Brake bore size?

[SinisterC10]

I have a 1981 2wd truck and am wanting to know what bore size the master cylinder and brake booster is? I don't have the ID sticker in my glove box so I can't look it up. I'm going with 4 way Wilwood discs and want to replace the old booster and master.

[zieg85]

in 81 the sticker is on the drivers side inner fender well under the hood.

[SinisterC10]

in 81 the sticker is on the drivers side inner fender well under the hood.

Mine is missing.

[zieg85]

The forth digit (letter) tells you what brakes you have
http://www.73-87.com/7387info/8187vin.htm

[SinisterC10]

The forth digit (letter) tells you what brakes you have
http://www.73-87.com/7387info/8187vin.htm

My vin has a "D", but that's not going to tell me what bore sizethe MC is. I took a dial caliper and the inside bore measures about 40mm or 1.57". I still need to know if this is considered a jb3 or jb5 system.

[Irish_Alley]

http://forum.73-87chevytrucks.com/smforum/index.php?topic=28592.0

[zieg85]

The forth digit (letter) tells you what brakes you have
http://www.73-87.com/7387info/8187vin.htm

My vin has a "D", but that's not going to tell me what bore sizethe MC is. I took a dial caliper and the inside bore measures about 40mm or 1.57". I still need to know if this is considered a jb3 or jb5 system.

JB3 will have 1" rotors and JB5 will have 1.25" rotors, both share the same master cylinder it seems.

[Irish_Alley]

jb 1 had the 1.417" bore while jb 3 and 5 had the 1.574"

[SinisterC10]

Thanks for the info guys. I've decided to put a Hydratech Hydroboost system in the truck. I have one that I had on my Camaro and am going to have Hydratech change out the mounting plate and pedal rod. Gonna cost me about $275.