210 + cranking compression, 10.73 CR and a 509 cam. I guess i screwed up!

[Kern Dog]

Thanks to all that responded in the other thread I started "Living with 10.8 compression of the street".
The calculated comp is actually closer to 10.73, but I realized it after starting the thread. I have received much help and have been asked questions that I cannot answer. One of which is the ROD LENGTH. I am unsure of how this affects the issue of detonation.
I just finished doing a compression check. Here are the results. All plugs out, throttle open, engine cold.

#1) 215 #2) 217
#3) 210 #4) 220
#5) 213 #6) 211 ** Pretty consistent numbers, huh?**
#7) 211 #8) 215

Seems pretty high, huh? When I first built the engine in 2004 I had a buddy help me degree the cam. He suggested that I advance it, so we set it to 4* advanced. THEN the cranking #s were all over 230.

So the threads and posts I have read say that most of the time, anything over 190 means pump premium will not be good enough. I already knew that, but now I have the numbers to prove it.
Seems like the advice I have been getting is starting to sink in. I'll need a bigger cam!

 

[Hemirunner]

Thanks to all that responded in the other thread I started "Living with 10.8 compression of the street".
The calculated comp is actually closer to 10.73, but I realized it after starting the thread. I have received much help and have been asked questions that I cannot answer. One of which is the ROD LENGTH. I am unsure of how this affects the issue of detonation.
I just finished doing a compression check. Here are the results. All plugs out, throttle open, engine cold.

#1) 215 #2) 217
#3) 210 #4) 220
#5) 213 #6) 211 ** Pretty consistent numbers, huh?**
#7) 211 #8) 215

Seems pretty high, huh? When I first built the engine in 2004 I had a buddy help me degree the cam. He suggested that I advance it, so we set it to 4* advanced. THEN the cranking #s were all over 230.

So the threads and posts I have read say that most of the time, anything over 190 means pump premium will not be good enough. I already knew that, but now I have the numbers to prove it.
Seems like the advice I have been getting is starting to sink in. I'll need a bigger cam!

Put the new rocker arms on and do that test again.

 

[Supershafts]

The rod length is what is making the problem and why the need for a different cam, the rod length even if it stayed with the factory rod has now changed the motors rod ratio and the motor is moving air entirely differently than a 440.
If you're motor had the 6.7 rod you changed the 440's lazy 1.8 ratio to a sucking in tons of air 1.6 RR now and that changes EVERYTHING and makes it better on the low end WITH a much larger cam, but to make it perform better it needs a totally different EVERYTHING thought process and we ignore what a 440 likes because we no longer have a 440 except in view.
.
Now you want big cam, large volume, larger carb, big runners, big heads

 

[Sweet5ltr]

Thanks to all that responded in the other thread I started "Living with 10.8 compression of the street".
The calculated comp is actually closer to 10.73, but I realized it after starting the thread. I have received much help and have been asked questions that I cannot answer. One of which is the ROD LENGTH. I am unsure of how this affects the issue of detonation.
I just finished doing a compression check. Here are the results. All plugs out, throttle open, engine cold.

#1) 215 #2) 217
#3) 210 #4) 220
#5) 213 #6) 211 ** Pretty consistent numbers, huh?**
#7) 211 #8) 215

Seems pretty high, huh? When I first built the engine in 2004 I had a buddy help me degree the cam. He suggested that I advance it, so we set it to 4* advanced. THEN the cranking #s were all over 230.

So the threads and posts I have read say that most of the time, anything over 190 means pump premium will not be good enough. I already knew that, but now I have the numbers to prove it.
Seems like the advice I have been getting is starting to sink in. I'll need a bigger cam!

That's good to know you followed my advice and took out the ol' pressure gauge. I would be looking into a camshaft with a large amount of duration, around 270*+ @ .050 or around 320* advertised duration/.600+ lift. I am running around 180PSI and it is borderline pump fuel. I have also heard of companies like this
http://www.headgasket.com/gaskets.html that create custom head gaskets that could possibly get you a 1/2 point lower on your compression ratio. May be something else you could look into. Check out that article I sent you from Mopar Muscle as well.. Could lead you to a few more pointers to get your Mopar street friendly.

 

[Meep-Meep]

Granted that rod length will affect the cam selection based on piston acceleration away from TDC but I'd sure like to see how going from a 1.8:1 to a 1.63:1 ratio (or vice versa) will make a hill of beans worth of difference in the OP's pinging problem. Assuming his timing isn't overly advanced, any or all of these factors: Compression ratio vs. combustion chamber shape, mixture strength, intake charge temp, bore size, possible fuel distribution problems and engine temp has exceeded the requirement of pump 91 gas plain and simple. Just a simple jet change exceeding the normal range for the carb used can affect fuel distribution. Rod length is hardly on the list in my opinion.

