Tuning with jets, Power valves and an O2 guage

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I would have to guess you can't get 93 octane ( that's what I use and can get easily here ) and your stuck with 91.
If you had to guesstimate your cranking pressure where are you p.s.i. wise?
Did you talk over build/selection with a builder/Lunati?
Are your Eddy's closed or open chamber?
Are you running vacuum advance on top of mechanical or just mechanical?
Are you using timing tape or a gun with dial +/-
I like the vacuum leak thought, but if your sure that's out of play lets move on.
I take it with your RPM drop you have an auto trans?
What was you "old" cams specs that seemed to run less det?
10.7 for your static comp ratio should be no problem with the right complimenting components, I'm curious as to what your dynamic comp. ratio is.
 
It sounds like it is in the timing curve. You do not mention curving any of the distributors you tried. Most distributors will have too much total with enough initial to run well. If you have not limited any of the distributors total advance curves that you've tried, I think that's where the problem may be.
 
ray426 said:
What kind of spark plugs are you running? I have Champion RC9YC plugs gapped @ .038 How do they read? I don't know. The 2" headers make it a hand burning experience if I wanted to check them after a WOT run. Are they fouled? No, they are actually cleaner that they ever were with the old cam. I am going through a similar problem with the 383 in my Road Runner. The problem ended up being a vacuum leak in the intake valley pan. Interesting. Maybe I'll recheck mine. Recheck yours carefully. Does your vacuum guage hold steady at idle or is it moving slightly around?
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The guage waivers a bit, but not too bad. I expect that with the lope of the cam. It is about as steady as it was with the 509 cam. The 750 carb gave the highest vacuum numbers, also the steadiest.
 
BB73Challenger said:
I would have to guess you can't get 93 octane ( that's what I use and can get easily here ) and your stuck with 91.
If you had to guesstimate your cranking pressure where are you p.s.i. wise?
Did you talk over build/selection with a builder/Lunati?
Are your Eddy's closed or open chamber?
Are you running vacuum advance on top of mechanical or just mechanical?
Are you using timing tape or a gun with dial +/-
I like the vacuum leak thought, but if your sure that's out of play lets move on.
I take it with your RPM drop you have an auto trans?
What was you "old" cams specs that seemed to run less det?
10.7 for your static comp ratio should be no problem with the right complimenting components, I'm curious as to what your dynamic comp. ratio is.
Click to expand...

* I tested cranking compression on only one hole, cyl # 6. It was 188 before with the '509 cam. It tested 173 with this one.
*The cam suggestion came from a FABO member. I was asking for help on how to stop the detonation with the engine and the Lunati looked like a winner. I never spoke with a Lunati tech about it.
* The heads are the 84 cc closed chamber versions, unported. My pistons are .017 in the hole and the head gasket is .039. The calculated comp is 10.73 with .056 quench .
* I was running vacuum advance with the 509 cam but plugged it to stop detonation. It is still plugged.
* I am using a dial back timing light.
* 727 trans with a 9 3/4 converter. Stall is unknown.
* The old cam was the Mopar 292/509. The duration @ .050 is believed to be around 248. I tried using 1.6 rockers, thinking the additional lift might cut down on the detonation. It did not.
* My old dynamic with the '509 cam was in the upper 8 range. The dynamic now is around 8.13.
 
RustyRatRod said:
It sounds like it is in the timing curve. You do not mention curving any of the distributors you tried. Most distributors will have too much total with enough initial to run well. If you have not limited any of the distributors total advance curves that you've tried, I think that's where the problem may be.
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I looked through my parts shed and found another RB distributor similar to mine. It has the same Mopar Performance guts that are noticeably different than the stock distributors. These MP ones have an adjustable baseplate. It allows from total advance lockout to around 25 degrees of centrifugal advance. The springs feel pretty weak in both. This tells me that they probably advance quickly, maybe too fast. With the timing light flashing, I bumped from a 1000 idle to around 1600-1800 and the advance already jumped several degrees.
Correct me if my logic is flawed, but it seems an overly fast advance would result in part throttle knock. If I am running at 2500 rpm (part throttle, NO knocking) with the full advance already all in, why would it it knock once I floor it?
 
A guy on Moparts mentioned a buddy had a similar problem with a 496. He was using the same Fel-Pro head gaskets that I have and the Fire-Ring that surrounds the bores had burned! The guy apparantly found that the fire ring was slighly smaller than the size of the combustion chamber and had melted at least one ring.
I just went out and laid a Fel Pro 1009 on a the deck of a .030 over 440 short block. I can see that once the gasket is compressed, this is possible. I don't know exactly how this could translate into detonation, but for that guy, his fix was to use a gasket with a bigger bore diameter.

http://www.summitracing.com/parts/edl-7325

This one has almost the same compressed thickness, but a bigger bore size. I don't know how a burned "fire-ring" translates to detonation except that it is a hot spot igniting in the chamber? How do you know if it is an issue without a teardown? I'm not against pulling the heads, I'm just getting tired of chasing dead ends!
 
