Stopping the knock: Lower compression and ported heads...

-
No. I said that because you talked about putting a smaller cam in it now. All that will do is make cylinder pressure increase and you will be right back where you were.......especially since you cannot understand what any of us are talking about regarding the timing curve. Here you are once again still arguing against proven methods.

Why are you even still shopping around for cams? I thought you had the problem fixed now and there is no detonation any longer. If that's the case, I'd leave well enough alone.

I don't care whose advice you follow. Makes no difference to me. It's not my car. You asked for advice. You grabbed hold of and followed what you wanted, leaving critical parts of it behind. That's no one's fault but yours. Then you want to come back on here effectively blaming others. you cannot see the forest for the trees.

You've never had any of your distributors apart to limit the advance. Not one. You think we're talking about the springs and we are not. You cannot half *** this stuff. You have to disassemble the distributor and weld up at least one of the advance slots to limit the total amount of advance. The reason is because the engine requires so much initial timing that without limiting the total, you will have dialed in too much total from having so much initial. You've never done that. You've argued every way sideways against it. You simply cannot understand what we have been trying to tell you all along.

Your **** is no different than anybody else's and that's how they do it. I have no idea how else to explain it to you. You're doing it wrong.


Frankenduster said:
You say this because I didn't follow your advice to the nth degree?
Many (Not all) thought the thicker head gaskets wouldn't help my situation, yet it has done just that.
Regarding the ignition mods you suggested, I tried slowing the curve. Funny, the word curve doesn't really factor in since a 14 degree amount of advance in a dead straight line hardly appears like a curve...
RRR tried and tried to get me to delay the full advance until 3500 or so. I explained that when I eased up the rpms, THEN floored the car at 3500 or higher the car still detonated. I wrote MULTIPLE times that I felt that if his suggestions made sense to me, at 3500 (When in theory, the full advance would be in under RRRs advice) the car should have not knocked. This may be one of those things where two people are saying things that the other doesn't fully understand.
Again, whether I delayed the advance by way of distr. mods OR waiting until 3500 to floor it, I personally cannot see where the difference lies. There is no reason to insult anyone here either. If anyone cares to help me understand how or why I am wrong here, I'm willing to read. I'm not claiming to be the master of anything. I'm willing to admit where i am wrong.
These internet forums are voluntary. If someone reads my advice on something and decides to go another route, I don't continue to respond to the thread with..."Well, if you would have just done it MY way..." I figure that these threads are a guide to be used, not a recipe carved in stone.
Finally, I am not totally sold on a cam swap just yet. The Lunati was tried as a means to stop a detonation problem and it didn't work out. No biggie, that is life. Its not as if I raided the orphanage fund to buy these parts.
I am considering opening up the valve lash a bit to make the engine see "Less" cam. I might also advance the cam 4 degrees. These 2 moves may shift the power band a bit lower and soften up some of the bite. In reality, I shouldn't have wrote that the cam makes the car shake a bunch. It was an exaggeration. It shakes in comparison to what I'd prefer. No, I'm not looking for a totally smooth idle either. I just want something a bit more street friendly.
Click to expand...
 
Frankenduster said:
RRR tried and tried to get me to delay the full advance until 3500 or so.
Click to expand...

Once again, it's not about delaying anything. I think the only thing you'll understand is a ***** slap and I'm not sure you'll get that.
 
Frankenduster said:
Read this again.

93 octane? I have 91 here. 2 points does make a difference.
11.5 with a more aggresive cam? Sorta sounds like a wash to me compared to mine.
I was at 11.0 using 91 octane.
Click to expand...
'

I'll play a little devil's advocate too...you've seen other folks on here with greater cranking pressure (which is every bit as important as mechanical compression ratio) than you and can run with the same pump swill you are. There was another with locked out timing @ 35*, and his didn't detonate either. The difference among those combos may be a wash, but there's something amiss in your build...it's also a different engine than he's running.

I'm somewhat relieved that it went back together and doesn't detonate now, but you said yourself it needs to be dialed in again. As far as the timing comments between you and Rob, he also suggested limiting your timing amount, as well as messing with the "curve"; on that, yes, although it's a graphed straight line most of the time, it's still considered a curve...would you rather turn terminology accepted for 50+ years into a timing "line"?...also take into consideration, vacuum referenced timing alters that "line" based on engine demand...changes it to a curve-if you use a vacuum can, that is. OK, getting back on point here, I don't recall because this thread has become convoluted, if you did indeed limit your timing to 30-32* as was suggested...only that you changed your springs, and altered your timing rate, but I also don't recall seeing your effective timing mapped out in a document or in a thread.

