Distributor Over-Advancing

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Interesting, I have a set of Hughes 1110 springs and retainers just waiting to be installed, when I changed the timing chain I installed the cam straight up dot to dot, I have about 150psi cranking pressure, down low torque on it is quite good but gives up pretty quickly as the rpms increase, but that may just be because of the timing issues I've been having
 
At 150psi you are right on the predicted pressure.
If my internet sources are right, about the cam, the dot to dot method may actually get you close to the designed Ica of 64*.... because the keyway on the cam may have been put in the right place to make it easy to install, on the stock cam. Again, I don't actually know that what I was told is true.
But if I had a 5.2 Magnum,in a lightweight performance car, capable of reliably reving to 6000, I would be ripping the front off and putting a degree-wheel on it,to find out; because 19psi, and a 27point VP difference, is a massive, massive, change. It's so massive, I doubt I could run that cam in my 367 combo,as the pressure would rise to 200psi.
There is a slight downside to this cam advancement; the powerstroke falls from an excessively high (probably done for fuel-economy), extraction number of 127*, to a more-normal number of 114*. This does not make it a gas-hog; (99* makes a gas-hog,lol). In an A-body, 114 can still get into the 20's; your results will vary,lol.
So what you get is; more torque, more power, a snappier more eager to go engine, and in all likelyhood, more mpgs in steady-state cruise.
The new effective overlap of 36* will like headers for a little power increase.
 
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Edit: changed out the coil and module to a 4 pin and it fixed the issue!! :thumbsup:
 
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No, I changed both at the same time, I'm a believer that when one goes, it has the possibility to take the other one out with it, and I didn't want to take a chance of potentially hurting a new module or coil
 
I didn't keep it, it was strictly for testing purposes to eliminate the possibility of it being a vac can issue.
 
Wide LSA cams decrease degrees of compression, leading to soft bottom ends; and also decrease degrees of power extraction, leading to poor fuel-economy.The numbers with this Voodoo in at 106 are; 127 compression/107 power extraction/ with an effective overlap of 34*
At 150psi, I woudn't want to lose any more pressure, especially with small gears and a stock-TC.
 
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So, what you're telling me is, this is a bad choice? For reference the car has an a500 trans with a factory high stall, and 3.23 rear gears, soon to be 3.73 or potentially higher.
 
If you have another suggestion I'd love to know, as I can still cancel this order, its backordered. I chose this cam because it seemed to fit my intended usage perfectly, I wanted something that pulls fairly hard, pretty much maxes out the lift of my magnum heads, and will still start up in our -40 weather (the car is daily driven in the winter also)
 
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Would the thinner Mr. gasket head gaskets for slightly more compression help? Or is this just a poor cam choice for this combo in general?
 
No it's a great cam, just not for a 318 engine that is already down to 150psi.

Hydraulic Roller Cam. Great performance cam in 340+ c.i. applications. Works well with computer modifications or increased induction systems. Likes headers and 3.42+ gearing.

  • Advertised Duration (Int/Exh): 264/270
  • Duration @ .050 (Int/Exh): 213/219
  • Gross Valve Lift (Int/Exh): .485/.485
  • LSA/ICL: 112/106
  • Valve Lash (Int/Exh): Hyd/Hyd
  • RPM Range: 1200-5200
  • Includes: Cam Only
Part Number: 20200717
With flat-top pistons .040 in the hole and closed chamber heads, you are walking a thin line to detonation. To stay out of it with iron heads, your Quench needs to be between .030 and .050, or greater than .080; and not in the range of .050 to .080 which is a known detonation-prone zone..
By installing an .028 Your Q becomes .068 right in the middle of the detonation-prone region. The .039 gasket gets you to .079, the upper end of the zone.
You didn't answer my previous questions so I don't know what you actually have.
But the stock cam, if it is what I was told.(250/264/110 in at 119), then it has a very broad install window that could easily pump your pressure up, as I earlier got into. For nearly zero dollars, I would certainly give it a chance. But you won't know until you actually degree it.
I really am trying to help.