 

[Kern Dog]

I wonder if the some of the guys at "performance" parts stores are trying to avoid offending people when they call to order parts.
Of all the parts that I have ordered over the years, I have rarely had someone ask detailed questions or try to steer me away from my selection. Obviously I have made some mistakes with this engine. In 2004 when I ordered the rotating assembly from Hensley, they said the engine would run fine on pump gas. Being inexperienced bit me in the rump though, because the run fine on pump gas phrase should have come with a disclaimer...(ONLY if the proper camshaft is selected as well as having the proper quench. Tuning to be performed by consumer at considerable cost. Side effects of improper tuning can and will result in loss of power, excess fuel consumption, failure to impress chicks and ridicule among internet tech forums)

I have ordered from Summit racing plenty of times and they have never tried to steer me elsewhere. TTI never told me that 2" headers would be too big for my last build, a mild .030 over 440.
I was very late to get on the internet and join these types of tech forum boards. I joined Moparts in 2010 FABO and here a bit later. I have decided over the last 2 years that i want to drive this car MORE, and this motivated me to correct some errors in the car.
Thanks to all who cared enough to contribute!

 

[Supershafts]

Granted that rod length will affect the cam selection based on piston acceleration away from TDC but I'd sure like to see how going from a 1.8:1 to a 1.63:1 ratio (or vice versa) will make a hill of beans worth of difference in the OP's pinging problem. Assuming his timing isn't overly advanced, any or all of these factors: Compression ratio vs. combustion chamber shape, mixture strength, intake charge temp, bore size, possible fuel distribution problems and engine temp has exceeded the requirement of pump 91 gas plain and simple. Just a simple jet change exceeding the normal range for the carb used can affect fuel distribution. Rod length is hardly on the list in my opinion.

RR is the entire hill of beans and changes everything about the motor and it's ability to pull in, push out, flow, velocity and fill those cylinders, that in turn makes more power sooner and longer depending on how everything else was put together. Bigger RR are lazy at low end and move nothing compared to small RR at the same.

 

[Hemirunner]

RR is the entire hill of beans and changes everything about the motor and it's ability to pull in, push out, flow, velocity and fill those cylinders, that in turn makes more power sooner and longer depending on how everything else was put together. Bigger RR are lazy at low end and move nothing compared to small RR at the same.

Cough, cough, cough.... please pass some of that over here..... rod ratio is about the very last considerations when we're limiting our discusion to one family of engines (RB mopars in this case). The change from a 6.760 rod to a 7.100 rod is a change of less than 5%. True it will affect dwell slightly, but you could not change rod ratio enough in a given combo to see dramatic results. There are so many other factors in building one of these that have such a larger effect on performance that rod ratio is nearly insignificant.

 

[Meep-Meep]

GregC, just so you understand, your problem is too much compression for the available fuel. It's that simple. Anything else is a band-aid. Installing a bigger cam means setting valve springs for said cam and checking all clearances - a fair amount of work. Just get a grog of 110 Sunoco and blend it with pump 91 for this engine. Run it for the summer and have fun then sell it to someone who wants to build a track car. The proceeds will fund your next build, and when you get ready to build it, you will have all you need to know to do a true pump gas street stomper. By the way, when you told the sales people "pump gas" they probably thought you meant 100 octane Street Blaze available at the pump. Yeah, it's pump gas!

Just to give you something to think about, my standard rod ratio 440 is running 10.1:1 CR with 915 iron heads and it's barely livable on pump 91 with the singe 4 BBL (more on that later). With the single 4 BBL (750 Eddy AFB) and factory iron intake it pings like an SOB under hard acceleration. I added some 110 race gas and the problem went away and the car ran great at Sac Raceway and on the street throughout the RPM range.

This combo is running a cam that most people wouldn't use as a hood prop rod but I have no complaints. Also the 2" Hooker headers into 3" TTI system with noise masters (mufflers were hand me downs) seem to work well too even though the headers are "too big". My build has so much going wrong with it, that if you listen to some people on the forums, that's it's amazing it even gets out of the driveway. The end result is it runs high 12's in a 4000 lb car with traction and low 13's without at 105-109 MPH. Gears I have tried are 3.55 - 4.30 but it likes the 3.55's the best. Throttle response is crisp like a motorcycle and it has all the power a street engine needs from 1500 RPM to about 5500.

