ZQV8

I have a 97 gmc sonoma with an ls1/t56 combo
Im running a brand new gm slave, ls7 clutch, brand new line and a stock master. Like most 4th gen f-bodies I seen, my master cylinder wont keep up when shifting at high rpm.

Its time to upgrade and I will need a universal master with a flat mounting surface for the firewall. Just seeing if anyone has had good luck with a certain brand or bore size so I can better determine what my truck will need.

usdmholden

I have been working on basically the same thing you are, but I have not bought any parts yet.

I believe the OEM master cylinder is a 3/4" bore diameter and has a 1.2" stroke, but I don't have one, I only found the info through searching.

Most of the T56 swaps I have seen used a Wilwood master cylinder in 3/4" bore diameter and the 1.4" stroke length. They have other bore diameter options here:
http://www.wilwood.com/MasterCylinde...erLanding.aspx
http://www.wilwood.com/MasterCylinde...ter%20Cylinder

From looking at pictures I believe the I believe the Tick master cylinder is a Tilton series 75, and doing some searching on this site the bore diameter is 7/8". That Tilton 7/8" bore unit has a stroke of 1.1" More info is here:
http://www.tiltonracing.com/sites/de...0Cylinders.pdf
http://www.tiltonracing.com/sites/de...MC_updated.pdf

I plan on buying Wilwood p/n 260-3376 (7/8" x 1.2") because it offers several mounting configurations, it has enough volume to be tolerant of non optimal pedal travel and pivot points, and has a bleeder build into it which may eliminate the need for a remote speed bleeder if you hook it up to a hand vacuum pump.
http://www.wilwood.com/MasterCylinde...temno=260-3376

If I can't make that Wilwood fit in the space I've got, I'll probably buy the Tilton 75 (7/8 x 1.1) since it's overall length is about 2" shorter.

The extra capacity of the aftermarket master cylinders will require a mechanical stop to keep the clutch pedal movement from forcing the slave cylinder to over travel which will pop the seals on the slave. I think this will need to be done with any of the aftermarket masters.

Turtle Bite

iTrader: (3)

That sums up the information I did find while searching myself and I ended up buying a Tilton 3/4" bore (also has a bleeder BTW). From my understanding the OEM/ stock replacement style slave cylinders do have travel stops built in, but most aftermarket slaves do not have travel stops. I believe there is one exception, but I am setting up my clutch pedal bracket as carefully as possible. My car is not together yet, I have been mocking up the the bracket/ master so it is fresh in my mind.

Have you tried drilling out your master orifice? "Drill mod" as they as they call it these forums?

usdmholden

I don't have mine up and running yet, and do not have a OEM master, so I have not done the drill mod.

Once I get my LS1 back together (reseal, new oil pump and timing chain) and build a transmission mount, I'll stat working on the clutch hydraulics.