Living with 10.8 compression on the street ??

[Kern Dog]

The reason that I first chose the '509 cam is because when I first decided to build the engine, Mopar Performance had a crate engine program with 2 versions of a 4.15 stroke 440. They both used the '509 cam, but the more powerful of the 2 used 1.6 rockers to bump the lift to .543.
I knew very little of the relationship of high compression & camshaft selection and how it affects detonation. Heck, I'm still fuzzy on some of it. I used a cam that was used in a crate engine, so I thought I'd be doing the right thing.
Another question then: Supershafts suggests a cam MUCH larger than what I am using. This is beginning to form a pattern. MOST everyone suggests a much larger cam. Isn't it fair to guess that a much more aggressive cam will result in a more powerful yet less streetable car? Wouldn't the bigger cam make the car more tempermental? Please remember that I ask this only because I really do not know. I built a big inch engine because I wanted a quick/fast street car, not a dedicated drag car.

 

[19polara64]

They are suggesting bigger cams because it is assumed you have too much cylinder pressure (too much compression). Knowing the cranking pressure would help! The bigger the cam, the more pressure it will bleed off. And yes it will be more radical. But short of different pistons, it is a viable option. Rene'

 

[Hemirunner]

The most logical way to approach this issue would be to go ahead and install the new rockers you already have and see what the results are. If not satisfactory, order a new cam. A 500 inch motor will swallow a lot of cam and still maintain decent street manors. I run a 572 cubic inch hemi on the street and it's cam is a big roller with 276 degrees at .050 lift. It idles nice and cruises well even at that size.

 

[Supershafts]

The reason that I first chose the '509 cam is because when I first decided to build the engine, Mopar Performance had a crate engine program with 2 versions of a 4.15 stroke 440. They both used the '509 cam, but the more powerful of the 2 used 1.6 rockers to bump the lift to .543.
I knew very little of the relationship of high compression & camshaft selection and how it affects detonation. Heck, I'm still fuzzy on some of it. I used a cam that was used in a crate engine, so I thought I'd be doing the right thing.
Another question then: Supershafts suggests a cam MUCH larger than what I am using. This is beginning to form a pattern. MOST everyone suggests a much larger cam. Isn't it fair to guess that a much more aggressive cam will result in a more powerful yet less streetable car? Wouldn't the bigger cam make the car more tempermental? Please remember that I ask this only because I really do not know. I built a big inch engine because I wanted a quick/fast street car, not a dedicated drag car.

My street car has a roller in it even larger than what i suggested for you.

YOU changed EVERYTHING about that 440 and made it ACT and WANT TOTALLY DIFFERENT than what a 440 wants...

The larger cam in a motor that has the stroke you have will run with a 260+@50 cam like a 440 will with a 509, there is no low end loss or poor driving issues.
My 418 in my truck has more cam than your 490, and it is used for pulling and is wonderful doing it, you won't lose low end.


WHAT IS THE ROD LENGTH IN YOUR MOTOR ? ? ? ? ? ? ? ? ? ?


WHAT IS THE ROD LENGTH IN YOUR MOTOR ? ? ? ? ? ? ? ? ? ?




.

 

[Kern Dog]

Rod length? I'm sorry, but I do not know. The rotating assembly came from Hensley Performance in the summer of 2004. They are H beam Manley.
I JUST completed a compression test.
Engine was cold. All plugs out and throttle open.
#1) 215 # 2) 217
#3) 210 # 4) 220
#5) 213 # 6) 211
#7) 211 # 8) 215

Seems a bit high, huh?

 

[Supershafts]

that's up there, what was the kit part # ?

 

[Kern Dog]

Looking at their current catalog, they only show a 6.768 rod option for the 440 RB block, 4.15 stroke, Ross Piston package.
I looked through my receipts, but can't find the invoice... Pretty embarrasing, I know.

 

[Supershafts]

i answered the other post

 

[Meep-Meep]

Rod length? I'm sorry, but I do not know. The rotating assembly came from Hensley Performance in the summer of 2004. They are H beam Manley.
I JUST completed a compression test.
Engine was cold. All plugs out and throttle open.
#1) 215 # 2) 217
#3) 210 # 4) 220
#5) 213 # 6) 211
#7) 211 # 8) 215

Seems a bit high, huh?

Yes, that is high. Too high for pump gas. My hemi Charger blows those numbers and I have a hard time dealing with pinging at WOT - and it's a hemi with supposedly superior combustion chambers. It cruises fine but you can't really get on it hard. Again, many factors contributing to pinging but 10.8:1 CR with 215 PSI is a big one.

Go buy a 5 gal can of high octane gas and start spiking your pump 91 until the problem goes away. You may find you only need about 15% good gas per tank - or $27.00. Depending on how much driving you do this might be the cheapest and easiest solution you have until you redo the engine.

 

[Kern Dog]

I was down to 1/4 tank and I poured in the last of the Sunoco 110 leaded (about 2 gallons). Thats about 40% 110, right? I left the timing at 31* and it runs totally knock free.

