Over the past several months I've been wrestling with the idea of upgrading the AFR 195 heads(non Eliminators) on my 406 to the new 210 Eliminators.....and I think I'm about ready to pull that trigger.

The question I have is chamber size options. I now run 75 cc chambers, and with that I calculate a 10.1:1 compression ratio....verified by my machinist years ago. I run a flat tappet solid cam with 254@.050 duration, and 36 degrees locked out timing. Never pings, starts like a new car, and overall performance is great. The 210's are available with either 65, or 75 cc chambers, and I am tempted to try 65 cc to raise the compression to 11:1, and for the mean time....keep the same cam.

I'm thinking it'll work fine because of the cam duration, but want to hear from those that are running similar combinations. Also in the future I do plan on doing a solid roller cam, but with less duration, so that needs to be considered also. And really long term.....a 427 short block,.....but the wife doesn't know that's coming yet.

 

I am running a 10.6 to 1 406 with 200 Dart Pro 1's and a 244/244@.050 cam and it is 93 octane friendly.....
I do have a curve in the distributor......21 initial...34 total.
Do the new AFR's have a "fast burn" chamber? That helps a lot.
Same type of chamber design is used on factory LS engine at 11 to 1.
I personally think you will be fine.......
I like compression....makes an engine have a crispy sound.....

Jebby

 

Motorhead, Diehard, and myself are running 250 ish solid roller cams in our 427's and I think 11 or more compression. very doable on pump gas with higher stall or even better manual tranny.

I worked on locked out magneto ignitions @ 30 years ago. The old salty guard had been using them for 20 years and couldn't see why you would change. We showed them that optical triggered or crank triggered ignition and changeable race battery with some advance was far superior.

Modern chambers like these AFR's tend to make the most power at sea level @ 32-34 degrees. I'm a fan of 18-20 initial and adding 12-14 degrees mech advance and limiting vac advance to 10 or less more like 6-8 degrees.

The point of when to have the all timing in VS rpm is a war that will rage on the internet for a long time. But this is the facts, so I did not make it up and a reasonable person should be able to grasp it.

It comes down to volumetric efficiency, period. Flame travel does not do well in a exhaust diluted poor stock gen 1 chevy chamber design. small cam, poor intake, restrictive exhaust, EGR 80% cylinder filling.

Of course you need all the advance you can and all in at sub 2800 rpm.

As volumetric efficiency and flame travel increase the less timing required. Period.

In real race engines they actually pull timing out as the rpm increase because the flame travel increases with highly atomized fuel

 

The locked timing is kind of a band aid,...one of these days I will fix that. With the 7 inch vacuum at idle, I found any sort of vacuum advance was just "hunting", and my idle was all over the place. Now with it locked it's rock solid at 1000 rpms in gear.
If I had a manual trans,...would not have had any issue for sure.

I figured that 11:1 wouldn't be an issue, but before I order the heads,...just want to be sure. Like to hear from a few more with similar builds.

I really don't expect to drop the cam size that much either when I do go solid roller. I love the rpms, and that oh so nasty idle.

 

ported vac advance keeps it from hunting all over the place. Have you ever put a timing light on a computer controlled car? The ignition is bouncing all over the place. I don't think that it ever holds a steady advance time

 

My 383 is a hair under 11.2:1. AFR 210's, Chris Straub Hyd roller with 233/235@.05" and 91 octane. I do get a touch of pinging right at tip in when starting to accelerate from cruise. Other than that, no problems with pinging. My vac advance is already limited to 10 (mech adv is 20 initial/33 full adv.), but like George said above, limiting it to 6 or 8 would solve that for me and is on my to do list.

 

At the time I was trying to resolve the idle issue, I did try ported and manifold vacuum ports,...neither made any difference. I had just swapped in the solid cam, which is the biggest cam I'd ever run, and wasn't sure if the idle issue was timing or carb related. I tried various limiter bushings in the MSD, a few different vacuum cans,....with no success. Even swapped intakes from the Vic Jr to the RPM.....

I went back into the carb, tweaked IFR and IAB jets, ended up replacing the throttle base plate, and converted to a four corner idle. I also later converted to annular boosters......That may have fixed the issue,...but at that stage I had already locked out the timing. At this stage,...it's running great.

Once I pull the heads for the swap,...maybe I will once again tinker with the timing...if I get around to it. Got a lot of other projects on deck.

 

So... Is pinging not as disastrously bad for an engine as I think it is?
(I'm kind of shocked that you're ok with it pinging under hard acceleration.)

Doesn't retarding the timing hurt performance, too?


How much would reduced temperatures help with pinging? -If you could reduce engine temps by 10 degrees could that theoretically get you back into the safe zone? (switch to an aluminum radiator; configure electric fan or fan clutch to come on sooner; intercooler out in front of your radiator, cold air intake, etc...)


