Maximum advance curve on my 360

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Billbo

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Hi all.
I have a query in regarding how much advance is apropriate. I myself cannot run more than about 27 degrees total advance. At the moment I am running 10 degrees initial and about 16 degrees in the curve and seems very good on 98 octane fuel. Any more initial and the engine will ping when hot. The best allrounder is 10 degrees initial. Is this a problem? Do I need to reach a magic figure of 30 degreees and over for optimum performance? Or is this ok. Its been set up to have 10.1:1 comp with a Comp cams (xe274 230/236 @0.050) with stock heads. From my understanding I think I am not bleeding enough compression with this cam and compression is too high.
Can anyone give some advice?
Regards
Billy D...
 
That sounds a little odd that you can't put anymore than 27 degrees in your motor with only 10.1:1 and that octane of fuel. I wonder if your balancer is off and you really have more advance than it seems? sure sounds like it. Most LA's with stock heads and decent 9 or 10:1 compression like 32-34 degrees total and can handle that much with decent fuel. I'd check your balancer.

Chuck
 
What is the sylinder pressure readings? You can run what the engine allows. Things like sharp edges from a valve job, or excessive carbon, or too hot a spark plug heat range, being too lean or carb issues..the slipped or mismarked balancer...All could cause pinging. SO could faulty math during the build. If your psi is over 180 with the engine hot, the carb wired at WOT, and all 8 plugs out, it's a mechanical situation in the build. If it's below 180, chances are good it's a tuning or slipped timing mark deal. Lose outer rings on balancers slip backwards fairly often. So they will read a retarded amount.
 
Billbo said:
Hi all.
I have a query in regarding how much advance is apropriate. I myself cannot run more than about 27 degrees total advance. At the moment I am running 10 degrees initial and about 16 degrees in the curve and seems very good on 98 octane fuel. Any more initial and the engine will ping when hot. The best allrounder is 10 degrees initial. Is this a problem? Do I need to reach a magic figure of 30 degreees and over for optimum performance? Or is this ok. Its been set up to have 10.1:1 comp with a Comp cams (xe274 230/236 @0.050) with stock heads. From my understanding I think I am not bleeding enough compression with this cam and compression is too high.
Can anyone give some advice?
Regards
Billy D...
Click to expand...
As said by others you need to find TDC and then check the balancer for TDC mark.
I've run 10.2 actual on 91 with 34*total and all in by 2300rpm and not had pinging.
Let us know what you find.
 
FWIW, I am running 10.6:1 in my 360 with a XE268H cam. I run 33 total (magnum heads like a little less total than open chamber 340/360 heads) with 15 initial. The total is all in at 2800 rpm. My cranking pressure is 180-185 psi.

This engine runs fine great on 93 octane and will run with no audible ping on 89 octane.
 
Thank you all for your replies.
My car is a VC val with 3.23 gears, 904 trans 2000 stall and runs a MSD 6AL ignition.
I had this problem with my earlier 318 engine in the exact same car. Since the 318 engine had stock 360 heads installed, I rebuilt them again and reused the heads on the 360 block. So in fact I am using the same heads. The dizzy is the same off the 318 which I had recurved for this problem. Before I was running at 14 degrees with 35 total. But then I was using AV gas (30%) to shut it up. I recurved the dizzy to have 10 degrees less in the curve so I can get rid of the AV gas (it is illegal now on the street and expensive). So I ran 12 initial and 15 centrifugal total of 27 degrees. All O.K. But now with the new 360 block using the same heads and dizzy I am getting the same characteristic as before. This new engine likes this curve. I cannot give it more than about 27 to 28 degrees total advance. I am tending to lean towards the fact that I am not bleeding enough compression with this cam profile. It should have been around about the 9.5:1 mark. The 318 was in the same boat. Also I think these heads may produce hot spots in the chambers. Apart from shaving the heads to 65cc's They have not been touched anywere else. Or the combination of small valves and close exhausts (block huggers all into a single 21/2" outlet out the back) can contribute to high cylinder pressure also. Don't get me wrong the 318 with that dizzy curve went hard and this 360 feels much stonger. The 318 was dyno tested to have 192Hp at the rear wheels at 5000RPM. 380FTLB at 3000RPM. This was with a 218/224 .447 lift cam profile and a 600 vac sec Holley. This 360 although it has stock heads was dyno tested to have 252Hp at 5200RPM (238Hp with the 600 Holley recalibrated to 12.6:1 AFR @ WOT) with a 770 vac sec Holley set to 12.5:1 AFR @ WOT. Tractive effort was only measured instead of torque and it was in excess of 1250 pounds ( I don't know what that would be in ftlb's) at 3300RPM all at the rear wheels. 1/4 mile times best on the 318 was 14.2 seconds @ 95MPH at Eastern Creek. The 360 has not run yet. I am sorry that I wrote so much but all my mates don't want to listen to what I have to say because they drive Fords. I hope I have put enough info for you all to read.
Kind Regards
Billy D>>>
 
