vortec heads

[4x4k20]

anyone out there running vortec heads on a older eng. with carb. i have a 383 in my 79 3/4 ton 4x4 good strong eng but cant get it to stop pinging i run 93 octane timing at 12 with no vacum advance thats where it runs best with less pinging anybody else have this problem with your vortec head eng.

[swervin ervin]

There is another board member who posts here some, (bored & stroked) that has a 383 with Vortec heads. I have never seen him say anything about his engine pinging.

What I would suggest is working with your distributor weights and springs to help stop it. I am making a guess here but with the 64cc Vortecs, you are probably around 9.5 to 10 to 1 compression. You are on the edge with 92 octane fuel (with iron heads) but you should be able to run without pinging if you get the timing right.

I would also recommend using the vacuum advance for fuel economy. You can run both with a Crane adjustable vacuum advance canister and correct centrifugal settings. It will take some time to get it right, but nothing worth having is easy.

Just as an example, I know of a guy with a 454 running right around 11 to 1 with iron heads and he has no problems what so ever with spark knock. Of course it took him many hours to get it right.

A lot of the time it isn't the cc's of the heads causing the pinging. It can be too thin of a head gasket, too much quench area, too much initial advance and other things. Have you tried lowering the initial advance until it quits, just to see how far you need to go?

Just a couple suggestions.


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Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

[4x4k20]

mike i am running the 64cc heads and i have bought a crane adjustable vacum kit i read in a spot from as a matter of the fact from your pages you showed how to install it but i had no luck with it i tried many ways but anytime i run vacum it would ping real bad compression is at 10.9 do you think that is to much for pump gas i have never before built one with this much compression i dont know much about tunig it used to stock engs. thanks

[swervin ervin]

As a general rule of thumb, 9.5 is a good cutoff for iron heads. 10 to 1 or maybe just a hair more is fine with aluminum heads. 10.9 to 1 is definately way up the scale. In order to keep this high of compression you really need to lower the timing. 12 BTDC is going to be too much with your compression.

Also, if your springs in the distributor are letting the mechanical advance start fairly soon (which is good normally) it will help cause the pinging. Try lowering the initial advance to about 6 degrees and see what it does. Then you need to buy or borrow a dial back timing light to check your advance. Then you will be able to tell when your mechanical advance starts and when it is full in.

When does it ping? All the time? When cruising? Hard acceleration? If in the cruise range, you can overcome this. If all the time, it will be real hard to fix.

Just so I will know, what is your deck height? What is the compressed head gasket thickness? Flat top pistons or what?

One thing to check. Remove a couple spark plugs and see how they are running. This is always the best sign of what it is doing. While on the subject of plugs, have you tried running a cooler plug? If your plugs are too hot for your setup, it will most definately help cause pinging.

Let me know the answers to the above questions and maybe, just maybe I can make some suggestions to help. With 10.9 to 1 compression, it is going to be real tough to fix it.


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Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

[crossy]

if none of those other timing ideas work then you better think of buying a cam .One call to any of the major cam grinders could really pay off .By grinding a cam ,or suggesting the right "off the shelf" unit,the can really change an engines characteristics by changing cylinder pressures [effective compression rather than just the static ratio.Swerve was right in saying that you are really border line on your compression.I have done this in the past with great results in drivability.DAVE

[4x4k20]

mike i built my eng. using a 350 block 400 crank and rods bored 30 over with flat-top pistons with 2 dish releifs dont remember deck height head gaskets are gm with 051 compressed thickness new 350 vortec heads 64 cc edlebrock 600 carb and intake comp cams csxe 268-10 i built it over a year ago mostly drive on weekends it just pings at part-throttle and WOT i even have a jacobs ultra team igintion kit. i have a timing lgt. with advance last check it has 25deg. advance at 12 initail no vacum ad. if i just hook it up it advances it to 20 deg.at idle i have to keep it unhooked i am useing the blue springs that came with the crane kit my disturbator is gm hei with mr gasket recurve kit this may be on problem one thing i figured out last week that i was running the wrong sparkplugs the vortec heads take a longer reach plug i replaced them with the right ones still pings maybe some of my problem is in the carb thanks for your help

[swervin ervin]

Now we are getting somewhere. Put the stock HEI weights back in. 25 degrees is too much advance. They are probably advancing the timing too soon in the lower rpm. The stock weights are supposed to be 20 degrees. If they look worn at the pivot holes, replace them with some new stock ones or some good used ones. Also, check the pins to see if they are worn.

