A little cam help.

[Gunner1]

My package is a 63 Polara with I believe 323 gears. 727 with a 3000 stall 11 inch converter. The engine is a 030 over 440 out of a 76 motor home. It has 452 heads which are stock and L2355f speed pro flat tops. Calculates out to 9.37 to 1. The intake is an Air Gap with a Holley 750 DP. I am installing a MSD billet dist with a 6AL box. Timing is set at 12 initial 34 total at 3000. My cranking pressures are 175. The cam has a very mild idle. Problem is it pings like a B%$#^ when I get on it even mildly. Plugs read on the brown side of tan. I can’t put in new ones and do a pass with a cut as it pings so bad. I have no idea what the cam is but i I think I need a bigger cam to drop the cranking pressure a bit. The plan is to by a set of 240 TF heads when I save some more dough.

 

[Kern Dog]

The whole "Bigger cam to reduce cylinder pressure" routine is pointless.
Whatever pressure is reduced at idle and midrange is magnified at high rpms. That is how a bigger cam works....you lose a little low end to gain it at the high end. At the higher rpms, knocking can be hard to hear.
I have 175 cranking compression with 10.07 compression. I barely get knocking with 91 octane and 31 total degrees of timing.
Colder plugs, less total timing, reduce some of the vacuum advance and the highest octane gas you can find and you'll see some improvements.
No Big Block ever came with an "Air Gap" intake. The LA series engines did. Maybe you have the Edelbrock Performer RPM ?

 

[Gunner1]

The whole "Bigger cam to reduce cylinder pressure" routine is pointless.
Whatever pressure is reduced at idle and midrange is magnified at high rpms. That is how a bigger cam works....you lose a little low end to gain it at the high end. At the higher rpms, knocking can be hard to hear.
I have 175 cranking compression with 10.07 compression. I barely get knocking with 91 octane and 31 total degrees of timing.
Colder plugs, less total timing, reduce some of the vacuum advance and the highest octane gas you can find and you'll see some improvements.
No Big Block ever came with an "Air Gap" intake. The LA series engines did. Maybe you have the Edelbrock Performer RPM ?

Yup RPM. The air gap was a slip up from my Chevy days. My compression looks to be about 9.4. So 175 seems high to me. I can’t get it over about 3500 because of the ping. Fuel is 91 with a can of booster. I gonna keep tuning to see what’s what

 

[hunt2elk]

For the heck of it, try running it with your vac advance plugged off to see if the detonation stops. Another thing you can do is put heavier springs in your distributor to slow down the advance curve.

 

[Curiousyellow71]

What sparkplugs are in it? What is your engine temp.. stock carb jetting?
For starters take some timing out, till it's drivable.. There are also other factors such as elevation and how poor the gas is in your area. What works for one person doesn't always translate.
Yes...a cam that keeps the intake open longer will bleed off compression. Cam timing could be off if it wasn't degreed in. If you don't know what cam you have a compression check should help tell.

 

[BeepBeepRR]

You did not mention what cam is in the 440 Pretty much the same engine I built. 440 30 over 452 heads and speed pro pistons. I ran the Summit K6401 cam and had 16 degrees initial and 36 all in. No pinging. But then again it was not on a drag strip. Hell we even used the same pistons. My numbers were 9:64.1

Edelbrock 750 cfm carb.. A little small for the intake used. Should have had an 850 or a little bigger. Mopar Performance M1 single plane intake might be the difference between your engine and mine. I did have the heads worked a little in the bowl area and slight port matching. Also had 4 new valve seats installed.

 

[biomedtechguy]

For starters take some timing out, till it's drivable..

...and before you wreck your engine.

 

[zyzzyx]

Double check your compression ratio. Sounds like you may have more than you think! You have
to cc the heads, make sure you know where the piston is in the bore, and make sure you're using
the right thickness head gasket. It might be as simple as pulling the heads, measuring, and changing
head gaskets! Good luck!

 

[727]

Have built a similar combo twice.
One with the .455 lift purple cam
One with the summit 6401.
The purple cam did the same thing. Switched from pertonix to a MP electronic distributor 18 degree mechanical advance plate 36 degrees total mechanical and chrome box and it solved it.
The 6401 used a 13 degree advance plate, 32 all in no vacuum advance. Still borderline on making noise. Try to use non ethanol gas if available

 

[PRHeads]

If the cam is on the small/short duration end of things, that’s usually going to exacerbate the no quench/iron head/likes to ping situation.

I’d see if there is some way of determining what exactly is in the motor, and where it’s installed.

Depending on what it is and where it’s installed, a cam swap “could” certainly get you closer to getting it to run on pump gas.

As was mentioned, a slower advance curve and less total timing is a place to start.

Using the Wallace calculator, plugging in a basic combo......

440, Comp 280h cam in at 106, 9.4cr, sea level..... shows about 145psi on the compression tester.

If the lifters were bleeding down pretty fast, the gauge would read a bit higher.

