350/255HP Help please

[Mark Ugrich]

Originally Posted by Alan Roehrich

Agreed. Cold leak down is useless. Honestly, on these engines, you need to be using a Dwyer gauge, or something, to test blow by on the dyno. Leakdown, even hot, can be misleading. Measuring blow by eliminates all of that.

Alan, could you describe how the Dwyer gauge works?Is it basically installed like a vacuum gauge? I've never heard of one.Looks like there are several different calibrations.Which is correct to use to measure ring seal as you described? Thanks,Mark

[Alan Roehrich]

Originally Posted by Mark Ugrich

Alan, could you describe how the Dwyer gauge works?Is it basically installed like a vacuum gauge? I've never heard of one.Looks like there are several different calibrations.Which is correct to use to measure ring seal as you described? Thanks,Mark

Mark, if memory serves correct, you want one that reads 0-10 scfm. The 12" tall model is probably the best.

What you do is connect the gauge to the only outlet where any crankcase pressure can escape from the engine, everything else must be completely sealed. The easiest way is to connect the gauge to a breather with a tube outlet, such as the one used in a crank case evac kit. The gauge must be mounted perfectly vertical.

You then make dyno pulls as you normally would. We normally use our vacuum and or evac system for a while to seal the engine up, then after we've got it where we want it and tuned, we make a couple of pulls with the Dwyer gauge on it to make sure it is sealed up.

[V M Kauffman]

The one I used was a Fisher-Porter same one Chryser Race Group used was about $300.00 30 years ago. I could hook it up as Alan described and if it was bad enough the weight in tube would bounce just spinning on starter. We would check engine every time we loaded car to come home by hooking up meter and just free rev engine to 6500 rpm if Blowby was over 2 cfm engine would come apart we we got home. Difference on a 740 hp engine on dyno at 6 cfm down was down 60 hp to 1 1/2 cfm. Ted Flack showed us how to use it.

[Mark Ugrich]

OK , I get it now.All I could find online the other day was a round gauge with a bunch of NPT fittings and hoses stickin' out of it.Thanks Guys!

[Kevin Panzino]

Look at a Dwyer Model# RMC-121. 1 to 10 Cfm range, 10" tall, 1/2" fittings.

[henrys57wagon]

What I don't know about building engines seems to outspace what I know.

[GTOMayhem]

Originally Posted by henrys57wagon

What I don't know about building engines seems to outspace what I know.

Same here. I have learned so much in two years of lurking on ClassRacer.

Rick Thomason
GTOMayhem

[Chipper Chapman]

Finally got time to do a hot leak down. All cylinders are 5-6% both at tdc and approximately halfway down, at 150 degrees. No access to a dwyer guage here to check that.

[Dwight Southerland]

Originally Posted by GTOMayhem

Same here. I have learned so much in two years of lurking on ClassRacer.

Rick Thomason
GTOMayhem

Great testimony! Lurk on!

[GTOMayhem]

Originally Posted by V M Kauffman

We would check engine every time we loaded car to come home by hooking up meter and just free rev engine to 6500 rpm if Blowby was over 2 cfm engine would come apart we we got home. Difference on a 740 hp engine on dyno at 6 cfm down was down 60 hp to 1 1/2 cfm. Ted Flack showed us how to use it.

What would the fix be after you tore it down? I know, probably a novice question. Also how would a supercharged engine change what you would be looking for as far as ring seal and blowby?

Rick Thomason
GTOMayhem