Depending on conditions and the type vehicle and the tire you can use slip can be a lot or negligible. Our roadster was there also, not running a y-block but a different vintage engine. We fought gremlins I had never encountered in 45 years of attending many Speedweeks and World Final events. Our car runs in the 150-160’s and for a roadster is fairly light weight with 350 or so HP and normally does not slip. We use a 4 speed dog synchro G-Force transmission, a vertical gate shifter from Long and the driver doesn’t come off the throttle to shift. It sounds like an automatic for-as long as we can hear.

For us, this year the salt was hard and firm and did not see any slip of wheel spin. I’m sure with 800+ HP the conditions would be different. When running a spool or locked rear end your tires MUST HAVE THE EXACT CIRCUMSTANCE or you will be fighting it an more than likely get to see the entire course as your spinning once or twice trying to regain control. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Too bad about Tim's spin! 
I've been wondering how slippery the salt is and if you have to shift fast but easy to avoid spinning the tires?
I'd love to drive my Ranchero out there and compete, but it's a long haul.

"FREE SAMPLE"

Here are some pics of Tim’s car waiting at the starting line for the go ahead to make his run.
 

 

 

Lorena, Texas (South of Waco)

As far as I know, Tim’s 416 car was the only Ford Y that was racing this year on the salt.  Tim’s goal was to make the 200 mph mark but a spin out at 195+ ended that attempt.  Did not get a chance to talk to Tim after the spin out but there was apparently enough damage to prevent a speedy return to the track.  Great effort by Tim.

Keith’s AIR 560/C car dropped a valve in the M-E-L engine a couple weeks prior to the Bonneville Speed Week at the Maine event.  That prevented Keith from running at Speed Week this year.

Lorena, Texas (South of Waco)

Not sure how many YBlocks will be there competing but Tim McMaster has posted on the SCTA Facebook page that he will be with his gas roadster.
Not a Y Block but I will be attending with my oldest grandson driving our families vintage gas roadster powered by a 311” 1952 GMC 6 cylinder. It’s black and #49 if anyone can stop by who are attending. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.