Living with 10.8 compression on the street ??

[SwedCharger67]

...Last year I ran an ignition box that some here may have read about: The REV-N-NATOR. It was tested in Mopar Muscle last summer. The testing was performed by Dunnuck Racing. Kevin tested it against 3 other Mopar ECUs. The baseline was a replacement unit from Wells, then they used an orange box and a chrome unit. The Wells had a tendency to retard timing in the midrange, costing power. The Orange unit also had a pull back of timing, though less so. The Chrome box was the best of the first three. The Rev-n-nator unit has improved circuitry and has no hiccups in the curve. It made the most peak power and the most average power of all they tested...

One test I saw had the air-fuel ratio set wrong for the competing products while it was set spot-on for max power for the Rev-n-ator.

 

[RustyRatRod]

I like the good old Standard Ignition LX101. It's just as hot as the orange box but has no timing retard at any RPM. Of course depending on the application, you might want some timing retard.

 

[coloradodave]

Having just dealt with the 'pinging' problem, I'll throw my 2 cents in. I recurved my Mallory Electronic distributor, with vacuum advance, so that the curve starts at about 1300 RPM (my idle is 1,000). It then advances in a pretty straight line to 24* at 2,800 RPM. I use 12* initial and have adjusted the vacuum can to add 10*, on full manifold vacuum, not ported. Thus I have 46* total advance cruising down the road. If I bring the mechanical advance in sooner it pings on light and medium throttle. If I limit the mechanical and add more initial, same results. If I start the curve sooner, same results. This is with 91 octane CA gas, 10-1 compression and iron max wedge heads. Crossram and 500 CFM Edelbrock carbs with stock rods and jets. Street car with great throttle response and good manners. I pulled this distributor apart so many times making changes that I bet I can do it in my sleep. Hope this info helps.

 

[Kern Dog]

Dave... You are just right down the road from me! Hows life since the 65 Bypass has been completed?
Thanks for the help everyone. I drove the car almost 175 miles today. Without any vacuum advance, it had zero part throttle detonation. It did once I got deeper into the secondaries . I was running straight 91 octane from Chevron.
To all still chiming in...I have read what everyone has posted. I appreciate every suggestion and I absolutely mean NO disrespect to anyone. I understand what it is like to give advice and see people do something different. The whole issue of quench and high compression ratios is a little hard to grasp. I am not saying that I don't believe it, just that it seems odd. The claims that quench actually increasesdetonanation resistance with a higher compression ratio seems amazing. With this logic, I should run a thinner head gasket and a bigger cam and I'd be okay? PLEASE forgive my skepticism. It really seems to good to be true. I was already leaning toward a bigger cam when Ken Hensley suggested the smaller one. I should have stood my ground, thanked him for his advice and called someone else.
I liked the performance and sound of the XE285HL Comp. It was 285 I, 297 E with .545 lift I & E. I'd need to know more about the specs to learn if it would improve things. I ran one in 2006 but had Cometic .060 head gaskets in at the same time.

 

[RustyRatRod]

Yup, you're catchin on. Tell you what you can do. Go to the United Engine compression calculator here:

http://www.kb-silvolite.com/calc.php?action=comp

Enter all the info, including the dynamic compression calculator at the bottom. Get the dynamic compression under 8.5 and you're good. I like it even under 8.0 because then you know it will not detonate, regardless of outside conditions. You'll notice the later you make the intake valve closing, the more dynamic compression goes down, because you're bleeding off more cylinder pressure. If you ger dynamic under 8.1, you will never spark knock, because you have quench on your side, too. Quench causes turbulance and that makes for a more complete burn. IQ52 knows a lot more about that I do. Maybe he'll chime back in. But yes, reduce your quench to .035" and use a cam with later intake closing (probably a larger one) and I bet you'll be spot on. IQ52 has run ratios approaching 12.1 on straight pump gas with zero detonation.

