383 pings at full throttle over 3500

TomG · Sep 20, 2008

New 383 stroke pings over 3500 rpms at full or 3/4 throttle.
Here are the specs on the car and engine
69 chevelle 2dr
turbo 350 shift kit ATI converter 2500 stall
12 bolt 4.11
383 forfed flattop pistons
Aluminum Patriat heads 210 intake runners 2.02 valves 64cc chambers
Crane blue Racer cam 510 lift
Weiand Team G single plane
Holley 6777 650 dp 71 front 75 rear 31 squirters
Holley Hp mechanical pump with reg set to 6.5psi
MSD Ecurve distributor set to slowest advance curve with 30deg total 10 base 20 mechanicaltried other curves with 30 total and it pings even worse. Speed shop recommended 36 deg all in by 3k.
A new stock HEI did pretty much same thing This was in before the E curve MSD.
Plugs look decent tan color about half way up the cone. Little fat at idle but liveable
I don't have cam specs here with me at moment but I do have sheet for it. Also motor is all new top to bottom with just breakin time on cam and about 100 miles.
I have to get rid of the pinging I am wondering if I have more compression than I have been told which is approx 10,3 I beleive it is over 11-1.
Doesn't crank hard I also have a high tq starter in it. I have been running premium in it but with todays crappy gas who knows what your getting.
Does this sound like a timing issue or a lean out due to maybe a wrong Power valve or do I need a bigger carb?
Help please
Thanks Tom G

Tom Mobley · Sep 20, 2008

Yeah, you've got it alright. That 10.3 is more like for a 350. For a nominal values 383 I get 10.99:1. call it 11. That's 4.03, 3.75, 0.00 deck, .039 head gasket, 6cc valve notches, 64cc head.

Trick is, you've gotta do this calc before the build, not after.

If the machine shop led you to believe it would be 10.3 they're clueless. Worse, they don't even know they're clueless.

Got race gas?

A set of pistons with a 16cc dish will get you to 9.8, which would probably allow to run the timing advance needed to make that engine come alive. You need to be able to run 16-18 initial, 36 total with another 10 or 15 vacuum.

Sorry, no good news here.

Tom Mobley · Sep 20, 2008

What pistons do you have? It's possible a decent shop could mill a dish in them if they're thick enough on top.

ahh, probably not. 3.5" diameter dish x .100 deep would get you almost 16cc with a little quench area around the outside but most modern pistons won't allow a .100 dish I don't think. Can you nab a spare piston of the same part number to measure thickness of the deck? Might be looking at a little tune-up on the balance job too. Probably easier getting the right pistons.

Sorry, wish I had better news.

Dave427 · Sep 20, 2008

Does it ping under light throttle I doubt,,, I calculated almost 11:1 with flat tops also. The aluminum heads might of or should of helped soak up some compression. Kind of an old wives tail a bit. Stock jetting on your 650 double pumper is 67 primaries & 76 secondaries. So you are a bit out there. Leave the fronts alone and jet up the back a few maybe 79's. Try that,,,

Dave

SWHEATON · Sep 20, 2008

different carb or power valve are not normally the cause of detonation unless maybe your running extreemly lean .

Asumming your running 93 fuel and not 87-89 fuel.

If your running vac adv try unhooking it (to ensure its still not partially activated when it shouldn't be) @ WOT to se if that stops the ping.

If yes you found the issue and you need a vac adv with a higher cut off value.

But if it still pings you have 2 easy fix options,either retartd the timing untill it stops loosing some perf/power or run kemco Lead supreme.

I use 1qt Kemco with 18 gals 93 fuel which increases the octane to approx 97.5 for my 396 which should hopefully be enough to stop the ping in your motor too.It could also add a couple hp esp if you put the timing back to where it was prior to retarding it in an attempt to stopthe ping.

But if you try it buy it at the 2 case/12qt pre case discount that that also includes free shipping too,could share 1 case with a buddy if you dont go thru over 12 tanks of fuel yrly.

You can store it in the trunk of your car to put in the fuel tank when you fillup,ithas an 18 month shelf life per mfg.

It costs approx 50-55 cents to per gal to get 93 fuel to 97.5 octane,its still considerably cheaper then race fuel and much easier to deal with since its delivered to yourr door and you dont have to drive special wasting miles/fuel/time doing that.

If you dont want to try the kemco and you had to retard the timing too much to stop the ping and doing that left the motor soggy & down on pwer/perf you can install more cam/or replace heads with larger chamber heads,try thicker head gaskets,change pistons ,etc,now the kemco is starting to look a lot better isnt it.(LOL!!!!!)

