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Old 06-24-2020, 07:29 PM
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Default Vacuum pump on Dyno

What's the Consensus. Should a vacuum pump to used on the dyno while breaking in a new engine and seating the rings?


Thanks

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Old 06-24-2020, 08:24 PM
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Yes

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Old 06-24-2020, 09:11 PM
Slick Poncho Slick Poncho is offline
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Here is mine
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Old 06-25-2020, 07:47 AM
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Thanks guys.

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Old 06-25-2020, 08:08 AM
HoneyHush HoneyHush is offline
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Can you guys elaborate on your answers as to why the “yes”. This is something that intrigued me because I’ve honestly never researched vacuum pumps enough. I did a search on yb and others and it was probably a 50/50 as to run it on the break in or not. Doing my 535 Butler said it is very important especially on a 535 with its windage to help seal the rings but on the searches you read where guys are saying it pulls oil out of the bores and hurts rings etc. I don’t see that personally but....

There was also talk about it lowering oil pressure slightly. I always thought a vacuum pump was very good for an engine all the time. I suspect the ones saying not to run one are cranking them way up on the vacuum?

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Old 06-25-2020, 09:38 AM
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Tony didn't use one on dad's 571 while on the dyno, only because one wasn't available at the time, and the custom valve covers came later anyway.

So it was broken in and dyno'd without. Even with the 4.750 crank, the PCV setup worked fine and was driven on the street like that for quite a long while with no issues despite what same say about windage with these big cranks.

Tony did experiment with oil level in the pan while on the dyno however.

The engine does now have a vacuum pump on it, because he wanted it more than needed it.

I've read and been told that pulling much more than about 12 inches at peak RPM is all you want otherwise they do tend to pull oil away from the wrist pins.

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Old 06-25-2020, 12:31 PM
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I'm not a big fan of vacuum pumps on street cars. If you are going to run a street engine on a dyno it's beneficial to use a vacuum pump. It takes several pulls before your rings seat and the vacuum pump will help deal with the initial crank case pressures created by the unseated rings. You can certainly dyno without one but it is better to use one if it's convenient.

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Old 06-25-2020, 08:53 PM
Slick Poncho Slick Poncho is offline
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I am certain Not a master engine builder but basically what Paul said was my reasoning. Also just showing that I used mine while on dyno for break in and pulls

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Old 06-26-2020, 01:45 AM
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When my engine was run in on the stand for the first time the Chevy II radiator that we were using was not able to keep up to “my” standards. The engine was being run with no fan and just a little Chevy II radiator with a big shop fan running on it. After about 10 minutes it would heat up to 200 with a 180 thermostat in it so I had him shut it down and let it cool off and then start it again and run for another 10 minutes. Both times going between 1500-2000 RPM. The engine then idled fine at 180 for another 5 minutes at which time we shut it off and called it a day. This was done with an HEI with no vacuum advance hooked up and a borrowed carb that was too small just because I am running sniper FI and I didn’t want to try to fool with that on initial run in. When I get the car on the road is there anything I should do additional to make sure the rings are seated besides avoiding synthetic oils for the first few thousand miles?

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Old 06-26-2020, 07:27 PM
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Run a pump on the dyno even if you are not going to use one in the car?

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Old 06-26-2020, 08:42 PM
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I don't know John, that doesn't really jive with what I've seen on the dyno over many years. Usually any time I've seen a vacuum pump on the dyno it's on a max effort deal when the plan is to also run the pump in the car.

Probably 95% of what I've seen, and built myself and dyno'd, for street/strip applications, has always been run in on the dyno without a vacuum pump. For many reasons. Usually it's not convenient, one isn't available, or the valve covers for a particular engine aren't set up for a pump, unless the plan is to run one in the car from the start, and it gives what ends up being slightly inflated numbers to those that don't plan to use it once installed in the car.

So while it may be a good idea to do so for ring seat reasons, and I can see the argument for that, I've rarely seen a street strip build on the dyno with a vacuum pump. Besides, with a proper break in oil to promote ring seal, a good hone job, done properly to work with the rings being used, ring seating happens almost immediately anyway.

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Old 06-26-2020, 10:40 PM
Dragncar Dragncar is offline
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I know someone who has a race engine that pull well over 20" at idle with NO PUMP. Engine is sick.

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