400 and purple cam

-

Dusty1970

Member
Joined
Apr 25, 2017
Messages
20
Reaction score
26
Location
Dallas Texas
What timing should I set for initial in my Chrysler 400 with mopar purple cam (509/292)?
I have stock heads. It seems to like around 15 degrhanoi has a edge rock 600cfm (which isn't enough) and a wetland perf intake dual plane. Thanks
 
well, this topic could open a large can of worms but worms can be a healthy nutritional snack so I will take a stab at it. If you twist the distributor to increase the timing and the rpms immediately jump up then you need the extra timing [more initial advance] if you twist it some more and it starts to gallop [not a technical term ] then you have gone too far. back down the timing til it sounds nice and smooth. adjust the rpms wuth the throttle adjustment. you really dont want too much timing. it causes hard starting and unpredictability of the idle [bad for emmisions too]use of a vacuum gage is also helpful. the needle on the gauge needs to be as steady as possible with a good signal without going to far. I would guess between 16 to 20. more leaning to 20 would be my guess. Of course you will need to check for toral timing. you should not need over 36-37 degrees of mechanical advance. this is important and may require a narrowing of the slot in the dizzy advance mechanism. my 2 cents
 
I'm not familiar with the edge rock carb and wetland intake, must be a new combo.
 
IIRC the 509 liked some compression, and the poor 400 didnt have jack ~ 8.2:1. youll have to work around that. But the bottom end is bullet proof, beefy stuff down there.
 
IIRC the 509 liked some compression, and the poor 400 didnt have jack ~ 8.2:1. youll have to work around that. But the bottom end is bullet proof, beefy stuff down there.

Sounds like the perfect combination for a turbo :)
 
IIRC the 509 liked some compression, and the poor 400 didnt have jack ~ 8.2:1. youll have to work around that. But the bottom end is bullet proof, beefy stuff down there.
That's an optimistic 8.2.
 
If you wanna sell the 509 cam ,and get a more street friendly cam I'll buy it lol.im a die hard big block 509 purple cam fanatic.
 
That combo will probably need at least 20* initial. Maybe more. I would start at 20 and limit mechanical advance to around 16* all in by 2500 RPM. It may want even more initial, if so, you will need to limit mechanical accordingly.
 
That combo will probably need at least 20* initial. Maybe more. I would start at 20 and limit mechanical advance to around 16* all in by 2500 RPM. It may want even more initial, if so, you will need to limit mechanical accordingly.
Asking a question here. Isn`t 36 in at 2400 a little too quick for todays pump gas? That's the way we used to run them when we had good gas. I`m running 21 initial, 34-all in at 3400. Is my thinking wrong on this, w/ 91 real gas ?? All opinions welcome !
 
The all stock 400/.509 combo's a mismatch. Fix that first because it's never going to be tunable to anything many would be happy with.
Also - OP needs to either overide spell check or turn it off and type carefully. No offense but we can't what you're talking about easilly and certainly will struggle with any responses.
 
IMO bad combo.
4.34x3.38, 292* cam in at 104, 70* ICA
Static compression ratio of 8:1.
Effective stroke is 2.48 inches.
Your dynamic compression ratio is 6.09:1 .
Your dynamic cranking pressure is 111.49 PSI.
V/P (Volume to Pressure Index) is 97................................................97
This is slanty territory, how are you gonna deal with that? 3600TC and 3.91s? Ok then go for it. Just don't run it on the hiway; the total lack of energy efficiency and the 3500/3.91s will make driving more than 80 miles at a time, risky business and very expensive.

