911 engine test stand

[Forrestkhaag]

Does anyone have a proven or reliable diagram of a 911 engine test stand that I could fabricate? I would like to fabricate out of box tubing using my stock oil tank, 901 bell housing for the starter etc.

My goal is to run in my newly rebuilt 3.0 while refining jetting and tune on headers and muffler choices etc.

I have the Rich Johnson 911 engine mount for my 914-6 which includes all mounting hardware and engine yoke or bracket.

Also, Is there a specific relationship between the elevation of the engine sump and the oil tank as I no longer have a 911 to measure that for mounting bracket locations?

Thanks in advance for any help in this area.
Cheers

[chris_seven]

What are you going to use for the 'load' for the engine?

I would strongly advise against trying to break-in any engine at zero load.

[KTL]

I was thinking of doing the same thing. The test stand would be nothing more than a substitute for the engine stand, allowing me to fill the engine with oil and fire it up to check for leaks before installing in the car.

I too have an empty/junk transmission case that I can use to mount the starter and also use to support the flywheel side of the engine.

With carbs, the fuel setup is very easy with a low pressure pump sucking out of a small fuel tank, the basic PMO style regulator feeding the carbs, and a return line back to the tank. Tank of course vented.

Factory 911 oil tank is simple and ideal to supply the oil, being that it has simple oil in/out & venting connections. Oil tank should be oriented on your stand similar to how it sits in the car. The outlet of the tank should be level with the inlet tube beneath the oil cooler

Agree with Chris that the only break-in you can achieve with the stand is the 2000+ rpm running to adequately break-in the cams. But i've always thought that the cam break-in period has been misunderstood by a lot of people. I interpret it as keeping the rpms at no lower than 2000 rpm for the first 20 minutes of running to ensure the cams and rockers receive adequate lubrication as they're running-in their wear pattern. In other words, I don't like the idea of the engine just sitting there running for 20 minutes at a 2000 rpm idle speed. because doing that goes against the goal of breaking in the rings by varying load and rpm during the initial period of running the engine?

[chris_seven]

Kevin,

What do you think about cam break-in issues?

Are we being led by the 'Pushrod' engine crowd where cams were only lubricated by 'splash' systems and didn't get enough oil at lower engine speeds or do you believe it is generally true that cams need to be treated as a separate part of the engine when it comes to break in .

When we first started Rallying we used to use SOHC Coventry Climax based engines and Twin Cam Lotus engines, we revved the hell out of them and abused them very weekend and we never paid much notice to breaking in cams - we used to build them and run them and never had any cam problems.

In the early Eighties all of the UK 'Tuning' magazines suddenly started publishing articles about cam lube and the essential requirements of running in a cam and we all slavishly followed along.

I have to say that we now follow the procedure but we never had any issues prior to being 'correctly educated'.

Are we just being 'politically correct' ?

[KTL]

Chris,

I feel the same way as you do. The general rule of thumb that's been passed along from many years of building pushrod style engines with splash oiled cams seems to have become gospel.

Considering that our overhead cams are typically swabbed with assembly lube, the bearings are direct-oiled via the oil feed bar in the cam housing, and the lobes are spray oiled by the oil feed bar, I really don't see how the 20 minute break in at 2000 rpm is critically necessary. That said, it certainly doesn't hurt the cams to run them in like that.

But I just think the cams are getting PLENTY of oil right from the start when oil pressure is established. What I don't like is running the engine at a steady rpm with no load right from the initial startup. I don't think that helps at all with seating the rings.

[chris_seven]

I agree,

I think a steady speed and zero load for 20 minutes is a bad idea.

We used to run our BDA engines in in a dyno and varied the load and speed as soon as they ran reasonably well.

[boyt911sc]

Originally Posted by KTL

I was thinking of doing the same thing. The test stand would be nothing more than a substitute for the engine stand, allowing me to fill the engine with oil and fire it up to check for leaks before installing in the car.

I too have an empty/junk transmission case that I can use to mount the starter and also use to support the flywheel side of the engine.

