493- 10.7 compression-detonation issue...NEW info inside.

[Kern Dog]

First up, thanks to all who have followed along and offered advice to me with the problems that I ahve been dealing with.
To REcap:
I'm having some detonation issues running my Charger 440/493 on California 91 octane fuel. The engine has NO detonation when running 110 octane leaded fuel. It is a 440 block .030 over, 4.15 stroke, 10.7 calculated compression with 84 cc Edelbrock aluminum heads, Performer RPM intake 850 Demon, TTI 2" headers. MP electronic ignition with a chrome ECU.
On the advice of several members, I did a cranking compression test. I recorded some abnormally high numbers and posted them here. Some members were surprised at the numbers, thinking that they seemed wrong.
I decided to make the switch to new adjustable roller rocker arms in the 1.6 ratio. I installed them on the left side first. Just for the heck of it, I decided to recheck the compression numbers. When I went to grab the hose and guage, I noticed this:

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The guage on the left STARTS at 30 PSI !! I never noticed it until now. What a rookie mistake!
I rechecked the compression numbers with the guage that starts at zero.

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Dwayne Porter was one guy that suggested that I try using another guage to see if I had made a mistake. Now that I am recording numbers closer to what is considered "streetable", I will finish the rocker install on the right side. I have new spark plugs and wires to install and a new 6 quart oil pan. For now I'm hoping to get it to run without spark knock. Later I will consider steps to increase the power.
Thanks again everyone.

 

[benno440]

sweet, good for you bud

 

[Sweet5ltr]

Nice numbers Greg. Still borderline though, unless you have a complete MSD/high energy ignition system to burn the fuel completely this is not much of an improvement; but better than none! I would look at a camshaft swap in the future.

 

[Kern Dog]

Another thing that I found impressive: The close spread in numbers with the new rocker arms. There is only a 3 PSI spread. The stock rocker arms had much more variance.
The switch to a different cam is still in the works. Ive been selling off some car parts to generate some cash.

 

[Ghosty]

Learning a lot from the various troubleshooting advice throughout your original thread. Glad to see you got it going in the right direction. What are other stroker guys saying your range should be roughly, for pump gas with your setup?

 

[Kern Dog]

What are other stroker guys saying your range should be roughly, for pump gas with your setup?

I can't recall seeing anyone else post up their cranking PSI numbers in a similar build.
Dwayne Porter was one that thought my numbers seemed higher than expected and he suspected a faulty guage. I read on another forum a guy with a mid 70s stock bore 440 with a '509 had 135 PSI readings. The 8.2 compression of the 70s big blocks surely figured into that low number.
I would LOVE to see what other FBBO members have as far as cranking compression numbers. The general guideline is that 190 is the upper limit on what you can run on pump gas. I am headed in the right direction here.
After I finish installing the right side rocker arms, I'll retest the PSI numbers and report back. I'm also going to retard the cam 4 degrees and see what it does to the PSI #s. I hope to see another 5 point drop. That might be enough to satisfy me for a while. Once the cold weather sets in, I'll probably make more changes. I want to have the heads ported and matched to the intake. I might even decide to go with a Cometic .027 MLS gasket to get back some quench. All of the talk of roller cams sounds cool, but I am still leaning toward a flat tappet. The idea of the new solids with the EDM type lifters that deliver pressurized oil directly to the cam lobes sounds interesting.

 

[lewtot184]

when you increased the rocker ratio did you check the springs for possible coil bind. all of the aftermarket adjustable rockers i've checked have a ratio that is higher than their rating.

 

[Kern Dog]

The springs are rated to .600 lift. Good point though. The valve covers are still off so I will check.
Thank you.

 

[Meep-Meep]

My 440 is at 190 PSI and 10.1:1 CR and it still won't run on pump 91 with the Eddy AFB and factory iron intake. Remember what I said about many factors contributing to detonation? Well, the factory 6 BBL is now installed, and with no other mods to the engine, it runs fine on pump 91 - and it's lean according to the O2 sensor. It only takes one cylinder to lower the bar on detonation resistance.

