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

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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!

No, I am done giving you advice after the nasty PM I got from you. You can wallow in it far as I am concerned.
 
So I get insulted by you in this thread, respond back to you in private, yet the end result is more unfavorable posts and no explaination of your theory?
Got it.
 
Have you looked into running vacuum advance hooked to the manifold?

This will give you favorably high initial timing and will "lessen" or drop the advance down to where it runs only on your "mechanical curve" under high load.

The result is good low rpm part throttle response, good idle and good cruise power.
The other result is when you have more fuel-air in there under mid to full throttle when the mixture is "burning faster" actually just more filling cylinders resulting in less needed timing, you have less timing which prevents knock under load.

You will probably like it if you get it dialed in using that method.

There are a number of good threads here regarding using manifold vacuum and alternately "port" vacuum. Depending on the curve and build of the engine, both have their place. There are lots of debates as well but many have had good results with manifold vacuum advance. Essentially running manifold vac advance is like having a crude MAP sensor on your advance system.

There are a few tricks or setup details to get this to jive with your engine needs. Your mechanical curve needs to be right for the engine and then you add in your vacuum advance for idle quality and part throttle driving. You must limit your vacuum advance "distance" or total amount and you must adjust the spring pressure in the vac can on the dist so it will respond favorably to your manifold pressure response from throttle input and engine load. You basically create two curves. One mechanical and one based on MAP. They are directly related because they depend on each other to yield total timing at a given rpm / engine load.

Some of the EFI guys on this site can shed more light on the need for mixing MAP inputs and mechanical or predetermined curves combined to yield favorable timing events under varying conditions.






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!
 
So I get insulted by you in this thread, respond back to you in private, yet the end result is more unfavorable posts and no explaination of your theory?
Got it.

If that's all that you see, then yeah, I guess so.
 
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 ?

Your experiments yielded a solution that did not have any audible issues: 6° initial, and 14° centrifugal. You said it didn't ping. Then you chose to have the heads ported and run special head gaskets. All you needed was to give the distributor some beyond-the-norm effort and the carb needed some further tuning to get rid of your idle issue. This could have been done without ever even changing the cam judging by the lower pressure from the first cam.

The solution was giving it more initial and less centrifical and slowing the rate of advance until you found what worked best, retuning the carb as you changed the timing. It would have taken a lot of finely detailed work and little cash for carb parts and gas. In terms of where to set it - there's over ten pages (and that's just on this board - not including the others you have threads on) of ideas, timing adjustment, setting, and rate of advance details, carb tuning details, and competing mechanical concepts helpful people added. Nothing has been left out.
 
If it is the belief of some that I could have "tuned" my way out of the knocking, that is an opinion that may or may not be true. I enjoy working on the cars but it is not the only thing that I do. Maybe by starting these threads I give off a sense of "urgency". Often times I see online Q & A a matter of conversation that may not ever go anywhere.
This car will never be my daily transportation. It is a hobby car that will never be raced on a dragstrip for money. There is no financial gain or loss due to being a 1/2 second slower or faster than the next guy.
I just enjoy tinkering on this and my other 8 cars and trucks. The thicker head gaskets may have been the easy way out of knocking. Some of the tuning suggestions I've read here and elsewhere are made by seasoned professionals with many years of experience. Frankly, the methods are often miles over my head. I've done what I can with my limited time and skills. I've wished that some of the smart guys were located close by, but it seems that Northern CA isn't a hot-bed of Mopar Tuner guys.
The car no longer knocks. That was the main goal. Looking back in this thread and others can show what to do and what NOT to do in future builds.
 
Have you looked into running vacuum advance hooked to the manifold?

This will give you favorably high initial timing and will "lessen" or drop the advance down to where it runs only on your "mechanical curve" under high load.

The result is good low rpm part throttle response, good idle and good cruise power.
The other result is when you have more fuel-air in there under mid to full throttle when the mixture is "burning faster" actually just more filling cylinders resulting in less needed timing, you have less timing which prevents knock under load.

You will probably like it if you get it dialed in using that method.

There are a number of good threads here regarding using manifold vacuum and alternately "port" vacuum. Depending on the curve and build of the engine, both have their place. There are lots of debates as well but many have had good results with manifold vacuum advance. Essentially running manifold vac advance is like having a crude MAP sensor on your advance system.