Costs me approx $110 yrly for a 12qt case with discount 2 case purchase & free shipping for the Kemco ,thats a lot better then tearing down a perfectly good running motor with no leaks or issues going on just to do mods to reduce compression to stop detonation IMHO.

Scott

TomG · Sep 20, 2008

Thanks for the info. Do you have a website for the additive?
The vac advance is locked out in the distributor. I got another suggestion to check the balancer marks, though it is a new Pro Comp balancer.
Thanks again
Tom

66 Buick Special · Sep 20, 2008

Tom,

I agree with Scott that running Kemco is probably the simplest way to correct your situation.

I've been running Kemco 130 all summer in my new motor.
It's a forged rotating 10.76:1 355, GM Phase II heads (iron) and Lunati 60104 cam, and HEI with Accel parts added.

I'm running 1qt per 16 gallon fill up and have no detonation issues.

Good luck getting your problem resolved.

Here's the website Tom..

http://www.kemcooil.com/specials.php

BillsCamino · Sep 20, 2008

:yes:
As Tom M. mentioned, you generally have to use a dish piston in a 383 built with 64cc heads.
I'd unlock the distributor, run 16 degrees or so intiial, 36 total in by 3K rpm, and hook up the vac advance to manifold vacuum.
It may help...
Also try to run the engine as cool as possible. An 11.0 CR is a lot with the pump gas available now days. Be sure to use a quality, brand name gas...stay away from the cheap stuff. I've noticed a big difference between the Chevron type brands and the QT/Racetrack stuff sold around here.

TomG · Sep 20, 2008

Her are the cam specs as much as provided on the card Crane did not list centerline on intake so degreeing it was useless.
Crane Cam blue racer cam NO ICL listed on card here are the numbers
part number WG1064
GRIND 300-2H
DURATION INT 300
EX 310
CAM @050 INT OPEN 5DEGBTDC CLOSES 46ABDC MAX LIFT 109 ATDC DUR 234
EX OP 61 BBDC CLOSE 3 ATDC MAX LIFT 119BTDG DUR 244
VALVE LIFT INT 488
" " EX 510
cRANE DID NOT LIST A CENTERLINE ON CAM so DEGREEING THE CAM WAS NOT POSSIBLE DOES THIS HELP?

yellow heap · Sep 20, 2008

Have you done a cranking comp test?
With that much compression a total timing of 32-34 might help.
My 383 had 200-205 psi spankin new-now that the rings are sealed up it's in the 220-225 range-I run 16 initial-34 at 3000 and a 1765 vac can.
At 36 I had minor pinging with 34-none.
What is your piston to head clearance?Makes a hell of a difference.
Also make sure your timing tab/balacer/timing light are accurate.
I run a 650 dp also-great driveability

Tom Mobley · Sep 21, 2008

Tom,

the .050 lift points are clearly specified in those specs. You don't need the ICL to degree if you have the .050 numbers. IMO the .050 numbers are more accurate than finding the exact CL of a lobe.

You see that little piece there where it sez "MAX LIFT 109 ATDC"? what do you think that might mean?

You have enough information there to degree it in using two different methods.

Does the crank gear have 3 keyways? If so, which one is it on? If you have it on the 4° advanced keyway along with the 11:1 deal you're really set up for race gas.

77 cruiser · Sep 21, 2008

Tom don't feel so bad my 9.7-1 combo pings with more than 30 deg. so I just run it @ about 29.

2nd2ja · Sep 21, 2008

Saw this thread, had to reply 4 im having timing issues myself. 383 Vortec heads, flat top pistons, 274 XE cam- I switched distributors from a Pertronix unit (mech advance failed after 6 years) to a MSD pro Bullet dist. I tried using vacumm advance- it pinged under slight load (@ 2000rpms or so.)
I dropped my timing down from 12-13 to 10-11 and changed the mech advance button from blue stock(21 degrees w/ 13= 34)) to siver (25 degrees w/ 9=34 total). My engine liked 34-35 max timing best and never pinged (even going to 40 degress) before swapping tho i never used vacumm advance w/ pertronix. Now I want to...

I find it odd that the expensive MSD distributor wouldn't have an adjustable vacumm advance (like the pertronix). The MSD has 10 degrees of vac adv it says. Now I guess I'm looking at buying an adjustabel MSD vac advance and limit it to 8 or less untill it stops pinging.

I drove it around with 8-9 initial and vacumm plugged- runs great. Then I went to put vacum advance- the idle went up. It seemed to like it- but part throttle it slightly pinged but not as bad as before. Any suggestions?

