Hi Guys, sorry to put in a question of my own her - what's the best juice to put in my spitfire 1500 (UK 9:1 compression)? Currently running on the cheap stuff, Static timing 8deg BTDC, dynamic figures just within or on top end of BL manual limits (bearing in mind it was written for that toxic leaded pooh). I've recently rebuilt the engine and there's this nasty tinkly noise (like someone shaking a load of pins in a biscuit tin) coming from it - not sure if pinging (pinking?) or small ends. I've checked the backlash on the timing chain and seems ok. Thanks, Dave.
Hi Dave, is this noise all the time or only when you put your foot down especially at lower revs in a higher gear going up a hill? If its the latter it'll be pinking so try running it on super unleaded. If it still does it try gradually retarding the timing (less degrees BTDC) until the noise just stops at 2000rpm in top gear under full acceleration on a flat road.
Anyway, as above it sounds like pinking. Just keep retarding the ignition until you no longer get pinking. Higher octane fuel will also help.All as glang has said.
Location-Brighton, East Sussex Foxy is here, 1500od tax exempt Toledo. Now has the decent engine back in Slant 4 engine bolted in, sprint box and axle.Now has fresh MoT. Needs paint though. Spitfire Zetec project is started work progressing slooooowly on the road!
Thanks Glang and Cliftyhanger, Yesterday I put some of the expensive juice in (Shell V-power nitro) - 99 RON, currently a 50% mix in the tank. Went for a good old drive yesterday but still noisy when I got home - seems to be on acceleration, deceleration and light running, so not too optimistic
Have been plotting the dynamic results on a graph, along with the BL advance curve envelope and it's now advancing well above envelope limits. I think the engine's been knocking all along and now might be too late.
I'm going to retard the ignition to 4deg BTDC to see if it helps, also in the distributor the secondary spring, which is supposed to come into play at 1400 rpm is not cutting in until 2000 rpm, I know it's worn / stretched as it measures 0.722" inside the hooks, which I think should be 0.700" I bought a range of springs from Moss but none seem to give the right curve. Looks like I'm going to be into some experimentation with dizzy springs - even winding my own as I can't find the exact Leyland one (wire dia 0.051", 4turns, o/d about 7mm). Interesting read here:
Dave, I just remembered that mines a lot worse if I dont keep the oil level topped up in the stromberg dashpots. However that again only really gives you pinking under accelelration so if yours is all the time it might be something else.... The good news is, as I understand it, that its pretty difficult to do really serious damage just with pinking - youre talking race and drag engines rather than our lowly examples
Thanks Glang, I've got twin SU's on mine but I'll check the dash pots and top them up. Got the distributor stripped down at present, to find where all that stray advance is coming from. There also seems to be some residual backlash in the distributor drive which doesn't help.