There are a few tricks or setup details to get this to jive with your engine needs. Your mechanical curve needs to be right for the engine and then you add in your vacuum advance for idle quality and part throttle driving. You must limit your vacuum advance "distance" or total amount and you must adjust the spring pressure in the vac can on the dist so it will respond favorably to your manifold pressure response from throttle input and engine load. You basically create two curves. One mechanical and one based on MAP. They are directly related because they depend on each other to yield total timing at a given rpm / engine load.

Some of the EFI guys on this site can shed more light on the need for mixing MAP inputs and mechanical or predetermined curves combined to yield favorable timing events under varying conditions.


There are also issues with running direct MAP vacuum to the distributor, especially at idle. When out of gear, the vacuum is higher, therefore, the idle artificially increased, when placed in gear, the vacuum drops (i.e., closer to 0" mercury) therefore the timing drops, sometimes several degrees. This will often cause a rather large rpm drop when going into gear, and therefore exacerbate issues caused by timing instability. When you toss a lopey cam in the mix, this only makes things worse as vacuum signal is erratic or at least not completely steady. I found this out the hard way when I accidentally connected my vacuum advance to the wrong port on my carb. I encountered a 300rpm drop simply by putting the car in gear. Disconnecting and plugging the vacuum removed that problem altogether. I'm pretty sure there are at least a few others in here who would affirm that, if used, vacuum advance needs to be ported from a "timed" source.
 
Well sir, I'm glad you're satisfied with your results. At least you can drive it.
 
I hear ya. A more modified engine may benefit and be more consistent from the vacuum port which is exposed by the throttle blade just off idle rather than manifold vacuum.

There are also issues with running direct MAP vacuum to the distributor, especially at idle. When out of gear, the vacuum is higher, therefore, the idle artificially increased, when placed in gear, the vacuum drops (i.e., closer to 0" mercury) therefore the timing drops, sometimes several degrees. This will often cause a rather large rpm drop when going into gear, and therefore exacerbate issues caused by timing instability. When you toss a lopey cam in the mix, this only makes things worse as vacuum signal is erratic or at least not completely steady. I found this out the hard way when I accidentally connected my vacuum advance to the wrong port on my carb. I encountered a 300rpm drop simply by putting the car in gear. Disconnecting and plugging the vacuum removed that problem altogether. I'm pretty sure there are at least a few others in here who would affirm that, if used, vacuum advance needs to be ported from a "timed" source.
 
Today I finally checked the cranking compression.
Before with the Fel Pro .039 head gaskets and nearly 11.0 to 1 compression I was at an average of 191. Now with the 10.07 to 1 ratio my average went down to around 160 !
I checked every hole twice. I had the battery charger on the battery to maintain an even charge. I was amazed that the cranking numbers dropped off so much compared to before.
I decided to start playing with the lash to see what effect it had on the cranking psi. Wow, what an eye opener! The Hot Lash specs are .020 IN and .022 EX. I normally set them .006 tighter (.014 & .016) when cold to account for the expansion of the aluminum heads. This time I set them cold to .022 IN and .024 EX. That is .008 wider spec. This raised the cranking compression to an average of 170.
I haven't driven the car yet. I figure I'd see how it feels after the lash adjustment. If it feels more responsive down low I might leave it as is as long as it isn't knocking.
I was really surprised to see what an effect the lash really had on the cranking compression
 
He may have. Sometimes I get so caught up in a project or an idea and miss things.
 
How far can you open the lash before you miss the opening ramp and stick the edge of the lifter into the cam flank?
 
Cam flank.... there is a term I hear 500 times a day. ( Not )
Huh? You really think I went too far? Every MP solid cam in the catalog calls for a 28/32 lash. Maybe oranges to mandarins but do you think going .008 wider is going to cause an early failure?
I'll call Lunati tomorrow regardless.
 
Different cams require different lash...it's no secret that opening lash on a solid cam will effectively lower the duration, but opening up the lash too much will, as Jim said, allow the edge of the lifter to basically crash into the ramp and eat the cam.
 