But if you boost the compression;
Static compression ratio of 10.8:1.
Effective stroke is 2.46 inches.
Your dynamic compression ratio is 8.13:1 .
Your dynamic cranking pressure is 163.26 PSI.
V/P (Volume to Pressure Index) is 143.............................................143

That's an improvement of 143/97= plus 47.4% That is a huge boost in low-rpm performance.
The 10.8 will show a huge boost in the midrange,and
The 292 will make the power at the top
Plus the 163 psi will make hiway travel possible cuz you no longer need the 3500/3.91s, but can run maybe a 2600TC and 3.23s, so 65=about 2500 with 28s and zero-slip.
I would run it with 3.23s and the stock TC until you figure out what you don't like about the stock TC and the 3.23s,lol.
Cuz 3.23s will get you 60mph at 6000...............at the top of first gear, and that means no shift. About the only gear faster on the street might be 3.55s, getting you 60=6600. But the difference is hardly worth the install. A 2800TC tho might be worth doing.

I don't know what the specs are on the factory 400 cam, but if it was a 252 cam, then here's what the stocker might look like;
Static compression ratio of 8:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 6.92:1 .
Your dynamic cranking pressure is 132.21 PSI.
V/P (Volume to Pressure Index)is....................................................134
134 is pretty good

But if you boosted the compression and left the 252 in there, this is what it might look like

Static compression ratio of 9.5:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.19:1 .
Your dynamic cranking pressure is 164.83 PSI.
V/P (Volume to Pressure Index) is167..............................................167

This is an improvement over stock of 167/134=plus 24.6%, again a huge boost in low-rpm performance, and the potential to make excellent fuel-economy. The power peak of the 252 might be down around 4400 and the shift rpm with a 2.45-1.45-1.00 trans might be around 5500; so 3.23s will get you 5500=55mph. I would just put some valve springs in it to safely pull 60 mph at 6000 and call it done. The stock TC would be fine with this.

A VP of 167 is pretty awesome, especially with such a tame cam.
You could easily re-configure and run a 268 cam with a bit more compression, and have a real performer. Might look like this;
Static compression ratio of 10:1.
Effective stroke is 2.70 inches.
Your dynamic compression ratio is 8.19:1 .
Your dynamic cranking pressure is 164.83 PSI.
V/P (Volume to Pressure Index) is 158.............................................158
So here you gave up some of that tire-frying bottom end, but moved the power peak up some 500 rpm, and moved the shift rpm up accordingly. Now you've got it all; bottom to top, a real strong streeter, with just a small for a BB 268 cam.
With this engine you might still get away with the stock TC and 3.23s. But with the extra 500rpm this combo will be quicker to 60 with 3.55s. Of course a 2800 would be gravy.

Remember that VP is just a tool that helps us predict thelow-rpm performance, that's all. On a streeter, low rpm perf is pretty important. So these are just comparisons that show how various combos might play out. Now go back and look at the first combo; the one with the VP of 97. Do you really want to take off like a slanty?
Here's one for RRR
292 cam in at 98
Static compression ratio of 8:1.
Effective stroke is 2.60 inches.
Your dynamic compression ratio is 6.38:1 .
Your dynamic cranking pressure is 118.67 PSI.
V/P (Volume to Pressure Index) is 110...........................................110
And compare that to a totally stock teener
Static compression ratio of 8.0:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 7.04:1 .
Your dynamic cranking pressure is 135.24 PSI.
V/P (Volume to Pressure Index) is 111............................................111
 
Last edited:
Asking a question here. Isn`t 36 in at 2400 a little too quick for todays pump gas? That's the way we used to run them when we had good gas. I`m running 21 initial, 34-all in at 3400. Is my thinking wrong on this, w/ 91 real gas ?? All opinions welcome !

That 400 piston is close to .200 in the hole at TDC. I think he will be ok........of course no way to tell but to try it.
 
Bad combo this bad combo that. Remember, all of hooha's figures up there are with the cam installed straight up. Lotsa people have made "bad combos" run damn good with tuning. If you have the cam and have the engine, put it together. Advance the cam down around 100 or even 98 ICL, curve the ignition like I outlined and it will run well.
 
