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

[RAd28]

Not sure what Morgans is, but the Century has been in the garage all day so no.

Morgans Seafood at Scarborough... saw a black Century on the side of the road with some young guys sitting nearby keeping a close eye on it...


anyways, Back on topic

[The Witzl]

88270 and 88253 heads are definately not identical. They have the same valve assemblies and use some of the same gaskets.

88253 heads have cast bridges on their top deck and a foot long casting line that is prone to cracking. They use a four bolt front inspection plate.
These heads have three air injection ports onto some of the exhaust ports.

88270 heads have no bridge reinforcement but are better reinforced throughout the rest of the top deck and don't have the problematic casting marks. They use a two bolt front inspection plate and have injector reliefs.

If the 88253 and 88270 share the same valve assemblies, then they also share the same valves yes?

I can confirm that the valves of the 88253 and 88250 are the same diameter.... therefore if 88253 valves = 88270 valves, then 88250 = 88270.

Then the old myth that the 88270 has larger valves than the 88250 is disproved.

I cannot comment on the 88230 or 88210, because i have never had a stock version of these heads to measure the valves.

For reference:
88250 and 88253 valves diameters....
INTAKE - 45mm
EXHAUST - 38.5mm

[timbosaurus]

Then the old myth that the 88270 has larger valves than the 88250 is disproved.

I know a show on TV you could get a job with Karl...

But seriously, that's what I was getting at.

Steves info is great, and points out that the 270 castings are superior (really benificial for most of our levels of hp though??) compared to the 253.

But piecing together some of the info posted recently has changed my (completely uneducated) understanding of the variants.

I used to think the 250 was the least desirable variant, having the less agressive cams (i'm assuming we are talking duration here too, not lift), single valve springs and smaller valves.

But someone mentioned that they have measured the 250 cam profile and found that they are not noticably different to the 230's which is rumoured to be the same as the 210, and if the valves in the 250 are as big as the 270's, then the only disadvantage is the single valve springs (which would be replaced in a decent rebuild anyway).

hmmm... maybe I shouldn't through 250 heads out after all

Timbo

*all just hypothesisisissses, trying to stimulate some more info from those in the know*

[river]

Hi,

Wasn't the 250-head the 18R-GU engine, which was the least powerful of the 18R-G family?

However, this does not necessarily mean the lower power is entirely the fault of the head. The 18R-GU had lower compression pistons, a domesticated cam-profile and the carbs had emission control stuff on them... which all conspired to lower the power. It was designed to run on lower octane petrol and was probably a result of the growing concerns over pollution, and maybe the oil-crisis of the early-mid 70s.

seeyuzz
river

[Steve M]

The 88250 head has the same bridging set up as the 88253 head.
Yes, 88270 valves are the same as 88253 valves.

When comparing 88210, 88231 and 88250 cams, there is only 2 degree range for duration at 0.050" and 0.1mm lift difference at full lift on the inlet cams. The exhaust cams have less difference in their lift.

[timbosaurus]

When comparing 88210, 88231 and 88250 cams, there is only 2 degree range for duration at 0.050" and 0.1mm lift difference at full lift on the inlet cams. The exhaust cams have less difference in their lift.

Sweet F.A. really!!!!

Thanks Steve!

[Omegaman]

As i went from 270 cams to the 231's you can notice some difference.
the obvious though, rougher idle, slightly torquer, also the kick in in the power curve compared to a smouth acceleration. As I said noticable, BUT and there's a but. I did change to 9.7.1 comp pistons. So those in the know could blow this out of the water.

[tricky]

I can without a shadow of a doubt confirm that the 210 valves are appreciably smaller than the later variants. The exhaust valves are 37mm. I'm pretty sure that I can remember the intake diameter off the top of my head, but I will confirm it first for fear of posting misinformation...

[Steve M]

The inlet valves for the 88210 head were 44mm.

[tricky]

Yep, that's what I had in my head... That good enough independent verification for me. Just to put it into Karl's format:

For reference:
88210 Valve diameters-
INTAKE: 44mm
EXHAUST: 37mm

[The Witzl]

Steve - your comparisons of the 88250 and 88251 cams are interesting!

I have a mix of 88250 and 88251 cams in my engine at the moment, i would've never thought there was a difference between the two.

Perhaps it's possible the 88251 cams were for the 88253 head, which donned a little more pollution gear than the 88250 engine - keeping in line with the wussier cams for emissions theory.

In any case - it would be a difference of about 2kW at the wheels probably.

[Lambolica]

I measured the Valves in the 230 head I have
Intake 44mm (44.5?)
Exhaust 38mm

Interesting graph on the Cams I was lead to believe there was more difference than that, Particularly in the lift.... Mine Aren't on there

Cheers
Simon

[timbosaurus]

Something I have always wondered is whether series' on cams are supposed to line up with the series' on the heads?

I have 2 RG heads handy to look at, they may or may not have original cams.

1) 88250 head. 88270 cams. Lift appears to be (only measured with verniers though) ~10mm. Has "adjustable" cam gears.
2) 88253 head. 8825 cams (no last digit). Lift also appears to be ~ 10mm. Has "adjustable" cam gears.

Any idea what cams don't have the last digit?
The 270cams/250head came off a "bitsa" engine. Is it likely that these cams were just whatever was lying around?

[Steve M]

Cam series and head series don't always line up.
I've seen 88230 and 88250 heads with 88231 cams.
I've never seen 88230 cams. That's not saying that they don't exist though, I don't know. If anyone can clear that up for me I would be interested to know.

88253 heads came with 88251 cams (timbo, yours were probably poorly stamped, sometimes the last digit is really hard to read, or Toyota just forgot)
88270 heads came with 88270 cams
88210 cams came with 88210 heads

Here's the lift comparison graph for all our 18RG cams.
They have been adjusted to suit factory and spec clearances.

[The Witzl]

would 0.5mm of lift really make much difference? Just wondering if it's worth throwing my 88250 cams into the current engine

i've got the parts to do it, but i CBF unless there is a *real* benefit to doing so.