Living with 10.8 compression on the street ??

[Kern Dog]

This engine was my first foray into a long stroke Big Block. I've rebuilt many engines in the past, but this was my first with a combination of aluminum heads and a long stroke. I put it together in 2004 and at that time, I wasn't active on any internet forums like this. The guys I knew around here either knew only stock rebuilds or hardcore race stuff. This engine was intended to be a solid street performer. I had limited knowledge of high performance cams...Heck, I still don't know that much about them. the '509 cam may be a bottleneck in terms of performance, but the lobes on it keep hanging on. Maybe it is because I stepped up my oiling needs after wasting 2 Comp cams. I just made the switch to 1.6 ratio rocker arms from Mancini Racing. Yeah... all this time I have been using the stamped steel rocker arms.

 

[BeastlyBirdie]

Dumb question, how does it run with real rockers? If the rockers weren't pushing the valves open the proper amount, you had basically less cam, and....more compression. I wore a set of stock stamped out 20 years ago against an old 509. It started running bad, finally realized the shafts were wearing into the rockers. Isky/erson/ductile rockers or modern stuff (not my area at all) with anything near .500 is a more sure way to go.

 

[Kern Dog]

The new rocker arm kit is still in the box. It all looks nice, but there were no assembly instructions. Kinda silly IMO. Not everyone has experience assembling these things . You'd think they'd have a schematic showing the orientation with all the shims and spacers. Half the rockers are offset, half are standard, I understand that. I'm going to call Mancini in a moment.

I would expect the engine to make a noticeable improvement after getting these dialed in. The stock based stuff was bought NEW in 2006. They are the HD Mopar Performance replacement rockers, so they are a bit thicker than the originals. They still could have had what many experts say is the "exaggerated" ratio of lift. I've read that in most cases, the stock arms were in the 1.38-1.45 range instead of a consistent 1.5. These 1.6 should be not only consistent, but a higher number as well.

 

[Hemirunner]

The new rocker arm kit is still in the box. It all looks nice, but there were no assembly instructions. Kinda silly IMO. Not everyone has experience assembling these things . You'd think they'd have a schematic showing the orientation with all the shims and spacers. Half the rockers are offset, half are standard, I understand that. I'm going to call Mancini in a moment.

I would expect the engine to make a noticeable improvement after getting these dialed in. The stock based stuff was bought NEW in 2006. They are the HD Mopar Performance replacement rockers, so they are a bit thicker than the originals. They still could have had what many experts say is the "exaggerated" ratio of lift. I've read that in most cases, the stock arms were in the 1.38-1.45 range instead of a consistent 1.5. These 1.6 should be not only consistent, but a higher number as well.

And you may very well have the solution to this entire thread right there in the box. My guess is that your 'issues' will go away once those are installed.

 

[Kern Dog]

And you may very well have the solution to this entire thread right there in the box. My guess is that your 'issues' will go away once those are installed.

Lets hope! Each journey begins with a single step.

The guy at Mancini agreed that there should be some sort of instructions with the rocker arm kits. He said that he was trying to get management to figure something out.

 

[Meep-Meep]

What are you trying to figure out? There is a left and a right rocker. The shaft oil hole orientation can be found in the FSM, or just aim them toward the exhaust ports. Can you post a pic of what you got? You will need to figure out proper push rod length or at least check what you have. This is very important.

A stronger and more rigid rocker is better by far for precise translation of the cam to the valve, but I won't hold my breath as far as a new set of rockers curing your pinging problem. The higher ratio will change the acceleration and deceleration of the valve, but it won't change the precise time the intake valve opens - at least at low RPM anyway.

 

[Kern Dog]

I probably sound like I am whining. That was not my intention.
I know that the rockers are supposed to be positioned so the pushrods are square to the lifters. No problem. I'm sure that once I get my eyes on it, it will all make sense. I just like to have more info before beginning a project. I often research the shortcuts and problem areas so I know what I am getting into.
I do not expect the detonation to be cured with a single change. (UNless those changes were a piston change or a BIG cam)
This is merely a step toward a better combination. I probably will go with a better cam eventually.