Frankenduster said:
I looked through my parts shed and found another RB distributor similar to mine. It has the same Mopar Performance guts that are noticeably different than the stock distributors. These MP ones have an adjustable baseplate. It allows from total advance lockout to around 25 degrees of centrifugal advance. The springs feel pretty weak in both. This tells me that they probably advance quickly, maybe too fast. With the timing light flashing, I bumped from a 1000 idle to around 1600-1800 and the advance already jumped several degrees.
Correct me if my logic is flawed, but it seems an overly fast advance would result in part throttle knock. If I am running at 2500 rpm (part throttle, NO knocking) with the full advance already all in, why would it it knock once I floor it?
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Well, I think I will back out of it. I am in complete disagreement that a fuel issue is creating your problem, so I don't need to participate in this one. I know fuel issues can cause this to some degree, but not to the degree you're experiencing, IMO. Since you're working on the fuel here, I don't want to get you off track.
 
I see no mechanical reason why it would ping given the specs you list. Also - the fire ring deal - I would say the ring burnt as an affect, and replacing it with a larger bore dropped the compression enough to fix it. But that's a guess on my part.
What is the rpms where the centrifical advance starts and when does it end? With an advance light you should be able to find that out.
I'm with RAT on this - What I would suggest is you rethink the timing curve and use the 750 as the "base carb" for this as I trust a Holley far more than Demon to stay consistent. Drop the initial down to 12° and find a stiffer spring to slow the advance. You can also lighten the weights but I'd try to find a stock "light" spring from a factory stock type distributor. If you can't find any let me know and I can mail you one. I have some of them and some Mallory ones that might work too. I'd like to see the timing curve start from a lower number, and come in more slowly, like starting at 1500 and not coming all in until 3K. The "two light" springs start it early and it's all in early.
 
Dwayne Porter suggested using a light spring and a heavy one. His thinking when I spoke to him 2 months ago was that this would give some advance early and fast then the rest would come in slower.
 
RustyRatRod said:
Well, I think I will back out of it. I am in complete disagreement that a fuel issue is creating your problem, so I don't need to participate in this one. I know fuel issues can cause this to some degree, but not to the degree you're experiencing, IMO. Since you're working on the fuel here, I don't want to get you off track.
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I was working on everything, not just the fuel. I have tried everything I know plus several things suggested by others. I am not convinced of anything yet because the car still knocks!
I can't really get off track because I haven't made any improvements yet.
 
IMO, unless you limit the amount of advance and delay when it all comes in (which I see no evidence of you doing yet) I don't think you will make any headway now. I think the cam change certainly went the right way with cylinder pressure, don't you? I've certainly seen engines with around the same cranking pressure run on pump gas. I think yours can too. You're just gonna have to find the right combination. I wish we were closer. I'd ride over and help you with it.
 
Here is where things get really weird. I have no way to explain it either.

I did a compression check an hour ago. I duplicated the conditions I used during the other times beforehand with the '509 cam in place. Cold engine with all the plugs out.

509 cam:

#1: 188 #2: 188
#3: 185 #4: 190
#5: 188 #6: 189
#7: 185 #7: 190

Lunati cam:

#1: 190 #2: 190
#3: 189 #4: 190
#5: 192 #6: 195
#7: 190 #8: 192

Yeah, I was surprised too. I mentioned earlier that I had tested #6 and recorded a 173 number. It was a typo. It was #5 and I have NO idea why the number came in so low. The engine was still warm though from a test drive. The engine knocked with an average of 188 per cylinder with the '509 cam and now it is 191.
I checked these numbers twice today because I simply wasn't willing to believe it. I was really hoping for there to be something else to fix or change, but I am back to where I was before: Too much compression for the available pump octane. I might run up and get a jug of 110 octane leaded and see if the knocking stops with that. I'll pull the O2 sensor to avoid contamination of course.
 
Boy that's a bummer, I wouldn't try a thicker head gasket, as you say your at about .056" on quench and don't want to get carried away.
190 psi is up there for pump gas engine ( I know, you know that )
Yeah, guys have made it work, with fuel injection, spot on quench, polished components, yada yada yada.
I don't buy into the current head gasket being your detonation problem right now ( could be A problem if it does over hang )

So for now, I like the thought of kicking that octane up to see where you are.
Then if you do a lot of driving you may be stuck pulling MORE timing out of it
 
I'm just sitting here on the couch. From here I can see the car sitting out there in the workshop. I'm happy to see such consistant numbers in compression but ......
I see conflicting opinions on running a thicker head gasket to lower compression. Smart guys are on both sides of the arguement. I actually tried this back in 2006 when I was dealing with the same problem. I went with Cometic .060 gaskets and changed to a Comp XE285HL cam at the same time. This was in the Spring of 2006. I keep a notebook of what I do to the car, but I wasn't very specific about how the car ran afterwards. In a few pages, I wrote that the car ran great with NO detonation. I didn't do a compression check afterwards.
 
