Hello all ..

Any one see any corrolation between their piston domes and timing required? What have been you expriences?
My BB Camaro with 049 heads and (est) 13.5:1 is liking a 47* number no problems.
Now I dont know if part of that is due to the HEI/Retard effect? any thoughts out there?
I keep gaining et and MPH every time I bump it up a * or 2.

The only problem is when it warms up it is getting hard to crank.

Oh by the way This is for track duty only.

Current best is 11.45 at 118.38. with a 1.63 60'.

Thanks
Milan

What kind of balancer? The outer ring may have slipped. If it has, you want to replace it before it slips off :( You are reading 47 but its really at something lower. What is the intial timing at?

Its a new balancer. I checked it upon install... but worth checking again.

I have about 30* mechanical adv all in at 2500. base would be around 17. I never checked it cause its strip only.

Milan

Did you use a piston stop after installing the balancer to make sure the TDC of the pointer & balancer truly match up with TDC of the #1 piston???

You need to use a degree wheel as well, just like degreeing in a cam and establishing TDC.

unless the cam is 1 tooth off..

Well I had a scribe in #1 and followed it up... The engine was already together... I replaced the original balancer because it slipped. Honestly I did not use a degree wheel. but I have done this before and the marks were right on based upon the method I used to check it..

The cam is installed straight up. I am positive of that!

Does anyone else run monster domes and need a ton of timing?

??

Milan

I've got 50cc JE dome pistons (true 13 to 1 static measure compression ratio) and so far haven't taken my timing above 38 degrees. I'm gonna do more testing in the future to see if it likes any more.

PLease post your findings I am curious.. It makes sense that the more difficult it is for the flame to travel around the dome the more lead required. I have never encountered this before. My chevelle likes 38* and thats it...

Milan

there was an article in hot rod on a couple big blocks, one with a small roller and one with a big roller and I think both of them made best power with over 40 degrees of total. I will look for the article, I can't remember any specifics but I think one was up at 44 total.

Please let me know what you find. I want to know if something crazy is going on.

i looked this afternoon but no luck finding it, the magazine is at my dads somewhere. I do remember they were comp cams rollers both in street gas 454 motors, maybe some other members saw the article, it was either in an o4 or early 05 magazine. I have 781 heads with 207kb hypers and I am running right at 40 total and it seems to really like it, it also has me thinking that I don't have 10.25 compression like it is supposed to cause it will run on 90 octane ethanol with out turning the hypers to gravel from pinging. My heads where done Iselin racing in omaha so maybe that has something to do with it, I always thought a good head doesn't need much timing but I am not expert by any means.

I think you need to refind TDC. and go from there. I have not ever had an open chamber motor even with alum. heads that liked that much advance.

My 468 liked 38-40*. I had .700" dome closed chamber pistons in it. I agree that I think you need to find TDC and be sure your pointer is correct.

Okay I fabricated a piston stop from an old plug a long allen bolt and a section of 3/8 fuel line. The balancer and pointer are on the mark. I will verify the timing light is accurate with an old sears non dial back light. any other thoughts or experiences?

I think a little looky into the cam specs may help also, if the cam was cut with 4 deg. advance, straight up will give you 4 more degrees than normal and show up on the balancer as higher degrees. Like mentioned, you need the wheel to check out the exact degrees for this cam. Yeah, takes a lot of time, but when it is right, you'll be smiling more!!!! My 2 cents.
Also, what may be happening is flame propigation may be effected also, are your plugs indexed with this big dome you have? Engine may like more leed to completely fire the whole charge of air/fuel, I have heard of a Pontiac having as much as 47 degrees because his domes were so big, the thing needed much lead to completely fire all contents in the chamber, no lie, can send you to the people who know about it, especially with longer strokes, they seem to like more leed. I too will go thru this hopefully soon as my 505 is almost ready and it has big JE domes and a 6.800 long rod, so my leed will be up there. Hope you understand my term leed!! (adv.) if not!
Done

John

Well I checked my dial timing light against the old sears stand by and It's on the money. I set it to 49* and Ill see how it is next Tuesday at the test and tune.

Milan

Are you sure about what kind of fuel is in the tank? Nitromethane likes near 50 degrees advance, then has detonation issues up to about 70 degrees, then runs good again past 70 degrees.

There is more going on here than pop up pistons shrouding the spark plugs. I don't know if this even possible, but by chance are your cylinder heads threaded for deep spark plugs and you instead have short spark plugs?