Sure; you can advance the berries out of that 292, but now your trading stuff away
The 292/108 cam has 76* of duration. That makes the total available time for all events; 720 +76 =796. Subtracting out the 2x292, we are left with 212 for compression and power extraction.
If you then install this cam at 98*. that leaves just 96* for power extraction, making an already poor steady state cruiser into a real gas guzzler.
But worse is what happens to the overlap period. This cam is blessed with 76* of overlap, the cycle where headers can add a tremendous boost to the power curve by creating an environment inside the chamber that atmosphere is desperate to fill. It's bad enough to install this cam at 104 and give up 4* of scavenging but by going to 98 you give up another 6*, so now the overlap is effectively reduced to 56* or so,and so the power is in like fashion reduced
So now you have a boosted the VP by 14 points, that's very nice now you're up to 318 territory, But the rest of the cam is a waste, plus with the intake opening at 48* btc, you get lots of EGR, on account of there is still so much energy in the exhaust cycle. And there you have the very endearing quality that the 292 is known for, it's delicious idle lope.
I played with this cam for about a year in my 360streeter with 11.3 Scr. I really wanted to make it work,but no matter where I put it I found no good tune. That was at least 3 cam-timing changes. Yeah it ran like the proverbial raped-ape from 5000 and up, But with 3.55s, 5000 doesn't come around that often. So I woulda lobbed that cam into outer space if I could have, but thankfully a racer came along and made me an offer I couldn't refuse.
The current cam in my now 10.9 Scr 360, has the same ICA of 64*(as the 292cam, in at 98) . But the effective overlap is 2* more at 58*, and the power extraction is 7* more at 103*. So I get more of everything except perhaps power from 5000 to 7000, no big deal for a streeter. It has way more average power in the rpms that it is normally driven,way more.
So yes, you cam make the 292 work, in at 98, but, why bother, when a 276/110 with optimized compression, in a streeter,will do everything better.

As always, just my 2 cents
 
Last edited:
Other people have made it work well in low compression applications, including myself. That's all I got man.

You can have all the numbers in the world, but they don't add up sometimes.
 
If it was mine I'd call it a turd. By some people like driving cars that run slow and easy.
Advance it all you want. Add timing all you want. Still will never be as good as a better cam choice.
 
That combo will probably need at least 20* initial. Maybe more. I would start at 20 and limit mechanical advance to around 16* all in by 2500 RPM. It may want even more initial, if so, you will need to limit mechanical accordingly.

I run 20* initial in my HP 383 with zero or + deck height. Limited to 15* mechanical, with 906 heads with that cam advanced at 4*. That cam would be a dog in the 400 with 8.5. CR. I would either change my choice of cams or rethink my piston combo! I have enjoyed that grind over the years but going back to the RR grind to get get closer to stock.
 
Last edited:
My old (Direct Connection) engine "Bible" shows testing various purple shaft cams in a 3000 lb Duster with an 8.5 CR 400... they ran mid-11's.
 
I've been thinking of throwing one (292) cam in my 360. However, i put kb 107 pistons and x heads but not sure of compression. 3.55s in rear but have 3.91's to go in. Now have a 280/474 but seems tame for my taste!
 
I've been thinking of throwing one (292) cam in my 360. However, i put kb 107 pistons and x heads but not sure of compression. 3.55s in rear but have 3.91's to go in. Now have a 280/474 but seems tame for my taste!
It's hard to build a 360 with too much compression for a 292; it wants 11.3 and the bottom is still soft. Mine wanted 4.30s with a 2.66low trans, for a starter gear of 11.44. If you have an automatic, it will want to be shifted at about 7000 for low ET, and a lotta stall. For the engine to live at those rpms,it means special build procedures need to be taken.For best results your X heads will need some work.You may have trouble escaping detonation with the lack of tightQ in this combo.
IMO, if the 280 isn't doing it for you, and you are a streeter, you'd be better off with a bigger engine, or a new combo.

I run a 276/286/110 in an Eddie headed 367 at 10.9, that goes 93 in the 1/8th which the Wallace calculator says can be an 11 second car. That car is always tame to me by midsummer. But the next spring, it is always a surprise, the tame is gone! This engine will spin 295s to waaaay past the speed limit, anywhere in Canada. This not to brag on my tuning skills, but to say what the combo can do. If your 280 cannot do it, then perhaps the combo, or the tune , is off.

