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how much are you pulling for adv with vac hook up? have you added a race fule to see if it go s away ? for plugs just a AC 44 or cross it over to auto lites .you want to pull as much adv as you can off idle. use a justable vac adv to pull some out if needed and it needs to drop out under load .or go full mechanical adv .i start at getting it all in at 2800 and 32 to 36 total to start.did you try ligter set up springs in the carb ? how much vac is it pulling when its pinging ?
Real good questions Pat, I'll do my best to answer
Current timing looks like this: 34* total advance, 10* initial, 14* mechanical, 10* vacuum adv w adj canQuote:
Originally Posted by pat mccarthy
RPM - Advance
1000 - 12*
1250 - 16*
1500 - 23* - HUGE jump in curve, must be where the vac kicks in...
1750 - 29*
2000 - 32*+
2250 - 34* - All In
It still pinged a wee bit with light throttle from cruise and if I hammer it out of the hole - I did note that if I ramp up the throttle evenly it will not ping under either of these circumstances. FWIW I drove the piss out of it late last night but the air is much cooler at night, no wonder it behaved!
Not yet, still working with 87 octane, not sure if the next step will be 89 or 91, trying to keep it cheap-pump gas friendly if possible. 95-97 octane race juice is available here but I think it is still over $5 a gallon :CRY:Quote:
have you added a race fule to see if it go s away ?
I am not sure if AC44 is correct for my application, it is a 14mm thread but only 7/16 reach and 13/16 wrench - I cannot fit a 13/16 socket on #1, #2, #7 and #8 cyls due to head bolts, the vortec heads need a 5/8 spark plug and the reach needs to be over .7" to get into the chamber from what i have found... but what the heck do I know?Quote:
for plugs just a AC 44 or cross it over to auto lites
The Autolite plug I found was a 605, the next colder is a 104 (5144) and the second colder is a 103 (5143) all three are resistor plugs
I am down around 8 to 10 degrees at idle to avoid pinging while under load. The adj vac can i have ADDS advance, so I have been retarding the initial timing and adding it back with the can. I was running with full mechanical advance but did not get more than 22* total and was all in below 2000 RPM. I will go to lighter springs in my dist to see if I can milk out more mechanical advance than 15 to 18 degreesQuote:
.you want to pull as much adv as you can off idle. use a justable vac adv to pull some out if needed and it needs to drop out under load .or go full mechanical adv .i start at getting it all in at 2800 and 32 to 36 total to start.
I did put stiffer step up springs in to keep it a bit richer with good results so far, I am sure I will need to consider different metering rods/main jets ultimately, probably larger secondary mains too...Quote:
did you try ligter set up springs in the carb ?
Ah, the $64,000 question! I didn't get a chance to look but I did think ahead enough to run a vac gauge into the cab, I just couldn't get a look at it fast enough to see it happen - next time I take a passenger along as an observer!Quote:
how much vac is it pulling when its pinging ?
Thanks for the help Pat!
yep heavy power springs should help in the carb keeping it abit rich on the thinner part of the power rods but small rods may help.yep i know this just a$$ backward today :LOL:. the plugs are AC RT 44 i think cross over to a R8c champion and is a tapper seat plug 14mm fit SBC tapper seat heads
I totally understand how the step-up springs work and only went up one step, with only 1 step more to go, but like said will probably be going up at least one step richer for power mode, possibly cruise mode too - which would keep the same jet just change the rod. For grins and giggles I will check/set my float levels too.Quote:
Originally Posted by pat mccarthy
Since she bogs/hesitates to accelerate a bit a higher RPMs I was thinking about bumping my secondary main jet one size, and possibly my pump nozzle (accel pump rod in highest hole already) but I will only make ONE change at a time and test.
I will try the autolite plugs I have before ANY other changes, if no better, I will go back to the champion plugs I have in now and mod the carb - I will try both sets of plugs with each change to carburetion I make - that way I have an excuse to pull ALL plugs each time :D
As you found out temp. will cause it to ping. Motor temp. and induction air temp. will affect the pinging also. Under hood temp. If you want to run low octane fuels you have to detune the motor. This is where knowing to DCR is inportant.
As we all know temp is a big factor in any machine situation. I was always taught cooler is better, not cold, just cooler rather than hotter. Regarding operating temp for MY car, I am trying to find the balance point between reasonable power, what my cooling system can provide and what my engine likes or runs best at ;)Quote:
Originally Posted by Mikej
Ultimately I do want a pump gas driver, but for now while things are new I want a rocket and the extra $0.10 per gallon for premium won't kill me... In your opinion, what would de-tuning the motor look like? Down the line I may want to reintroduce some sanity :cool:
Clue me in please, what is DCR? :o
Mostly I have found that you need to retard the timing. Total mechanical timing. Which if I read yours correctly you are at 24 ( int and mechanical adv.) I'm running about 28. Ideal seems to be 34 to 38 to make power. I run the carb alittle rich. Lower engine temp. Not all good for making power. The other guys on here can explain what the Dynamic Compression Ratio is. But it is what you are after to keep the motor from pinging on lower quality fuels. By the way I'm running 11:1 BBC with iron heads on 91 octane fuel. Pinging is a problem from one tank of gas to the next.
