Thanks Ron and Micky. In some of my engines I have worked on over the years the clearances have increased with wear and I didn't know which wears faster on this engine (seats or everything else combined.) That's why I asked Brian For anyone who hasn't followed this journey of mine (or has a bad memory, like me) I am a total amateur, unqualified, uncertified, and often a bit obtuse. I am doing this for fun and I don't mind asking questions or displaying my ignorance in this public forum. I appreciate all of the advice I get and will try to share my reasons for making the decisions I make to help others who take on this challenge. I won't always follow the factory-approved processes and am consciously trying to improve things where I can. I welcome criticism and disagreement as without it I'd learn nothing. I have been warned off some of my ideas and am grateful for the warnings. At breakfast this morning I checked the two exhaust valves with least clearance (.22-.26mm with 3.30 shims) and both were similarly proud of their seats as the others (i.e. not sunken into the head.) I measured the base circles of the cam and those two were .17-.14mm bigger than the others so that explains the difference. I have found a good source for the shims, $3 ea from 2.55-5.20mm thick (autoricambi.us.) Does anyone know roughly how fast the shims get smaller? (e.g. at 30k miles the clearances typically narrow by 0.XX mm.) Thanks. I may get a few smaller shims to keep for future adjustments. Image Unavailable, Please Login
To further information about shim thicknesses I urge you to read the following post I made in my restoration blog: Dino 246 Restoration Blog: The right shim: Blueprinting the valve train As you will see you want to keep the shims between 3.400-4.000 mm and the perils of going outside these numbers are outlined in the link. Regarding shim wear rates this week I checked the valve lash on my 308 for the first time in 15 years and 20K miles when they were last set. EVERY shim was within spec and NONE of them were yet half way to the adjustment point. Shame, all that disassembly for nothing
But there are too many variables to list to predict that. My 328 motor originally came apart for that reason. Got a rebuild by someone who had no clue. The OE Ferrari guides had lousy concentricity up until the 90's. Put in modern guides that are true and grind seat to new guides and poof, no shim left. I have used machinists for years that put in under sized guides, indicate off the seat and bore the guide to the seat. Clean up the seat and you are done. Its more work but a lot less than replacing seats. For proper breathing the valves need to stand proud, not down even with the chamber. Otherwise they are shrouded at low lift and do nothing.
Thanks Rob, I hadn't seen the 246 link and it is a good summary. I thought about using the lighter shim-under-bucket setups as there are so many people making them for the other 33mm engines (Fiat, Alfa, BMW, Volvo.) As I said above, "my Cat cam lobes (10.75mm lift) and they still have plenty of space to the edge of the shim." Nothing surprises me anymore with this engine. I was checking the new cams in the second head before finishing the shimming and again the one cam tightened with one of the caps. Had a look at the journals (clean and smooth), mic'ed the cam (same as the others), so I turned the cap around so that the stamped number was on the inside. Worked like a charm! Since there is no sign of wear on the cap or the head side I can only guess it was put on that way before line boring. I just finished the second head and all are now within spec with 3.55mm and up. Since it will take me less time to switch the two tight exhaust valves than wait for thinner shims, I'll probably do that. It helps to have a box full of valves I'll find the two shortest and put them in.
It may sound crazy but be sure to check the final valve lash with the heads installed and torqued down. I have seen the numbers vary from having the heads on a bench to on an engine. I must have a really good engine from Ferrari because I also ran a compression check and with 37K miles on the clock every cylinder was between 187-200psi. Not bad for a 40 year old engine that has never been opened.