1)I'm guessing your sitting at maybe 9.2 Scr, and if your ICA is 64*, then here's what your combo might be sitting at
Static compression ratio of 9.2:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 7.39:1 .
Your dynamic cranking pressure is 144.16 PSI.
V/P (Volume to Pressure Index) is 123........................................................123
And that will certainly be tame to about 3500rpm, very tame indeed. And the 292 will only make it worse.
I get the Scr from a total chamber volume of 90.8cc, which is 72 in the heads, a gasket of 8.9, 5cc eyebrows and the pistons down about 4.9cc or .023 down.
The solution is to increase the compression and simultaneously bring the Q into the "tight" zone of .035 to .045. This will require some creative engineering on your part with the parts you have.Or swap out the heads, or the pistons.
2)This is what you might want
Static compression ratio of 10:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.01:1 .
Your dynamic cranking pressure is 160.14 PSI.
V/P (Volume to Pressure Index) is 136.......................................................136
This would feel like an increase of nearly 11% on take-off, and diminishing somewhat up to 3000/3600. But the increased compression would still be felt all the way to the shift.
Bringing the Q into the zone with open-chamber heads is not possible with KB-107s tho, so something has got to go, or you will be stuck running premium grade gas forever.

3)If you swapped out to closed chamber heads and machined the decks down to zero, then your Q will equal your gasket thickness.So then you can run the .039 FelPros.
This will make a lot of compression,perhaps too much. It might look like this
Static compression ratio of 10.8:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.64:1 .
Your dynamic cranking pressure is 176.62 PSI.
V/P (Volume to Pressure Index) is 150.......................................................150
Hyup you are committed to Premium grade, but it will be wicked out of the gate. 150 is a lotta VP.
So now, it makes sense to put that 292 in or to retard the 280
4) Say you put that 280 in at an ICA of 72*, this is what it could look like
Static compression ratio of 10.8:1.
Effective stroke is 2.58 inches.
Your dynamic compression ratio is 8.06:1 .
Your dynamic cranking pressure is 161.44 PSI.
V/P (Volume to Pressure Index) is 127.......................................................127
Yep that will work, but the bottom went soft again

5) So let's try that zero-decker with 63cc aluminum heads,and put the cam back at say an ICA of 66*, and here it is; this is still the 280 cam
Static compression ratio of 10.7:1.
Effective stroke is 2.69 inches.
Your dynamic compression ratio is 8.29:1 .
Your dynamic cranking pressure is 167.44 PSI.
V/P (Volume to Pressure Index) is 137........................................................137
Well that's looking better. this will run on pump gas

6) But say you wanted more at the top, and were ok to run a 3500TC, let's put the 292 into it with an ICA of 70*
Static compression ratio of 10.8:1.
Effective stroke is 2.64 inches.
Your dynamic compression ratio is 8.23:1 .
Your dynamic cranking pressure is 165.87 PSI
V/P (Volume to Pressure Index) is 133.......................................................133
See what happened there? we gave up a little on the bottom again,and got a little on the top, but to take advantage of it, she's gonna have to spin up to 7000 to find it ,on the 1-2 shift. Well hang on, how fast is that with 3.91s? That's about 56 mph. So then you bang it into second and the Rs drop to 4100 and you pull to the speed limit at 4800. See what I mean mine wanted 4.30s. It liked 4.88s even better.
IMO, if you are a streeter, it would be better to go the other way, the way of the smaller cam.
Take a look at the VPs here;they range from a possible current set-up of 123 to a high of 150.
To give you an idea of what these VPs mean;
A totally stock teener comes in at about 111VP, and a totally stock 360 comes in at about 120. So your bottom end performance currently might be feeling pretty much like a stocker. But it rips pretty good after 5000 right?