 

[coloradodave]

Greg,
Life in Lincoln was slow before the bypass and just right now that the Hwy 65 traffic is gone. lol About the vacuum advance; it should have NO effect on your detonation IF you are taking it off a full manifold vacuum source. As soon as you open the throttle, the vacuum is gone and the advance plate reverts to the mechanical limits. If, however, you took it from a ported vacuum source (no vacuum at idle), the vacuum advance can contribute to the problem. I posted a really good primer on vacuum advance units a while back by one of the engineers at GM whose expertise was in that area. As a side note, my Mallory distributor as delivered provided 22* of vacuum advance! Adjusting it down to 10* worked well for me...

 

[Kern Dog]

I was hooked into ported vacuum. It runs exactly the same at part throttle except no knocking.

 

[IQ52]

My question to you is....Can camshaft timing make the engine more resistant to detonation? If I need to pull the engine to install a dished piston, so be it. I just want the ability to drive in any weather without rettling apart. I want to maximize the potential of the build.

Yes, camshaft timing can make the engine more resistant to detonation.

Reducing the compression would be helpful. Are you willing to do this?

The reduced quench will be helpful.

If you want to "maximize the potential of the build", the build in it's present form is not maximized. Choose which parts you must keep and those that can go. Some decisions must be made.

As I said in the P.M........."Anything is possible."

 

[Kern Dog]

What is involved in making the conversion to E-85 ?
I have a Holley High volume mechanical pump and a Barry Grant 850 VS carb. I have read a little on this, but I have yet to see a point by point blueprint of what is involved.

 

[Garys1969RR]

I have a Holley guy here in Denver that has modified metering blocks for converting your Holley carb to E 85 fuel. I believe the idle restrictions have been opened up, and I think the power valve channel restriction (PVCR) would also need to be enlarged. He charges $20 per block. And main jet size needs to go up about 10 steps. There are also complete carbs that are designed for use with E 85. Just google E 85, and there is a lot of info there. You can also locate all of the stations that have the fuel on hand, at one of those sites. I understand it works best best with C/R of 13 or 14 to 1. I am at 13.3 to 1, and thats 1 reason I built that much into the motor. I plan to check 1/4 mile times with Sunoco 100, then try E 85 and see what the results are. Hopefully May 29 will be the first tryout.

 

[IQ52]

Been there, done that E85 conversion. E85 isn't as corrosive as methanol but it will still attack exposed aluminum that isn't anodized and the rubber connections. Found the inside of my carburetor that wasn't designed for E85 starting to corrode.

The folks at Quick Fuel were the easiest people to work with during my conversion. They have metering blocks designed for E85 and can help you with getting the correct boosters installed in the carburetor.

As I said, I converted to E85. Then went back to race gas, decided never to use expensive race gas anymore, and now build to use pump gas.

 

[Kern Dog]

Thanks guys. I am not commited to any one direction yet, I am just exploring the options. As has been stated, I probably should just optimize my current combination.

 

[Kern Dog]

Here as well as other places, I read that a cam with a LATER intake closing event would help reduce cranking compression.
What would be the effect of retarding this '509 cam 4 degrees? Wouldn't this result in a reduction of cylinder pressure?

 

[Meep-Meep]

Yes, and most likely make your street car run like crap. I'm going to say the best possible situation is to build it right for the task from the beginning. For the street select a CR that will work for the fuel desired. Then select a cam that will work in the RPM range that closely follows your driving habits and the actual compression. Taking an engine that is not street friendly and trying tricks to make it work on the street is a band aid IMO. Either run race fuel on said race engine or build a street engine.

 

[Kern Dog]

Yes, and most likely make your street car run like crap. Taking an engine that is not street friendly and trying tricks to make it work on the street is a band aid IMO. Either run race fuel on said race engine or build a street engine.