Now about the carb set up I wanted to elaborate on. I installed a factory 6 BBL setup and changed nothing else. The result? The car made less power! For one I haven't done much tuning and I know the 6 BBL is lean, BUT, it doesn't ping on pump 91! It's lean AND doesn't ping. Think about that. The point is what I have been making all along. Many factors related to why an engine would tend to ping and pretty much all are centered around compression, inlet charge temp, timing, fuel distribution, cam timing and a few others.

- - - Updated - - -

RR is the entire hill of beans and changes everything about the motor and it's ability to pull in, push out, flow, velocity and fill those cylinders, that in turn makes more power sooner and longer depending on how everything else was put together. Bigger RR are lazy at low end and move nothing compared to small RR at the same.

Sure, on some level this is 100% true, but............. THE OP'S PROBLEM IS TOO MUCH COMPRESSION FOR THE AVAILABLE FUEL

 

[67Satty]

- - - Updated - - -




Sure, on some level this is 100% true, but............. THE OP'S PROBLEM IS TOO MUCH COMPRESSION FOR THE AVAILABLE FUEL

If have an easy solution for the OP's problem: send the carb out to someone to convert it to use E85. Looks like there are plenty of stations near Granite Bay that sell E85:

http://e85vehicles.com/e85-stations/e85-california.html

 

[lewtot184]

anything over 180psi blow is going to be an issue with pump gas. i don't understand why when people build these engines they never allow for a carbon build-up in the chambers. just .010" of carbon on the piston and head will raise static numbers about 1/2 a point, and .010" ain't nothing! there will be twice that long term. change the pistons and be done with it.

 

[RustyRatRod]

I forget.....is this an iron head motor? If so, stick some aluminum heads on it and a bigger cam in it. Band aid or not, it'll work.

 

[Kern Dog]

i don't understand why when people build these engines they never allow for a carbon build-up in the chambers. just .010" of carbon on the piston and head will raise static numbers about 1/2 a point, and .010" ain't nothing! there will be twice that long term. change the pistons and be done with it.

I don't know why people that work at engine parts supply stores don't offer better advice to guys building engines. When I bought the crank/rods/pistons, the guy said it would run fine on pump gas. He should have stated that it would if I had the right cam. These guys that take orders and ship parts are doing a DISservice to their customers that rely on them for advice.
Ultimately the responsibility falls on ME, but a little help on their part would have saved me a bunch of frustration.
Yes...I have Edelbrock aluminum heads on it, the 84 cc ones with closed chambers.
At what point to I need to do a piston to valve clearance test? I had a .545 lift cam in it before and had no problems.

 

[Sweet5ltr]

I don't know why people that work at engine parts supply stores don't offer better advice to guys building engines. When I bought the crank/rods/pistons, the guy said it would run fine on pump gas. He should have stated that it would if I had the right cam. These guys that take orders and ship parts are doing a DISservice to their customers that rely on them for advice.
Ultimately the responsibility falls on ME, but a little help on their part would have saved me a bunch of frustration.
Yes...I have Edelbrock aluminum heads on it, the 84 cc ones with closed chambers.
At what point to I need to do a piston to valve clearance test? I had a .545 lift cam in it before and had no problems.

I would check the PTV clearance, especially if you are considering a much larger camshaft. Ordering some of those cylinder head gaskets, built to be a band-aid fix to lower compression for blown applications, would also help as I was considering going the blower route at one time. I am just letting you know, I have the same cylinder heads, but the .590 camshaft which is extremely radical (spec wise) and I am borderline pump gas friendly with the Eddy RPM's at 84cc. I previously ran the .509 with the Iron Heads and had no issues what-so-ever with 88-90cc Open Chambered Iron Heads with 9.8:1CR. I run pump gas only, and run a 160* thermostat in Florida and the hottest I will get in traffic is 180 (or 190* on 90* sunny, humid days). Letting your big block mopar cook at 200+ degrees with a 180+* thermostat will probably cause detonation as well. The Mopar Engine Manual states a 160* thermostat is best used for racing/performance applications. 30* timing is absolutely nothing (but recommended by one of the best "Ford" tuners in the nation for pump gas 30-32*), but if I run anymore than 34* (34* being what Indy Cylinder Heads stated is the best timing for Aluminum headed applications), it is too hard to crank when cold with a starter rated for 12.5:1CR. At 34* locked out, it will crank anytime. The .590 from Mopar, will cost probably $300 with lifters, and with your 1.6 rockers will be around .600 lift after setting valve lash, which at .600 lift the Edelbrock RPM's flow 290CFM which is well enough for make 600HP. You won't gain much by going to any larger of a camshaft, as the flow of the RPM's stagnates at that lift range, and only gains a few CFM at any higher lift ranges. This camshaft shouldn't work and my combo shouldn't work as it is all devoted to 4000+RPM ranges, but lets be serious.. If you have 400ft/lbs of torque off idle and 500ft/lbs by 3,000-3,500RPM in a 3200-3500# car, do you really need any more to get through traffic? I get 14-15MPG on the interstate... My Z06 Corvette gets 30MPG at the same speed.. Driving one of these cars isn't about fuel economy, but the love/dedication of driving around a piece of history to show kids that cars at one time were not built to just drive A-B..

