Dan_the_C5_Man

A brief refresher - It's a bit surprising that it took almost exactly a year to get this far..

https://www.corvetteforum.com/forums...-analysis.html

What this is -

1. Testing performed by an un-biased, independent shop, no ties to any OEM or part manufacturer.

2. These tests were sponsored on our behalf by Brian at BTR - a big THANK YOU for his persistence and support in getting the shop to complete these tests.

4. An equally big THANK YOU to B.J. (vertC6) - he stepped up to supply the rockers for testing when YT did not. Good thing my company does business in Australia - I called and spoke to the owners and various staff members at YT begging for a pair of rockers to test so many times - the time difference meant those calls were all after hours as well.

5. The testing parameters were not set up exactly as I asked for - what we all should remember and appreciate is these tests occurred without all the drama of the previous VT testing (begging for folks to pay for the tests, bickering after the fact about releasing the results to the public (or not), etc.). There is no free lunch.

What this isn't -

1. I have no intention of engaging in a debate with anyone over the method, documentation of the results (yes, there are typos - shops typically don't hire college English professors for data entry into a spin-buck rig), setup parameters, parts that were or were not tested, or the type of equipment used to obtain these testing results.

2. The results are what they are, for all to see - you either choose to accept them or not. Draw your own conclusions.

3. Please DO NOT contact Brain Tooley regarding these tests results. He had an independent shop perform these tests as a favor to me, because he was as curious as I was and he had other parts he wanted to test as well. He can't give you any more detail than what I've posted below.

I can attest to just how busy Brian is - we've been working to perform these tests since March of 2016 - many. many emails and phone calls were traded back and forth to get to this point - he can't tell you any more detail about these tests than what you see published below. PLEASE do not make him regret volunteering his time and resources to help out LS7 owners by bombarding him or his staff with questions related to these tests.

That said, please remember who stepped up to sponsor these tests the next time you need a part(s) that BTR sells, including Yell Terra rockers.

4. These are NOT any "special" version of the YT half-shaft LS7 rocker - these are the standard production items YT has sold for the last several years.

5. Not going to argue the about the "value" of running these rockers on a stock cammed motor - I have my reasons (reduced valve tip scrub, don't like the sloppiness of the stock rocker, I enjoy the noise reduction (the injectors are louder than my valve train)).

Drum roll....

I've highlighted the pertinent details in the images below.

To summarize -

1. Below are the details for two tests -
a. - Stock LS7 cam, PSI 1511 springs - Ferrea hollow-stemmed valve - stock LS7 rocker
b. - Stock LS7 cam, PSI 1511 springs - Stock LS7 intake valve - Yella Terra 6670 roller-tipped rocker

2. The spring install high was not what I asked for - in the test, it is set to 1.85" - I asked for 1.775" / 1.785" (and that is my recommended install height for the PSI 1511 / YT combo) - the additional pre-load would only serve to improve the measured results.

3. They used aftermarket (heavier) push rods - factory PR's will result in less mass, less mass tends to equal more stability.

4. During the last round of testing, the vendor performing the tests stated that 0.016" was a "safe" level of maximum bounce.

5. The TY / PSI 1511 combo was measured to stay within 0.016" of bounce up to 7250 RPM - For my application (stock red-line) this provides an adequate over-limit buffer, especially considering the stock cam stops making power well below 7,000. I am pleased with these results, and the YT's are staying under the valve covers at this time (I've been running this combo for about a year and a half, 12K miles).

Enjoy.

Ps - Additional testing with other components (cams, springs, etc.) were performed - if and when those are released, with permission, I will post them.

vertC6

After a year of working together on this and at times ready to call it quits I am glad we stuck it out and even though we didn't get everything we asked for I am very satisfied with the results!

My YTs will be going on next month and I will share my build with everyone here.

MTPZ06

Sub'd...too tired to read all that right now.

Too-Fast

Thanks for posting this and the perserverence to get it done and kudos to vertC6.

Undy

Thanks to all involved. A set of YTs will go on during my next wiggle test.

shane p

Thanks to everyone for the results. Does anyone think bounce would happen sooner or get worse with a higher lift cam?

vertC6

Yes, how much depends on the cam and spring combo.

Dan_the_C5_Man

In general, you need more spring to control the mass, depending on the specifics of the cam. But without testing, how much is enough will be an educated guess.

double06

Thanks for the effort for everyone involved here.

vertC6

My pleasure guys I know everyone here wanted to see proof as much as Dan and I did.

shane p

Thanks guys. I would love to try these out, just a little nervous because I do have SS valves so that adds more weight on the exhaust side but I do have dual springs around 400# open so that may help but I don't think I need to run much over 7000 rpm so that helps also.

vertC6

In your situation the only two options I would suggest are getting with Brian Tooley he now has the titanium retainer for the PSI 1515 spring. That will offer more control and still use the beehive spring that does not bounce like the duals do.

However the best option is to pull the heads and put the Ferrea hollow stem valves IMHO. They weigh 15 g less than the solid stem.

Nowanker

Thanks for the info! I volunteered some $$ for the test, PM me if it's needed.
Steve

Dan_the_C5_Man

Nope, it was completed at no cost to the CF community.

olddragger

Guys yall rock ( no pun intended)!

MTPZ06

Nothing surprising or out of the ordinary in the results (to me at least), but its great to have those assumptions validated and documented. Thanks again to those involved.

Too-Fast

Premiumspeed

Great information guys.

redbird555

This is fantastic! Looking at the test if I'm interpreting it correctly the yella terra spun to 7665 rpm and only records .0141 of bounce is that right? If so where did the 7250 number come from.

sorry I don't quite understand what all the graphs mean lol

vertC6

When you look at the second graph with the titanium intake and YTs at the 7250 rpm mark is where it begins to really bounce. Under that RPM it is minimal bounce.