With the stock weights (20 degrees) and initial advance of 10 to 12 degrees it may be OK. The two blue springs should work just fine. This is what I have been running in mine. I plan on trying a blue and silver to see how I like it. A silver would probably be too much for you.

Try the stock weights and maybe lower the initial a little and see what happens.

Also, you might try richening up the carb a little. If it running lean, it will ping like crazy. 600 CFM is on the low side for this beast. You could run a 750 with no problems and would really make it come alive.

One more suggestion if I may. The first thing I would do is replace the distributor with a MSD Pro-Billet HEI. Of course they are not cheap, but you get what you pay for.

The second thing is get rid of the Jacobs crap. I had a Jacobs Omni-Magnum on my truck. I got tired of it messing up on me and took it off. I used to think Jacobs was good stuff, but I found out the hard way. From now on it's MSD for me.

Just my $.02

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Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

[This message has been edited by swervin ervin (edited 12-27-2000).]

[4x4k20]

thanks again mike i am going to replace my weights with stock ones i bought a summit dist. but did not like it put my old gm back in i will check out the msd one .the jacobs kit i dont know what to do with it paid 400.00 for it .it was supposed to cure all my problems but i have noticed no improvement whatso ever since i installed it what would be a better carb for it i always thought it was too small thanks johnny

[swervin ervin]

Johnny,

I also bought a distributor from Summit. What a piece of crap. I sent it back to them. This is when I bought the MSD. The MSD Pro-Billet HEI is one of the best quality products I have ever bought. It is pricey, as any thing good is. I have not regretted buying it once, would do it again in a minute.

The Jacobs I had (still have laying in a drawer) would get hot and my truck would start skipping and popping like crazy. I would pull to the side of the road and let it cool off. It would be fine for a while, then it would do it again. I got tired of that crap and took it out.

The MSD comes with all the good MSD components. Nothing else to buy. If you can swing it, you would fall in love with it.

I know what you mean about paying $400.00 for something and not like it. Been there, done that.

On the carb, Edelbrock makes a 750 CFM Perfomer square bore carb. Holley also makes them, but I am not a fan of Holleys. My carb of choice is a Q-jet. I bought the Edelbrock 1904 Q-jet (795 CFM) and absolutely love it. Of course it would take some tuning to feed that 383 of yours. Whatever carb you choose, it will usually take some tuning to get it right.

You won't believe how much better it would run with a little more CFM's. You don't want to go overboard though. Then you are just wasting gas. For my use, I would use a good ole' Q-jet, but that's just me.

Let me know what you decide to do. I am really interested to know if you get it to quit pinging.



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Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

[swervin ervin]

Johnny,

if you get a chance, pickup the latest issue (February 2001) of Chevy High Performance magazine. It has a section devoted to octane and HP. It also has a section on how to beat the detonation game.

I think you will enjoy the articles and it will probably help you with your problem.

Just so you can spot it easier, it has a picture of a red 57 Chevy and woman with a gas hose.

Later,



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Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

[Tom]

hi guys, sorry im late Yes mike I do have vortecs on my 383. I have had problems pinging in the past, but my intial timing was way to advanced when that was happening. I have stock flat top pistons with 4 valve reliefe so 10:1 is the compression. 92 octane is all it let it use and it runs fine.

I suggest a MSD Super HEI kit myself. No need for a new distributer. I got tired of the chip in my ACCEL HEI distributer giving me problems so I bought the MSD kit. Awsome product. Comes with either 6a or 6al box, a blaster 2 coil, new cap and all the wiring and instuctions [the instructions are great, really easy install] Its like $150 or a little higher for the 6a box package, $250 or sumthing for the 6al package.

As for the carb, I was running a 600cfm cater AFB on my 383 when it still had the stock 76cc heads, no problems. I also had it on for about 3 weeks after the head swap with no problems. I then was running a demon 650cfm double pump, mechanical secondaries carb, and that woke things up a lot. That was stolen 2 weeks ago so I am now going to get a demon 750cfm double pumper. I suggest you get AT LEAST a holley or if you can afford it a demon 650 double pump. Get the 750cfm if possable.

P.S.- mike, in some forums for some reason I have my id as tom ,not bored&stroked, wierd eh?
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1978 chevy c10
383 stroker,10:1 compression,vortec heads, roller rockers,performer RPM intake, Demon 650 double pump carb, MSD ignition, headman headers, muncie four speed, 3.73 12 bolt rear.




[This message has been edited by Tom (edited 12-31-2000).]