It was suggested 20* initial, due to the rather large cam, and limited to 30-32*, which would mean you'd only have an effective timing range of 10-12*...did you ever actually limit it? IIRC, you were pushing 35* total timing, and regardless of where it comes in-2200 or 3500, or even 4000 rpm, those 3* may've made the difference between rattling, or not.

...I dunno man...I'm about to say hell with it, and quit commenting altogether because I'm clearly not providing anything value added.
 
I don't think anyone is able to add anything constructive at this point because it is not getting through.
 
You can lead a horse to water but you can't force it to drink....

Applies well here
 
Oh well. Not our money being flushed away...
 
to the thread owner:

2 things.

1. please please please verify no vacuum leaks. this means getting the documentation for your carb and knowing exactly what each and every vacuum connection is, what is is for, what you should use, what you are not using, what should be capped off if not used.

2. here is a pdf file. click on instructions about 2/3 way down. on the instructions tab you will see a link for a pdf you can view. (RRR dont go here. i know you dont like msd). it's instructions for installing a distributor that has ample explanations of advance curves, springs etc. study how it all works. understand what is meant by limiting total advance, setting initial advance, and how the springs can be changed to slow down or speed up when you are "all in"
http://www.msdignition.com/Products...hrysler_383-400_Ready_to_Run_Distributor.aspx

i'd also recommend visiting other sites or getting a book about distributor curves etc.
 
I just cant keep myself away from this thread, no matter how hard i try.
 
RustyRatRod said:
You've never had any of your distributors apart to limit the advance. Not one. You think we're talking about the springs and we are not. You cannot half *** this stuff. You have to disassemble the distributor and weld up at least one of the advance slots to limit the total amount of advance. The reason is because the engine requires so much initial timing that without limiting the total, you will have dialed in too much total from having so much initial. You've never done that. You're doing it wrong.
Click to expand...


Sorry Rob, but you may not be remembering this right.
The 2 MP distributors that I have here are essentially Mallory distributors. welding up the slots isn't necessary on these 2. The baseplates have Torx screws and slots that allow adjustment to the total advance the distributor can have. At the wide open setting, it can have as much as 28 degrees of advance. If I were to set the initial at 12*, it would top out at 40*. If I closed the slot, the total advance is zero. If I set the initial to 12, the total would be 12 since there is no movement of the baseplate at that setting. THIS is where the Mallory tuning kit came into play. I wrote about this in September before I threw in the towel and pulled the heads. From 2004 until last year, the distributor advance was limited to approx 13-14 degrees. During this time I ran the timing at 17* initial and approx 30-31 total. This was by way of the adjustment of the baseplate. The Mallory tuning kit came with different width plastic keys/guages that were labled as to the effective advance that they would allow. The thinnest key/guage was 14. The kit also came with several pairs of springs. I took the heaviest springs in the kit and put them in both distributors. The result? They delayed the full advance about 400 rpms later than before. As was, the "curve" began immediately off idle and was all in by 1900-2000 rpms. The stiffer springs delayed the "all-in" until about 2400 rpms. on test drives, the car responded the same as before. I considered distributor tuning to be ineffective, so I moved on with another angle.
Consider my reasoning. I had over 190 psi cranking compression and 91 octane CA gas. I was around 11.0 to one with meager quench. I took the advice offered regarding cam swaps, colder plugs, researching vacuum leaks and distributor tuning. I installed an Air/Fuel guage and found that I was not running lean. All the while I swear I heard detonation no matter what I tried.
 
txstang84 said:
'
I don't recall if you did indeed limit your timing to 30-32* as was suggested...only that you changed your springs, and altered your timing rate, but I also don't recall seeing your effective timing mapped out in a document or in a thread.

It was suggested 20* initial, due to the rather large cam, and limited to 30-32*, which would mean you'd only have an effective timing range of 10-12*...did you ever actually limit it? IIRC, you were pushing 35* total timing, and regardless of where it comes in-2200 or 3500, or even 4000 rpm, those 3* may've made the difference between rattling, or not.

...I dunno man...I'm about to say hell with it, and quit commenting altogether because I'm clearly not providing anything value added.
Click to expand...