Thomas

dont worry about it if it likes 48 and runs sweet there thats ok...

my old 350 runs 45 plus on avgas and loves it 12.8 comp,iron heads and 10.92s at 3400lb...
if i retard the timing to anything less than 40 were back in the 11s..

I would hazard a guess that your static compression is not what you think, combined with slow burning race fuel, and the result is that it likes alot of advance.

TJC what do you mean about the static compr. Do you think it may be higher?

No lower is what he meant, combined with slower burning fuel = need for more timing. Cranking compression should be north of 210 psi. Well north I should think.

So I may be able to dilute the race gas and bring the timing back down?

I think a little looky into the cam specs may help also, if the cam was cut with 4 deg. advance, straight up will give you 4 more degrees than normal and show up on the balancer as higher degrees. Like mentioned, you need the wheel to check out the exact degrees for this cam. Yeah, takes a lot of time, but when it is right, you'll be smiling more!!!! My 2 cents.
Also, what may be happening is flame propigation may be effected also, are your plugs indexed with this big dome you have? Engine may like more leed to completely fire the whole charge of air/fuel, I have heard of a Pontiac having as much as 47 degrees because his domes were so big, the thing needed much lead to completely fire all contents in the chamber, no lie, can send you to the people who know about it, especially with longer strokes, they seem to like more leed. I too will go thru this hopefully soon as my 505 is almost ready and it has big JE domes and a 6.800 long rod, so my leed will be up there. Hope you understand my term leed!! (adv.) if not!
Done

John

I don't think cam timing can effect the amount of degrees show on the balancer in anyway.

1) The balancer is stuck to the crank, not the cam.
2) The only mechanical relationship between the cam and the ignition is the gear on the back of the cam that turns the distributor gear. Whether you install the cam 4 degrees retarded or 4 advance, the distributor will still "see" the same gear. The distributor doesn't know the cam timing.

3) As always, I could be wrong. :D

Should I start with pump premium and 38* and see what happens?

Of course it wants more if your checking the timming with the vacuum advance connected and the car at static. If you have for example 14 degress initial and 10 degress vacuum and 25 degress mechanical your timming light is going to show 49 degress advance. You HAVE to subtract the vacuum at wide open throtle. The vacuun falls off and disappears at WOT which leaves you 14 degress initial and 25 degress mechanical for a total of 39 degress TOTAL at full throtle. Thats why a stock HEI shows almost 50 degress at static with the vacuum hooked up. Some of those stock vacuum canisters with the long arm have 20 or more degress built in.

Mark

The Vac advance is not used on the Camaro.

now i have had some big blocks that took alot of timming, i have been building and racing bbc's for about 15 years now and i can recall a few,most have been 36 to 40, had a 396 that would take on almost 50 degrees before it died off but that was a 7.7 to 1 engine...lol...., and another 396 with 10.5 to 1 comp. that would take on 40 to 46 degrees with out a change in mph. and even a 454 14.5 to 1 tunnel ram engine with a big o 50 cc dome that would take on 44 degees never went any higher then that short lived at the track started off with 36 then next pass just pull dist. forward and ran it, went faster, so dont know where the end of that would be, have a 454 right now with 049 heads comp. 10.5 with 48 degrees total i just heard slight ping out of the motor , thats with 33 cc domes. no track times......still in the tunning stagges at home butt dyno thing..............

I'm assuming that you are checking total with vacuum advance disconnected (but thought I'd mention it just in case). As far as cam postion, it makes no difference. While the distributor is driven off of the cam, the timing reading is the relationship between TDC #1 and when the #1 plug fires. While advancing or retarding the cam would change ignition timing, setting it with a light would compensate.

Years ago when I had a `67 SS (my first new car) I played with more advance and wound up learning an important lesson. The more I gave it the better it felt. I knew it was making more power at 44º total because the tires broke loose easier and it felt much stronger. I was running it at the strip weekly and was confident that my next run would be my quickest yet. WRONG! My et's were down about .2. One of the more experienced racers helped me see the error of my ways (and he takes his timing light to the track). He backed it down to 38º and I got my best run yet. The extra timing did feel better on the street but I was sensing it's low end power, not it's top end power. Soon after that I recurved the distributor and had the best of both worlds, more timing sooner but without too much total.

My tuning was at the track..... back to my question should I try prem pump gas and 36* to see what happens? My DCR falls around 9.2-9.5

There are a few posts going on that would probably benefit from this but....

Based upon my deduction for standalone GM HEI (you MSD... and others dont apply). Please keep in mind this is under a load....

at a 4500 rpm Launch there is only 60% of the 5.5 max amps going to charge the coil.As a result the coil is less than fully charged. The module is programed to increase the dwell in these instances. When this happens the timing is retarded 2* for every 1 degree of dwell increase.

