How tight to set solid lifters

66 Sat said
Well I finally checked the hot lash this afternoon and Newbomb Turk is correct - there is slightly more lash hot than cold on my iron block, iron heads engine. I set them .016" cold thinking I'd get to 0.014" hot, but they are at .018.
Now I have to fix them all, I'll set them to .012.

Another question - when I removed the plugs a few look dodgy - especially drivers side, nearest firewall (labelled Drivers Side No. 4) These are new plugs - I changed them a few weeks back when I did the lash the first time. That plug that came out from that same location looked similar then too, with the central electrode looking burned up/lumpy deposits on it.

The plugs I had in it were NGK BP5S and I went one colder to a BP6S.

I've probably driven the car about 8 times on these plugs, with two long 120 mile highway trips on Saturday and today.

Any ideas what's going on there?
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I’m glad you took the time to do your lash. Now you know the truth.

BTW, Bewy is correct. I think that 6 is pretty cold. The 5’s look a bit cold.

Some of what you are seeing is fuel distribution. Sometimes you can jet a corner of the carb to clean up a cylinder but it’s a bit harder with a dual plane intake. You just need to be careful and sneak up on it while making sure you don’t change the tune up on a hole you don’t want to change.

If you are running into detonation issues with the 5 plug, you can do some things to get that under control.

First is your timing curve. Without knowing the rest of your combo it’s just a guess but I’m betting you have a fairly fast curve.

Every engine I know of wants a curve. Every engine I know of wants less timing at peak torque and more timing at peak power.

If you think about that for a bit (I’m going to assume some things here) and we say your torque peak is 3800 RPM your engine may only want 24-26 degrees of advance. If you have a curve that’s all in by 2500 (or even 3000) that means whatever your total advance is, you now have way too much timing at peak torque. Thats not only a power killer but it can cause detonation.

Getting a proper curve goes a long way to reducing detonation.

Another way to reduce the tendency to detonate is lowering your coolant temperature. If you are running at say 195 degrees and your cooling system is capable of controlling the temperature at 180 that 15 degrees of coolant temperature will reduce the tendency to detonate.

Between a proper curve and possibly lowering your coolant temperature some you can probably clean most of that up if not all of it.