Very excited, first start after rebuild!

[zachmac]

So I finally took the leap tonight and fired up the newly rebuilt engine. Overal pretty good, nothing major wrong and soundsgood overall. A few questions:

1) I have a significant oil leak past the mechanical fuel pump blank (electric pump on car). It never leaked there before but when I took it apart it had a roughly half inch thick rubber spacer between the plate and the block with a gasket on either side. When I reassembled everyhting I thought "why do I need that, why not just use one gasket and the plate directly bolted to the block with shorter bolts?" But, as I said it is leaking like a sieve there now. Do most people have that rubber spacer (non-mechanical pump cars)? Was the rubber spacer a factory part when they went to electric pumps? I am thinking maybe the plate is cutting or over "squashing" the gasket and preventing a seal and the rubber spacer allowed for proper sealing and over came any irregularities? Item 1 will be fixing that leak.

2) I still need to tune the engine, check timing, adjust carbs, etc. The car came to me with twin 42 DCNFs and I rebuilt them during the process. # 3 cylinder is popping back through the carb pretty well and I have an irregular idle with some exhaust popping as well. As I said, haven't had time to adjust anything yet, justa trial start with a check for oil pressure (good even with leak) and then wram up and shut it off. It also has adjustable cams wheels and when I dialed them in it drove me to advancing the exhaust cam about 4 degrees. Thinking maybe I dial back to zero advance / retard on that cam, dial everything in and then play with cam advance / retard later if I feel the need. That may be the cause of the pops through the exhaust?

3) I am thinking for the carb setup, dial back the exhaust cam, check #3 intake valve clearance again, check ignition timing with light (I set static at 10 degrees advance with one of Allison's distributorless ignitions doing the sparking), balance air flow through all four barrels (twin two barrels with individual runners to each cylinder) and then dial in mixture using a colortune. Sound like a logical sequence?

I will also check for any air inleakage as certainly a lean condition may be causing the backfires. Any and all insights welcome. BTW, medium street grind cams from Bayless with 4mm domed pistions from AR.

4) Lastly, due to scope creep I also don't have any seats in the car at the moment (nor any tie rods on the car, ) so clearly I can't drive it. Am I risking damage to the car by just running it at idle for now and should I be doing something different to help the rings seat? Fresh overbore to max spec with new pistions and rings.

[bradartigue]

I wouldn't idle it, the rings might glaze. There are a lot of opinions on how to do it, most center on getting it up to around 1200 RPM and holding it, letting the temp rise, then keeping it around 1800 RPM for a while. The "for a while" is what is unknown, some guys run their cars for a half hour or so at that speed then bring it up to 2500 for a while. I've never done that. I run it up to around 1800, get it to temp, and hold it around 2000 for a while, then let it drop to idle speed, then back up and down. I've never had anything glaze up yet, but I've rebuilt maybe a dozen engines, not hundreds like some of the mechanics here.

What say ye, mechanics? I think we all agree idling for extended periods on a new motor is a bad idea, but how would you break it in?

[So Cal Mark]

if your cams came with break-in instructions I'm sure they would tell you NOT to let the engine idle initially. The goal is to have everything close enough to start the engine and run at 2000rpm for 20 minutes or so. Cams fail during break-in, that first half hour is critical. I'm hoping you used a good break-in oil with lots of zinc

[grisoni]

The age old question on break in...
In the 80 early 90 all (Japanese anyway) motorcycle mfg would tell you to not rev it past a certain rpm for 100 miles and then gradually increase rpm by 500 to 1000 for each 100 miles, had customers rev the snot out of them right out of the box and no ill things happened for 10000s of miles.
Cars had no break in at all after about 1985

Now, on big air cooled aircraft engines you have to run "non detergent" oil at high manifold pressures (the higher the better) for 25 to 50 hours to seat the rings properly or else one glazes the cylinders and you get to hone cyl and change rings again. Never heard anything about cams having issues during break in, (they do sell additives under the camgard name that are supposed to be great for said aircraft engines).

Personally I use Castrol GTX as it has one of the higher zinc contents around 1200 or so I believe, It kept various of my OHC engines happy for 300k plus, but to have 2000 ppm zinc (or whatever the measurement is) in the little FIAT motor seems excessive unless you run some pretty gnarly cams at high RPM. IF it makes you happy, go for it and spend the 10-12 $ a qt on VR1.

[So Cal Mark]

wow, you're advising not to break-in cams or use zinc? I suppose you have a reason to give advice that's opposite of every cam manufacturer, but I can't imagine what it would be.

[bradartigue]

wow, you're advising not to break-in cams or use zinc? I suppose you have a reason to give advice that's opposite of every cam manufacturer, but I can't imagine what it would be.

