Hi!What do you think will be the best setting for timing?428cui, Edelbrock heads 72cc, SCR 10.6:1, MSD ignition with a Pro Billet distr. without vacuum advance, headers, camshaft 230/240° @ 0.05.Would like to know 3 things especially:1. initial timing2. curve (all in how fast and at what rpm)3. total timing4. problems with wrong settings such as too low or too high initialI'm curious if you recommend the same setup that I would use (and have used before the engine rebuild).Thank you very much!Chris
Chris,my 428 is set at 15 initial with total of 38 degrees all in by 2800RPM
Thanks for the information!I've had 18° initial and 38° total timing. All in at about 2800rpm as well and it ran nice.I'll not change much probably, maybe I can retard the timing 1-2° because of the aluminium heads? Can't find it anymore but I think I saw an article about the E-heads and it said it didn't make more power with more than 36° total timing.
18 initial might be fine. You can also hook up a vacuum gauge and vary a few degrees from 12-18 and see if it makes any difference as far as engine vacuum. I beleive the original factory specs called for 12 degrees initial timing.
hello chrisgood to see you here again. thanks for the last graphs you pm'd me and i'm glad you picked a cam and hopefully resolved your hc/co issue.hopefully you'll get some suggestions in addition to my71's [which are good] so you have a broader understanding of initial advance. i know you love your sym's.not being a pontiac specific engine expert [though it doesn't matter a lot in this case] this is all i can offer at the moment. others ideas will vary.1. i think if you contact butler performance and comp cams and describe your upgrades and cam they can offer you their opinions also.2. in lieu of that here's a GENERAL rule of thumb.3. i have used this exact cam in many motors and have never run over 14 degrees in one and typically only ran 12.4. the amount of initial timing is dictated by the cam and compression you have etc.5. my experience is that the amount of initial timing has nothing to do with whether you have a full centrifugal distributor or vacuum chamber type. i know you think it does but my hands on experience including physical dyno tests and existing articles on the subject strongly contradict your "theory". now i could be wrong but this is what has worked for me for many years. it's possible that your level of experience with this is greater than mine and you and others here have achieved different results. i would then refer you back to butler and comp and your own personal results. in other words just use what ever you think is right. you can't go wrong this way [hopefully].6. rule of thumb - if you forget sym's and compression ratios for a minute, the general rule of thumb is the bigger the cam the more initial advance you can [or is required for max perf etc.]. this means that if a stock cam has around 6 degrees of initial and a huge cam has around 18 max then a medium cam [typical street] has around 10 - 14 max. your cam easily fits into the medium category so 10 - 14 max is theoretically what you should use. WARNING this info WILL NOT be found in your sym program. lol7. From my knowledge of my71's car which is EXTREMELY little. pontiacman says his car is fast, my71 says his car is fast. he has so much hp he can't hook up and was just recently looking for traction and front suspension improvement suggestions although i'm pretty sure he already had some good ideas himself. he also suggests his car is going through the 1/4 at 120 mph plus with poor rear traction. now based on that i'm guessing the cam he has is MUCH, MUCH bigger than yours. I'm also guessing that he has his timing pretty much dialed in. Based on this he says he runs 15 degrees which for all intent and purposes, because your cam is MUCH smaller than his you should need less than 15 initial timing. Does this theory at least seem plausible?8. now since the cam is [in my opinion anyway] the determining factor of initial advance and not the distributor type then why would your 041 cam [even though it is a modern grind replica] require 18 degrees of advance when the original advance from the factory for that cam is around 10?9. i think either rowsley or pontiac iron posted that they run 15 max with a non orig and non comp brand of 041 cam. hopefully they'll show up here. 10. re your pm theory you sent to me re vacuum advance timing - assuming your carb is working properly and idle mixture screws are set properly, with a vacuum advance dist the vacuum hose is disconnected, carb port is plugged, idle is set, initial timing is set. when the vacuum hose is reconnected the timing is supposed to remain the same [not jump to 20 degrees like you mentioned] because there should be no vacuum at the carb port at idle with a cam your size. if the port has vacuum at idle your throttle plates are too far open. if you close the plates untill there is no vacuum at the port and the idle is either too low or it simply dies before the vacuum at the port stops then you must drill two small holes in each throttle plate and try again. increase the hole size untill it idles properly with plates about one turn of the idle set screw from being fully closed.11. your cam may have come with a recommended timing setting, did it?12. re the pm you sent to me re your full centrifugal dist total advance theory - running 18 degrees initial advance simply so you can run 36 degrees total is incorrect. don't worry your theory is common with many people that are new to these things and are learning as they go. if your dist is US made and not chinese it should have come with instructions. often [but always] the instructiins will ytell you that "the total advance is adjustable on this dist etc". some dist also include a 2" long piece of red or black plastic with graduated steps and numbers on it. this is for adjusting the dist total advance, they are always set on the lower settings as delivered. Did your's come with one of these? You can read my71's post titled "question for all you suspension gurus out there". Perhaps he might also share his cam and compression specs with you so you can compare to your's. That would be cool to see.PS - I know by the pm's we have exchanged that you understand the dryness [directness] of my comments and will realize they are simply offered to help you. thanks again
