|
OKR
Jul 5, 2022 4:54:39 GMT
Post by dave1800 on Jul 5, 2022 4:54:39 GMT
Yes, that's what the 0.020" "Timing" means. The closest I can find is the cam fitted to some Mk1 cars 5,45 51,21 ie the same inlet as the Mk11/111 cars with the exhaust timing of the Mk11S/MGB. This has a tappet clearance of 0.018" so a bit noisy! I think BMC used this profile on early Mk 1 Sprites and maybe elsewhere. The Downton tuning kits were made for MK1 cars that had this cam profile and still used a single carb but required twin carbs for engines with the softer cams (5,45,40,10). My Mk1 crab had this cam and was very free revving especially at the top end. Ok a very rough check with 0.050" as valve clearance gave roughly 5 in 45 in 15 ex 48 ex I just noticed a value of 0.020" in the WM that says "Timing" is that what that means for cam timing? Nick
|
|
|
OKR
Jul 5, 2022 5:34:32 GMT
Post by andrewa on Jul 5, 2022 5:34:32 GMT
Looks about the same as a 270 cam which is what I ended up with in my S. A great cam - I didn't notice any particular drop off in bottom end torque, rock steady idle and really gets up and goes over 1500 rpm. It was all over by 5500 rpm but little point taking it that high as max HP was around 5000 rpm from memory. Really good for the road.
|
|
|
OKR
Jul 5, 2022 6:36:03 GMT
Post by dave1800 on Jul 5, 2022 6:36:03 GMT
Hi Andrew I seem to recall you had a programmable ignition that allowed the timing to be compensated to match the engine requirements across the range. Nick's cam seems to be asymmetric whereas Piper and Kent cams with 270 degree duration are not; unsure about other brands. As I mentioned the whole issue of measuring cam duration is a minefield making it difficult to make direct comparisons. Cam lift is another variable of course. For comparison just using the BMC measuring method, the MGB/1800S duration is 252 degrees, the Mk11/111 is 232 degrees and Nick's latest measurements suggests 232/243 degrees. Not sure what the 270 cam measurements are when measured with the BMC 0.020" clearance setting. I know you "experimented" with several cams until you found the one most suitable. It's a shame Nick won't be able to do this without having to remove the lump and separate the transmission. All I an say is that a cam similar to the one Nick appears to have ran much better for me than the one used in Mk11/111 cars - and I didn't have to tweak the timing . David
|
|
|
OKR
Jul 5, 2022 7:06:03 GMT
via mobile
Post by 1800heap on Jul 5, 2022 7:06:03 GMT
Certainly difficult to get the numbers. Did another rough check at 0.20" and got In open 16° BTDC In close 62° ABDC Ex open 53°BBDC Ex close 30 ATDC Plus of minus a couple of degree at least. Also I am only checking no 1. Perhaps an average of all would be more accurate. I am happy with that anyway. Good job as I already put the box back on. Still got to do clutch side. Found a bigger clutch so not all bad. Definitely rather be able to get it out easily but 1968 cast looks like a nogo.
Thanks Gentlemen
Nick
|
|
|
OKR
Jul 5, 2022 7:40:36 GMT
Post by dave1800 on Jul 5, 2022 7:40:36 GMT
Based on your new measurements of no1 it look to be symmetrical after all and a bit hotter than a MGB/1800s cam. It could well be a 270 as Andrew suggested, he is our "still resident" expert. David Certainly difficult to get the numbers. Did another rough check at 0.20" and got In open 16° BTDC In close 62° ABDC Ex open 53°BBDC Ex close 30 ATDC Plus of minus a couple of degree at least. Also I am only checking no 1. Perhaps an average of all would be more accurate. I am happy with that anyway. Good job as I already put the box back on. Still got to do clutch side. Found a bigger clutch so not all bad. Definitely rather be able to get it out easily but 1968 cast looks like a nogo. Thanks Gentlemen
Nick
|
|
|
OKR
Jul 5, 2022 12:05:48 GMT
Post by andrewa on Jul 5, 2022 12:05:48 GMT
This is the thing I used - went with the "Tune" version which was very good - and had two maps - one for excellent fuel and one for rubbish fuel! 123ignition.com/It's a good device and can certainly help you get the best out of the engine but it's quite an investment and you really need a rolling road session to set it up properly. That's when it gets complicated...trying to find someone who is great with SU carbs and modern technology and owns a rolling road......
|
|
|
OKR
Jul 6, 2022 2:10:51 GMT
Post by dave1800 on Jul 6, 2022 2:10:51 GMT
Thought it might be a good time to post this video again from several years back as a reminder and a surprise for many "carb tuners".
Naturally getting the mixture right is essential from the point of reliability, and longevity if not quite so critical for power delivery as optimum ignition timing.
I think a good starting point would be the SU needles from a 1800S if using 1.75" SUs or from the MGB if your carbs are 1.5". Andrew may have better suggestions based on real life experience.