Rob, I think I'll check the clearance once it has run for a few minutes. I'm sure the block/head stresses affect it once assembled plus everything usually seats-in once running. So this morning, before taking out the two valves that needed a bit more clearance, I used my biggest micrometer and a bolt to measure the length of the valves. I then looked through my box of new valves and found two that were about .15 shorter (tip to face.) So I pulled the two valves out, lapped in the two shorter valves and then tested it with the cam in. The gaps had opened about .09-.12 so I put bigger shims in and will order a few 3.25 and 3.20 for the future in case I need them. While I had the cam in, I put a thin film of oil on the lobes to get a photo of the wiping pattern. You can see that there is about 1.5-2mm to the edge of the shim. This was the 10mm lift exhaust lobe and the inlet is 10.75 so there is still some clearance but I would not go much bigger without switching to the bucket-over-shim setups that gives you more space (and lightens the valve-train.) Image Unavailable, Please Login
that is real close to the edge, as in 'spittin shims' close... seriously consider shim under, flipping a shim at 8k rpm makes for a BIG $$$$ mess...
Scott, I've never used a higher lift cam on a bucket tappet so this is new territory for me. Thinking about the mechanism, I can't think how this clearance to the edge of the shim might be reduced and lead to a problem. I suppose that if the opening ramp of the lobe wears badly enough the tip could move closer to the edge and eventually hit it? Anyone else have thoughts on this? I will call Cat cams on Monday and ask their recommendation. Their cam spec sheet says OEM followers but they say the same for their 13mm lift cam and I can't see how that would fit on a 33mm shim. camshaft details | CAT CAMS performance camshafts
I'm short on time so I'll give the short answer Valve train harmonics... high rpm 'float' and very close to edge contact will lead to 'spitting' a shim. The mass of the bucket shim, valve train etc.. all need to be calculated against the cam lobe profile and spring rate to check acceleration and jerk, are the springs able to hold it all in contact to the lobe up to ~9k? quick link to one of many racing sites covering spitting shims.. http://paradiseracing.com/blog/why-should-you-use-shim-under-lifter-buckets-larger-diameter-lifter-buckets/
Thanks Scott, Great link and I can see how it happens-- the momentum of the closing and (relatively) heavy shim is pushing it up while the cam lobe is pushing down on the edge so the shim can unseat and lift on the opposite side. I think that since both of my cams are wiping inside the edge I should be ok. The article says "...if it leaves a nice rectangle on the bucket ending BEFORE the edges of the bucket its very safe." I have no intention of ever going over 7500rpm and will have a rev limiter thanks to the programmable 6AL2. I have the new springs from Cat cams that go with these cams and they are actually softer than the originals. I have seen in this forum that the originals are a bit too much for normal use (hence the 10k+ rpm stories from standard springs.) I will look into the shim-under-bucket options because I like the idea of lightening the valve train.
Why not just replace the valve seats? A competent machinist can do this in relatively little time. The labor and materials at this point is small compared to the cost of a failure.
The seats are fine. It was a combination of valves at the long end of the range and cam base circles a bit on the big side. Neither are factory parts so more potential for problems. When choosing a set of valves I chose a set at the top of the length range to minimize the shim weight. My mistake as some noted was not putting in lifters and cam and then putting valves in to check clearance and select valves based on the cam (and have a shim a few sizes bigger than minimum for future adjustments.) With standard cams and valves things should fit a lot easier. I'm just a sucker for punishment.