With carbs, the fuel setup is very easy with a low pressure pump sucking out of a small fuel tank, the basic PMO style regulator feeding the carbs, and a return line back to the tank. Tank of course vented.

Factory 911 oil tank is simple and ideal to supply the oil, being that it has simple oil in/out & venting connections. Oil tank should be oriented on your stand similar to how it sits in the car. The outlet of the tank should be level with the inlet tube beneath the oil cooler

Agree with Chris that the only break-in you can achieve with the stand is the 2000+ rpm running to adequately break-in the cams. But i've always thought that the cam break-in period has been misunderstood by a lot of people. I interpret it as keeping the rpms at no lower than 2000 rpm for the first 20 minutes of running to ensure the cams and rockers receive adequate lubrication as they're running-in their wear pattern. In other words, I don't like the idea of the engine just sitting there running for 20 minutes at a 2000 rpm idle speed. because doing that goes against the goal of breaking in the rings by varying load and rpm during the initial period of running the engine?

Kevin,

You must have read my 'problematic engine rebuild' that took me a long time to determine the root causes of the problems. If I remember correctly, I even asked for your opinion. I am not a professional engine rebuilder and that's a good reason I should have a test stand. An engine test stand like mine is simply a convenient set up to inspect, test, repair, and run the engine briefly before doing an engine break-in procedure. Whether you want to do the engine break-in with or without a load is a choice.

I am very happy and satisfied with my home made engine test stand and building a second one that is more versatile than the first unit. Since I only get the motor for the rebuild project, it gives me full satisfaction and confidence that the engine is running and ready for pick up. Rather than turning over the engine sitting on a pallet to the owner and hope that everything is good and working.

Now that the 13th. motor has been delivered to the owner from out of state, the 14th motor is scheduled for mid Dec. start-up and another one in January 2017. BTW, I assemble the engine in my basement and bring it up by myself. No further assistance from anyone (solo job). Preliminary hazard analysis was done for moving this heavy load and has safely transported four (4) engines from my basement to the garage. I am doing another one next week.

Tony

[Forrestkhaag]

Thanks to all for the experiences and the sage advice. The load issue is an interesting question. My read is that there is no different load on startup on a stand verses one's engine mounted in the car- assuming fine tuning of the carbs and linkages may be necessary to give it a go on the street under varying loads. That said, my goal was to have a shop environment where i could fine tune the carbs after warmup and vary the rpm blips under 3K to confirm no leakage or electrical issues /and to refine my wiring harness to my new gauges needed to address a 914-6 conversion with oil level, pressure, fuel pressure, etc.

Thanks again for the input. Its off to the industrial metal store......

[chris_seven]

Originally Posted by boyt911sc

Whether you want to do the engine break-in with or without a load is a choice.

Breaking-in an engine at zero load contradicts virtually every published work on this subject.

Shell published a guide to engine Break-In many years ago where they clearly state:


However, successful break-in not only means the use of a straight oil of the correct grade but also the use of high power settings. High power settings mean high combustion pressures which, due to the piston ring design, forces the piston ring out to rupture the oil film. This is the key to the break-in process.


The time taken to set up cabs and balance on an engine that hasn't had the rings bedded in has the potential to cause serious problems.

How can you set up carbs on an engine that hasn't reached its stable operating condition?

How long do you guys think you can run a fresh engine at zero load before you do damage?

I would argue that the best procedure is to run on a dyno and set it up once broken-in. This would be considered Best Practice.

If you don't have a dyno chuck it in the car get it running as quickly as possible don't let it idle for long, and if you can't make it run well enough to drive turn off and try again.

Once it runs well enough to run, drive it load it up, break it it in and then do the detailed set up.

If you don't think it has been built correctly just don't start it up.

Zero Load and new engines - very worrying.

[chris_seven]

Originally Posted by boyt911sc

Whether you want to do the engine break-in with or without a load is a choice.

Breaking-in an engine at zero load contradicts virtually every published work on this subject.

