cliff.b

I'm thinking of using something on suspension components and other parts underneath prior to painting and then applying Dynax UC.

Seen several that say that chemically convert rust and form a "primed" surface suitable for painting. I used something like this about 40 years ago and the rust soon came back but wondering if they are better now. Does anyone have any experience and if so, what is worth using?

And triumph derived

Staying at the adjacent hotel this weekend and surprised to find a large classic car show unfolding. Hundreds of cars of all types and more than a few Triumphs. I

Yes, of course. I just meant it's not important that you can't directly relate a compression test reading to the CR.

Yes, that is my understanding. Was just curious when someone appeared to be suggesting otherwise but clearly it is far more complicated and of no real importance anyway.

Aha, I suspected there may be a little more to it 🙄 Further reading uncovered a more detailed calculation. "Gauges very, as does valve overlap. The actual formula for comparing pressures and CR is P = Po X CR^g where P is the achieved pressure, Po is the ambient pressure, CR is the Compression Ratio, and g is gamma, or the specific heat of the gas, for air 1.4 may be used. The ^ means the CR is raised to the gamma power. In practice this doesn't work anyway because of the aforementioned valve timing and the following relationships. Since CR is derived from volumes, not pressure, CR is V1 / V2. Pressure Ratio PR is P2 / P1. Assuming an adiabatic compression, and air being a perfect gas, we can define the change in volume and pressure as follows: P1V1^g = P2V2^g implies P2 / P1 = (V1 / V2)^g. Because, in reality, the specific heat will change with temperature and significant deviations from adiabatic behavior will occur, there is no good way to relate CR to the compression readings" So there you have it 🤔

I thought it sounded a bit "simplistic" lol I tested as you described and the gauge appeared to read 150/148/148/150 Only checked out of interest as I had never done it before 😊

Read this on another site and wondered if it is accurate information "To calculate the compression ratio, try this formula: compression gauge reading divided by 14.7 (atmospheric pressure) i.e 140/ 14.7 = 9.5; 110 / 14.7 = 7.5" Makes sense I suppose and just wondered as I tested mine today and all cylinders where reading very close to 150psi, which this calculation suggests means a CR of about 10.2:1 I know nothing about the history of the engine so it could be, I suppose, or maybe the gauge isn't accurate 🤔 What's a normal test pressure for a 1500 engine, measured warm?

Ok, changes due to meeting emissions requirements makes sense. I try to ensure my car doesn't run hot so if that's the reason, it's probably not an issue anyway.

Just as a follow on to this, I had all the plugs out today to do a compression test, as I had access to a gauge, and noticed they are NGK BP6ES, which is what I was sold for a Spitfire, but I now see the 1500 engine specifies a BP5ES. Just wondered if anyone knows why it is different to the 1300s and what, if any, difference it might make. Seems to run ok but that is what has been in there since I bought the car.

I assumed it was the closing the throttle at highish revs that caused the vacuum advance just when you need it. Certainly replacing my faulty vac advance cured the popping etc on my car.

It's the mechanical, centrifugal mechanism that increases advance with engine revs. Two weights that try and fly outwards with increasing engine speed and two springs, a primary and a secondary which restrain this movement and define the advance curve. Also, a stop which limits total maximum mechanical advance. When you use your timing light, you should have the vac pipe disconnected but will see that the advance increases with engine revs. You should be able to match it with the chart that you have. This shows the mechanism

I got popping & banging on the overrun when my vac advance unit seized up. Presume it should advance on a closed throttle but wasn't doing so.

Just an update, as promised. I was looking at the rear brakes on Sunday and a quick check of the spring buttons led me to conclude that, so far, they look the same as when I replaced them in December. I would judge that the improved rise height has been maintained as well. Early days yet but I must have covered at least 1500 miles since I fitted them. I will check them again when I have the wheels off and report back.

Just read this thread and a couple of others as thinking of applying something to the underside of my Spitfire. I sprayed Dynax S50 into all the cavities and wondered if anyone has experience of using Dynax UC on underside? Or, as it seems to be advertised everywhere at the moment, Lanoguard. I'm looking for something clear that I can put over the existing paint which is in good condition and will hopefully help keep it that way

That sounds like an interesting journey if avoiding all Motorways etc. Very scenic in places 👍

Ah yes, I know it well. Definitely not the ideal spot to be stranded.

Were you on the A419. If so, not the ideal place to break down 🙄

I thought there must be a correct way to do it lol

Ok, to update, and for your amusement. New black pearlescent top coat applied, a can that has been in my garage for several years after it was used to touch up a previous vehicle. All looking good 👍 So fitted in place and secured with the 4 bolts to the overiders. Then opened the bonnet to fit the other bolts and "scrape", the lower edge of the bonnet removed the new paint in exactly the same place as it was missing when I started this misadventure 🤬. so clearly this was the problem all along. After a bit more investigation I could see the bonnet was definitely fouling the bumper but what to do about it 🤔 Then I decided to fit shims between the bonnet and the frame at the front mounting points and that did the job. A 5mm shim gave a couple of mm clearance at the bumper. I will probably do this again with washers later. Anyway, bonnet now definitely not hitting bumper so a quick repair to the damage using the very last dribble out of the spray can and I think it's ok, at last 👍 Also note overiders polished up a bit after advice on another thread. Spoiler and grill also treated the same

I didn't think I would ever raise mud flaps as an issue but I am wondering if anything is available to limit the splatter onto the bulkhead and front quarters from the front wheels in wet conditions? Been thinking about making something but easier if already available.

No problem, I have spent half of today removing it all again. Apart from not being totally happy with the way it looks, I felt it is too delicate to use unprotected on a bumper and using anything on it to try and solve that makes it look worse. It might have been ok but the bumper has been stripped now, new primer applied and will paint over the weekend.

Have you ever tried painting over it. Just wondering if it will need to come off if I decide to go back to black 🤔

It's probably more like the finish of the plastic screen trim.