As noted before, With the timing at 14/35 with 30% AV gas aditive on top of the 98 fuel I ran best time of 14.35 seconds. With the the dizzy recurved to 12/27, straight 98 octane fuel, best time was 14.21 seconds with the the 318. Did not lose anything. In fact it had a little better response. If you can advance the engine to just before detonation, whether it is 27 or 35 degrees, Do you think this is an optimal setting for your engine? Can someone vouch for that? Or advise me otherwise please. Just more food for thought.
Regards.
Billy D from down under>>>
 
Billbo I still think the timing mark on your balancer is not accurate and your timing readings are probably 7 - 10 degrees off. I am running 32 total and all in @ 1500 with 14:1 and 105 octane fuel with no detonation. This is why I think your readings aren't accurate.

Granted if the car runs best at, as indicated on your balancer @ 27 degrees and is not detonating and you really don't care if it shows 5 or 100 degrees or whatever on the balancer then I would just run it as is. But if you start talking with some buddies or other Mopar guys don't say you only run 27 degrees total because I don't think you actually are running 27 degrees total, I'm thinking more like 37 or 38 total.

Chuck
 
What cam is in the 360? The 360 will make the engine behave like it's got longer rods, even tho it doesnt. A lower rod/stroke ratio can be more tempermental because the piston dwells at TDC for a longer time. So it has more chance to ignite a hot spot. Do you have any pics of the head's chambers when you pulled them off the 318?
 
Thanks 340mopar and moper. It seems quite weird that both the 318 and the 360 balancers are both out. Also I did check the TDC mark on the 360 when I had the engine on the stand with the heads not installed yet. I measured TDC with a dial guage on No. 1 cylinder and checked the actual mark on the balancer before bolting the heads on. The cam is a Comp cams xe274 profile dialed in at exactly .082" lift on No.1 intake (Comp cams advised 0.80"). Sorry I do not have any pics of the chambers but the cast No. is 3418915 with 1.88/1.60 valves and they were U.S. heads with the hardened exhuast seat, stainless steel exhaust valve and they had holes just underneath the exhaust ports which indicate they are for the air pump used for emissions which I blocked of with grub screws. The cast No. was stamped underneath the head not on top on the port runner. They have been milled to have a 65cc chamber. I had these heads on the 318 for almost 10 years which had the same max advance. I rebuilt them and reused them on the 360. I am thinking this problem has something to do with these heads since both engines had the same max advance curve. I hope I have described the heads enough for you Moper.
Kind regards
Billy D>>>
 