Based upon this... I deduce the following... my timing at 47* degrees under no load may only be 32-38* under load due to an increased dwell situation. All the while the system is still putting out well below the advertised max of 35-40KV. It MAY be putting out enougn to light the mixture??? I will find out one day....

Any thought on my thoughts.......

buy MSD PN 83645 digital HEI module or better yet - find a 6AL and then you will know...

anybody got a used 6AL they want to loan me...

The module is programed to increase the dwell in these instances. When this happens the timing is retarded 2* for every 1 degree of dwell increase.

HEI does vary dwell based on current flow to protect the module from overheating. Dwell is shortened at low rpm to lower current flow.

As RPM increases, the dwell is added to the front end (beginning) of the dwell cycle, not to the back end. Therefore the timing does not change based on dwell variation the way it would on a points system.

Source for above: Pages 04 and 05 of: http://fiedlerh.home.att.net/HEI.pdf

I have heard--fairly recently--that the HEI will retard at higher RPM, but if I understand this correctly, it's because of the dynamics of the pickup coil, not the module circuitry. I have not personally verified this, I'm just passing along what I read in another thread, attributed to Ignitionman Dave Ray, a recognized and reputable ignition vendor and guru.

The old (mid '60's to early '70's) Delco transistor ignition was said to retard timing 1 degree per 1000 RPM. I wonder if that was because of the pickup coil like the HEI?

So what kind of AFR are you running.

Very lean conditions need higher timing. BUT makes alot less power than a optimum air/fuel ratio.

Well there goes the dwell retard theory. Thanks for clarifying that Schurkey.
I still have the theory of inadequate coil saturation time. I have also learned that there is a built in 1ms lag in the module after plug fire to allow all of the coil energy to disipate before the module alows "coil on" time. This will remove even more critical coil saturation time. unless there is a flaw in my thought process on this......Anyone know How many KV will be generated based upon limited amperage and on time say 2ms and 3amps or less. This seems to be a realistic if not optimistic scenario for the coil to deal with above 3500engine rpm


The plugs are anything but lean. I have yet to be able to make a WOT pass and read the plugs properly but if anything it's rich.

Milan could you explain the method you used to find TDC,and why have you not been able to make WOT passes?

TDC on balancer was verified using a piston stop. I said I was unable to make a plug reading after a WOT pass. in addition if I happen to foul out the current plugs I clean them with a propane tourch so I do not need to buy plugs everytime I happen to foul them out. So I dont believe a plug reading would be accurate. At least not the timing/ground strap portion I am most interested in..

I should have been more specific,when you used your piston stop did you use a degree wheel,or did you take the motor up against the stop,mark the balancer,then rotate the motor 360* and up against the stop again,mark the balancer and then measure the distance from the marks to TDC on the balancer to see if they were equal?

I did not use a degree wheel. I used the balancer method as you indicated.

I say this just so we can eliminate a crazy mistake, but.....you did disconnect the vaccum advance when looking at the timing, correct?

Have you tried another timing light to see if it's within a degree or 2 of the old one?

Wow, that's a lot of timing.

Well I just wanted to share one of my discoveries.
The plugs that were in the engine were Autolite 145. They should have been Autolite 24 plugs. I asked for plugs based upon the donor vehicle 84 one ton P/U. Those plugs were not of the projected nose type. The result is a seriously inefficient spark kernel location,vs a projected (#24) nose type commonly used in the 454 engines of the muscle car era. Obviously I will verify clearance but I beleve this is at least part of the timing issue. I will keep this post up to date with any additional info I uncover.


Milan

If you were using the non projected plugs would you not have noticed a foul "rich" smell from the unburned fuel??

Well I had a scribe in #1 and followed it up... The engine was already together... I replaced the original balancer because it slipped. Honestly I did not use a degree wheel. but I have done this before and the marks were right on based upon the method I used to check it..

The cam is installed straight up. I am positive of that!

Does anyone else run monster domes and need a ton of timing?

??

Milan

You said the engine was allready together, are you sure about the pistons ? You should do a cranking compression test, and as mentioned on another post it should be north of 210 psi. 47 degrees just doesnt make sense.

BTW you need to be extra careful installing the projected plugs, they don't like large domes, if thats what's really in there.

I purchased the parts and I built the motor. I am sure whats inside. I will run the accel module and see how she runs down the strip soon. runs fine in the drive. timing set at 37* and we will just go from there.


Milan