Yea, retarding the timing should be my motto these days... Right now I am running around 24* of timing w/o vac adv. I am going to switch weights and springs in my dizzy and blueprint it to get the most out mech adv I can - until a few days ago I ONLY drove it w mech adv and it ran OK, until I changed the plugs... I have a std dist with a pertronix module I could swap back to to test but wanted HEI - always the trouble maker me :toocool:Quote:
Originally Posted by Mikej
In regards to IDEAL timing, 36 seems to be the number to reach, but a total timing of 52* is not out of the question according to Lars Grimsrud, if I read his papers correctly... I would like to get more mech adv and reply on vac less if that is possible - not sure that is even good, just seems so to me
I found a good article on DCR here, time to dig up that cam card :p
11:1 is really high IMO but not too unusual, I just didn't want the kind of performance/problems associated with high compression engines - as far as the consistency of pump gas goes, that is the one variable we will NEVER have control of so a-tuning-we-will-go all year long :D
I honestly hope I can run 87 all year long but it looks like not, perhaps 89 in the winter and 91 in the summer cause as we know once the air heats up here in So Cal I get to do this all over again **)
yes you can pull 52 with vac adv thats why i ask what the vac was when it pinged you do not want 52 under a mid load if your hi on vac. your pulling adv and your rpm will be pulling more mechanical adv as rpm s go up you want to be droping the timing out under a load .unhook the vac and set timing as hi as you can get to 32 or 36 see if it will start with out bucking the start off the engine if it seams ok take it for a ride and see how it runs then work with a re curve kit .i have not played with a GM dist in 20 years . use the MSD set them up all the time for blower engines hi CR race engine and street strip.air boats .offshore boats. EZ to set up they have a limt bushing to set the curve in the dist i put about 10to12 on the crank and the rest in the dist use a lite sliver and lite blue spring it all comes in at about 2800 .they are pricy but you can tune them in for just about any job
I won;t be able to check vac under load till Sunday night at the earliest so we will just have to wait on that info, but I can tell you this, it pulls 14" of vac at idle and 23" cruising above 1500 RPM, not sure about the rest under load but I will test and document as soon as I canQuote:
Originally Posted by pat mccarthy
If I run more than 8-10 degrees of initial timing she will ping, I can start it with 20 degrees advance but it is not drivable without sounding like downtown compton on a saturday night - boom pop boom boom pop
I want to keep this car parts-store friendly, no gucci parts on this one, this is my driver/dirt bike hauler and if I break down in podunk, AZ I need to be able to buy parts at any local store, no time to wait for summit or jegs to ship fancy stuff - but I know MSD exists for a reason
So far after playing around with my current HEI and springs I can tell you that ligher springs only allow full mech adv to come in sooner, it doesn't go higher. The most timing I can get w/o vac advance is 22 to 24 degrees, I will have to blueprint my dizzy, I am sure something is hanging up in there...
Will the MSD weight/spring kit work/fit in a standard HEI distributor? Otherwise I was going to order the Mr. Gasket version that *guarantees* full power at 2000-2800 RPM
Once upon a time, in a far away place( with $.30 gallon gas) I did a lot of tune ups on various cars----it was quite common to get a car with a GM dist that had re occurring pinging or sluggishness---it generally came dowm to a seized or partially seized upper shaft in the dist. It would keep the dist from advancing, the timing would get set up and then it would advance and pinging would start---then timing would get set back and eventually the dist would retard and stick again causing lazy/sluggish---
If you have a stock type GM dist, I suggest removing it, taking off the lower gear, removing the shaft and the the advance mech and polish/free up/lube the shaft making sure it is free as can be.
Another area of concern with vacume dist is the proper type vacume unit hooked to the proper source of vacume---ported or timed---
If all else fails get an msd retard thingie and when it pings just dial it back a few degrees--at least you will find out what it wants for timing and you can recurve the dist to suit the fuel
I am researching how to blueprint my distributor, seems like a good thing to do short of buying an aftermarket billet one :rolleyes:Quote:
Originally Posted by jerry clayton
HEI-specific adjustable vac can is in there now, took the stock one off, it was an X-out, probably a rebuilder's special. Dist connected to timed vacuum, if I go straight mainfold vac my initial advance climbs to like 50!Quote:
Another area of concern with vacume dist is the proper type vacume unit hooked to the proper source of vacume---ported or timed---
Good advice on using the can as a tool, if I understood you correctly :o then adjust the initial/mechanical/vacuum advance to not ping - makes sense if I got it rightQuote:
If all else fails get an msd retard thingie and when it pings just dial it back a few degrees--at least you will find out what it wants for timing and you can recurve the dist to suit the fuel
I have an adj vac can on now, it is set to give me about 10 degrees of advance for a total of 34 degrees, I was going to try adding the extra 2 degrees to get to 36 total timing mechanically but I can always dial in/out on the can assuming it is not bottomed out in one direction. More than 10 degrees initial timing and it pings a lot - but I have a set of colder plugs to try and a few easy carb mods I can do with my current setup but re-curving my timing is in the near future
Nice post Jerry, thanks