 

[Meep-Meep]

OK, I guess the thread sort of wandered through different topics and I didn't keep up. In any case the .509" is not a terrible cam.

Getting back on the detonation topic, have you considered changing intake and / or carbs? Through my own experience effects of fuel distribution and mixture strength can be huge. If you have parts lying around this is as you know very easy and cheap to do.

 

[Kern Dog]

I have an AEM wideband guage ready to go in. I had bungs welded in the header collectors several months ago. The guage will mount in a custom twin pod that I made to fit in place of the ashtray. The guage has both analog and digital readouts. Next to that will be a vacuum guage that I also have waiting.
There are numerous threads on FABO and Moparts about tuning with the wideband guage. My Demon 850 is similar to a Holley, so parts for tuning shouldn't be too hard to find. I have some accelerator pump cams, power valves, Jets of many sizes and gaskets. Anything else I'll just buy and try...

 

[HT413]

I know you probably know this, but since no one mentioned it, you'll need different pushrods to run those adjustable rockers. They need cup ends rather than the ball ends you currently have.

 

[BeastlyBirdie]

What are you trying to figure out? There is a left and a right rocker. The shaft oil hole orientation can be found in the FSM, or just aim them toward the exhaust ports. Can you post a pic of what you got? You will need to figure out proper push rod length or at least check what you have. This is very important.

A stronger and more rigid rocker is better by far for precise translation of the cam to the valve, but I won't hold my breath as far as a new set of rockers curing your pinging problem. The higher ratio will change the acceleration and deceleration of the valve, but it won't change the precise time the intake valve opens - at least at low RPM anyway.

Actually it might stop the pinging. We can agree his effective CR is over 10.8:1 due to lack of lift. At idle, the engine can choke down pump gas. As he gets on it, the timing advance would make it ping. A lot of people wouldn't notice a problem at idle, they'd just think its the cam being lopey.

 

[Hemirunner]

I do not expect the detonation to be cured with a single change. (UNless those changes were a piston change or a BIG cam)
This is merely a step toward a better combination. I probably will go with a better cam eventually.

Changing from a factory rocker arm with a ratio of somewhere less than 1.5 to a roller rocker with a TRUE ratio of 1.6 is a BIG change. It will open the valve faster, farther and hold it open longer as it will close it quicker. The engine will effectively "see" a bigger cam. I'm guessing most of your issues will go away. BTW, from my experience, of the 20 or so Demon carbs I've used, 1 worked OK, on a small block, the rest I'd use for doorstops. Just my opinion.

 

[Kern Dog]

I know you probably know this, but since no one mentioned it, you'll need different pushrods to run those adjustable rockers. They need cup ends rather than the ball ends you currently have.

Thanks. I ordered a length checking pushrod. The man at Mancini said in most cases, the length works out to be 9 1/8" but it is best to be sure. These ARE like you say... ball type at the lifter end and cup at the rocker.

- - - Updated - - -

This Demon carb has performed well. It idles consistently. It makes power. It doesn't load up or flood. The plugs stay clean. I cannot say how easy it will respond to fine tuning for razor sharp emissions coupled with the best power, since I have yet to take it that far.

 

[Sweet5ltr]

Why not go with a classic bullet-proof Isky/Crane Ductile Iron adjustable setup? You can find them used and cheap, and they will probably out last your current engine build for sure. Almost no proven HP gain off of going to an aluminum or roller rocker setup, other than hassle's and broken parts for a street car.

Stick with what works. If it is a street car, you can just toss half the information most people tell you out the window, as most don't put thousands of miles on their cars a year in the rain or shine. Places a different level of reliability you must respect, other than pulling it off a trailer at the show once every few months!

BTW, I ran stamped steel rocker arms (factory, new replacement) for a while with the comp XE285HL series (.545/.545) without any issues if you want some advice on if that would cure any problems...