I agree with what you say about cam size and timing. The cam didn't come with a timing setup.Maybe a year before I talked to some Pontiac guru's about timing and especially about my distr. without a vacuum advance.I was told that the 6-10 degree initial was used along with a vacuum advance control unit that added some degrees to the initial setting at idle, resulting in a stock car idling at over 20 degrees of timing. There are 2 ways to connect the vacuum advance.. ported vacuum or manifold vacuum. Manifold vacuum is the way to go most of the time, but not every engine will react the same as another. So I cannot agree to the fact that a stock Pontiac engine with lets say 6° initial (hoses disconnected, holes plugged) will idle at about 20° as soon as the engine build up the vacuum in the manifold. If I would use 20° or more with my Pro-Billet the engine would probably kick-back so I have to use the highest possible number that won't get me in trouble. The engine needs to start even if it's hot. Initial timing shouldn't be a big concern, the important factor is total timing and the advance curve. My timing will always be lower at part throttle and idle than it would be with a vacuum advance. Maybe My71 has got a vacuum advance? If so I would say his initial timing is just perfect if his cam has a duration of lets say about 220-240°. With the high initial he can make sure to create a little more idle vacuum with the big cam that may be on the edge for power brakes, automatic transmission or anything else that needs vacuum.My cam is upper mid-range I guess, but I have used the 16-18° initial timing with my non vacuum distr. and never had problems. When I got the car the timing was set to 8° initial. It ran hotter and I could feel that the throttle response has improved with the higher initial that I used after I got these information I share with you.The rule of thumb (if you ask me) should be:- use about 34-38° total timing- the initial timing is less important and a result of how you can make the correct total timing- use a curve that builds up total advance as fast as possible without getting into detonation- the more initial timing you have, the more idle vacuum can result (thats why a bigger cam should have more initial)- don't confuse non vacuum distributor with others that use a vacuum advance- there will be no vacuum at WOT, that's why you should set the initial timing with the hose disconncted and plugged because the most important thing is total timing and it will always be initial timing + mechanical advance (no vacuum advance)- high initial timing will affect idle quality, fuel economy, engine temps and throttle response- the vacuum advance will add 10-15° at idle and part throttle to the initial timing (that was set without the vacuum advance connected and you will even have a higher timing as soon as the engine is running than I have with my Pro-Billet and 16-18° initial)- retarding the timing will result in higher engine temps, better emissions, less power, less idle quality...If someone likes to disagree feel free, hope I could remember everything like I was told from the expert!For my application it's pretty easy.. I will test if I can use a faster advance curve than before, set the initial either to 16° and add 21° mechanical advance = 37° total or use 18° initial and add 18° mechanical advance = 36°. Can't believe I need 38° total timing with the aluminium heads. Maybe I will retard one of the settings even 1° to be at 35-37° total timing.
hello you have confused me a bit at the moment with your comments and the way they are phrased so i can only address the ones for you that i think i understand. i am also not quite completely sure you understood my post however here goes. sort of from the top. i'm sure some of it is the difference in language. i'm sure you know in your head what you want to express however it doesn't always translate exactly. i know just barely enough german to understand the difference. that being said your english is far superior to my german at least. i have no idea why your pontiac "guru" as you call him told you that. most of the thousands of gurus that live here in the US do not connect the vacuum advance to the NON ported vacuum port. however some may do this for their particular reason or application. i am not in dispute with you there, what i mean is in my experience i have never seen it done that way.i never said a car would idle with 20 degrees advance using a vacuum distributor. please re read my post again so you understand it more clearly.i never suggested you use 20 degrees advance with your centrifugal dist if that's what you are inferring. if not i don't understand the purpose of the statement.ignition timing does affect starting too much like 19 degrees and it will be more difficult to start with the 194 lb's or greater amount of cylinder pressure you calculated you have with the 041 depending upon your initial cam advance set up.you will definitely NOT have less initial timing with your centrifugal dist vs a vacuum chamber type [unless you increase your distributors advance], providing you hook up the vacuum type to the PORTED side of the carb just like virtually every single us auto mfg did untill the their implementation of the "dual vacuum chamber" which came into use on most [but not all] us cars around 1968 due to tighter emmissions requirements. Are you familiar with what a dual vacuum advance chamber is and how they work on a car?i don't know what type of dist my71 is using or how he set up any potential vacuum hoses etc and i would never venture a guess and base anything upon that guess. i would ask him if you want to know.my replies to your "rules of thumb".1. close enough depending on the cam/motor etc. sometimes less but not more for the street.2. sorry i have no idea what you are saying so all i can say is that initial timing is EXTREMELY important.3. yes however one can not always hear detonation/preignition etc even if their hearing is good, so what about the unfortunate people that don't hear so well? also it can only be determined 100% by using a $6000 detonation sensor under varying conditions. so tuning by ear or computer simulation is not an exact science. 