head gasket shim

Bru · 01-19-2022, 02:10 AM

I'm going to resurrect this old question with a brand-new answer. Heads and blocks tend to be over cut and and you need to get back to stock dimensions. Toyota allows a total of 0.010" total removed from stock head and block. If you're not going to use a thicker stacked metal head gasket, you can get a cold rolled steel shim gasket from Innovative Machine & Supply. They are located in Missouri. Their most common on the shelf thickness is 20 thousandths, but you can also order 30, 40, and 60 thousandths by calling them. I put on a 0.020" Shim gasket under a stock Toyota head gasket 8 years and 30K miles ago without issues. For best results you need to have a freshly shaved block and spray the underside of the shim gasket with something like Permatex copper spray. Just the bottom of the shim, not the top where the head gasket will lay. And from experience, you might want to put a little dab of Permatex Black Ultra Silicone around the edges where the main round oil journals drain just before laying the head on and torquing it down. The standard new head thickness is 4.570". It's pretty easy to measure when the head is off with a vernier caliper. The other measurement is a little more difficult because you need to have the engine disassembled to get the measurement from the deck of the block and the saddle point of the main front bearing surface with the bearing out. If you're having your block shaved (and don't forget the front aluminum cover with it), the machine shop can get that number for you by request. The standard deck to saddle point distance is 7.815". You can run the numbers to see what thickness of shim gasket to get. The part number for the 0.020" gasket is HSTO30. Here is a link to their website: https://www.innomach.com/cylinder-head-shims

One way to visually tell if a head has been cut down quite a bit is to look at the bottom of the thermostat standpipe attachment point. When new it's rounded, and as the head surface gets cut down repeatedly, it becomes flat. If you're going to purchase a head, keep an eye out for that.

06/21/24 update: After 10 years of service, the head gasket needs replacing. Combustion pressure is leaking into the coolant jacket and / or the head is cracked. I don't know yet until I get it off for an inspection. I'm on the fence about going with a stacked metal head gasket, since the surfaces need to be really smooth. A standard head gasket is more forgiving, but may not last as long. 10 years was a good run. I retorqued the head bolts about a year and a half ago. That might have started it downhill, since only the exhaust bolts moved about 1/8 of the turn each. The exhaust side of the gasket gets cooked more than the intake. I'm sending the head to the machine shop for an inspection and surface cut. It's time for refresh. New timing belt, water pump, rubber coolant hoses, and copper fuel connection seals for the top end. I'll post an update when it's done.

06/01/25 In August 2024 I took the head to the local machine shop for a minimal cut. The total taken from the head since new turned out to be 0.029". Add that to the 0.020 taken from the block since new equals 0.049". The block surface was still smooth, because the shim gasket had been laying on it protecting it. Stock head gaskets are 0.054" thick. The grand total comes to 0.103". Cometic makes a stacked metal head gasket that is 0.098", which is within the 0.010" variance Toyota allows. After 2 months the head gasket began to leak externally on the exhaust side, so I re-torqued the ARP stud nuts from 75 foot-pounds up to 90, and it hasn't leaked after 10 months. A couple of months ago I replaced my aged copper radiator with a new Mishimoto all aluminum radiator. That solved the heat soak problem causing the temperature gauge to rise above normal after about 20 miles. It also solved the vapor lock issue on a heat soaked engine. The auxiliary fans only run now when the AC is on, because it's mandated by the control computer.

01-19-2022, 02:10 AM	#4
Bru Bone Stock w Upgrades ;-) Join Date: Apr 2010 Location: Tampa Bay Posts: 213	Shim gaskets are available from Innovative Machine & Supply I'm going to resurrect this old question with a brand-new answer. Heads and blocks tend to be over cut and and you need to get back to stock dimensions. Toyota allows a total of 0.010" total removed from stock head and block. If you're not going to use a thicker stacked metal head gasket, you can get a cold rolled steel shim gasket from Innovative Machine & Supply. They are located in Missouri. Their most common on the shelf thickness is 20 thousandths, but you can also order 30, 40, and 60 thousandths by calling them. I put on a 0.020" Shim gasket under a stock Toyota head gasket 8 years and 30K miles ago without issues. For best results you need to have a freshly shaved block and spray the underside of the shim gasket with something like Permatex copper spray. Just the bottom of the shim, not the top where the head gasket will lay. And from experience, you might want to put a little dab of Permatex Black Ultra Silicone around the edges where the main round oil journals drain just before laying the head on and torquing it down. The standard new head thickness is 4.570". It's pretty easy to measure when the head is off with a vernier caliper. The other measurement is a little more difficult because you need to have the engine disassembled to get the measurement from the deck of the block and the saddle point of the main front bearing surface with the bearing out. If you're having your block shaved (and don't forget the front aluminum cover with it), the machine shop can get that number for you by request. The standard deck to saddle point distance is 7.815". You can run the numbers to see what thickness of shim gasket to get. The part number for the 0.020" gasket is HSTO30. Here is a link to their website: https://www.innomach.com/cylinder-head-shims One way to visually tell if a head has been cut down quite a bit is to look at the bottom of the thermostat standpipe attachment point. When new it's rounded, and as the head surface gets cut down repeatedly, it becomes flat. If you're going to purchase a head, keep an eye out for that. 06/21/24 update: After 10 years of service, the head gasket needs replacing. Combustion pressure is leaking into the coolant jacket and / or the head is cracked. I don't know yet until I get it off for an inspection. I'm on the fence about going with a stacked metal head gasket, since the surfaces need to be really smooth. A standard head gasket is more forgiving, but may not last as long. 10 years was a good run. I retorqued the head bolts about a year and a half ago. That might have started it downhill, since only the exhaust bolts moved about 1/8 of the turn each. The exhaust side of the gasket gets cooked more than the intake. I'm sending the head to the machine shop for an inspection and surface cut. It's time for refresh. New timing belt, water pump, rubber coolant hoses, and copper fuel connection seals for the top end. I'll post an update when it's done. 06/01/25 In August 2024 I took the head to the local machine shop for a minimal cut. The total taken from the head since new turned out to be 0.029". Add that to the 0.020 taken from the block since new equals 0.049". The block surface was still smooth, because the shim gasket had been laying on it protecting it. Stock head gaskets are 0.054" thick. The grand total comes to 0.103". Cometic makes a stacked metal head gasket that is 0.098", which is within the 0.010" variance Toyota allows. After 2 months the head gasket began to leak externally on the exhaust side, so I re-torqued the ARP stud nuts from 75 foot-pounds up to 90, and it hasn't leaked after 10 months. A couple of months ago I replaced my aged copper radiator with a new Mishimoto all aluminum radiator. That solved the heat soak problem causing the temperature gauge to rise above normal after about 20 miles. It also solved the vapor lock issue on a heat soaked engine. The auxiliary fans only run now when the AC is on, because it's mandated by the control computer. Attached Thumbnails Last edited by Bru; 06-01-2025 at 05:17 PM.