Jason, I had a very similar problem on my 455 engine. I looked at my ign. timing at approx 3000 rpm or so and noticed that the ign. timing was varying approx 5 deg or so at a constant rpm. I went to a MSD distributor and solved the problem. Poor bushing in the distributor? What does your timing do at a steady rpm in the range your talking about?
Carl...Off-topic question for you here...The pic in your avatar...How in the heck do you get your garage door opened to get your cars out??? Isn't the car on top in the way of the door???
What about better gas? How about running an EGR valve. I know it would cause some power loss, but? John
I've never really seen this before but the timing on the dis. I have comes in during 2 dif. stages. It doesn't seem to care what kind of springs I use. Light, medium or heavy seems to be all the same as far as the curve is concerned. The first stage comes in by around 2500 rpm the second stage doesn't come in until around 3400. It's kind of strange but I don't think that it's a problem. I haven't seen a timing curve come in at different stages before. Any thing after 4k rpm and the timing seems to be rock solid. There is no way that I can use a EGR valve. My intake doesn't have the port for one and evan if it did I had a lot of problems with the EGR that was on the origional intake manifold. I don't think that any one could convince me to use one again. As far as better gas. I'm at 4300 ft in altitude. 91 octain gas here is the same as having 93 or 94 at sea level. With 10 to 1 comp. I shouldn't be having any detonation problems. I know of people at this alt. that are running 11 to 1 comp. and don't have any issues.
Jason, are you absolutely sure your distributor is not advancing further after 4000 rpm? I've seen situations before where it appeared all the timing was in by 2500 or so, yet in reality, the thing advanced further as the rpm went up. Jim Burek
Did I miss the cam specs somewhere? The wrong cam design can contribute to detonation... -Bob Cunningham bobc@gnttype.org
If you have a cam with a tighter lobe center, such as a 109*, verses a 114*, you would 'effectively' have a built in EGR with that extra overlap. It will help to bleed off some of that extra cylinder pressure at the lower rpm's, from what I understand. A little extra duration might help too. Utimately, I think you'll need to deck that block to get a more suitable piston to deck clearance. Along with the appropriate head gasket for the combination.
John F, At the present time, I have to get the cars off very carefully. I lower the top car down to approx. 57" and am able to raise the door about 56" and drive the bottom car out. I plan on extending the door panels up one section and consequently raising the door roll up frame to get myself added clearance. My ceiling is 10 1/2 ft.
Jim I'm almost positive that the timeing isn't changing after 4k rpm. I'll double check this morning to make sure. The total timing right now is 35* at WOT. At cruse it's about 35* due to the fact the timing comes in at two stages. at 2500 rpm I get 10* of advance and 10* of vacume advance. I'm almost thinking of putting the HEI back in just to check what happens. The only problem with that other than the hastle of taking the cap off to tighten the dis. bolt is the pins are worn and it only gets around 7* of mechanical advance. Jim I'm sure you remember what it was like to play with it at Vegas last November. I have to set the initial at like 25* to get the right total advance. This may tell me weather I'm getting and pinging after 4k rpm with a dif. dis. Bob to answer your question I have a TA212 cam which has a 110 centerline and is advanced to 106.
Why the TA212? I was under the impression that that cam was intended for lower CR, like 8.5:1. Why did you advance the cam 4 degrees? What is your cranking compression? -Bob Cunningham bobc@gnttype.org
And if any one is interested here is a pic of one of my spark plugs with the current jets installed. 78 pri. and 86 sec.
Bob the TA212 is the right cam for a 350 street driven car that you don't want to spin up past 55 to 5600 rpm. any cam bigger than the 212 would need a lot of gearing and increased stall. 3K or higher. Plus the bottom end on such a cam grind would suck. Ta recommends advancing the cam 4* to achieve a responsive bottom end. I believe the static compression ratio is about 145 psi. I haven't checked it lately but that is what it was 2 months ago. Right after the rebuild and before I started it for the first time I had a compression of 130 psi. I hope this answers your questions.
I've put together several 350s and whenever I've had a problem with high rpm driveability it always turned out to be the distributor. Most likely the stop bushing is gone and after you wind it up tight the timing just keeps walking upwards. I had one that gave us over 50 degrees at 5000rpm, I'm surprised it stayed together! Timing stayed steady until you really wound it up though so it was hard to diagnose. When you talk about the timing moving after you start bringing the rpms up real high, sounds like the same problem we had. As far as jets go, I've never worked with a Demon carb. I've run 800cfm quadrajets with 73 mains and never had a problem. Unless a Demon 650 can flow more fuel than a 800 quadrajet, I wouldn't think you're running to big a carb! Ken McMillan Duluth, MN
Hey Ken The Demon that I have is a 750 and it will out flow an 800 Q-Jet any day of the week. The 650 will actually flow 780 cfm. the 750 I have will flow 890 to 920. So I've been told. Now these numbers are if you use the same flow machine as a holly or any other carb. The cfm ratings on a Demon are wet flow numbers and are more acurate than any other method. Q-jets were flow tested with air only. When you add the fuel into the flow it takes the place of the air and you get a much lower flow number. If I remember right the Q-Jet 800 flows around 600 cfm on a wet flow bench. I could have my numbers wrong and be full of crap but I think that is what I read some where. Sorry if the info. is wrong.
The stop bushing would fit to the limit pin protruding through the points cam plate, from the center scroll plarte on top of the mainshaft. I need to see the curvature of the scroll on the top of the mainshaft. In other words, directly down from the top of the distriburtor with the rotor off. Your pics really don't tell me muchm except you have a PerTronix Detonator, and one funny yellow spring in the dist. Would you send the pic to me via personal e/mail, and we can get into it further there. I won't be spending a lot of time here on this site or answering questions here much anymore, either.
Dave can you tell from the numbers on the casting? I believe they read 1112108 11E02 or they could be 1112109 11E02. If these numbers don't tell you any thing than I will post a new pic. tonight or tomorrow. As to the limiter I took the bushing off the advance pin so I could get a full 22* of advance. With the bushing in place I can only get a max of 12* advance.
dist. bushing Here is a picture of the dist. bushing. I had a thread asking about what dia. the bushing is (.300", .280"or .250") only had one reply. I made my own bushings in several sizes trial and error to come up with the right one. ((.300") seems to work) Don