Curious - What is there to "break in" on a camshaft? I'm not talking about the valve train, I can understand a break in procedure if you have a new head, new valves, springs, tappets, etc., but the cam rotates in a low tolerance bushing cast into the head. Is this an actual break in or just a test to make it doesn't shatter the first time its turned?

[So Cal Mark]

lobes must go through a break-in. Every aftermarket cam mfg in the world recommends a similar procedure

[baltobernie]

Thinking maybe I dial back to zero advance / retard on that cam, dial everything in and then play with cam advance / retard later if I feel the need.

That's what I'd do; start from the stock specs and work from there. You already have a big mod with the twin carb setup, so I'd hope that the PO had the carbs pretty well dialed-in before you got them. The "order of the march" is usually valve clearance, cam timing, ignition timing, then carbs. As you mentioned, vacuum leaks, crossed wires, etc. can all mask other problems.

There's nothing like the first start-up after all your work, isn't there? The sealant stink, paint smoke, you running around with a flashlight Be patient, you'll figure it out.

[bradartigue]

lobes must go through a break-in. Every aftermarket cam mfg in the world recommends a similar procedure

I've never installed "just cams," it was always part of a broader rebuild. Makes sense I guess...still not sure what is being broken in though. Sounds like more of a test than a break in.

[So Cal Mark]

This is from the Driven Oil website and mirrors every other cam or lubricant manufacturer's recommendations;


Proper Camshaft Break-In

Proper flat tappet camshaft set-up and break-in, as any engine builder knows, are keys to how long a camshaft will last, both short and long term. The correct procedure allows the lifters to establish rotation and develop a good wear pattern.

Break-In Preparation

Always remove the inner spring during break-in when using dual or high pressure valve springs. An alternative solution that addresses this same concern is using a set of low-ratio break-in rocker arms. Both of these solutions provide your best chance of proper camshaft break-in and long term durability. While these tips may be a slight inconvenience, a little time and effort on the front-end is much better than destroying your new engine.

Proper Procedure

As soon as the engine fires, bring the rpm up to 2000 to 2500 during the first 30 minutes of operation. Slower engine speeds will not supply the camshaft with an adequate amount of oil for the break-in period. The engine rpm may be varied periodically from 2000 to 2500 to direct oil splash to different areas of the camshaft. After the 30 minute break-in period, the inner valve springs should now be replaced and the correct rocker arms installed.

This entry was posted in Tech Articles, Tech Guides & Tips on April 4, 2010 by admin.

I've got a shelf of flat-lobe cams we've taken out of Fiat motors as evidence

[bradartigue]

Interesting. I guess at low speed it's just kind of slowly slapping the shim and flattens. Interesting.

[timinator]

Interesting. I guess at low speed it's just kind of slowly slapping the shim and flattens. Interesting.

The cam is being burnished during break-in. Burnishing is the plastic deformation of the surface of the cam due to sliding. Break-in oil is used to aid this process because it contains higher concentrations of ZDDP. The usual additives in motor oil are left out of break-in oil because they compete with the ZDDP for space on the surface of the mating parts. Burnishing smears the surface of the cam without allowing the metal to micro weld or gall. The ZDDP is sacrificed or consumed during burnishing. Commonly referred to as "zinc", ZDDP is just the best way to introduce phosphates into the interface between the contacting metals. The phosphate is what is consumed during the burnishing.

[azruss]

This implies that every time you change the valve shims you need to go through a break in.

[bradartigue]

This implies that every time you change the valve shims you need to go through a break in.

I bet 0% of the entire world of FIAT owners has ever bothered. None of these procedures are in the FIAT service guides; i'm not saying they're wrong, but they aren't OE.

[timinator]

This implies that every time you change the valve shims you need to go through a break in.

Not really, everything is relative. If you notice the shims have a polished appearance and are hard. Once the cam is burnished it could be compatible with next shim. The problem would be when the valve spring pressure is increased which would cause a higher point contact load on the face of the cam. Or if the replacement shim was not in good condition.

I bet 0% of the entire world of FIAT owners has ever bothered. None of these procedures are in the FIAT service guides; i'm not saying they're wrong, but they aren't OE.

Unless the Fiat service guides were written in the last ten years they would not have to address the problem of the lack of ZDDP in motor oil. The race engines I build get the break-in Mark described and then go straight to the track. Idle speed is set at 1500rpm to insure sufficient oil supply. Nitrided steel top rings on a properly prepared cylinder wall seat almost instantly. Leak down after the first night of racing is 0-2%. Cam, rod, and main bearings don't need to break-in. If something is wrong they just break down.