 

[Hemirunner]

Why not go with a classic bullet-proof Isky/Crane Ductile Iron adjustable setup? You can find them used and cheap, and they will probably out last your current engine build for sure. Almost no proven HP gain off of going to an aluminum or roller rocker setup, other than hassle's and broken parts for a street car.

Stick with what works. If it is a street car, you can just toss half the information most people tell you out the window, as most don't put thousands of miles on their cars a year in the rain or shine. Places a different level of reliability you must respect, other than pulling it off a trailer at the show once every few months!

BTW, I ran stamped steel rocker arms (factory, new replacement) for a while with the comp XE285HL series (.545/.545) without any issues if you want some advice on if that would cure any problems...

He'll get a gain from these parts due to having an accurate ratio on the rocker arms. I'm sure with the stamped steel rockers he had 16 different ratio rockers. Now he'll have 1.6 on them all. HUGE gain. I ran stamped steel rockers too until about 1989 when I figured out that they're all inaccurate. They have their place, but on a 500" stroker isn't where they belong.......

 

[Sweet5ltr]

Not going to argue with that, as it is correct (most factory stamped rockers are in the 1.4 range when they are listed as 1.5). With a correct ratio rocker arm, he isn't going to see much gain from the upgraded rockers per/dollar. I would highly recommend a camshaft change, regardless if this is the issue or not, to a solid flat tappet grind. Mopar, Lunati, take your pick, they will all 'more than likely' build much more power than the .509 in your build. Just make sure you do a proper break-in and use a zinc additive in all your oil changes. The only reason I went with the .590 is that it performs very well per/cost (few hundred for a cam and lifter kit), is very reliable in a street application (I have a few thousand miles of stop and go traffic on mine), and doesn't require sky high valve spring pressures as the ramps are not as aggressive as newer grinds (their for, being easier on the valve train).

Every get a chance to check your cranking PSI?

 

[Kern Dog]

Every get a chance to check your cranking PSI?

Ha ha... Not yet. Maybe I'll take a look tomorrow.
EVERY time I read someone suggest this I get a D'OH ! (Homer Simpson) type of feeling. I know that the cranking compression number is a critical aspect of the issue and I keep forgetting to check it.
In Feb 2012 I pulled the motor to hone the cylinders and put in new rings. Before the teardown , the lowest hole read 178 and the highest was 192. I'm sure that with a better ring seal, I must be over 190 in all holes now.
I REALLY wish I had better advice on compression when I first built the engine. I could have replaced the pistons last year when the engine was out, but like a cheap***, I just had the old pistons bead blasted and reused them.
I know that many here have said that this compression ratio can work if I have quench and the right camshaft, but a reverse dome piston with an even 10.0 to one would have allowed me some wiggle room.

Regarding solid lefter camshafts: WHO the heck do you trust? I've had a W I D E range of quality on advice. The guy I talked to at Comp Cams thought my '509 cam was adequate and even suggested using a THICKER head gasket to drop compression. I posted that here and faced a barrage of responses telling me that the thicker gaskets would eliminate any "Quench" I may have and actually increase detonation. I googled Quench and spent a couple hours reading about it on several engine forums.
I am fully aware that there isn't any one perfect camshaft for any engine, only a few that work well and a bunch that will not. I'd be happy to try a solid lifter cam if I knew who to trust. I am not married to the Mopar Performance brand, but I have heard the .528 is popular. Subtract the lash and I am no bigger than I am now though, right?
I recall reading some responses suggesting a minimum duration of 240-250 @ .050. I am already there with this 292/509 cam.

 

[Meep-Meep]

A few thousands in head gasket thickness isn't going to make a hill of beans worth of difference in quench or the amount of swirl it provides.

I ran the .528 in my 383 and it was great. Way more streetable than the .509 because of the longer lobe separation.

 

[Sweet5ltr]

http://www.moparmusclemagazine.com/techarticles/mopp_1302_tech_pump_gas_power/

Check out this article..