This morning I went out to the car again. There has been a little collection of oil below the intake. Today was the second time I wiped it clean. Sorta odd, since this used to happen before with the 509 cam. I checked the intake bolts. I was able to turn them an additional 1/4 turn.
I went for a drive after rigging up a long hose and a fuel pressure guage. I was asked about the fuel pressure at WOT, this was the only way I could test it. I get 7-8 at idle, around 7 at cruise and at WOT it drops to about 5 but not below that. In my first 2 WOT runs, the engine DID NOT detonate! I was friggin happy, but cautious, I made 3 more WOT runs, but the detonation came back.
Along with the oil in the valley pan, I've also seen a thin film on each head between the valve covers and the intake. I don't know if oil is pushing up from the intake/head seals or if the valve covers are leaking there. The sides of both valve covers are wet across from the intake.
I'm going to change both valve cover gaskets. I'll surely look for any signs of leakage. I'm going to replace the valley pan too. I understand that even a drop of oil can cause detonation, so I want to make sure the oil stays out of the intake tract.
 
Yup - oil will make it ping. Are you certain there's no air in the cooling system?
 
Its a cross flow radiator. I have the water/coolant about 1& 1/2" from the top.

I got the car back together but the RH valve cover leaks. I'm using cast aluminum valve covers but I sure have spotty luck with gaskets!
 
Frankenduster said:
This morning I went out to the car again. There has been a little collection of oil below the intake. Today was the second time I wiped it clean. Sorta odd, since this used to happen before with the 509 cam. I checked the intake bolts. I was able to turn them an additional 1/4 turn.
I went for a drive after rigging up a long hose and a fuel pressure guage. I was asked about the fuel pressure at WOT, this was the only way I could test it. I get 7-8 at idle, around 7 at cruise and at WOT it drops to about 5 but not below that. In my first 2 WOT runs, the engine DID NOT detonate! I was friggin happy, but cautious, I made 3 more WOT runs, but the detonation came back.
Along with the oil in the valley pan, I've also seen a thin film on each head between the valve covers and the intake. I don't know if oil is pushing up from the intake/head seals or if the valve covers are leaking there. The sides of both valve covers are wet across from the intake.
I'm going to change both valve cover gaskets. I'll surely look for any signs of leakage. I'm going to replace the valley pan too. I understand that even a drop of oil can cause detonation, so I want to make sure the oil stays out of the intake tract.
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This is problem I had. My 383 was sucking oil through the valley pan. And like Moper said even a small amount of oil will cause detonation. Thats why I asked about reading the plugs, try to find signs of it burning oil.
 
Do you have gaskets on the valley pan or not? You're supposed to run the "gasket sammich" with the valley pan when using aluminum intake and or heads. Otherwise, it will leak.
 
..... And RRR is BACK!
Thanks, Rob. When I pulled the valley pan off a few weeks ago, I saw that I only had the gaskets on the intake side. I read a few threads on the issue of using the paper gaskets and found that most people seem to skip them. Because of this, I put the valley pan on the engine without any of the paper gaskets, just gaskacinch around the ports. Yeah, I found oil in the intake ports of the heads. I found oil film on the intake manifold ports. Both sides of the valley pan ports were wet with oil.
THIS time I put the paper gaskets on both sides of the valley pan and cranked down the intake. I wanted to drive the car first thing this morning but the NEW valve cover gaskets leaked. THIS is an interesting story:

Yesterday I decided to change the valve cover gaskets since both had a small leak at the rear. I usually use the hard fibrous black gaskets, but all I had here was some rubber ones. I installed them with a thin layer of RTV on the covers to hold the gaskets still. This morning I came out to see both sides were still leaking. Looking up from the bottom, I could see the underside of each valve cover overhung the head by 1/4". The gaskets hung out at least 1/8" This is because the Mopar Performance cast aluminum valve covers are over 1/4" wider than the gasket rail on the Edelbrock heads. This isn't normally a problem when the hard gaskets are used, but the soft rubber ones distorted and allowed leaks. I guess now that I know this, I can use rubber gaskets as long as I made sure to hold the valve covers UP toward the intake to make sure the lower section of the valve cover makes FULL contact with the gasket rail on the head.
I removed the rubber gaskets, the RTV and cleaned the VCs again, then RTV'd on the better fibrous gaskets. I got busy with other things today and ran out of time. I may get the valve covers on tomorrow. If I do, I'll report my findings, good or bad.
 
Here's a trick... Get all the oil and grease (including oil from your skin) and take 3M yelow weatherstrip adhesive and glue the gasket to the cover. I used the same stock cork gaskets on my old 440 from 1995-2003. Checked the valves 3 times a summer and they never leaked. Did it when I was a mechanic, they never leaked or moved and as long as you don't overtorque you're golden.
 
I got called to a job that is out of town, so I haven't been able to work on the car. I hope to spina wrench or two on Friday.
 
desmo900 said:
Can you clarify?
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I'm talking about the valve covers... Not the intake. I don't use paper gaskets and do use a little ultra grey or ultra black around the ports. I've never had an issue that way.
 
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