The A500 has ratios of 2.74-1.54-1.00-.69od and is a great item. It allows you to run a super low rear gear, and so make the teener come alive. That, with the higher stall TC, will really make the 5.2 come alive.
But with just 3.55s or 373s; between the compression loss of that Voodoo cam, and it's attendant short extraction period of just 107*, around town it will be a wicked gas-hog...... because you will always be driving deeper into the carb than you should be, to get the effective pressure that you are craving.
But with 4.10s in the back, a soft bottom end wouldn't be the end of the world. Except for that doesn't solve the fuel consumption issue. And gas, IMO,is not ever gonna get any cheaper ever again.
On the hiway, 4.10s will get you ~2400rpm, so if your cylinder pressure is low, it will suck gas here too. 2400 is a good number...... if the pressure is up; because you can throw some ignition timing at her and lean her out; that's how to get hiway economy; the one-two-three punch of; effective pressure, timing, and lean-running. If you miss on pressure, it reduces the efficiency; and if you miss on timing you can't run lean and it all goes to heck.

318LAs were low compression ratio engines. But with the cams they had, they had pretty good pressure. And because of that,their Effective pressure was really good at hiway rpms. Actually almost all the time because they were usually geared to be stuck in an rpm where the effective pressure was working for them. They were application-specific engines. If you needed more power, the solution was just another SBM size away. There's a good reason they were built in ~41 cube increments.
The Magnums neatly solved the power issues, and the roller cams were a good idea too.But if your pistons are .040 in the hole,it's making things tuff.
 
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Well, any suggestions would be mighty helpful, as you're the guy who's good with numbers haha I am not so much. Smaller cam? Re-ring and more compression? Both?
 
mchartier105 said:
Well, any suggestions would be mighty helpful, as you're the guy who's good with numbers haha I am not so much. Smaller cam? Re-ring and more compression? Both?
Click to expand...
Personally I would not opt for a Hydraulic roller cam, source a good solid or hydraulic flat tappet cam of your choice.
Speaking from experience Hyd roller lifters in an LA block can be problematic and are way over priced. Just throwing money down a rat hole for a street application. I have seen many flat tappet SBM that make nice power and are very streetable.
Just my opinion, I sure try are some that may disagree.
 
No problem haha i'm just looking for suggestions on how to add a little bit of power to this engine, as its a bit of a dog as it is now.

Its a 1998 5.2 with an Airgap Manifold and 750 Annular booster carburetor (I had a 600 holley and did find an improvement in power with the bigger carb), factory 1998 Magnum exhaust manifolds with dual 2.25 exhaust through glasspacks, factory high stall, and 3.23 gears
 
AJ/FormS said:
No it's a great cam, just not for a 318 engine that is already down to 150psi.

Hydraulic Roller Cam. Great performance cam in 340+ c.i. applications. Works well with computer modifications or increased induction systems. Likes headers and 3.42+ gearing.

  • Advertised Duration (Int/Exh): 264/270
  • Duration @ .050 (Int/Exh): 213/219
  • Gross Valve Lift (Int/Exh): .485/.485
  • LSA/ICL: 112/106
  • Valve Lash (Int/Exh): Hyd/Hyd
  • RPM Range: 1200-5200
  • Includes: Cam Only
Part Number: 20200717
With flat-top pistons .040 in the hole and closed chamber heads, you are walking a thin line to detonation. To stay out of it with iron heads, your Quench needs to be between .030 and .050, or greater than .080; and not in the range of .050 to .080 which is a known detonation-prone zone..
By installing an .028 Your Q becomes .068 right in the middle of the detonation-prone region. The .039 gasket gets you to .079, the upper end of the zone.
You didn't answer my previous questions so I don't know what you actually have.
But the stock cam, if it is what I was told.(250/264/110 in at 119), then it has a very broad install window that could easily pump your pressure up, as I earlier got into. For nearly zero dollars, I would certainly give it a chance. But you won't know until you actually degree it.
I really am trying to help.


The A500 has ratios of 2.74-1.54-1.00-.69od and is a great item. It allows you to run a super low rear gear, and so make the teener come alive. That, with the higher stall TC, will really make the 5.2 come alive.
But with just 3.55s or 373s; between the compression loss of that Voodoo cam, and it's attendant short extraction period of just 107*, around town it will be a wicked gas-hog...... because you will always be driving deeper into the carb than you should be, to get the effective pressure that you are craving.
But with 4.10s in the back, a soft bottom end wouldn't be the end of the world. Except for that doesn't solve the fuel consumption issue. And gas, IMO,is not ever gonna get any cheaper ever again.
On the hiway, 4.10s will get you ~2400rpm, so if your cylinder pressure is low, it will suck gas here too. 2400 is a good number...... if the pressure is up; because you can throw some ignition timing at her and lean her out; that's how to get hiway economy; the one-two-three punch of; effective pressure, timing, and lean-running. If you miss on pressure, it reduces the efficiency; and if you miss on timing you can't run lean and it all goes to heck.