7) I tell you what, lets put a smaller cam in there for a sec, say a 268 fast rate in at 106, for an ICA of 60* and lets go back to the possible current Scr of 9.2. Here it is
Static compression ratio of 9.2:1.
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 7.60:1 .
Your dynamic cranking pressure is 149.54 PSI.
V/P (Volume to Pressure Index) is 131......................................................131
Wouldja look at that.This is already 8 points stronger than your current combo.

8) Lets pump it up a bit
Static compression ratio of 9.8:1.
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.08:1 .
Your dynamic cranking pressure is 161.96 PSI.
V/P (Volume to Pressure Index) is 142...........................................................142
Look at that! just a modest increase in Scr to 9.8 and with the Dcr at about the limit for iron heads and pump gas, we get a big fat bottom end, another 11 points higher. This will feel,perhaps, 142/123=15% more powerful at take off, than your current combo. This is like putting 15% more gear into it, or from 3.55s to 4.08s; isn't that nice. The power peak of a 268 cam in a 360 might be at about 5200. And the automatic will want to be shifted at 6400 on the 1-2 shift. This combo is now strong enough to run the 3.55s so outshifting at 6400 will get you 56 mph imagine that. And it will drop into second at about 3800. With any luck the 268 will be making more power at 3800 than your current 280 cam, so it will rocket to 60mph@4100. Certainly not ideal Rs, but that's 3.55s for you. Sometimes less is more.
9) But lets say you zero decked it and swapped to aluminum heads. Still the 268 cam Ica of 60* but now the Scr pumped up
Static compression ratio of 10.8:1.
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.88:1 .
Your dynamic cranking pressure is 182.96 PSI.
V/P (Volume to Pressure Index) is 161...........................................................161
Holy Smokers!!
This is again at about the upper limit for Dcr/psi with aluminum and tightQ, so you can't get much better than this. 161 is warmed up BB take off power, so basically it will bust any street tire loose at 35 mph with 3.55s, on the downshift.It might even do this all the way to 45/50mph

10) This is so much bottom end we can easily give some up.What happens if we retard the cam to an ICA of 62*
Static compression ratio of 10.8:1.
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 8.77:1 .
Your dynamic cranking pressure is 180.05 PSI
V/P (Volume to Pressure Index) is 156...........................................................156
There you go

11)
by way of comparison,I currently run this; 276/286/110 in at 106, with OOTB Eddies, and ICA of 64*
Static compression ratio of 10.9:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.72:1 .
Your dynamic cranking pressure is 178.73 PSI.
V/P (Volume to Pressure Index) is 153........................................................153
I run 3.55s and it busts the 295s loose at up to 50/55 in second gear (M/T), and It's a dump it and go deal from the stoplight. (3.09 low gear), and best of all?
It burns 87E10

So there are some ideas. Always be aware of the Q; for best results, it needs to be in the .035 to .050 zone
Also keep in mind that the VP numbers are just tool to help you understand why your bottom end is so soft..................or not soft,lol. Read about it here
Cam Timing vs. Compression Analysis
 
Wow! That is something to think about. Very well put. I will brainstorm all info. I forgot to mention I already have a 3400-3600 stall 9.5 FTi converter in the 727 currently.
 
Well there's your answer right there.
That 280 with a 3500, and 3.55s should be anything but tame.
However, by 3500 rpm,VP is nearly meaningless And so is Dcr. From 3500 on, the engine is just a big air pump.Even low-cylinder pressure is fast becoming a moot point. So if it seems lazy, try to find the choke point.
You may need to look at how the air is or isn't getting into the engine, and is or isn't getting out.You aren't still sucking hot underhood air are you?
But it may be that your engine is totally up to speed and yes, that you are just wanting more. This happens to me every summer as I acclimate to the power.
To help you figure it out, I suggest time trials. The fastest way to determine how much power your engine is putting out is to qtr-mile it and compare your trapspeed with known combos. And the trap speed varies quite a bit with the weight of the vehicle,and the power, but not much else.
Chrysler helped us in the 60s and 70s by compiling charts, that are still fairly accurate today. From those charts, we can get a pretty good idea of the power to weight ratios from the trapspeed. Not the ET so much,lol, cuz that is a very muddy pond.
And once you have determined your P/W is is a simple matter of back-calculating the power from the weight.
Just one example is this; at 400hp and 3600raceweight, you have a W/P of 3600/400=9.0, and the chart says this should trap at about 111 mph. If your car does not trap at 111, then either it does not weigh 3600 or it does not have 400hp; it's that simple. Of course there may be mitigating factors that can skew the numbers a tad,but by and large the charts work.
So once you know the engines true power level, and you think something is wrong, it's time to figure out where it's lacking. That may be a little harder to do, and may cost a lotta money to rectify.
But just throwing a cam in it, IMO is not the best idea.Especially with an unknown compression ratio.

