Don Terrill’s Speed-Talk

YOU’RE DOING IT WRONG. Thanks, captain obvious. Work on your reading comprehension. Calculating dynamic compression to compare part-throttle ignition maps is good starting point, but valve timing isn't part of that calculation, engine load is. So if your engine 100% VE is 500mg/stroke and compressi...

I've never measured it for this engine. It's got a relatively small cam, four valve head, etc. I've got a cruise ignition map from the factor for an engine that has about 8:1 "effective" compression ratio computed from the engine geometry and valve events. This engine has a 6.7:1 "effective" compre...

You will struggle shimming anything with a much smaller base circle also. I've used 2mm lash caps on occasion, but shaft also becomes too thin for strength. With Fiat TC you could shave cam trays instead of lash caps and save weight. With bucket follower regrinds there's usually no strength effect ...

If these are for a bucket type follower, there will be no difference between the two. If this is for a finger follower, or rocker follower type system, then a change in base circle will effect the lift curve at the valve. Only if geometry is left as it is, finger and rocker arm geometry could be co...

panic wrote: ↑Mon Oct 19, 2020 8:51 am Regrinding is limited to within 2-3 degrees of the original LSA.

Beauty of DOHC-engines is that timing for intake and exhaust cams can be set separately - so LSA isn't tied to cam profile at all.

If the limiter cuts sparks, which is likely, it would load the exhaust with an ideal air fuel mix. Retarded timing would drive up EGT, promoting light-off. He also might be using a spark plug in each collector for the purpose: https://www.thevehiclelab.com/exhaust-flames/#:~:text=In%20essence%2C%20...

Exhaust is red hot indicating late ignition timing. Probably due to too much boost and trying to prevent detonation. Combine that with too rich a mixture to equally prevent detonation and that is what you get. They are burning rubber - so retard ignition timing is from soft rpm limiter. Without sof...

Just use it, little bit of water in gas only matter if there's freezing temperature and fuel pickup freeze. And to prevent that you just add alcohol to gas to solve that water into gas instead of it freezing in tank bottom.

Prior to TDC, squish motion is inward toward the spark plug. After TDC, the squish motion is reversed and moves outward toward the perimeter. Naturally if squish area is in edge and spark plug in center of cylinder. But squish motion can be aimed to different location, aiming towards spark plug wil...

It shows to me like squish in this engine is directed towards combustion chamber roof. Squish should be directed to piston top instead, target is to make charge motion to where combustion takes too long time - gases stuck to piston and traveling downwards are main priority so targeting squish to tha...

The GL ratings is a gear pressure rating, has nothing to do with if it works makes syncros work better or worse. EP additives are specially meant for lubricating sliding gear contact like hypoid gears. Syncromesh is also sliding contact which works better if oil don't have additives to lubricate sl...

I do use synthetic ATF in manual gearboxes - it usually works much better than GL-4 grade oils. Redline MTL is one excellent product that have both GL4 and ATF grades but it's expensive, any thin synth ATF works usually also well.

What if a PCV system could be equipped with a 5 psi (~10 inHg) check valve on the inlet, filtered side going in the engine with the PCV to manifold side left alone. When vacuum exceeds 10", the valve opens and regulates fresh air into the crankcase at that depression. Late 90's up BMW has this kind...

Te lead did work to lubricate valve stems. Today's head rebuilds of older engines require additional stem-to-guide clearance to avoid hanging a valve on startup. The old guys had to learn new tricks when unleaded and now ethanol became the standard. Lead increases heat transfer between seat and val...

Main protection from lead is for exhaust valve/valve seat contact. Lead plating in those surfaces prevented material welding together and so reduced wear greatly. But lead stuck everywhere, sticking into hot valve stems was harmful side-effect not desired. Lead also stuck to other parts of valve fac...