As Hemirunner wrote... I will install the 1.6 rockers and report back. I already spent the money on them and they are just waiting...
I understand that different cams often have different base circles. If I order pushrods for this '509 cam setup and decide to switch to another hydraulic cam, is there enough adjustment in the rockers to reuse the pushrods? Jim at Mancini said most apps like mine use a 9 1/8" pushrod.

 

[Sweet5ltr]

Edelbrock states a basic measurement as 9.250” for a solid flat tappet camshaft and 9.150" for a hydraulic flat tappet camshaft for pushrod length with the Performer RPM Heads. Remember, you will need ball and cup pushrods for the adjustable rocker arms. I went with the 9.250" setup for my 440, and luckily it worked with my application. You won't be able to use the same pushrods with a solid lifter camshaft, if that's what you are wondering, but another hydraulic flat tappet camshaft shouldn't be too much of an issue.

 

[Kern Dog]

Thanks 5 liter,
I figured that I'd need the different type pushrods. This length checking tool came with no instructions, just like the rocker arm kit. The checking tool has notches in it, but no numbers like I've seen with micrometers.
I'm no idiot. I am a carpenter by trade and am quite familiar with measuring and making things fit. It just sucks though to get parts or tools that are outside of my area of expertise and then find they have zero instructions or guidelines to steer me the right way.
How am i supposed to check pushrod length? I could install the rockers and check one cylinder, but then how does that show up on the checking tool if there are no actual numbers on it for reference?

 

[Kern Dog]

Forgive me for appearing dense and slow to catch on here...
I have been digesting all of the responses from everyone. In the past I have been guilty of being impulsive and making quick decisions. Sometimes things worked out, other times it did not. In the case here, I have been trying to make sense of everything.
To recap what I have read and learned: My engine has a high static compression ratio that could be streetable if the rest of the combination is correct. The 210+ cranking compression is direct evidence that the engine is building and retaining too much cylinder pressure to properly run on 91 octane pump gasoline. The 292/509 camshaft that is currently in the engine was not chosen by an experienced high performance engine builder, but by me, a man who had previously only rebuilt engines to stock specifications.
Sound correct so far?
I have been slow to catch on. I appreciate those who have been patient.
I have been hesitant to make the switch to a roller cam. The idea of not having to worry about cam and lifter failure is very attractive though. The only drawback I see is the cost.

 

[Kern Dog]

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.

Okay. I wasn't able to calculate the dynamic rate until tonight when a guy on FABO listed the specs for the '509 cam. He showed that it had an intake closing of 58 degrees ABDC. This, along with with my 6.7 length rod has me at 8.99 dynamic.
I have been looking at other camshafts to swap in and found that the Comp 294H looks like it could help. 250/256 duration @ .050, .553/.558 lift with my 1.6 rockers...... AND a 73 degree intake closing! This puts me at a 7.99 Dynamic ratio!

 

[19polara64]

Hi your cam has 74* abdc intake closing. Here's the cam card I copied from another site.
Jesco:
Hi,
Need camshaft card for Mopar Performance P4120237 (509). Can I find it on the web to download or else?

Thanks!
c00nhunterjoe:

Manufacturer's Part Number P4120237
Part Type Camshaft and Lifter Kits
Product Line Mopar Performance Purple Camshaft Kits
Summit Racing Part Number DCC-4120237
Cam Style Hydraulic flat tappet
Basic Operating RPM Range 2,600-6,000
Intake Duration at 050 inch Lift 248
Exhaust Duration at 050 inch Lift 248
Duration at 050 inch Lift 248 int./248 exh.
Advertised Intake Duration 292
Advertised Exhaust Duration 292
Advertised Duration 292 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.509 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.509 in.
Valve Lift with Factory Rocker Arm Ratio 0.509 int./0.509 exh. lift
Lobe Separation (degrees) 108
Camshaft Gear Attachment 1-bolt
Intake Valve Lash 0.000 in.
Exhaust Valve Lash 0.000 in.
Jesco:
Thanks, but this is the generel info - need more. Like the card/paper that you get when you purchase a new camshaft.
c00nhunterjoe:
this is the best info i can get off the card-
292° Hydraulic: P4120237
Intake Duration, Nominal

292°

Exhaust Duration, Nominal

292°
Intake Duration @ .050”

248°

Exhaust Duration @ .050”

248°
Intake Lobe Centerline

108° ATDC

Exhaust Lobe Centerline

108° BTDC
Lobe Separation Angle

108°

Overlap

76°
Intake Opens

38° BTDC

Exhaust Opens

74° BBDC
Intake Closes

74° ABDC

Exhaust Closes

38° ATDC
Intake Lift

.509"

Exhaust Lift

.509"
Note: 242° @ .050” (Herb McCandless)
Note: as installed on 108° centerline per Chrysler

Also here's a list of specs from other mopar cams http://victorylibrary.com/mopar/mpcam-tech-c.htm#b

 

[Hemirunner]

Rocker arms, rocker arms, rocker arms!!

 

[Kern Dog]

If I read Polara's text right, the '509 cam shows a 74 degree intake closing???? That would be ONE degree more than the Comp cam. If this is the case, my dynamic with the MP '509 cam should be UNDER 8.0 and all would be okay. Something is messed up.