VR V6 heads on a VP V6 problems

[TimWalton]

G'day all,

Has anyone else done a head swap from VR to VP or even just done head gaskets and had an overheating problem afterwards?

I had a problem with the driver's side head on my '92 VP Toyota Lexcen in which one of the exhaust bolts rattled loose, buggering the thread so i couldn't just throw a new bolt in. Of course, it was the hardest hole to get to (the one at the back near the brake booster and heater hoses) so i couldn't get a tap in there to clean it up.

I had a spare set of heads from a '93 VR sitting at home so I got them serviced and threw them on. I had overheating issues the instant I did this work so I talked to the blokes at work who said I probably put the gaskets on wrong. I pulled the whole lot apart again and found (as I suspected) that there was nothing wrong with the way the gaskets were positioned as there is no possible way to put them on wrongly. The problem I could see was that the spaces for the coolant to flow through the gasket were far too small, being reduced from the size of the passages in the heads and block to 3mm holes instead.

Note that the gaskets I took off in the first place were original and the coolant passages in the gasket were the same size as those in the block and heads.

The next set of gaskets I looked at were exactly the same. The blokes at work now say it's the heads themselves that are the problem, having come off a VR and going onto a VP, despite the fact that VN series II through to VR were all more or less the same with few changes.

The heads are identical to the original ones except for the VR ones having roller pivots in the rocker gear instead of the slipper bearing style of the original. All coolant passages on block and head line up perfectly, the inlet manifold lines up perfectly and no gaskets cover any holes. I've replaced the radiator as it needed doing anyway and that didn't make a difference. Its possible it could be the thermostat and I have a new one waiting to go in anyway but I'll be royally p***ed if that was the issue all along.

So before I potentially get another bum steer from work I'll see if anyone's encountered this problem before.

Cheers,
Tim

 

[Terminal]

This might be a bit obvious but did you bleed the coolant system correctly when you filled it back up with fluid, sometimes the commodore motors can be a bitch to bleed and will overheat if there is air in the system. A good method is to actually jack the front of the car up when you're filling the radiator and warming it up so that gravity can do most of the work.

 

[TimWalton]

Yeah I bled it correctly, I knew they were a pain sometimes so I parked it facing up a hill.

 

[Jxfwsf]

the heads are interchangeable with no problems.
Yes the gaskets can be put on wrong, read the instructions regarding which way the arrow should face, factory the arrow points to the back of the block, most aftermarket gaskets follow suit but some say to point the arrow to tthe front of the engine.
there is a small difference in the coolant flow holes, don't have a gasket on hand atm but the restriction holes are different sizes, put it on the wrong way and it won't flow coolant correctly, thus over heating in the heads.
Factory gaskets don't have have holes the same size as the head and block, simply what you pulled off must have decintergrated.

 

[Jxfwsf]

and here it is, a factory V6 head gasket that had been removed from an engine.
Marked with the red arrows is the coolant passages, clearly the holes at the back of the engine are bigger. (2 more coolant holes i haven't marked but you get the drift)
The green arrow is pointing to the mounting indicator, as it's a factory head gasket this needs to be pointing to the read of the engine (to the firewall)

They are designed to fit both left and right bank, can easily be put on upside down and back to front.