[Fot] TR4 Race Engine Break-in Questions

Mon Aug 27 09:44:58 MDT 2018

Amici...

When I was a teenager, I remember two adults discussing this engine break-in issue concerning for a new street car.  One insisted it was critical to go no faster than 35 mph for the first 1,800 miles, then go no faster than 50 mph until 2,500 miles.  The other said that's the way you make your car into a 'sheepish dog'.  He said if you wanted the car to be quick and responsive, you needed to give it some angry miles per hour early on.  He swore the most important thing was NOT driving it at one speed for any length of time.  Go fast, then slow, go fast then slow.  I just listened.

You should hear what they said about handling your Honeymoon.

Bill Dentinger

-----Original Message-----
From: Chris Marx via Fot <fot at autox.team.net>
To: fot at autox. team. net <fot at autox.team.net>
Sent: Mon, Aug 27, 2018 6:30 am
Subject: Re: [Fot] TR4 Race Engine Break-in Questions

My piston manufacturer says about braking in:
Put the pistons in, and then drive the car to pole.

Means: Reckless driving from the first second.

Cheers
Chris

Von: Fot <fot-bounces at autox.team.net> Im Auftrag von van.mulders.marcel--- via Fot
Gesendet: Sonntag, 26. August 2018 10:20
An: fubog1 <fubog1 at aol.com>
Cc: fot <fot at autox.team.net>
Betreff: Re: [Fot] TR4 Race Engine Break-in Questions

Probably much more horsepower is lost by being too kind on a fresh engine than by running it at full throttle too soon;

Marcel

Van: "fot" <fot at autox.team.net>
Aan: paulricco at att.net, "fot" <fot at autox.team.net>
Verzonden: Zaterdag 25 augustus 2018 23:33:25
Onderwerp: Re: [Fot] TR4 Race Engine Break-in Questions

The short version, rings flex.

Piston pushes ring up, it's flat and against the lower face of the groove. Gas pressure charge travels through the side gap on top past the upper face of the ring and gets behind it right before TDC @ ignition point.

At that point the ring flexes and seals the top and lower faces of the ring against the groove faces, and the charge is trapped behind the ring; this is for pressure retention & max ring expansion. When the piston starts to go down, the ring flexes back flat against the upper groove face and loses the charge behind it and relaxes a bit.

Repeat this every combustion stroke.

The above is with power on.

On closed throttle (decell), there's a vacuum on top of the piston so there is not a pressure charge to fully expand the ring, so it doesn't flex the same.

This flexing of the ring will give it a very very slightly ) face as a result, it's not perfectly flat.

So ring seating isn't just to to get the initial "burnishing" of ring/cylinder wall, it also establishes the profile of the ring face for the best seal under both full open and full closed throttle.

It's all in the ring FLEX!

This is also why ring side clearance is so critical, I scrap more pistons for this being out of spec than for any other reason, especially if the engine was running rich.

My break-in routine is-

Initial start, run to temp, 1 maybe 2 heat cycles, retorque & check all.

(If new cam, 15-20 minute @ 2k rpm)

No excessive running beyond cam break-in and basic tuning with no load!

On track, 2-3 warm-up laps @ part throttle, vary RPM 4-5k, use some engine braking.

2-3 more laps with more throttle and engine braking, same rpm.

2-3 more laps using full throttle, maybe 85-90% revs, and intentional repeated HEAVY engine braking from WOT in top gear.

After that I usually do a retorque and follow-up; next time out should be good to go. 

This open/closed throttle running subjects the rings to the loads that it will have under normal operation.

HTH

Glen

-----Original Message-----
From: Paul Ricco via Fot <fot at autox.team.net>
To: Friends of Triumph <fot at autox.team.net>
Sent: Sat, Aug 25, 2018 1:30 pm
Subject: [Fot] TR4 Race Engine Break-in Questions

FOT, Good afternoon and we hope everyone is having a great weekend. We have a couple questions for those who have had experience and success building TR4 race engines. The information might be helpful others on the forum as well. 1. We have seen a few different recommendations for initial run-in. They seem to range from 5 minutes to 20 minutes at approximately 2000 RPM’s. How long and how many RPM’s are people running them for? 2. How long are people leaving the break-in oil in the motor? a. Are people taking out the break in oil right after the run-in and replacing it with regular oil before leaving for the track? b. Are people running a few sessions under load at the track with it in and then switching? c. Something else? If so, what are you having success with? Again, we are really gearing the questions towards race engines due to complication of breaking in the race motors at the track with limited time and the track session schedules. We are trying to avoid re-starting the entire referendum up on oil brands again, so we apologize if we do. We are really trying to get to how people are breaking-in the TR4 motors successfully. Thank you for considering my questions, Paul Ricco _______________________________________________ fot at autox.team.net http://www.fot-racing.com Donate: http://www.team.net/donate.html Archive: http://www.team.net/pipermail/fot Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/fubog1@aol.com 

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