
Joined
·
11,215 Posts
Yes Milanoguy.SV-15 - Sunnen
The machine that does V8's is the one used. It also does all kinds of other stuff including individual liners. The shops that have these do Aircraft and Motorcycle liners..... as well as Alfa and Ferrari liners. No torque plates required. No stresses!
It might be worth contacting the Mfg to see WHO has one near your location. For Alfa liners, the cost involves paying the owner for honing stones that get used up as the machine works.
This is a very good way to get perfect liners.
From my experience over time.
 

·
Richard Jemison
Joined
·
7,075 Posts
Liners

Boring and finishing Alfa liners are uniquely difficult as the flat/thin front and rear area needed to Siamese these to fit into the block distort easily under the pressure of the hone, more than the thicker sides.

The shop I used in the past hated doing these and generally I would take 10 or 12 liners hoping to get 8 which were done exactly round. Never got 12 out of 12...
Measuring them with a bore gauge before accepting them didn`t help their attitude about this crap either.

When you buy liners bored by a "Supplier" absolutely do not use them till they have been re-measured and verified for roundness and without taper.
 

·
Registered
Joined
·
4,136 Posts
Well, now I'm developing an anthropological interest in the practical history of Alfa cylinder liner boring. I mention this because my back-in-the-day (although not that long ago) recollections of Alfa engine building don't include much concern about out-of-spec bored liners. The general practice was to simply send the liners to a good machine shop, bet them bored oversize, and then go ahead with the engine build.

Maybe I missed something (entirely possible) but I don't recall discussions about liner ovality being a problem. I'll add the usual caveat about being entirely wrong, but my guess is that lots of Alfa engines were built without much attention to whether the o/size liners were in spec. But here's the mystery: were back-in-the-day machine shops doing a better job of boring liners such that ovality wasn't the problem it is today or---to take entirely different approach---now that we know that closer tolerances are possible, is liner ovality now recognized as a bigger problem than it was in past years?
 

·
Push hard and live
Joined
·
8,919 Posts
Speaking from my several decades as a parts guy in the imported car parts business...

It was positively routine that a guy would buy all the bits to overhaul his engine, and come back in a month claiming the bearings, or rings, or pistons were defective, as proven by his recently destroyed engine.

We'd ask "did you measure everything to be sure the machine shop did everything right?"

We'd usually get a blank stare, and something like "waddaya measure stuff with?"

I doubt the shops then were better or worse....
 

·
Registered
Joined
·
1,733 Posts
Just a quick thought before going to work.
Would it be worthwhile to machine the outside of the liner to a set diameter and produce a full length jig with a matching bore for them to slide into?
The jig would simply be a large bit of steel round bar that the whole liner slid into and could encorporate a clamping plate to simulate head clamping/distortion.
By having an intimate contact with the outside of the Alfa liner, the jig would offer support to the liner while it is being machined to prevent distortion and help produce a much more consistant finish.
 

·
Registered
Joined
·
146 Posts
I don't know who he has to do the work but Paul Spruell has liners bored and I have not had an issue with the ones from him.
 

·
Registered
Joined
·
1,733 Posts
They are weak enough stock. Boring them will increase weakness, Turning the outside will be asking for failure.
How weak are they?

New idea, again before I go to work:

1: Machine the outside of the sleeve for a consistent finish.
2: Machine an interferance sleeve from a high strength steel, like 4140 and fit to the outside of the Alfa sleeve.
3: Create afore mentioned sleeve boring jig.
4: Bore and hone these impressively strong, mutant Alfa sleeves to amazing tolerances.
5: Profit.
 

·
Registered
Joined
·
276 Posts
can do them for you. my shop has fixtures for all the alfa liners. 4cyl & V6. if yours are not too far gone, tolerances will be on the money (i.e. in spec)... or money back.
andy
 

·
Premium Member
Joined
·
13,071 Posts
How weak are they?
I have seen a few cracked liners in racing engines so there is not a lot of safety margin.
 

·
Super Moderator
Joined
·
11,215 Posts
You can buy steel liners... The discussed weakness in Alfa liners is my own reason for not honing 1600 liners to 80 mm for 1600 blocks used in racing. I only go to 79, as once-- just once, we had a thin skirt crack off an 80 mm bore liner 1600 in racing. Very little was salvageable from the remains. The iron alloy used in older Alfa liners was generally sound, but as noted, iron wet liners are not as tough as racers want. Today you can have new "spun-cast" liners made up, of sometimes special alloys that are possibly better. Some new liners offered for rebuilds are pretty horrid, as noted in this thread. You BETTER measure them! Hidden flaws? They are there. Generally liners that fail, are new, unmodified, and they fail in different ways. If I use Alfa liners, old ones with lots of heat soak cycles are best, "use-stress-relieved". However, these usually need to be honed oversize, and you don't want to go too big!
From my own experience with disaster.
 
1 - 20 of 27 Posts
Top