Shell published a guide to engine Break-In many years ago where they clearly state:


However, successful break-in not only means the use of a straight oil of the correct grade but also the use of high power settings. High power settings mean high combustion pressures which, due to piston ring design, forces the piston ring out to rupture the oil film. This is the key to the break-in process.


The time taken to set up carbs and balance on an engine that hasn't had the rings bedded in has the potential to cause serious problems.

How can you set up carbs on an engine that hasn't reached its stable operating condition?

How long do you guys think you can run a fresh engine at zero load before you do damage?

I would argue that the best procedure is to run on a dyno and set it up once broken-in. This would be considered Best Practice.

If you don't have a dyno chuck it in the car get it running as quickly as possible don't let it idle for long, and if you can't make it run well enough to drive turn off and try again.

Once it runs well enough to run, drive it load it up, break it it in and then do the detailed set up.

If you don't think it has been built correctly just don't start it up.

Zero Load and new engines - very worrying.

[boosted79]

Engine break in with no load = oil burning engine with low compression forever. Don't baby it. Run in the cam and then LOAD it. short shift to keep R's down but full throttle to load the rings then close throttle decel and repeat.

[txhokie4life]

Originally Posted by boosted79

Engine break in with no load = oil burning engine with low compression forever. Don't baby it. Run in the cam and then LOAD it. short shift to keep R's down but full throttle to load the rings then close throttle decel and repeat.

How do you do that with a track only vehicle?

M

[boosted79]

On the track or dyno..

[JakobM]

Originally Posted by chris_seven

Breaking-in an engine at zero load contradicts virtually every published work on this subject.

Shell published a guide to engine Break-In many years ago where they clearly state:


However, successful break-in not only means the use of a straight oil of the correct grade but also the use of high power settings. High power settings mean high combustion pressures which, due to the piston ring design, forces the piston ring out to rupture the oil film. This is the key to the break-in process.


The time taken to set up cabs and balance on an engine that hasn't had the rings bedded in has the potential to cause serious problems.

How can you set up carbs on an engine that hasn't reached its stable operating condition?

How long do you guys think you can run a fresh engine at zero load before you do damage?

I would argue that the best procedure is to run on a dyno and set it up once broken-in. This would be considered Best Practice.

If you don't have a dyno chuck it in the car get it running as quickly as possible don't let it idle for long, and if you can't make it run well enough to drive turn off and try again.

Once it runs well enough to run, drive it load it up, break it it in and then do the detailed set up.

If you don't think it has been built correctly just don't start it up.

Zero Load and new engines - very worrying.

I think you misunderstand boyt911sc point and good reason for an engine stand.

It makes good sense to test oil leaks and even set up idling on an easy accessed platform. Same process is going on if mounted to a car on a dyno. Professional engine builders do not avoid oil leaks on their own freshly build engines sometimes, just look in this forum. The best of them even inform about when it happens and correct it. Time consuming to pull in- and out of car.

You asked the question your self without answer - you asked "How long do you guys think you can run a fresh engine at zero load before you do damage?"

Well to answer that question from my experience, I have never experienced or heard of any freshly build engine being damaged by setting up idle on a dyno. Neither have I ever experienced or heard of any engine damage when testing for oil leaks as a start. The engine do not care whether you put it on a dyno or on an engine stand in this required process. The wheels are turning, so why put it on the dyno. Neither have I experienced or heard of any engine damage from running in cams @ 2000rpm for several minutes after testing for oil leaks.

When you put a freshly engine on a dyno, lets say EFI, you obvioulsy dont put heavy load on it at once. What you do is 1) You set parameters to get the engine started, then "walk-around" test for oil leaks 2) You then start adjusting parameters to get stable idle. 3) You now, after several minutes, start tuning up the rpm scale on NA configuration, 4) Then gradually, and carefully you start put load on it, listning for detonation and tuning towards LPPBT (Location of Peak Pressure for Best Tourge) 5) If forced induction, you now start put really load on it and get above 0 sea level pressure. I can tell you this process takes time, and please note an engine is always under load from any combustion cycle, even when idling, hence the piston moving - the piston rings dosnt care whether you have bolted the engine to a chassis or a welded frame.