 

[Gunner1]

Cam is unknown, it came with the running car. Owner forgot what he put in it. I only found the piston numbers by using a borescope. I got it to not ping but I was at 0 initial 24 total. It was pretty lazy. Pistons looked to be slightly down by about .015. Hard to tell about the head gasket but it looks like a composition gasket like a Felpro. The Vacuum advance port is blocked off at the carb. Engine temp never goes past 185. The carb jetting is still stock. I have forgotten the plug numbers. I'll have to check again but not a severe extended projection nose. I chose the 750 because I didnt know what was inside and the gas miser eddy 600 was so bad and way to small. I want to put a Holley Sniper on it and link it to the MSD. I hope I've answered everyone. I'm probably over thinking this. I've never done a totally open chamber motor before. LOL wheres my quench band?

 

[Gunner1]

If the cam is on the small/short duration end of things, that’s usually going to exacerbate the no quench/iron head/likes to ping situation.

I’d see if there is some way of determining what exactly is in the motor, and where it’s installed.

Depending on what it is and where it’s installed, a cam swap “could” certainly get you closer to getting it to run on pump gas.

As was mentioned, a slower advance curve and less total timing is a place to start.

Using the Wallace calculator, plugging in a basic combo......

440, Comp 280h cam in at 106, 9.4cr, sea level..... shows about 145psi on the compression tester.

If the lifters were bleeding down pretty fast, the gauge would read a bit higher.

Hi All the holes were pretty close to a 175 average. It's hard for me to do my own work now. I have to rely on my mechanic. He's a good guy but wants to make a profit so I can't afford to pay him for chasing the issues. I have to pull the number one Valve cover for bleed down and cam lift. Also spark plug to verify TDC on the 1976 damper. It is suspect.

 

[PRHeads]

verify TDC on the 1976 damper. It is suspect.

Good call.

 

[Curiousyellow71]

0 initial and 24 total is a long ways to go to where it needs to be. I am sure you can gain on it, but paying someone else and trying to make 175 cranking work on California gas is a tall order.
Since you have a 3k stall...I think you have the right idea. Look into getting a bigger cam.

 

[Kern Dog]

0 initial and 24 total is a long ways to go to where it needs to be. I am sure you can gain on it, but paying someone else and trying to make 175 cranking work on California gas is a tall order.
Since you have a 3k stall...I think you have the right idea. Look into getting a bigger cam.

The OP looks to have tried what I tried.....reducing the timing as a test to see at which point the knocking goes away. Nobody with any sense would leave it at TDC for initial.

 

[Curiousyellow71]

The OP looks to have tried what I tried.....reducing the timing as a test to see at which point the knocking goes away. Nobody with any sense would leave it at TDC for initial.

Exactly. That is what I said earlier, pulling timing is to see where it doesn't detonate. You won't kill it at least trying to tune it.. Running it indefinately at 0 initial is not what I was suggesting. It's going to run like crap. At least he knows where he is at. Unfortunately, having to retard it that much says something is amiss. To small a cam on a engine in the 9s is a common mistake, on today's gas. The next common mistake is running to hot of plug.

 

[Kern Dog]

I had a detonation issue way back around 10 years ago. I was at almost 11 to 1 with aluminum heads with a 440 based 493. The smart fix would have been to pull the mill and swap in dished pistons. Several members advised this very thing. I was stubborn though. I looked for advice for remedies that were easier to do despite those efforts being less likely to work.
Sometimes we only believe what we want.
One suggestion was to slow and delay the rate of spark advance. I tried that, it didn't make enough of a difference.
I tried the "bigger" cam. The cam I first had was the famous MP '509 hydraulic. The replacement was a Lunati solid with 556/578 lift. (With 1.6 rockers) Yeah, the car knocked worse! It was hard to find specs on the '509 since Ma Mopar was weird about their numbers. Everyone else had clearly defined specs but Ma Mopar stuck to some bullshit- antiquated vague style of specifications. Comparing specs with other manufacturers wasn't simple. AS it turned out, the Lunati cam actually had an earlier intake closing event which increased cranking compression and cylinder pressure. My car ran fine and only knocked from around 3500-5800 when I shifted but if I only mashed it to 3/4 throttle, there was no knock. The Lunati knocked with less throttle opening but with 110 leaded gas, the car was faster than ever.
I ended up slipping in .075 Head gaskets from Cometic to drop the ratio almost a full point. I swapped in a milder cam, the MP 528 solid. I'm just over 10 to 1 now and it rarely knocks.

 

[Gunner1]

I'm at a bit of a loss here because I didnt build this motor. I have always been a Chevy guy. My piston to heads have usually gone from .032 to .040. My last motor was a long rod 400sbc with flat tops and 64cc heads. 11 to 1. cam was a 252/260 @050 600 lift and a 105 LSA at 99 ICL. Ported Chevy Iron 292 turbo heads with a victor Jr and an 850dp. She ran on 91 chevron and was my shop car motor in a 71 Nova. I hauled blocks to the machine shop and towed cars with it. 3k 10 inch converter with 373 gears. Never pinged a bit. I wanna build that kind of motor out of my 440.

 

[Geoff 2]

Every engine, every combo is DIFFERENT. You will read about 9.1 CR engines pinging on 93 octane....& 10:5 CR ratio engines running on 91 that do not ping...

 

[PRHeads]

I wanna build that kind of motor out of my 440.

Imo, you’re likely going to need some effective quench to do that, or run seriously low compression.

I’d be warming up to the idea of aluminum heads.

Of course, you could start with a cam that has some long lazy ramps first.
Can’t hurt.