While I appreciate the opinion, I would have to disagree with the claim that the car would run like crap. The typical result of a retarded cam is that the power band and peak shifts a few hundred RPMs higher. Fact is, the engine makes plenty of power down low due to the long stroke and cubic inches. 22 years ago I replaced a timing chain on a Chevy 305. The garage was dim and I accidently installed the timing set 1 tooth off. This meant it was 8.18 degrees retarded. It ran fine but was much slower. I knew something felt strange so I tore it down again and fixed the mistake.
I do agree that the most sensible approach would have been to order pistons with a reverse dome when I was building the engine. To do that now would cost upwards of $850.
Maybe down the road I will take that route.
Losing a little power on the bottom is a worthy tradeoff if it helps reduce spark knock. I can't hook up at anything over half throttle now anyway.

 

[383man]

I will agree the best option is to build the eng the right way. But that dont mean you cant try to work with what you have. I can tell you that I run 10.6 comp in my 493 with aluminum EZ heads and dished pistons. But the pistons have the quench pad on them as it has .046 quench with the 10.6 comp. I run a solid flat tappet cam that is 264 & 270 at .050 and with 1.6 rockers its about .631 lift. I use a Mallory dist with a very quick mech advance and no vacum advance. I have my 37 total timing all in by 2000 rpm amd this eng has never pinged running on 92 pump. And it has pushed my 3700 lb 63 to 10.70's thru the pipes on the 92 pump. Quench is very important in running on todays pump gas. But since your eng is all together you might as well try working with it first. Good luck , Ron

 

[Kern Dog]

Thanks, Ron.
I appreciate it.

 

[Meep-Meep]

Well, the stroker factor, which I wasn't thinking about, should make the low end loss more palatable (as you pointed out). All you can do is try it and see what happens. My guess is you will have a power band resembling a two stroke. When you get on the cam I have a feeling you better hang on! Shot lobe separation cams make more peak torque (as opposed to the 112 or 114) but it's scrunched up at a higher RPM - hence the two stroke comment.

 

[Supershafts]

WHY THE HELL is a dopey little 509 cam in that motor ??????????? and WHO the hell told you to use a cam like that in a 4.15 stroke motor ????????

I am so lost on why in the world that motor has that PERFORMANCE LOSS cam in it.... the power you could have with a better cam that is larger in EVERYWAY.... You aren't building a 440 you no longer have a 440, what rod did you use with the crank and by rod i mean which length rod, i hope you used the 6.5, but even if you went with the 6.7 wouldn't have been my choice even if i had the flu that day but... what do you have ???

.

 

[Sweet5ltr]

He stated why he installed it in the first original post. He kept wiping camshaft lobes with the Comp Cams which is common on that series as it is posted all over the internet.

I would seriously look into a Mopar Performance .590 solid lifter camshaft if you are looking for something reliable, with street friendly valve spring pressure, and performance (if you want to stick with a Mopar Performance Cam). This camshaft would also bleed off most of your compression. I get 14-15MPG on the highway with a 833-4 speed, 4.10 rear, and 30" tire now. With a factory 440 other than a comp .480 camshaft with 8.5:1 compression, along with 3.91 gears and a 26" tire, the car got 17mpg on the highway...

Your best bet obviously would be a custom ground camshaft... Just don't expect earth shattering performance if you stick with a hydraulic bumpstick.

I also run timing at a locked 34* on pump gas, as instructed by one of the top tuners in the state of Florida. I don't believe that engines with Aluminum Heads need as much total timing as engines with Cast Iron heads. So, more timing, does not equal more power. The Mopar Performance Engine Manual actually states to run TWO points of additional compression when switching from cast iron to aluminum to restore power loss, but the basic is just to add one point. What you are saying is that if your engine was running 9.8:1 compression with cast iron heads, it wouldn't run on pump gas? Get a compression gauge and check your cranking compression. If it is in the 200+ psi range, you are obviously over the hill' on pump gas. 180psi is about as high as you want to go. As stated before, a larger camshaft with much more duration and a tighter LSA would cure this problem by bleeding off cylinder pressure.