Frost Plug Failure

[EvnEvlr]

Anyone ever have or heard of a frost plug failing on an RB26? While getting my GTR dyno'ed one of mine failed and leaked coolant everywhere. Now my engine needs to come out and have a new one pressed in. It could have been worse but bummer none the less.

[Bruizer]

Yeah I've heard of it fail on gtrs and seen it fail on: GMs, Dodge, even ford! it's common.

How old are they?

[99_SI]

Not common on Japanese cars in my opinion and is a result of too much pressure in combustion chamber which leads to head warping or head lifting off the block. Check compression and do a leak down test to verify you don't have any other issues .

[EvnEvlr]

The engine was built in 1996.

Yes, my mechanic is going look in to all of that. Hope the head in ok. I just had the whole engine rebuilt.

[evilgtr]

It's not uncommon on RB's running 700+ whp, the block doesn't take the flex very well and they will leak. It was the first thing my tuner told me when we were doing the break in tune at Racing Greed. The 24U blocks don't seem to have the same problem.

Which one was it ? You can get blanks to put in that will never come out again.

[EvnEvlr]

It was the one in the head that let go. Head was coming off anyway to check for damage. We were only around 500 HP and 1.1 BAR when the plug blew out.

[Bruizer]

He had too much pressure? what about the rad cap? wouldn't it have popped first? Or even the plastic radiator end tanks which is what let go on my before the cap?

[Skym]

The head can lift if using the wrong headstuds. In rare cases the metal headgasket seal is not thick enough or headgasket leaks.

But if the rear frost plug on head (common on RB26), too much pressure from a higher pressure radiator cap / breather tank using stock radiator could cause it.

[EvnEvlr]

We used ARP head studs and the we are using a Gready rad cap. Believe it's at 1.3 bar. The rad is upgraded and not stock.

[Skym]

The higher pressure would do it. I think the frost plugs are welded in on Group-A RB race engines or at least upgraded. There was a writeup on the internet on how the 640hp Group-A shortblock was modified including photo's.

But there's many types of ARP headstuds, depending on application. Head lifting is common on higher hp RB engines.

On the HKS special RB28 blocks for drag racing they run extra / smaller diameter head studs x2 inbetween each of the cylinders (I think has a custom spacer plate with sleeves for the block).

Kakimoto makes something similar for their RB26 to RB30 engines and has custom crank, conrods, pistons, spacer plate with sleeves, etc.