Dyno break-in times

[wilf leek]

Help the further education of a poor Brit if you will.

I am puzzled.

Whilst I know that the extremely fine tolerances and surface finishes achieved in modern hi-tech engines means that break in periods are pretty much a thing of the past, I still see reports here of brand new engines , BBs and SBs, being given full power and full rpm runs on the dynos at the engine builders. These are dinosaur engines - they don't benefit from the new materials and superfine finishes you get in modern engines (do they????).

My question - since my own engine builder told me to break-in my 408W stroker in the "traditional" way before giving it the full monty, and this took all of 1000 road miles before I could safely bounce it off the rev limiter, how long is an engine usually broken in on a dyno, before a full power pull is recorded?

I can't see that any engine builder could afford to run an engine for the equivalent hours of 1000 road miles, so they must be seeing max rpm and output well before that.

How so?

[wilf leek]

Well, looks like no-one has an answer so far, which surprises me.

I get told to gently break in my easily-replaceable Windsor-based engine, and yet I see very high dollar engines, sometimes with irreplaceable "original" blocks etc., apparently being run up to max revs and power within minutes of the last bolt being tightened.

Like I said - how so?

[charlieh]

Hi Wilf,
One of the big inputs to shortening break in times for modern engines etc has been to wash the components during manufacture. They are washed very precisely and the 'waste water' is particle counted and then filtered. this has been a major contributor to extending the initial service period, oil change etc. It may not answer your query directly but plays a part in it. Personally I always like to run a new motor in gently, especially when the moving parts are very close to my body and there is potent horsepower to help hurl them at me.
Charlieh

[mr0077]

Wilf, I can't tell you the details, but everyone including my engine guy said a dyno breakin was the best way...they ran it in on the dyno with a light and varying load (computer controlled I think) for some period of time, watching all the gages and looking for leaks and problems, before running the dyno pulls. I'm like you though, how did he know when the motor was ready for a full power pull? Interesting question...

[MidOHasp]

Wilf,

My engine guy ran about 20-25 minutes of varied light to medium loads to simulate driving around town then ran it straight to 6K, full dyno pull, no questions asked.

His explanation:

Things basically get broken in immediately. If there is a microscopic "high point" on a cylinder wall or on a main journal bearing, it will get knocked down and smoothed out first time the starter cranks over. With a solid flat-tappet cam, I guess then you do need to really break it in for a while to seat the lifters or something like that. (OK that last sentence was my take, not his words. If he said that, I'd be out there disconnecting the dyno immediately).

Long story short, if you have a hydraulic roller cam, the motor requires no break-in. You could run it at 2-3K RPM for 10,000 miles of break-in and if it was meant to blow apart at 6250, then it still will. Or if your engine wasn't meant to blow apart at all, you could run it up to whatever RPM it was designed for immediately.

This guy explained "his" warmup as basically a diagnostic check. Check pressures, vacuum, check for leaks (there were a couple), set initial timing, etc... Once that's set, it's time to rock and roll.

[MidOHasp]

PS - It hasn't blown apart yet.

[REDSC400]

Hey Wilf!
I do not have first hand experience on this howevery I will recount the information given to me by the previous owner of my ERA. The engine was broken in and tested on a fluid dyno (flywheel connect not wheels) at the engine builder (Danbury Competition Engines) back in 1992. The engine was run for about 4 hours with one oil change at one hour and another at the end of the process. The engine was cycled thru various RPM ranges and not tested for max HP during the procedure. The carb was tuned at the end of the process while on the dyno.

I do have photos of the process (not digital) which show the ERA headers as being what appears to be red or yellow hot, but not being there in person, it could be just a photo feature.