Don't duck out yet. Things are not as bleak as some may think.

RRR has forgotten that I did follow the advice to tune the distributor. It wasn't as if I wanted to tear the engine down just for fun.
As stated in my last post, I have slowed down the advance curve. I have limited it as well. It made no difference. On the first test drive after the Lunati cam break-in, I had the timing set to where I had it with the 292/509 cam: 17 initial & 31 total. NO vacuum advance. The car knocked at WOT. I almost **** a brick. The cam was supposed to make things better, right? I pulled the car over and (Without a timing light handy) clocked the distributor to retard the timing a few degrees. I drove the car again and found that it still knocked at WOT. I pulled over a 2nd time and retarded the timing even more. At this point I had to crank up the idle speed because it would not stay running. This was all for testing purposes, by the way. Well, the 2nd adjustment resulted in crappy low speed performance, mediocre mid range and top end. NO knocking though. At home I put a timing light on it. 6 initial and 20 total. The car did NOT detonate on 20 degrees of total/ "all-in" timing. I obviously wouldn't be satisfied with that, nor would I drive the car around that way thinking that I was finished dialing it in. I was experimenting to see where the limits were.
Again, If I messed up along the way, I'm willing to face it. I think that I covered the bases well and ended up where I am now.
Maybe I am being too picky in what I want from the car. If all I cared about was getting in it and putting my right foot to the floor, then the car is the quickest and fastest thing I've ever driven. It is reliable. It actually gets decent mileage. It will outhandle 75% of the Mopars on the road. The brakes are nearly as good as a new car.
The car doesn't knock now and for that, I'm quite happy. I'm the type of guy that always sees room for improvement though. There is no urgency for any changes at this point, I just like the idea of having a smoother running, smoother idling engine that is a bit more responsive at freeway speeds.
Maybe many guys here get there cars 3/4 way finished and are happy with that. Maybe these guys never post here about their blunders or missteps for fear of looking human. I'm not built that way. If my mistakes can help someone, I'm willing to share them.
 
Just reread this thread. This is the first I've heard you played with the timing....
 
he did before...I think it occupied somewhere between pages 4-7...but I'm not here to start a **** storm. But, as I mentioned above, I'm not so sure my offerings are of any value, therefore nigh pointless to type anything new. Besides, he already achieved no detonation.
 
I see the spring part but not the limiting... must be blind
 
So, why not get a smaller cam that will give you a smoother ride. Call up a custom cam builder to build you a custom grind that'll bleed off some compression to give you the same dynamic cr you're at now.
 
This may minutely help or may not.I read many pages back that plug gap was .035. If you have an aftermarket ignition I would think you could open up the gap another .010. My stroker loves it.
 
I've just been lurking on this one for a while. Here's what I see as the indicator of the solution that was, in fact, brushed aside:
"Well, the 2nd adjustment resulted in crappy low speed performance, mediocre mid range and top end. NO knocking though. At home I put a timing light on it. 6 initial and 20 total. The car did NOT detonate on 20 degrees of total/ "all-in" timing."

If it didn't knock that way, you could have lightened the weights (as I suggested) and reset the timing for a higher initial, then retuned the carb, and been done. you were that close. Once I saw you were ignoring that, I figured it's not worth trying anymore. You wanted to spend more, port the heads, etc etc etc. I'm glad you like the way it runs now - but you were <> close to solving it without additional expense.
 
moper said:
I've just been lurking on this one for a while.

You could have lightened the weights (as I suggested) and reset the timing for a higher initial, then retuned the carb, and been done. you were that close. Once I saw you were ignoring that, I figured it's not worth trying anymore. You wanted to spend more, port the heads, etc etc etc. I'm glad you like the way it runs now - but you were <> close to solving it without additional expense.
Click to expand...

I read this and wondered if you left out something.
If I set the initial to anything less than 16 degrees, the idle suffered. If I ran the total up to around 30 degrees, the car knocked. I suppose that I may have been able to run the timing curve locked out but at what point would I set it ?

As with before, RRR has refused to respond to the question I asked several other times. He wants to bash me for not following advice but when I ask for clarification, he has nothing to say.
Regardless, the engine no longer detonates. Now I'm on to tuning and making the car a bit more "user friendly" for road trips. This includes quieter mufflers for sure!
 
You must log in or register to reply here.
-

Back
Top