David
|
|
|
OKR
Jul 6, 2022 9:39:18 GMT
via mobile
Post by 1800heap on Jul 6, 2022 9:39:18 GMT
Thanks some good info. Your distributor looks good Andrew.
I have found the electronic distributor I got a while back. It is a converted Hitachi D4R85-15. Was sold to me as suitable for an 1800S not sure how true this is. I need to do some research and see if it is any use to me.
Currently I have a standard dizzy with an old piranha unit attached. As long as it runs for the moment I am happy as there is still lots if other things I need to do.
This cam change has taken up more time than I wanted. I did gain a decent cam, new oil pump and will be putting back an 8-1/2" clutch instead of the 8 that was in it.
I am waiting on an asbestos test on the 8-1/2" plate that I have to hand. I also sent a roof insulation sample of the Oz crab and a bonnet insulation sample from the Triumph. Hopefully the clutch is ok as a new one is $400 on ebay it seems. The clutch supplier in town tells me they can get a Triumph 215mm plate that should fit shipped for $280. Any ideas for compatibility from other vehicles. Not sure what Triumph he was talking about. I should have asked. TR7?
Nick
|
|
|
OKR
Jul 6, 2022 9:44:31 GMT
via mobile
Post by 1800heap on Jul 6, 2022 9:44:31 GMT
Forgot to say I have S carbs with TZ jets.
|
|
|
OKR
Jul 6, 2022 13:13:57 GMT
Post by dave1800 on Jul 6, 2022 13:13:57 GMT
Should be a good starting point. If in future you need to tweak the needles there is a handy tool hereYou can search the whole database or enter the profiles you think you need and it should find the closest needle. The page formatting can be a bit weird and can appear just as a blank page but you should find the profile input at the bottom left of the page if you scroll down and it also allows you to view the whole database but that may be off the screen to the right! David Forgot to say I have S carbs with TZ jets.
|
|
|
OKR
Jul 6, 2022 16:12:08 GMT
Post by andrewa on Jul 6, 2022 16:12:08 GMT
I can't remember re the clutch plate but Tony Wood will know, if someone on here doesn't help soon. On the needle front I gave up with following the book and let the tuner chap sort it out as once on the rolling road he tried all sorts, filing some of them until he was happy! Waiting patiently for next welding instalment . Cheers Andrew
|
|
|
OKR
Jul 7, 2022 3:44:05 GMT
Post by dave1800 on Jul 7, 2022 3:44:05 GMT
....I have found the electronic distributor I got a while back. It is a converted Hitachi D4R85-15. Was sold to me as suitable for an 1800S not sure how true this is. I need to do some research and see if it is any use to me. Currently I have a standard dizzy with an old piranha unit attached. As long as it runs for the moment I am happy as there is still lots if other things I need to do. Nick Hi Nick I appreciate you have lots more to do than you anticipated, but I think it would be prudent to carry out one key check on the distributors before driving the car hard, hopefully not too far away now! Two of the MGB experts, Peter Burgess and John Twist, recommend that the mechanical plus static advance should not exceed 32-34 degrees with the standard MGB cam and twin SUs. There are debates as to the RPM by which this should be achieved. This figure is in line with the w/s manual for the 1800S ie 9 degrees static and 22-24 degrees mechanical advance at 4,800 rpm. I think the MGB can take more advance sooner as it is quite a bit lighter. For comparison the Mk11 single carb crab has 9 degrees static and 30 degrees mechanical ie 39 degrees. (All these figures exclude vacuum advance which is zero at wide throttle openings where damage would be more likely to occur with over advanced ignition). Your cam may require a little more advance to get a smooth idle. If it does it may be necessary to modify the mechanical advance stop in the distributor to limit the total advance from exceeding the 32-34 degrees. Hope this helps David
|
|
|
OKR
Jul 8, 2022 21:09:34 GMT
via mobile
Post by 1800heap on Jul 8, 2022 21:09:34 GMT
Thanks for the info David I will be checking the timing when I get it running again.
Nick
|
|
|
OKR
Jul 9, 2022 0:17:07 GMT
Post by 1800heap on Jul 9, 2022 0:17:07 GMT
Couple of engine pics. Splitting it so I can get the oil pump off to get the cam out Grrr! Now waiting for the clutch plate asbestos check and a locking plate for the flywheel to show up. Got the flywheel machined while it was out as there was some wear from the 8"plate. Putting an 8-1/2" back so I thought a start from fresh was a good idea! Also found a 70 amp alternator on eBay for $165 that looked like a good fit and was, so quite happy with that. The electric AC when fitted will need it. It really needs a 100amp unit but can't find a suitable one, so this has got to be better than 45amps! Apparently it fits a Massey Ferguson tractor among others. No tractor jokes pls Nick
|
|
|
OKR
Jul 9, 2022 6:58:44 GMT
Post by andrewa on Jul 9, 2022 6:58:44 GMT
Morning! Only thing that occurred to me whilst it's so accessible is just checking the can thing for the crankcase breather (looks like mini exhaust silencer underneath the carbs) isn't full of gunk - mine was! Cheers Andrew
|
|