I find this issue to be most interesting when you're right on the edge between pinging and not pinging and you're just so close to ringing every last drop of perf out of the engine AND not knocking.


Adam

 

Money Pit, like others have already said you should have no issues with a big cam and 11:1 compression. I have 11.3:1 in my C4 race car that I run pump gas in. I also have a tight quench and good cooling which help.

 

I'm only partially understanding this, but I find it interesting so I'll ask some clarifying questions.

I interpret what you're saying as "there are a number of ways to measure & control ignition timing and the old-school magneto+vacuum method has proven to be not as accurate as optical triggered or crank triggered ignition". (am I interpreting that correctly?)

I'm further then assuming that the implication of more accurate ignition timing is improved performance and improved ability to avoid pre-detonation/knocking when you're running at CRs that are on the edge of what your fuel, temperatures, head chamber design, and cam timing can tolerate. (Have I screwed it up yet?)


The reason I'm asking: I'm planning a throttle-body based EFI + ignition control EFI install this winter and I know there are a couple of options for ignition timing control ("Dual Sync" distributor or crank trigger, at least as options); additionally although my top-end swap will only have a static 10:1 CR, I'm planning on pushing the dynamic/actual CR to close to the limit with the cam (if Straub says it's ok); I'm mildly scared that hot weather (although rare in Seattle) or bad gas could result in pinging risk so I'm trying to reduce that risk in the planning stages as much as possible (quench/squish is already planned at ideal levels), I'm doing what I can regarding engine temps, but if the type of ignition control is another way to help control detonation / pinging risk, then I want to do that "right", too.


Note: I'm a risk manager for a living, so I kind of obsess over risk details like this...

Adam

 

Can you post your cam stats? (I have a conspiracy theory that a lot of you +11:1 CR pump gas guys have big long duration lumpy cams that reduce cylinder pressure / dynamic CR and that that's high on the list of items that "save you".)

-I'm also guessing that you can get 93 octane pump gas in Ohio (unlike me and my lowly 91 octane Washington State "premium") ;-(

Adam

 

If your long term goal is a 427 then I would opt for the 220's now.

 

You misunderstood. When I'm transitioning from cruise to light acceleration under part throttle, I get maybe 1 second of pinging at the moment of tip in. This is likely from the small accelerator pump movement which is not providing enough fuel at tip in or a bit too much vac adv. Hard acceleration at WOT is perfect with absolutely no pinging as is all other driving conditions.

 

I was thinking 220's....AFR recommended the 210s. What about chamber size then? Stick with 75 cc?

 

Plug the vacuum advance and try it. Bet you lose the ping. That's what lead me to locked out timing,....well one of the reasons. My cam is pretty big.

 

Thanks for the clarification. So when you just push the throttle a LITTLE bit harder, it thins out the AFR, which makes knocking more likely and for about 1 second you get a knock and then it's fine?


Adam

 

yes.

 

I had the same problem with my original crane SR cam 232/238 383 @11.2

I used octane booster and dorked with everything. I actually had very light ping at freeway cruise without booster. I had the crane cams adjustable vacuum can on my Unilite dizzy. I finally gave up and went to a bigger cam and wrote it off as a learning experience.

I would have told that cam of yours would not work

 

You might be to young to have owned point or dual point ignitions. from the minute you start a new point system it is degrading. The points open and close and the arcing sparks is burning the surface. dual points was an improvement it took more than twice as long to burn out. How fast you can open and close points was kind of a motor rev limiter

HEI was a big improvement. later it became optical like mallory and crank trigger from MSD. I don't know who patented the designs? The most accurate for the time.

A magneto looks like a tall distributor. Tall because the lower section is a generator (power source) and the top was a dual points under a rotor cap. They generally had locked timing and no vac advance. I was a pit crew person and at a young age I thought how stupid!!!!!!

I had a Mallory Unilite small cap on my vette with some super coil. I made a bet in the shop that I could make the sprint car run better with parts off my vette and a race battery that had to be replaced or recharged between events. It takes a small cap to clear 8 stack Hilborn injection. We went over a day early to an event for track testing time. I was right and they never used a mag again.

Look at a modern car and distributorless ignitions. coil per cylinder.

My advice is to get what you can afford.

 

Yes I have access to 93 which I use. My cam is actually pretty mild. It is a custom grind I came up with because my race class is restricted by power/wt ratio. My goal was a broad tq curve with lower HP.

Adv @0.050 lift w/ 1.6 RR
275 221 0.550 - intake
284 228 0.556 - exhaust
111 LSA
107 ICL

This is in a 355ci with ported stock L98 heads and custom single plane intake. Makes about 350hp and 390ft/lbs to the tire. Power peaks around 6200rpm and I shift at 6500 but I am able to buzz it to 6800 or so to eliminate a shift in-between corners as the power doesn't drop off much.