[flatliner]

My engine builder has built all my alcohol race engines as well as my Cobra engine. He says pretty much the same thing as Midoasp's guy...warm it up at 2000rpm for 20 minutes and then it's ready to go. I have watched him dyno some of my race engines and he will take them to 7800-8000rpms! His comment was "if it's going to blow it's gonna do it now". I have only blown up one engine and that was due to a thrust bearing failure after several races on this engine. My Cobra engine was warmed up with "light" valve springs, the springs were then repalaced with the ones that I now run. (this is done to ensure no flattening of cam lobes) The engine was then re-started, ran at 2000rpm for about 20mins. then it was straight to 6500rpm. I have nearly 6000 miles on this motor and it gets ran hard at times. I change the oil every 1500 miles and use full-syn 0-40w European Formula Mobil One along with a K&N oil filter. Hope this helps

[wilf leek]

Hmmm - so what this sounds like to me is that my engine builder was hedging his bets on his 3 month warranty by demanding that my engine was unnecessarily "babied" during that time?

Tough, 'cos it got the first 1000 miles within 3 weeks! And then it started being bounced off the rev limiter and has continued that way ever since! (actually, I do try NOT to do that to be honest).

[PatBuckley]

Wilf-

The shop that did the machining on my engine advised me that the thing will be 80% broken in by the time I gt done assembling it

Whether it is a race car or a new street car I have always done the same thing which is: During the first 5 - 10 miles I vary the rpms. In a race car it is red line in every gear after that. In a street car or open tracking it is your choice if you want to do the redline thing.

In a street car - change the oil after 3-500 miles.

In a race car - rebuild the engine after 800 miles (unless it is a FF in which case you do the top end every race and the bottom end every 800 miles or if a leakdown indicates otherwise.)

[Goober]

Wilf,
My guy said a similar thing. Run it at around 2,000 rpm for 20-30 min (cam break in) and then start pulling. I have a friend that had a 351 stroked to 427 a few years back and that is how they did his. He now has about 10,000 miles on the car and most of them are racing miles. still doesn't use any oil and compression and oil pressure just like the day it was built.
When I lived in the UK, I had Real Steel dyno my SBC and they more or less did the same. I wasn't there when they did it, but that's the way they described it.
Love your Crendon. I had a RAM from Adrian Cocking when I lived there. The Crendon is a cut above the rest.
Mark

[dscott]

Wilf, I have an engine dyno in shop so I'll tell you what I know. After everything is pre-set we prime the oil pump until we get oil pressure, then crank the engine and if it doesn't start within 4 revolutions we find out why. The initial start is very critical on the cam. We run the engine @ 2000 rpm for about 20 minutes at varying loads to break-in the cam, look for leaks, etc. We break each engine in on 30 weight oil. After the breakin we change the oil/filter and look for any excess metal. We also cut open the filter and see what we captured. The rings take a little longer to seat, especially the Chrome moly. We use a stethescope and probe the entire engine to listen for any unusual noises. We normally do about 5 full pulls starting at a max of about 4500rpm then work our way up to max hp. We usually see more hp each pull as the rings break in. After that we play with timing and carb, watch our exhaust temps and let her rip. We change oil 1 more time and use 20w50. We also add an additive like slick 50. We use this process on all street, circle track, drag, and tractor puller engines. No failures in about 12 years other than the guys who have assembled there own engines. Then we catch them after intial start. No blow ups on the dyno . If the engine is assembled properly and all clearances are double checked there is no reason for failure. The cam break in is most critical.
Don

[wilf leek]

Thanks all.

Looks as though I wasted 1000 miles in very light-footed driving when I first put the car on the road. Never mind, at least I got to know it well before I redlined it. Probably just as well.

[thardin]

I have always been under the impression that the 500 or 1,000 mile break-in periods were a precaution for "assembly line" produced engines. If a motor is properly "blueprinted", then all of the proper clearances are checked and double-checked during the motor build. The production line simply does not take the time to check every clearance. Running a long break-in period allows the motor to "wear-in" to the proper clearances without damage caused by tight parts heating too quickly (over-expanding).

In a blueprinted motor which is self built or built by a reputable shop, you will typically break in the cam, check for fluid leaks & temperatures, and go straight to dyno pulls (or the race track). You may want to watch out for some of the big crate engine producers that really pump them out!

Personally, sounds like your builder is a little conservative. Some of my best motors have been run hard "right out of the box". I only believe in a break-in period for mass produced vehicles.