An engine stand makes perfect sense to make a "walk-around" oil leak test + setting up the idling. This makes it much more easy to handover to 3rd party for tuning if not doing the tuning your self.

[chris_seven]

I haven't misunderstood, I just don't agree with running new engines at zero load.

The general advice on cams is not to let the engine idle for the first few minutes - now stretched to 20 minutes. No mention that this has to be zero load and loaded or not the cams will see the same forces.

I know how to run engines in on a dyno - I have been involved with building Race Engines for more than 35 years.

If you guys want to allow fresh engines to idle that's fine by me but I will always be sceptical and will always dislike the practice.

[JakobM]

If you have build engines for 35 year, then you know that you can not put full load on an "empty-brained" ECU on a dyno on first start-up....it has to start first and idle at some point

when doing so the wheels are not turning....so why the argument that you need to setup an engine on a dyno?

[JakobM]

Originally Posted by chris_seven

I haven't misunderstood, I just don't agree with running new engines at zero load.

...it would be misunderstood if you think of ZERO load in a running engine - a piston and rest of engine is always under load from any combustion cycle, even when idling, hence the piston moving.

[Tippy]

Jakob, not picking sides, but that's why it's been said (in general) to use carbs or CIS and a dizzy to "break-in" the engine, then remove for EFI tuning.

1st I've heard of loading being important too on break-in.

Good to know.

I've always babied my motors and luckily had the rings seal.

Phew

[chris_seven]

I think you need to be very clear about what I am trying to say.

I do not like the concept of trying to break in engines at zero load.

To advise that it is an option to break-in engines in this way, is I believe, mistaken and not a good idea.

Running them in at zero load conditions will generally glaze bores in relatively short time periods, which I believe need to be considered in terms of minutes and most certainly much less that the time to fully set up and finely balance carbs.

I can't quantify the 'safe' time period, hence my question, and we have always tried to keep this time to an absolute minimum.

I have never said that you need to set an engine up on a dyno.

What I said is that 'Best Practice' is to break in engines on dynos and then final set up is normally the final stage of this process.

I have broken-in many engines in this way and the final set up was always the last part of the process.

There are, of course, many other ways to break-in engines and before we had the money to spend on dyno hours we used to fit them to a car and drive them.

Originally Posted by JakobM

then you know that you can not put full load on an "empty-brained" ECU on a dyno on first start-up..

Breaking in an engine without a map in an ECU also seems an unusual choice.

It would never occur to me to try to run a brand new engine on FULL LOAD without a map - what on earth makes you believe I would do something so patently stupid?

We have just completed our first EFI system and fitted it to an engine that we have been running for around 3 years on a set of Webers.

This has enabled us to develop a 'conservative' map that we would use for both initial installation of the complete EFI system and for breaking in new engines fitted with this system.

I would not have considered developing this start up map on a brand new engine - I guess its a matter of confidence.

As most of the engines we built in recent years have been used in Historic Motorsport our EFI experience is limited which is why we adopted this approach.

Most of the ECU manufacturers we spoke with prior to making our choice said that they had conservative rev and advance limited maps available for just this reason.

All I believe that I am saying is that accepted wisdom dictates that engines should be broken in with some reasonable load applied as soon as possible after initial start up.

[boosted79]

"and please note an engine is always under load from any combustion cycle, even when idling, hence the piston moving - the piston rings dosnt care whether you have bolted the engine to a chassis or a welded frame."

That is simply not true. To get new rings to bed in to the wall you need to maximize the gas force behind the rings to force them into the wall. That can only be done if the combustion chamber pressures are maximized, that requires high throttle opening to get max air and fuel charge into the chamber, more air/fuel = higher chamber psi when it ignites. When a new engine is first started there is a lot of blow-by of combustion gases past the rings. If you do not force the rings into the wall that hot blow-by burns the oil on the wall and creates a coating that fills in the cross hatch on the wall. That's glazing. When that happens the rings never seat because they are riding up against a smooth surface instead of the relative rough surface created by the cross-hatch.