That,s a big B******r mine is from a different era and why you are confused it is belt drive so the the alternator runs at 1500 I think (will check with my tachometer tomorrow)
I will start a different thread showing photos
Seem to remember Vizard having something to say on the subject of boring out CD carbs (SU & Stromberg). Not sure it was all that positive though. I think combined with a lairy cam "street driving" would be tricky! Airflow difference between 6k and 8k is substantial mind.....
And as far as I can find never published, a few hints from Steve, and a piece by Tony Drew indicates that apart from bevelling the front of the piston, which it now appears from later flow bench test to be a waste, that the 150 CD (and the SU HS6) although nominally 1.5" .they aren't, the bore tapers from about 1.35 inlet to 1.5 outlet. So if you bore the carb out to 1.5" right the way through, it bugg.rs the choke mechanism (but who needs a choke) and rebuild a new bridge, you can get them to flow more, and still be a 1.5" carb.
From AFR logging the 1.5 carbs on the 6 have a tendency to go rich and stay rich above 6K, and as I think (correct me if I'm wrong) that high compressions love rich mixtures, I think that's how they got to claimed 8K.
As with the 1.5's and my fiddling I could get 6.5+K and with the 1.75 it will pull 7K (for the briefest of periods I let it), I think if you could afford the engine rebuilds I think a highly modified pair of 1.5's might just fuel a high compression 2ltr towards 8K, Not sure if it would be street drivable though!
Hello Alan and Nick
Alan I am in a more fortunate position than you as I have 3 cylinder heads(4 if I count the original one with a burnt exhaust seat! cam timing was wrong and opening to early I think it was!)
1) is a standard 1500 with hard seats(and ported by me!)swooped for a American spec differential(my Brother in laws but he has since sold the car after I got it going well for him)Pr**t
1) is the one I bought for £10 a 218141 1300cc Toledo with the bigger inlet valve.
Plus the one on the car at the moment is a KC1156 1300cc Dolomite smaller inlet valve which I cleaned up the ports and machined the step in the combustion chamber away between the inlet and exhaust valves opposite the plug! to get the compression ratio down to about 9.5 to 1(I wish I could find the article that said do that!) and had hard exhaust seats fitted.
This head has done 25,000+ miles with no problems.
So I think I will port the Toledo one as it has the bigger inlet open the chamber up a bit but not go to the expense of hard exhaust seats in case its a dog! and I can put the 1500cc head on if it is
Plus the face looks good and I think I can cut the 3 angle valve seats myself on the milling machine as it is only cast iron!
I assume the plug is opposite the grind area ie by B
I have ordered a set of inlet valves and bronze guides (valves are nos Triumph/Leyland ones) from these people.
Does that sound like a good plan ???
ps I have been servicing our old Lister generator this morning a SOM 8-1 built in 1958 runs at a nice steady 850 rpm(very restful) not like the modern ones at 3,000 rpm!!
I will post some photos later in a new heading
Also, some of the compression ratios (for 6 cylinder for sure, maybe not so much with the 4) were the result of Kastner having to run 150 Strombergs, limiting flow and I think he was tuning in a similar way to the restricted inlet series with a high CR to compensate for never getting a truly full charge at high rpm. Dunno how he got round the carb issues you were fighting Alan....?
I don't understand the combustion chamber you've posted Roger. Doesn't look like a 4 cyl chamber to start with - where's the spark plug?
Interesting selection of vehicles - some a bit unexpected. Reckon it will have been particularly challenging this time due to weather!
TR4 seems to have had a bit more than a moment..........
Compliments to the photographer for venturing out in nasty conditions!
Below are some photos of cars that completed this years"s LeJog, according to the local press only 39 out of 53 completed it.
Pictured is about half of the finishers taken outside three of the hotels in Wick.
The other accommodation is out towards the outskirts, which I didn't visit because of the bad walking due to the thawed then refrozen snow.
(My car was frozen in to its parking space!)
Apologies for the photo quality, I don't have a proper flashgun anymore so couldn't take balanced flash against the available light.
Don't forget that the compression ratios they were using were for racing, and with some now regarded legacy cam profiles, probably nothing tractable below 4K rpm.
That doesn't denigrate the concepts on good head work, the porting on my MK1 head was done by some who took Kastner's port & throat work, plus Vizard's chamber work and said "Wimps" fortunately he did it on a thicker saloon head, and I got it before anyone had ever used it/skimmed it, so I was able to keep compression ratio in the sane tractable band. If I could afford to I'd love to see what skimming it to around 10:1 would do, might be very exciting above 5K but I think would ruin the over all balance of the engine.
Kas Kastner shows this for the 1500 cylinder head which would be easy on my milling machine and burrs.
So now I am getting even more confused(not to difficult!)
They were running 12 to 1 compression ratio and probably avgas or similar?
There are more power gains by
modifying the combustion chamber.
The section that needs attention is the
area around the inlet valve. Grind away
the cast iron around the inlet valve as
shown in the drawings. This simple bit
of grinding will improve the flow
considerably and consequently the
power. My test engine was running a
12.0 compression ratio and has shown
no ill effects from the modification. It is
mandatory that an oil cooler be fitted
when you go to this higher compression
ratio. We have had no failures, but as a matter of good maintenance we checked the rod
bearings after several hours of running time. We found that the bearings were all in good
condition. It is only a matter of good sense though, to check after a hard race to see firsthand
how the situation appears. Since the original time of this writing many owners have reported
the great success they have had with this modification.
If you are using a gasket other than the compressed stock .035'' head gasket be sure to
measure the thickness so that all your calculations are true to the parts used. After all the
grinding and machine work has been finished, assemble the head with the valves and valve