Also keep in mind that a streeter is a completely different set-up than a race-car. Many, many sacrifices have to be made to get a nice streeter. Or perhaps I should say that a racecar must be a much more focused combo, and that the streetcar has a much broader operating environment. The 292 puts your streeter into the realm of racecar, in that the TC and gears have toi follow it, and the engines best operating range becomes very focused and somewhat narrow. Now the 3500TC is the first concession to that, as will be the 3.91s that you already have. And the very high operating rpm requires engine oiling mods to survive. If you just slap the 292 in there and start drivinig it into the deep 6s, the rodbearings won't put up with that for very long. Just a couple of seconds of detonation and you get to start all over.
But the 292/3.91/3500 combo is now limited to cruising at about 55mph, so it's become a city car, and a weekend warrior cuz the price of gas will really put a damper on the DD aspect. So there's nothing wrong with that except you got all this money tied up in a project that sits mostly in the carport all the time.
So just to remind you, there's more ways to get power out of an engine than just to throw more cam at it.
One of the problems I found with the 292 was that, to get the best out of it, the engine had to be really revved. Like the power didn't start until about 5000 and didn't really end, even at 7000 it was still pulling. Well this window from 5000 to 7000 with 3.55s occurs at 44 to 62 in first gear, and from 74 to 104 in second (automatics). So ok, it pulls really hard here, really hard. But really it has become a one-gear streeter, at WOT. Where you actually drive it is mostly not at 5000 to 7000. Mostly it will be doing say 20 to 40 mph, maybe occasionally 50. So really wouldn't you want the power to be there? I know I did and ditched the 292 almost as fast as I could.
To get the power from 20 to 40 is a real eye-opener. You might want to sit down.
With 3.55s , 30mph is about 3400 in first gear. Trying to get power out of a 360 at 3400 is a real chore, but the window from 20 to 40 is from 2200 to 4400. So this is where your 3500TC totally makes sense. But your 292 is way out in left field, as is the 280/484. No if the 3.55s stay then you want a cam to put the power where you need it,namely 3800.
But let's say you give a rat's behind about hiway cruising or economy. So work it out with the 3.91s. Now, the window from 20 to 40 is from 2500 to 5000 in first gear. So you want the power to be at about 35mph or 4400. Ok the 280 cam is out! Again.
So lets back up the bus, and just start with the 280 cam and see what gears we do need to work with it. Ok let's say the 280 is peaking at 5400 in your X-headed monster. This will take about 4.56s!in the window. Lets do the math. With 4.56s;20mph =2900, and 40 is 5800, BadaBing! Now with your 3500 TC, you may get away with 4.30s, which will at least get you 50mph revved out at the top of first.
My 292 combo an 4-speed liked 4.30s to 4.88s
But here's the rub;
If you get tirespin then all this means chit. If your tires spin from 20 to 40, it almost don't matter how much power your 360 puts out, it won't ET well in that zone,so you might as well put it back to stock,lol, cuz the difference in ET from 20 to 40 is just a couple of blinks of an eye, allbeit accompanied with all kinds of smoke and noise.
Yeah so there's my 2 cents.
Except to get a timeslip; which will spit out your W/P and tell the tale.
 
-
Back
Top