9 replies to this topic

[Dr Terry]

Hi Rory.

7438296 = 161 (not 186)
2811929 = 173 (not 202)
7420081 = 149 (not 186)
2811930 = 202 correct

The first 3 should have the smaller (kidney-shaped) combustion chamber, while the last one should have the larger chamber.

I'm referring to normal (hi-comp) motors here, the lo-comps complicate the issue and are super rare anyhow. The H & L markings are also confusing, because while they refer to the size of the combustion chamber, they can only mean hi or lo compression if they are fitted to one of the smaller motors (149/161/173).

Dr Terry.

[lakeside]

7438296 is a 2600S head / lc gtr

[Dr Terry]

Hi lakeside.

Yes, LC GTR (2600S/161S) use the standard 7438296 (161) head casting.

Dr Terry.

[micklx]

Did a low comp 149/161/173 run the 179/186/202 head or did they achieve the lower compression some other way?
And did the low comp motors actually use any less fuel ? I'm guessing thats why they had them.

[micklx]

aaagh yes, so we did. So the standard was a few cents cheaper a gallon but you needed the low comp motor to use it.
when I was a kid, Dad owned a BP Service Station in a small country town. We had a petrol bowser with a big rotary switch on the side, you could have Super, Standard, or a 75/25% mix or 50/50 or 25/75.

Sorry to go a bit off topic here.

[rodomo]

aaagh yes, so we did. So the standard was a few cents cheaper a gallon but you needed the low comp motor to use it.
when I was a kid, Dad owned a BP Service Station in a small country town. We had a petrol bowser with a big rotary switch on the side, you could have Super, Standard, or a 75/25% mix or 50/50 or 25/75.

Sorry to go a bit off topic here.

Did you used to mix your own BP Zoom too?
I was 10 and worked in a BP servo.

[Dr Terry]

2811930 = 202 correct

I have this head and it had the factory press in studs like 186 style heads (now has screw in studs). Are you sure 2811930 is a 202 head as I thought 202 heads used the bridges to secure the rockers and the 186 type heads had studs and where individualy adjusted.

Hi Guys.

Yes. I have also seen the 202 casting used as a late 186 head. These seem to appear in 1971 HG.

The only functional differences between a 186 head and a 202 head are the rocker gear and the machining for the spark plug. The 2 castings are very similar & in production it would be easy to machine the late casting to suit the earlier HG application.

The lo-comp engines were made to suit standard grade petrol. It was mainly for government & fleet use where they had their own in-ground petrol storage & all their other equipment also ran on standard petrol. It was easier to get cars made to suit their existing petrol supply, rather than have to store a separate (higher grade) petrol just for the cars. Seems a lot of trouble to go to. I also wonder how many were actually produced, they are rarer than rocking horse s#*t these days. How many have you guys ever seen in the flesh.

To answer micklx's questions. Yes, the 149/161/173 lo-comp motors simply had the larger 179/186/202 heads fitted. The rare lo-comp motors are the 186 & 202 versions (there was no 179 lo-comp). To create these, they dished the pistons (in the 202 it was a bigger dish than standard). No, the lo-comp motors didn't use less petrol, they probably used slightly more.

Lots of memories there about standard petrol etc. I remember those BP pumps with the selector switch, They used to advertise them as BP 'Multi-Mix'. This was in the days when cars were so varied in age and design that they could have had anything from 6:1 to 11:1 compression, so BP tried to cater for the whole market, with one pump. Apparently in the petrol bowser collecting/restoring crowd the BP Multi-Mix pump is a real treasure.

Dr Terry.