For the love of a tractor engine: The life and times of the 18R-G

[o_man_ra23]

Justen, I'll re-check the valve clearances, though again, I've never had valves close up in the past 4 engine builds.

So where would I get new head bolts?? I tried auto stores, but come up with nothing as the 18R-G doesn't run torque to yield bolts, and nobody changes them, so they don't re-make them. I am still waiting for a reply from YelloRolla, as he may have/be able to source some studs. Failing all that, I think it is back together with new head gasket, and keep the boost in the vicinity of 5psi until I can replace the head bolts with some studs. Sound like a feasible option??

[JustenGT8]

As a suck it and see, yeah just bolt it all back together and turn the boost down. I would still try and get new head bolts...tried Toyota? If you reuse still crank them up a bit more and use assembly lube on the threads to ensure even torque.

[timbosaurus]

agree. Checked valve clearances, and if OK, then new HG and studs for sure.

If it was me, and the HG is still in good nick as you say, then I'd probably put it back together with this HG with an extra 10% torque on the head bolts. If the HG was the problem, then put in decent studs and new HG to make sure it doesn't happen again. If not, at least you haven't wasted another new HG trying to find the true cause.

[old_school_jap1]

Yellorolla talked about the way he does head studs here; http://www.toymods.net/forums/showth...164#post984164

[o_man_ra23]

Timbo, although the head gasket didn't show visible signs of damage, it did go into a state of disrepair from removing the head, as the hylomer I used previously did a great job of sticking. The head gasket did not stick to the head between bores 2 and 3, and didn't look like it had any hylomer left on it, so it could well have been a path for cross pollenation.

I do want to go to studs, so don't really want to buy bolts, then buy studs. Will see what is around for stud options.

[The Witzl]

could be bent valves, or valves not fully closing on their seats.
I had a bent valve on a previous build.... pain in the anus it was. It would definitely show up when checking valve clearances.

[Omegaman]

unfortunately i had bent valve also. to confirm i had to take head of and do a leak test.
not so fun when your almost ready to register and drive.

[o_man_ra23]

A bent valve should have shown up when they were re-seating them right?? I got all 8 valves re-seated when the machine work was done. Yet to test valve clearance though.

[hosking1991]

If the head is off still owen i highly reccomend taking it to your local engine reco shop and get it vaccuum tested that will show if indeed your valves are seating properly!

[rallyra28]

Hi Guys.
I'm doing a rebuild of my 18rg after a piston ring/piston failure on the Alpine Rally.
MyYamaha head is damaged but repairable..I have several Toyota heads and was wondering what is the basic difference between the two ?.
When and why were Yamaha heads fitted ?
Hope you can help.
Rob.

[river]

Hi,

Toyota got Yamaha to build the heads for the 2T-G and 18R-G engines. The heads are the same, whether it is stamped Yamaha or Toyota.

seeyuzz
river

[airfireman1]

All the heads were designed by Yamaha. WHY? cause they could. Do some research and you will find a wealth of information about them. The early heads had quite a few differences to the later ones. The best combination is an early 18rg set of cams and a later model head. The later model heads had dual valve springs and better casting The early cams had a longer duration.
Cheers

[river]

Hi,

Yes... get a 270 head, with 210 cams, and 9.7:1 compression pistons.

seeyuzz
river

[rallyra28]

Thanks guys.
Will check the numbers on the heads and cams.
Rob

[roadkill]

From memory it's only the 88253 that has the dual valve springs

bEn