Breaking in a rebuilt race engine

[GLASEM]

Am in the process of rebuilding my 914 Type IV race engine
When breaking in a street engine.......I would drive it at various rpm limits for around a 1000 miles........change oil and filter......good to go
Rather hard with a race engine
How do you guys break in a new race engine?..............don't have an engine dyno at
my disposal

[cstreit]

Personally I beat the piss out of it to ensure the rings seat properly but limit the rpm for the first hour of use.

[9dreizig]

break it in on the dyno , you've got to tune it anyway right ?

[juanbenae]

Originally Posted by GLASEM

.don't have an engine dyno at
my disposal

neither did I, but I felt it was worth paying for a break in & tune by somebody smarter than myself... I did have new carbs just after the rebuild so monitoring AF, oil pressure and other things that required adjustment or syncing during the break in was accomplished in a controlled environment. I presume that the type IV motor is a carb'd 4cyl? is the car street legal? hard to things accomplished on track while driving & monitoring the vitals. I have ADD so I need to pay a lil more to clear my mind..


I did do a test day to break in just a top end, but only after installing an AF meter in dash that I watched the F out of all the live long day... all in all I was glad I dyno'd it. felt it was money well spent. I knew what my investment earned in HP & torque on paper, knowing the motor was running perfect when back in the car was one less thing to think about the 1st race weekend... is there not a speed shop near you with a dyno? rent time & a trusted hand... you or someone smarter than me...

t

[Walt Fricke]

I'm with Chris.

There is a theory out there that the best time to get the rings to set is when everything is very fresh, which paradoxically means that the cylinder wall and the ring faces are at their roughest, which means they can smooth each other out the fastest. Since by and large my rebuilds have been on motors whose needs I pretty much know, they have a reasonable tune to start with, so I can afford to go out on the track and pretty much put the hammer down, paying some attention to warming the engine (doesn't take lone).

Then there are theories of start it, run a minute, stop, change oil, etc etc. They may be good ones, but not practical for a race motor in a race car where you can only use it on a track.

[Plavan]

Run the snot out of it. I would usually increase the RPM's by a 1000- 1500 every 20 min test session. It only usually lasted 2 sessions until the devil on my shoulder said "GO FOR IT!"

[oliver88]

Warm it up and run the piss out of it. Lottsa breakin theories but i always had stronger engines that lasted longer when they had teir necks rung after a rebuild.

[chrismorse]

If you are just freshening up an existing race engine, rings, valves, bearings, maybe oil pump AND the engine ran well before you did the tear down, then yah, run it easy for a bit and go for it.

If on the other hand, you are doing different cams, pistons, carbs, (or jetting), you need to know that the mixture is very close to right on and the timing correct, so if you have any doubts about your ability to get there then I am with the guys that say get it on a dyno with a guy that knows air cooled.

For what it now takes to do a good build, a few hundred more spent optimizing the mixture and timing, while monitoring temps is real peace of mind.

I've never done it, but as I get older, I am becoming more aware of the benefit of hiring some pros that really know their "stuff" - saves time, and makes you a happier guy :-)
chris