- - - Updated - - -

Ha ha... Not yet. Maybe I'll take a look tomorrow.
EVERY time I read someone suggest this I get a D'OH ! (Homer Simpson) type of feeling. I know that the cranking compression number is a critical aspect of the issue and I keep forgetting to check it.
In Feb 2012 I pulled the motor to hone the cylinders and put in new rings. Before the teardown , the lowest hole read 178 and the highest was 192. I'm sure that with a better ring seal, I must be over 190 in all holes now.
I REALLY wish I had better advice on compression when I first built the engine. I could have replaced the pistons last year when the engine was out, but like a cheap***, I just had the old pistons bead blasted and reused them.
I know that many here have said that this compression ratio can work if I have quench and the right camshaft, but a reverse dome piston with an even 10.0 to one would have allowed me some wiggle room.

Regarding solid lefter camshafts: WHO the heck do you trust? I've had a W I D E range of quality on advice. The guy I talked to at Comp Cams thought my '509 cam was adequate and even suggested using a THICKER head gasket to drop compression. I posted that here and faced a barrage of responses telling me that the thicker gaskets would eliminate any "Quench" I may have and actually increase detonation. I googled Quench and spent a couple hours reading about it on several engine forums.
I am fully aware that there isn't any one perfect camshaft for any engine, only a few that work well and a bunch that will not. I'd be happy to try a solid lifter cam if I knew who to trust. I am not married to the Mopar Performance brand, but I have heard the .528 is popular. Subtract the lash and I am no bigger than I am now though, right?
I recall reading some responses suggesting a minimum duration of 240-250 @ .050. I am already there with this 292/509 cam.

I trust proven designs, as the .590 was designed initially by Racer Brown and flat out works. This is a 106LSA/312* duration camshaft. I have far less compression than it calls for, and far less gearing, but is docile with a 4-speed. I would at the very least run a grind similar to yours, but with much higher lift (.580-.620) or at least .550 lift after setting valve lash. I have always heard good things about Lunati grinds, but everyone has their preferences. You are leaving quite a bit of power on the table with the .509, unless you are looking for a stump puller.

 

[Supershafts]

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...

He said he built the 493 after he blew apart the 440, and put the 509, then a 285 and back to 509... WHY were any of those of cams given as a choice for that motor...

There is not enough cam in that motor period, not for low end, not for performance.

This engine was my first foray into a long stroke Big Block. I've rebuilt many engines in the past, but this was my first with a combination of aluminum heads and a long stroke. I put it together in 2004 and at that time, I wasn't active on any internet forums like this. The guys I knew around here either knew only stock rebuilds or hardcore race stuff. This engine was intended to be a solid street performer. I had limited knowledge of high performance cams...Heck, I still don't know that much about them. the '509 cam may be a bottleneck in terms of performance, but the lobes on it keep hanging on. Maybe it is because I stepped up my oiling needs after wasting 2 Comp cams. I just made the switch to 1.6 ratio rocker arms from Mancini Racing. Yeah... all this time I have been using the stamped steel rocker arms.

The rocker arms while a better idea aren't going to end all, however im still waiting for the answers to the questions i posted

So which rod did you use with the crank, what does the rod measure ? 6.5" or 6.7"

You should just go with a roller, in the cams you wasted already and the learning experience you're ignoring and money wasted you are still LOOKING to do it ALL OVER AGAIN...and maybe even AGAIN...

You should seriously be looking for a cam in the area of 260@50 or more and 580 lift or better, if this was my street motor i'd be starting there.

Which rods did you use 6.5 or 6.7 ???????????????????????????????????????????????????????????????

And you may very well have the solution to this entire thread right there in the box. My guess is that your 'issues' will go away once those are installed.

I don't think the problem will go away with the new rockers, it's needed anyway, but he needs a cam, and should be looking at a nice roller in the area mentioned.
.

- - - Updated - - -

You are leaving quite a bit of power on the table with the .509, unless you are looking for a stump puller.

Thats never gonna be a stump puller... If, If he got that to run where he could floor it, and not beat the bearings out of it in 1300ft it wouldn't feel so good and have a short window...