Yesterday's post seems to have gone awol. We had our last sunny day for a while (raining most of this week) so I did a final degrease and pressure clean of the block and I was pleasantly surprised that my modified brass BBQ brush found almost nothing in the oil galleries. Some of my engines I've rebuilt (admittedly old British iron) have had lots of crud hiding in the galleries. I also used the sunny weather to degrease and pressure clean the engine bay. It has a few chips in the frame paint (probably tool bumps and removing the drivetrain) so I'll touch up the paint. Any suggestions for a hard black paint for the frame? There is more paint off at the top (chassis number and emission plate areas so I'll need to prep and respray those areas-- what paint works well? Image Unavailable, Please Login
This evening I pulled the covers of the oil sump and gearbox. Was prepared for and found the springs, balls, and cylinder. No surprises but some black gunge in the engine oil sump. Tested it with a magnet and it was slightly magnetic-- very cool watching a black liquid head rise from the small pile of sludge on my finger (strong neodymium magnet.) The gearbox was clean. Is it possible to measure the synchro rings in-place? I sprayed brake cleaner into the synchcros and rotated while my friend Niall pushed it in and out of gear and then he pushed it almost into gear to push the synchro ring against the synchro hub while I got feeler gauges into the gap between them. 1st and 3rd were .70mm and 2nd was .55mm. The manual requires 17-25kg pressure to measure the gap-- anyone know if the in-situ measurement is any good? What are the gaps when new? The previous owner isn't sure as it's been 17+ years but he thinks it might have been harder downshifting into 2nd and 1st. The blind hole hasn't been drilled and the car has 36k miles. Thanks, derek Image Unavailable, Please Login
Por-15 is a very hard black chassis paint, but too glossy to be oem. A tough base to scuff and touch up with some satin black. You can buy in various kits. The little tins are quite handy
Thanks Guy, so brush touch-up with the hard POR15. Then spray on some satin black. Is there a good rattle can satin black someone can recommend or what is a good paint for my small touch-up gun?
If you are spraying, 85% flat black / 15% gloss leather brown Rustoleum paint roughly matches the factory color and sheen.
Thanks Brian, I'll see if my local paint shop can mix some up for me. Cat cams came back and said the standard buckets/shims are fine. I have a $45 credit with them in case anyone orders cams or springs (most would be lost if they refunded to my bank.) Does anyone know the new synchro ring clearance and how much wear from new to the 0.4mm limit? Someone must have checked this at some point or have a newly rebuilt gearbox handy for an in-situ feeler gauge check. Thanks, derek
Yes, brushed on - think they have their own thinner for lighter coats. Its a very thick paint. I've use some SEM products that are pretty good. I used the por15 on the engine mounts too. Cleaned, rust removed, scuffed and just painted with the little foam brushes that come with the Por15 kits and left it at that.
if it is too worn and old not, but a new one no problem, i did it many times in the communism era, when we didn't have parts from the west available.... also when we used in race engines and used longer custom valves so we can made the heavy shims lighter..
Just a correction to: "...The manual requires 17-25kg pressure to measure the gap-- anyone know if the in-situ measurement is any good? What are the gaps when new? " I have now actually read those pages of the manual (instead of just checking the table for the synchro ring wear limits.) The 17-25kg is the test weight for the 3 springs inside the synchroniser. I'll test those with a bathroom scale onto the fork rods. I will probably not rebuild the transmission as it looks to be in such good shape and I would like to get the car running before we move to the UK in August. If the 2nd synchro ring has worn for .70 to .55mm in 58k kms then it should last at least another 60k kms getting down to .4mm. They may actually work for a while below the service limit (anyone know?) I will drill the blind hole so the extra wear due to the design flaw will no longer apply. I'll also use Redline MTL which should help.
This evening I got the left fuel tank out and also all the old fuel and coolant hoses. I bought some aircraft cable to pull the new silicone heater hoses through the sill, will try that tomorrow. I believe the easier way is to pull them through forward to the front? The rubber hoses were all quite bad except the short fat fuel cross-pipe connectors but I'll change those too. I ordered some Gates green stripe hose to cut up and some ethanol tolerant fuel lines. It feels really good to get all that bad rubber out of there and it will save a lot of future headaches. The blue silicone hoses to the front will not look very original but if anyone ever cares they can be spliced behind the tank so that the long lasting blue hoses in the sill will be out of sight. I also changed the gearbox shift shaft seals to the quad seals and was surprised by the punch marks holding in the retaining washers. I don't think they expected these cars to outlive those seals. The original o-rings look fine but seem too hard. They weren't leaking but worth changing while it is easy. I still haven't decided if I should changed the 2nd synchro. Does anyone have any idea what the new clearance is. I am well about the limit at .55mm but is that half way to the .4mm limit or 80% to the limit? Image Unavailable, Please Login