 

[lewtot184]

I don't know why people that work at engine parts supply stores don't offer better advice to guys building engines. When I bought the crank/rods/pistons, the guy said it would run fine on pump gas. He should have stated that it would if I had the right cam. These guys that take orders and ship parts are doing a DISservice to their customers that rely on them for advice.
Ultimately the responsibility falls on ME, but a little help on their part would have saved me a bunch of frustration.
Yes...I have Edelbrock aluminum heads on it, the 84 cc ones with closed chambers.
At what point to I need to do a piston to valve clearance test? I had a .545 lift cam in it before and had no problems.

people are also a victim of internet/magazine hype-lies. if you try to do an in-depth study of detonation you will find definitive information difficult to obtain. the reason is that there are so many factors that contribute to the problem, and it is impossible to build a detonation proof engine. most people who build 10.5-11.0:1 engines and try to get them to live on pump gas will eventually have problems, sooner or later. if there's too much pressure for the fuel being used it will ignite too soon in the power stroke and cylinder head material or camshaft won't save it. you might take a good look at the pistons you have and see if its possible to mill a step in them. it wouldn't take a lot, maybe .060" across the top of the piston that is directly below the combustion chamber but still leave a quench pad for the quench area of the head. also, a solid lifter camshaft with an asymetrical lobe would be a nice tuning aid.

 

[GrabberOrange69]

Do you daily drive this car? And I mean REALLY daily drive it? If no, just use octane boost or mix race gas. I have an engine with 11.2:1 compression and I drive it on the street - 500-1000 miles a year - with $10 of octane boost for every full tank. I suspect your classic car habits are similar, and if so, popping 5-10$ a tank for boost just isn't that big of a deal. WAY cheaper than swapping heads and cam, but those will work. But would you like the way it idles?

Just my .02 cents...

 

[Kern Dog]

The Charger isn't a daily driver. I drive it about 1500-2000 miles per year. I see your point about the economics of it all. It makes financial sense to simply use a few gallons of 110 octane per tankful, but I'm tempted to pursue the potential of the engine.
All the responses have stirred up some inspiration to dig deeper. I wanted a big inch motor so I could have a fast and fun car. Running the engine with a series of mismatched components isn't going to allow me to reach what the engine is capable of. I cannot afford to dump a bunch of money into the car right now, so I'll make some changes a little at a time and report back. Thanks everyone, Greg

 

[Homstead]

Don`t sweat the rod ratio. I`ve tested 410 sprint car engines on the dyno with different rod ratios and although there is a slight difference in where the power comes in it is not really enough to concern yourself on a street engine. If it were me I would just use the octane boast or race gas as you have been doing. I do like the idea of bleeding off some compression with the camshaft. A few years ago we built a 540 wedge with 13.2 to 1 and bled off the pressure with a rather large roller cam. We were able to run it on pump gas. If I remeber correctly it produced 790 hp. Anyway goodluck!

 

[Kern Dog]

. A few years ago we built a 540 wedge with 13.2 to 1 and bled off the pressure with a rather large roller cam. We were able to run it on pump gas. If I remeber correctly it produced 790 hp. Anyway goodluck!

Holy crap... Almost 800 HP ???

 

[Supershafts]

Cough, cough, cough.... please pass some of that over here..... rod ratio is about the very last considerations when we're limiting our discusion to one family of engines (RB mopars in this case). The change from a 6.760 rod to a 7.100 rod is a change of less than 5%. True it will affect dwell slightly, but you could not change rod ratio enough in a given combo to see dramatic results. There are so many other factors in building one of these that have such a larger effect on performance that rod ratio is nearly insignificant.

Change of 6.7 to 7.1 in a 3.7 stroke motor is a small change 1.8 to 1.89 and a change in the wrong direction, make a even lazier motor.
Change of 7.1 to 6.7 in a 4.1 stroke motor is a significant change to 1.7 and a even better 1.6 , and as small as that seems to you it changes many things, ignoring that and making that you last consideration is bad.

As for it needing less compression, well Meep explain why my more than 10-7 to 1, more cam and even better RR of 1.5 is streetable on pump gas well beyond 270@50 and make over 700hp, and no pinging ?