318LAs were low compression ratio engines. But with the cams they had, they had pretty good pressure. And because of that,their Effective pressure was really good at hiway rpms. Actually almost all the time because they were usually geared to be stuck in an rpm where the effective pressure was working for them. They were application-specific engines. If you needed more power, the solution was just another SBM size away. There's a good reason they were built in ~41 cube increments.
The Magnums neatly solved the power issues, and the roller cams were a good idea too.But if your pistons are .040 in the hole,it's making things tuff.
Click to expand...

So what you're saying is, ditch the voodoo, advance the stock cam and either deck the block or install slightly taller pistons? And change the rear gear to something around 3.73-4.10?

I'm relatively new to all this so please bare with me, i'm trying to learn and get a better grasp on all of this
 
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You got ahead of me.

No, I'm saying if the cam is as I was told 250/264/110 in at 119 , then this cam has a very wide window of opportunity that with just advancing it back to normal, AND with no other changes, and with 4.10s in the back, it will already be a potent combination; based on the 150psi that the engine now has which is gonna climb quite a bit higher as the Ica is advanced some 9 to 12 degrees. It won't make near the peak-power of that Voodoo, but it will make waaay more power in the rpms that you normally drive.
By adding the 4.10s you will be increasing your TM (Torque-Multiplication) by 4.10/3.55= plus 15.5% throughout the entire rpm band from stall to shift. If your engine currently makes 300 ftlbs somewhere in the rpm band, say at 2800 with that 250* cam, then with the current combo, out the backdoor it will send 300x2.74x3.55=2918 ftlbs. But with 4.10s it will be; 300x2.74x4.10=3370ftlbs. This is sorta like your engine just became a 367 cuber.
Now if the cam in it is a 250/264/110 in at 119 with an Scr of 9.5, then the Wallace calculator predicts 151psi at 112VP@250ft elevation. And you already know how soft that performance is with the 112VP and 3.55s.... right.
But if you advance that cam to 108*, the pressure is predicted to rise to 163psi@132VP. This is a huge VP increase of 17.9% . Now if you had a 3500rpm TC, you wouldn't care much about VP, because VP is a low rpm ratio that tries to predict low rpm performance. But if you have a 2000rpm TC, this suddenly becomes very important, because with 3.55s you are stuck in that low-rpm band for most of your city driving. With 4.10s this will make a big difference. And if your TC is more like a 2400, then the high-pressure engine with 4.10s will become a blast to drive.
However, to run 163 psi may not be possible with .068Quench, except with full-time hi-test pumpgas.So with that large window of install, instead of a 108/53*Ica install, you could try 112@57* for a predicted pressure of 159@123VP. You might get away with 89gas at WOT/87 at cruising. It's gonna depend on how the .069 Q works out.

Now, to be fair, that Voodoo has a 58* Ica too, in at 106..... but it will have an effective overlap of 34* versus your 26 (in at 112), and it has only 107* extraction versus your 120 (still in at 112). So it will make a bit more power with it's higher lift and extra overlap, but it will also be quite hard on gas with that meager extraction. And to repeat, that power does not arrive until way on down the road with 3.55s.

So, IMO, get the 4.10s in there, and give your current cam a chance. Then if you still need more power down low, start advancing that cam until you get into detonation, and I would try a 112 installation right away with an Ica of 57*.
If you need to cruise at higher than 65(2400), then the 4.10s could be downsized a lil. For example 3.91s will get you 2400=72mph. With the 2.74 first gear, and higher pressure of the Advanced stock cam, I don't see this as a problem. And I like the 65=2180 with 3.91s. I have been cruising at 2140 since 2004; It's very comfortable. But hard to give the engine the mega-advance it wants.

But recall that I don't have a clue what cam is in your engine nor where it is installed; everything in this post is predicated on it being what I was told; namely a 250/264/110 with a stock install of 119*
 
On the topic of ignition,H.E.I toss it. I had 3 go out in less than a year, what ever chinese company that is making them now sucks. I had to replace my mopar ECU 1 time in 5 years. Yeah HEI does run better but going out that many times, from 3 different companys STANDARD, D.U.I, ACCEL. Also check all your grounds, even behind the gauge cluster at the ALT Gauge. Now i have to live the rest of my days hearing it from my buddy!
 
It was the 7 pin module that was advancing your timing. I am also having the same issue with my 8 pin module. Only way to stop it is going to the 4 pin, which you did. I Found this out the hard way!
 
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