I called the Lunati tech line today. "Mike" said that the most he would advise is .004 over the published .020 & .022 spec. He didn't elaborate on why, just that said not to go beyond that. It was nearing the end of their business hours so I figure that he wanted to cut the call short.
I'm not looking to shred the lobes off here. I'm curious as to how the Mopar Performance solid cams run a .028 & .032 lash without problems. Maybe they have less agressive ramps or something?
I'm still considering the 4 degree cam advance. There seems to be no downside since my piston to valve clearance was over .200 with the .039 head gasket and .236 with the thicker Cometics. I may still run a bit more lash, not sure.
 
The close lash and wide lash have different opening ramp design.

You'll be fine with .004" extra lash as you'll still be on the opening ramp. Give it a try.
 
Today I advanced the cam 4 degrees. I did a cranking comp. test on cyl # 4 to see what effect it had. It went from 160 to 165. This stuff continues to surprise me as I expected to see a bigger increase.
I am going to button up the car with the lash set to the correct specs and drive the car. If the 4 degree bump made enough differnce in the part throttle driveability, I'll leave it as is. If not, I'll try opening up the lash to the limit. I sorta feel like these moves are a crutch like some of the other shortcuts I have done. I may still be looking at another cam swap.
 
I finished up today. The timing was reset to account for the 4 degree cam advance. It fired up quickly and once it was warmed up, it seemed to idle smoother. I did go back and relash the LH bank to the spec on the cam card. I figure it makes more sense to do one change at a time so I'll know exactly what effect each change has. It was raining this afternoon so I have yet to road test it.
I didn't put a vacuum guage on it. I just didn't think of it until I started writing this just now. The idle speed went up about 100 rpms.
Along with trying to make the car more civilized, I'm still working on the Air/Fuel ratio tuning. Now that I have the MP Chrome ECU back in I'll probably go back to using vacuum advance. I'm sure that will improve the burn cycle at idle and cruise speeds
 
Thanks Sledge, It is looking like things are headed the right way.
 
Four months and the car is still running great. At WOT this sucker is faster than ever with NO detonation at all.
I've driven on road trips and around town. Idling, High RPMs, freeway cruising...NO knocking.
I'm still not 100% satisfied though. The cam and converter are great for WOT blasts but not so much for the type of driving that I prefer: Cornering and freeway cruising. The car feels lazy in OD at freeway speeds even with the 3.91 gear. I attribute this to the big cam and loose converter. I had a feeling that a cam this big may be too much for me but I was so caught up in trying to stop the detonation, I was ready to try many things.
I'm planning on calling a few cam companies and engine builders to spec out a better cam for my needs. Andy Finkbiener likes the MP 528 solid with 1.6 rocker arms. He says that it is a great street cam for people that want a decent idle & vacuum as well as great torque. I need instant throttle response when entering and exiting corners and the long duration of the Lunati isn't right for me.
I will also be calling about getting a new, tighter torque converter. The slip of this 9 3/4" unit is a poor match for the street as well.
Thanks again, Greg
 
Update:

I'm still running the same Lunati cam but I have a MP 528 on my shelf ready to go in. I also bought another set of the Johnson EDM lifters and a Cloyes 3 bolt timing set.
I pulled the loose converter and sold it. Lenny at Ultimate Converter Concepts built a nice 11" converter that really transformed the car. I pulled the Gear Vendors and sold it to a guy in Tennessee. I had a new 3.55 ring and pinion installed in another 3rd member along with new clutches in the SG diff.
My motivation for the 528 cam swap is to obtain better low speed performance as compared to this Lunati cam. At WOT the car still runs like a raped ape but it idles rougher than I want and feels a bit soggy below 2000 rpms.
 
Update:

I'm still running the same Lunati cam but I have a MP 528 on my shelf ready to go in. I also bought another set of the Johnson EDM lifters and a Cloyes 3 bolt timing set.
I pulled the loose converter and sold it. Lenny at Ultimate Converter Concepts built a nice 11" converter that really transformed the car. I pulled the Gear Vendors and sold it to a guy in Tennessee. I had a new 3.55 ring and pinion installed in another 3rd member along with new clutches in the SG diff.
My motivation for the 528 cam swap is to obtain better low speed performance as compared to this Lunati cam. At WOT the car still runs like a raped ape but it idles rougher than I want and feels a bit soggy below 2000 rpms.

The converter was a great move, it puts things in perspective. Stock stuff modifed intelligently, smokes overboard purchases with no thought. I'm glad , you are finding a balance.( you don't do this often, it's a learning curve)...
 
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