I could put black button in and lower initial timing to say 6-7 (with black 28=34-35). I want to get better mileage with the vac advance or should I run it like I have for 5 years w/out it and 11 mpg (my foot out of it)?

SWHEATON · Sep 22, 2008

Aaron,you may not realize but the 9 deg base timing your running is extreemly retarded for that xe274 cam your running and you think it runs great now?

Well tune it correctly to run approx 18 deg base timing which that cam should have and it will run a heck of a lot better when it comes to throttle responce/idle quality/fuel mielage/and run a little cooler in traffic too.

Try running 93 fuel and try 18 base timing with 18 mech in dist in by 2800 rpms and that will wake up the off idle /lower engine rpm throtle resonce a lot,trust me on that.

If you need to run the base approx 9-10 deg retarded to not ping i would run the kemo i suggested above so you can get the timing where it belongs.

But running only 9 deg base timing with a comp 274xe cam when they typically need approx 18 deg to run well means either something is wrong with your ballencer/timing tab etc and timing isnt reading correctly or if base timing with that cam is in fact 9 deg like you stated it has to run like a slug untill full total is in comapired to what it could run like with proper base timing.

If i were you i would verifiy tdc on ballencer with #1 piston @ tdc and if all chks out ok then a good place to start for a street perf ign curve is approx 18 base/18 mech in dist by 2800rpms for 36total by 2800rpms ,it should run decent there and it can be dialed in better later on if needed.

I would also hook up vac adv for approx 12-14 deg additional adv for 48-50 deg max timing with everything in for when at light load part throttle cruise.

If it pings on 93 with this ign curve back off the timing a few/2-3 deg to see if that stops it ,if yes great leave it there.

If ping doesnt stop then put base timing back to 18 and unhook the vac adv and test drive,if no ping at part or WOT (again on 93 fuel) that tells you a vac adv limiter plate mfg by crane & sold by summit is needed to limit amount of deg timing the vac adv gives.

If none of this tuning gets rid of the ping and you want to run the best street perf ign curve for best power/perf i would put the timing back to 18/18/50ish & try some Kemco Lead Suprime 130 octane booster like i suggested earlier in this post.

But again before you get heavy into getting the timing right verify ballencer /timing tab is accurate with #1 cyl at tdc to verify timing mark on ballencer is also at tdc at the same time.

Scott

TomG · Sep 22, 2008

2nd2ja said:
Saw this thread, had to reply 4 im having timing issues myself. 383 Vortec heads, flat top pistons, 274 XE cam- I switched distributors from a Pertronix unit (mech advance failed after 6 years) to a MSD pro Bullet dist. I tried using vacumm advance- it pinged under slight load (@ 2000rpms or so.)
I dropped my timing down from 12-13 to 10-11 and changed the mech advance button from blue stock(21 degrees w/ 13= 34)) to siver (25 degrees w/ 9=34 total). My engine liked 34-35 max timing best and never pinged (even going to 40 degress) before swapping tho i never used vacumm advance w/ pertronix. Now I want to...

I find it odd that the expensive MSD distributor wouldn't have an adjustable vacumm advance (like the pertronix). The MSD has 10 degrees of vac adv it says. Now I guess I'm looking at buying an adjustabel MSD vac advance and limit it to 8 or less untill it stops pinging.

I drove it around with 8-9 initial and vacumm plugged- runs great. Then I went to put vacum advance- the idle went up. It seemed to like it- but part throttle it slightly pinged but not as bad as before. Any suggestions?

I could put black button in and lower initial timing to say 6-7 (with black 28=34-35). I want to get better mileage with the vac advance or should I run it like I have for 5 years w/out it and 11 mpg (my foot out of it)?

Did you use ported vacuum or manifold? If idle went up when vac advance hooked up sounds like it is manifold vacuum. Idle will smooth out with more advance that it seems to be getting with that setting. Just my .02
Tom

2nd2ja · Sep 22, 2008

I thought the timing now was funny. Originally b4 all the swapping, I had about 16-20 degrees- I switched it around. Never ran the vacumm advance. It always ran great, but mileage wasn't too good (but it's a performance motor.)

But I have to figure out how to get only 18 degrees in the MSD dist. I can put in the black button back in (just switched too). So I'll set it at around 18 and go from there. Thanks.

383 pings at full throttle over 3500

TomG

Tom Mobley

Tom Mobley

Dave427

SWHEATON

TomG

66 Buick Special

BillsCamino

TomG

yellow heap

Tom Mobley

77 cruiser

2nd2ja

SWHEATON

TomG

2nd2ja

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