Well, it's been several weeks since I was at Ace's while he worked on the engine. I haven't seen it since the block was being cleaned, so I'm stopping by to check it out on my way over to my work week "apartment" in Ventura. As you all can tell, Ace is very meticulous in his work and it's an education for me whenever we get together.
Ron

So, have you determined why your engine only lasted 25k miles?

It had pre-detonation issues right from the beginning. I think that the biggest factor was compression was too high for the gas we have available in CA (about 10.6 CR) . I took a few measures to improve the condition (octane boosters, retarding the advance), but never got rid of it. The headgasket was partially compromised after about 5K miles or so, as detected by a slight loss of top end power (weaker when climbing steep grades), and confirmed by leak down testing (the fire ring was leaking between #4 and #3, and also between #3 and #2). The car would ping at lower rpms (1500 - 2800 rpm or so) if the engine was under load, so I just kept the rpm's higher, as most of us do anyway. All during this time, the compression remained high (around 200 psi), and the car ran stronger than most, so I continued to drive it. We drove clear accross the country and back in 2008 with the engine in that condition.

After about 20K miles the condition worsened gradually, and I made plans to pull the head and change the head gasket (remember I bought head gaskets from you, Mark??), but I never got around to it. In hindsight, I should have.

To correct the problem, I'm planning to try several things, . . . but one thing at a time, to evaluate the benefits of each. In order of priority:
1) Reduce CR to about 10.0 by using a thicker heavy duty head gasket. Then, if needed:
2) Lay down the advance curve. Currently, the distributor builds from about 5° initial to about 33° total advance at 3400 rpm, fairly standard. It's been suggested that I lay the advance curve down to achieve full advance at 4500 - 5000 rpm or higher, for this engine. Then, if needed:
3) Open up the exhaust to large diameter pipes. Currently using stock exhaust system. I agree that I would want to increase exhaust flow if shooting for top performance, but as to whether the stock exhaust would contribute to pinging at low rpms, I have a hard time buying that. Then, if needed:
4) Provide cooler intake air to the carburetors, by routing cooler air from in front of the radiator.

The latter two fixes are based on assumption that the combustion was possibly too hot, but I never really had any evidence to suggest that -- the spark plugs generally looked very good.

If you have any other feedback, I'm appreciative.

Alvon

depending on how your cam timing is set up, a stock exhaust would tend to lessen detonation. The stock restrictive exhaust will cause more exhaust to enter the cylinder during overlap, diluting the mixture and slowing the burning process. I've never heard of pre-detonation. Preigntion or detonation, and they are two very different events. From your description, I'm assuming you are fighting detonation and not pre-ignition

I stand corrected -- thanks, Mark. 'Pre-detonation' doesn't make any sense. If anything, it might be called 'post-detonation', since it is the ignition of the end gases well after the spark event, but I'll stick with the correct term: Detonation.

A

isnt 93 octane available in cali? back your timing down to 30deg, as race motors use less timing anyway. the more compression the less timing needed. just some thoughts

Thanks for your feedback, Beek. I've been using Premium grade from the beginning, and tried octane boosters, also. I did experiment with changing the initial timing quite a bit (from less than zero degrees to more than 10 degrees, and everything in between), but did not resolve the pinging. It will be interesting to see the effect of reducing the compression down to about 10.0, and laying the advance curve down some, if necessary.

Alvon

Maybe you'll get it back together in time for Mark's dyno day. That's how we set Gina's timing; advance until no additional power is produced, then back it down to the point where it began making that number. You'll also be able to see the mixture at RPM's and under load to rule out a lean miss.

That is FIAT porn right there! Very nice!

ventura ace wrote:Here are a few pics of my 1.8L engine coming back together finally, after a blown head gasket in November last year. I'm using a stronger heavy-duty head gasket this time (the Guy Croft heavy duty gasket). It is about 25mm thicker than the standard gasket, which should drop my compression ration down from 10.6 to a more manageable 10.1 - 10.2 or so. Also using the GC grade 12 head bolts, and changed the valve springs out for the GC triples, and am using total seal piston rings this time.

Buttoning up the oil pan, cylinder head ready to go:


Using the clutch pressure plate to lock the flywheel from rotating while tightening the flywheel bolts, and all the front pulley bolts:


Another peak at the flywheel :


Adjusting the timing of the cam wheel pulleys. For starters I have the intakes at 108° and the exhausts at 111°. I may play with these adjustments a little bit during the upcoming Dyno Day the Mark is planning:


Next: rebuild the carbs and the distributor, then drop everything in the engine bay.

Alvon