Fuel Pump Question:

[Kevin - Blown 95 TA]

OK, forget about your homebuilt engine flying apart & run the piss out of it.

I've never had an engine NOT break in from varying the RPM & load with progressively higher RPMs, but I worry a lot more about a custom setup than a new car or bike under warranty, that's for sure. I think putting it under a load is different than running the RPMs way up. And I think the heat cycles are important, too.

So, what rpms would you guys suggest on a fresh custom engine, and when? I'll be doing this again this spring, so do you think I should break it in with the blower to help seat the rings?

[raroZ28]

3 engines I broke in this way. Each one had awesome compression and ran super sound. 2 of them were g54 4 bangers, and I did an engine swap, and swapped heads. When I pulled the heads, the cylinders looked beautiful. Clean pistons, no signs of blowby, etc... One motor had about 15K on it, the other had 10k on the rebuild.

If you build your motor right, running it up the RPM range will not blow it apart. And a car or bike under warranty is already broken in very rough.

My G54 redlines about the same as the camaro. When I was breaking that car in, I would run it up to 4-4500 RPM, shift, 4-4500 RPM, let it wind down, and do it again. I would drive like this all over for a couple hundred miles. I was skeptical at first, but I heard a ton of people had success using moto-mans instructions. I mean, believe me, I was scared. I just put a ton of $ into this motor, and I started it up, it was all running good. No noises, great oil pressure, compression was perfect, and I took it out on the road and ran it up the RPM's, and everytime that little 4 banger went over 4000, it got loud, and I was afraid something was gonna blow.

I would probably use the same RPM range on the raro. I wouldn't hesitate to break any motor in this way. If you do everything right... Gap your rings properly, and USE PLASTI-GAGE ON THE BEARINGS. That's the most important thing. When I do bearing clearances, I will take my sweet time, you don't want to half ass in that department. Follow all torque specs. Don't bolt anything under the oil pan without a torque wrench.

Kevin, break it in like moto-man says. If you build it right, you will be fine. Just don't run a custom pulley. Don't floor it and boost it a lot, try to keep the boost down. I don't know if you can do that with a SC. With the turbo, I was able to run up to 5 grand without building any or very little boost.

[Kevin - Blown 95 TA]

The reason for my caution & skepticism is that building it right doesn't mean everything will go right. I was at the machine shop this Friday and the guys that make a living building high performance racing engines gave me 2 of their Snap-On torque wrenches ($$$$) to calibrate on the Snap-On machine at the metrology dept at work. Both of these were calibrated previously on 4/05. One of the wrenches was pretty close in the middle range, 3# high in the high end, and 3# low in the low end. The other, more expensive one was 3# heavy at 50#, 6# heavy at 100#, and 9-10# heavy at 150#. Now my wrenches were +-1 lb across the entire usable range, thank God. But just supposing you have the machine shop building your engine and they use the torque wrenches on the rod bolts instead of a stretch gauge (like most of them do) and it's off by a bit. You might either overcrush the bearings and possibly overstretch the rod bolts or not tighten the bolts enough to get the right torque on the bolts and correctly crush the bearings. This is assuming they even repeat it 3X with the right moly lube in the first place. Either case is critical to the rod bolts doing their job. Suppose the bearing starts to sling oil and the pressure decays. You rather notice that as it's happening or find out after it snaps or spins & wipes out your rods & crank? Anyway, that's why I won't go balls out on rpms for a while on a new motor that's all custom parts. Instead I got to drive around a while with my eyeballs glued to the gauges to see that I got the pressures & temps that should be there and do a few oil changes & look at the filters. If you could do the break-in on a dyno, then that would be a big load off your mind as far as that goes. Then if it lets go or loses pressure, it's still in the machine shop where it was built. IMHO, that's the way to do it right.

And as far as Plastigauge goes, that is a quick & dirty way to measure clearances. I use it, but only as a backup to measuring the mains, rods journals & bearings with the mic & bore gauge to figure the clearances. That tooling is getting affordable thanks to the Commies, so there's no excuse not to have it

Anyway, I hope to makeover 600 hp with my new setup. Got to stay ahead of the awesome new Z06s somehow

[fastTa]

Yeah, plastigauge is a very rough way to measure bearing clearances. I would not reccomend it even for a street motor. Bearing clearances are very important because they ultimately dictate oil pressure, friction coefficients, quench height, and ultimately power. Always use a bore dial indicator if possible.

MOT standards and Gauge R&R(Repeatability and Reproducibility) standards are performed at 68 degrees F. This means that whatever the temp of the shop or garage that you are working is, the crank, rods, bearings, and measuring tools need to be very close to the same temp to produce as repeatable and accurate measurements as possible. Just the heat in your hands can throw of the clearance measurements by a few thousandths, and since bearing clearances are measured in "tenth's", that is .0001", temp variances become very important. Most good bore dials come with little plastic handles.

On an LT1, you should look to set the mains at about .0024"- .0027". Ususallly you want the rod bearing clearnaces to be very close if not the same as the mains, but you can go a little tighter on the rod bearings.

[raroZ28]

i didn't know plastigage was so bad, I know a lot of engine builders that still use it. What is the other tool and where can I get it? Link?? I'm very interested in picking one up.

[fastTa]

i didn't know plastigage was so bad, I know a lot of engine builders that still use it. What is the other tool and where can I get it? Link?? I'm very interested in picking one up.

All the major tool manufacturers make dial bore gauges. Make sure the one you get is graduated in at least .0001".

Another thing that Plastigauge is not good at measuring is bearing tang depth. On most moderate HP street motors, inaccurate tang depth may or may not cause a bearing failure or low oil pressure, but it certainly plays a major role in determining the probability of these things happening. In order to precisely fit your bearings, you really need to have an idea as to what your bearing tang depth measurements are. On both the rod and main bearings, seat the bearing into place and then attempt to press it below the mating surface. If you can press it below the mating surface, you have improper (too shallow) tang depth. This is where good ole "feel" comes into play.

You should always transfer the measurements that you obtain from mic'ing the main journals, rod journals, and wrist pins to a dial bore gauge. You then just rock it back and forth until you obtain the "high spot". And don't worry if you slightly mark the bearing surface. This is normal.

[Kevin - Blown 95 TA]

i didn't know plastigage was so bad, I know a lot of engine builders that still use it. What is the other tool and where can I get it? Link?? I'm very interested in picking one up.

Really? Better than nothing at all and fairly accurate, but not a professional tool by any means. It's for a guy who can't afford to buy measuring tools for a one-time build in his garage. Fowler, Starett, Mitutoyo, Enco, and other make the thing. Finding a dialbore gauge in .0001 is a lot more expensive than one in .0005 though. At a bare minimum, you can get a set of 1-4" mics that read .0001 and a set of 1-6" telescoping bore gauges for cheap, though. Then get a digital dial caliper and a dial indicator and a magnetic base and you got 95% of the tools you need to measure an engine for blueprinting. You can get a base for the caliper and use it for a depth gauge. Once you build an engine with the right tools, you will wonder how you ever did it before.

[fastTa]

You know to be honest, I have bought a lot of used tools off Pro trailers at NHRA and IHRA big events. Just poke your head in one of their trailers and ask them for something specific. You would be surprised at how many Joe Blows like me buy stuff for really good deals off the Pro trailers. They are always pretty cool about it too.

[Kevin - Blown 95 TA]

Thanks for the tip. I never even thought about that.