 

[lewtot184]

The springs are rated to .600 lift. Good point though. The valve covers are still off so I will check.
Thank you.

i'm not sure i'd take .600 as gospel. i've noticed some springs that the dampner will coil bind before the spring gets into coil bind. if its possible take a spring off and check it. also don't forget retainer to seal clearance. if the camshaft lift is rated for a 1.5 ratio rocker i'd use a 1.65 ratio as final net lift at the valve for measuring; just to be safe.

 

[68 Sport Satellite]

Interesting. Not knowing much about what affects detonation myself, I would have thought with CR in the 10's and running the aluminum heads that you would be fine since aluminum is supposed to let you run one full compression ratio higher. Shows how much I know. I am sure glad Meeps is helping me with my engine build!

 

[Kern Dog]

I am learning more about it as well. Here is a short recap of what I have learned recently:
SOME guys have been able to built engines that can run over 11.0 to 1 with aluminum heads if the engine has been built to maximize quench.
Quench allows an engine to run higher compression ratios without detonation. Higher compression makes more power UNTIL detonation occurs.
A camshaft with a LATER intake closing results in LOWER cranking compression. THIS can make an engine less likely to detonate.

 

[383man]

What are the cam specs ? I did not see them or did I just miss it. Your 493 seems close to my 493 build. I use Indy EZ heads with 10.6 comp asI had to use a dished piston because them heads are 75cc. I also use a Holley 850 DP and the Indy dual plane intake. Timing is 37 total all in my 1800 RPM. Mine runs fine on 92 pump as it has no ping at all. I dont see 91 around here as its 87,89,92 and 93. Ron

 

[Kern Dog]

What are the cam specs ? I did not see them or did I just miss it. Your 493 seems close to my 493 build. I use Indy EZ heads with 10.6 comp asI had to use a dished piston because them heads are 75cc. I also use a Holley 850 DP and the Indy dual plane intake. Timing is 37 total all in my 1800 RPM. Mine runs fine on 92 pump as it has no ping at all. I dont see 91 around here as its 87,89,92 and 93. Ron

Hello Ron,
I am using the MP 292/509 cam. Yeah...I'm aware of the fact that it is considered way too small for this engine. I have learned much more about cams and cylinder pressure, dynamic compression ratio and quench in the last 2 months from these forums and helpful membe. A cam swap is in the future. Here in CA, the octane options are 87, 89 and 91.

 

[Kern Dog]

I drove the car yesterday and noticed a few things...
It idles a bit smoother. Not sure if it was from the new spark plugs & wires. It also idled a bit lower. Power may have improved a bit but it was hard to tell with just a seat of the pants comparison. No knocking/detonation at all, but it was a 50-50 mix of 110 and 91. To make it a fair comparison, I'd need to run the tank down and then add just 91 pump premium.
I'm getting anxious though. The thought of being able to switch a few parts and gain 80 or more horsepower is really tempting. One member spoke of the MP .590 solid lifter cam, but he has it in a 451. I'm curious if it would have as much bite in an engine 42 cubes bigger. The Ford on the dyno at IQ52 had a 260 @ .050 roller cam and made ungodly amounts of power. I considered a roller but the expense keeps steering me back to a flat tappet stick. I've heard that some hydraulic roller lifters have problems with oiling and that some require bushing the lifter bores. This gets into removal of the engine and more down time. If I wanted to pull the engine, I'd just pull the pistons and have the combustion side milled or get new dished ones. Two reasons I haven't taken that route : Expense and that I dont want to pull the engine right now.
The Comp Cam XE294H has a 250/256 @ .050 and the lifts work out to .553/.558 with my 1.6 rockers. I looked at the Lunati site but their cams listed seem smaller than what Comp cams shows. I have yet to see any site with a separate section for the stroked engines. Several here have made it clear that this is no longer a 440 inch engine and that it needs a cam for the engine size it is now. I finally DO understand that. I will have to make it a point to call and specifically ask for someone that is able to help me choose the right cam for me. I suppose that a custom grind will cost more. Some have suggested a cam with 260 degrees or more @ .050 and more lift. I will relay this to whomever I get to speak with at Comp or Lunati.