Well, you really need to know what the static compression is. But, there may be other things you can do, providing the timing mark is right. You have a low convertor, and a high rear gear. Those combine to try to pull the engine down in rpm, and as you have seen, that cam is ground to make cylinder pressure. I would pull a head, and cc the chamber. Detonation starts on the intake side of the cylinder in most cases. So if there is that normal "eyebrow" looking area around the intake valve seat, polishing that a little and smoothing the chamber would go a ways to helping. It would also give you the chance to figure (calcualte) your true compression. Use the 1" down method on the cylinder to account for the valve pockets, and cc the head. Depending on those results, you may want to swap cams, or retard that one you have. On the "easier" side of things, you can re-adjust your timing curve. All the books say "get it in as fast as possible". But you cant. So perhaps going to a heavier spring to delay the rpm that you reach full advance to about 3300 would help. In most cases, the later the spark on pump fuel, the better (more efficient) the burn will be, and the more pressure gets on the crank throw during each firing cycle. That's because the fuel burns so fast, it doesnt take long for the pressure to develop. If you develop peak pressure too early because of too much advance, you put stress on the lower end, push towards the detonation threshold, and waste power on pumping losses.
 
How about your timing light is not accruate? Is it an advancing timing light? I just don't see a motor this mild with 98 octane fuel not being able to take more than 27 degrees.


Chuck
 
My two cents say that your distributor is not advancing accurately every time. It may be showing one thing and doing another. The chances of 2 separate engines doing the same thing are pretty slim. You did use the same distributor for both right? Moper also has a good point regarding cam/converter choice drawing engine down. IMO you should spring for the MSD billet distributor and rule that out first. I run this on my street car 9.8-1 with distributor locked out at 34* total, with 4 speed trans it has never pinged on 92 octane even while heavy loading in 3rd or 4th gear.
 
Yes the same dizzy was used. You have a good point there. What I will do is recurve the dizzy. The dizzy is a Mopar performance dizzy running the MSD box. So I will lock out the vacum advance aswell ( I did this before but I will do it again). I read an article saying if the heads are designed for fast burning the advance has to be reduced. It come from page 4 of this article I read here. Very interesting article.

http://www.streetrodstuff.com/Articles/Engine/Detonation/Page_4.php

Can these heads be in this category? I have lived with it for years. I don't mind it but I am not sure weather I am getting muximum output out of this engine.I have figures but nothing to compare with. I should of installed alloy heads. But ran out of money.
Conclusion?
I blame the heads. They are emission heads.
Thanks for all you kind advise I will let you know how Ill go with the dizzy recurve.
Regards
Billy D>>>
 
I'm running 11:1 in my 360 and a total of 34 degrees w/open chamber heads. My cranking pressure is 195 psi. I run 95 octane becasue anything under 93 octane pings really bad.
 
ALL DONE!!
I have replaced the iron heads with Edelbrock performer alloy heads part# 60779's. I noticed that the Comp cams Xe274 I had in there, three lifters were not spinning all the time. They had wear indications of this on the lifters. This opened up a bigger job for me. I removed the cam and had it reground to a custom grind. The mass produced cams we buy are ground to suit the smaller lifter diameters of the Chevs and are not suited for Chrysler. They do not accomodate this since all these profiles are derived around GM and the only difference is the cam blank billet they stick into the machine. Comp Cams don't grind ther flat tappet cams. They are contracted out. They only grind there roller cams.
I found an old timer cam grinder which has been in the game for over 30 years and he measured the cam lobes to be 2.5 thou tapper. Also the noise that that these extreme energy cams produce was pissing me off. This was because of that aggressive ramps they have for opening and closing the intake valve. He refaced the cam to suit .904" lifters and machined a 4 thou tapper on the lobes. Also he slowed up the intake ramps. The 0.050" specs are the same. 230/234 degrees. All that tappet rattle dissapeared, The lifters spin like a yo-yo and the advance is at 30 -32 degrees (will go to 36 and try that as well) and there is no sign of detonation. I also received a full printout of the before and after specs of the cam from 0.004" to full lift. Car goes like a rocket.
My conclusion is that the iron heads were no good. They had hot spots in them.
Thanks for all your replies.
Billy
 
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