total seal gapless pistons rings

[bison]

^ ok i agree with that.

would you say the situation should be dramatically improved with thinner head gaskets ?

The head gaskets used won't matter at all. You could go even thicker and it won't matter but your CR will be crap. Thinner head gaskets might increase the detonation tendency. I ran double stacked factory steel gaskets for years from the mid 90's up till other options became available. Typically could get a .055" of feeler gauge between the head and block after torqued down. Stock pistons are .060" in the hole. Made 10 sec power this way for a long time tuning on a stock ECM with a multimeter that was tapped into the O2 circuit. Pre scanmaster or any of the other fancy tuning devices available today. I never had a piston failure back then. Plenty of stock head gaskets but never piston breakage. The best trap speed was 124mph back in 1999-2000 or so. That double stacked steel gasket combined with do it yourself methanol injection gave me a huge advantage in fuel delivery and ability to not blow gaskets at that time. The most injector any stock ecu car around here had was 42lb/hr. I ran those almost static and had the methanol cranked up. I was able to go 3-4mph faster with the methanol before I was out of fuel again. Most struggled to trap 117-118 back then with 42's on race fuel. A few went 120-121mph. I ran 27-28psi and everyone else was running 21-22 on race fuel because they thought they would break. It was simple. It was knocked by many. It worked.

 

[frank_ster]

ok what you say makes perfect sense.

I am quite sure that if i ran more conservative timming , and i stopped trying stuff it would be fine. I am using megasquirt and i can tune as i drive, so i have been open to trying stuff.

but it seems to me in my current configuration knock is at a higher tendancy than normal because the transition between no quench and quench, that spot on the head where the flat part begins is a perfect little hot spot.

on other engines detonation typically happens on the top of the piston, and in a more manageable- lasting way. and its the engine i have had the most trouble with. its extreamly knock sensitive and takes nothing to have it burning oil like a pig. i had my 350 with flat tops cast pistons and it pinged a bunch of times and never had any issue. the 3.8 i hear a few events let off the throttle and its burning oil. To me something is not right.

This engine I am targeting both economy and power, so ultra low compression isn't really a desire. the correct quench i agree with the other posters as a correct quench will make it more knock resistant because of the high velocity and other benefits of correct quench.

 

[bison]

ok what you say makes perfect sense.

I am quite sure that if i ran more conservative timming , and i stopped trying stuff it would be fine. I am using megasquirt and i can tune as i drive, so i have been open to trying stuff.

but it seems to me in my current configuration knock is at a higher tendancy than normal because the transition between no quench and quench, that spot on the head where the flat part begins is a perfect little hot spot.

on other engines detonation typically happens on the top of the piston, and in a more manageable- lasting way. and its the engine i have had the most trouble with. its extreamly knock sensitive and takes nothing to have it burning oil like a pig. i had my 350 with flat tops cast pistons and it pinged a bunch of times and never had any issue. the 3.8 i hear a few events let off the throttle and its burning oil. To me something is not right.

This engine I am targeting both economy and power, so ultra low compression isn't really a desire. the correct quench i agree with the other posters as a correct quench will make it more knock resistant because of the high velocity and other benefits of correct quench.

You had a turbocharged 350? If you detonate an engine making 100+hp per hole even a little it will do a lot of damage in a very short time. If you had a naturally aspirated 350 that had some light detonation it's not a big deal since the air mass in the cylinder is much less. These old design cylinder heads are what 98% or more of people are running to this day. Plenty of guys running 30psi on 93/alky and like I said I had nothing fancy to tune with and never tore up pistons. Sounds like you have more than one problem. How did you verify timing?

 

[frank_ster]

well i have been asking for a stock timming table on this forum for months. my timming is correct with a notch on the front pully that i marked years ago.
but i dont know what to set the base map too. i do have a pretty good idea now tho.

 

[RmvBfrFlght]

well i have been asking for a stock timming table on this forum for months. my timming is correct with a notch on the front pully that i marked years ago.
but i dont know what to set the base map too. i do have a pretty good idea now tho.

Here is the timing tables (main & PE mode) from a '87 TR. This is from ACXA, which was released for the '87 MY, and it also matches BBKJ which was release in '92 as the emissions fix chip. I can't guarantee that these are correct. Mainly because I didn't read the chips myself.

This table is from a chip marked as for the 89 TTA. Not sure of the BCC. The SA is different:

Next post will have a graph of each of the two main tables. Quite interesting.

RemoveBeforeFlight

{edit: OK have the images squared away}

 

[RmvBfrFlght]

And a graph of each the '87 TR and the '89 TTA main SA tables. Note how much smoother the TTA SA table is.

RemoveBeforeFlight

 

[bison]

That table on the right has too much timing to maximize most combos without detonation. 26* is more timing than I have ran on anything unless it had terrible mass efficiency because of stock heads or nearly stock combo even with 116 octane. That's probably fine at 13-14psi on 94-95 octane in 1st and 2nd but 3rd and 4th will detonate on todays crappy fuel.