4. different way of repeating what i mentioned in my post. so basically yes.5. good tip however i have never personally seen anyone here in the US confuse a centrifugal dist with a vacuum chamber type. i hope they don't over there.6. can't reply i'm a little lost on this one7. i think you mean any initial timing [not just high] will affect these items. yes except not so much for fuel economy. overall timing curve affects fuel economy more than initial. yes i know they are connected.8. i think i understand you so yes.9. yes however excessive timing curve and total advance can also increase heat also.yes from my experience with chris in our pm discussions he truly is not offended if you disagree and isn't mad that i did so here in some areas. i think he just wants more input from others experience.since you have you're own "expert" over there as you refer to him or her i'm not sure why you still need further info. after you recieved mostly different suggestions for your cam other than the 041 including butler performance also recommending the xe274h you still decided on the cam you originally had your mind set on. this is fine but it appears you are going to do exactly the same thing with your ignition timing no matter what others suggest. i just don't quite understand but that's ok i don't need to.PS - Who made your distributor? if it is from pro products it is chinese this might explain the lack of the plastic timing tool if it uses one of those.thanks
Pontiac V8 350-455 Pro-Billet DistributorPart No. 8563 MSD’s Pro-Billet Pontiac V8 Distributor for Pontiac engines built for either street performance or hard core racing applications. Special features include a fully adjustable mechanical advance assembly. For all-out racing, the advance mechanism can also easily be locked-out. For stable timing, a high-output magnetic trigger pick-up is used to supply the ignition with a trigger signal. Additional stability is achieved via the 0.500” hardened distributor shaft that is supported by sealed ball bearings.Features•CNC machined billet aluminum housing and billet aluminum base•Easy-to-adjust mechanical advance with supplied springs and stop bushings•Maintenance-free magnetic pickup and precision reluctor create stable trigger signals throughout the rpm range•Polished steel shaft is QPQ coated and guided by a sealed ball bearing•Advance plate and weights are fine blanked from chrome moly steel and QPQ coated for friction reduction•Mechanical advance assembly can be locked out for crank trigger systems•Advance weight pins are staked and tig welded to the plate•Nylon pads ensure smooth operation of the advance weights•Supplied with an HEI style distributor cap and rotor (accepts Cap-A-Dapts)•Must be used with an MSD Ignition Control•Will not accept a vacuum advance canister•No CARB Exemption Order Number
When The Flag Drops.,. The Bull ***t Stops.,. P. Engineer, Engine Builder
hello chrisas you can see by tuffnuff's post if this is the distributor you have and not a "copy" then it definitely is adjustable like i originally mentioned to you. did you not receeve any springs or stops or receive this type of info on a sheet of paper in your dist box? PS don't confuse an MSD PRO BILLET DISTRIBUTOR with a PRO PRODUCTS BILLET DISTRIBUTOR. The chinese can use some creative marketing strategies sometimes. it should say MADE IN USA in english [not chinese]. lolyou can see the ads for chinese pro products distributors at summit racing.thanks
+1 Tuff I've used MSD products for 38 years. They stand behind their products. Usually their distributor kits are complete. Shows what springs to use, and the advance curves to use. What color springs do what, in the curve.Way back in the day they came out with their soft touch. I ran it almost all summer long 2.5 month's up here...lol...Then I noticed a slight miss in the engine. So I played with it during the winter, I disconnected the soft touch the miss was gone... I was running solid core steel wires. NO-Where in there product literature or tech info, did it mention not to run the soft touch with solid steel ignition wires. I called them to have the box fixed/or replaced. I was talking to their tech Guru. Told him what I found, and he said I don't think they can warranty it then. I told him if it's my fault I'll pay for it, but they don't say not to run it with steel wires....Back then I send it out COD back to me... They saw their faux-pas. Sent it back to me fixed FOB. I know Pro-Comp electronics has a good product so, what does chris have? Dave the Dyno guy uses their distributors. He runs so many different engines...Bob
hello prpsi1yes i agree pro products has some decent products some not so decent. i was a pro products dealer. i suppose i should clarify my comment a bit. the msd unit should have come with the parts and instructions suggested in the msd ad tuffnuff posted. it sounds by chris's comments that he did not receive any parts kit or instructions with it. i was therefore suggesting it might be a pro products centrifugal instead which may not be adjustable which could explain the lack of the parts and instructions in his box! hope this clarification makes everyone happier.thanks
Chris,Typically distributors that have only mechanical advance are used for strip only applications. Vacuum advance play a critical role in a cars road manners and drivability.If I remember correctly you have access to some higher octane gas there and that may very well let you get away with the higher initial setting. The thing to be careful of is detonation that you may not hear with your ear.While there are two schools of thought on where to hook the vacuum advance hose, general accepted practice for older OEM engines (And Pontiac specifically states in thier service manual to hook it to a ported source) is to hook the line up to a carb ported source and not manifold vacuum.This link gives the basics of how vacuum advance works on engine timing.I'm sure you already know most of this but thought it worth posting anyway.http://classicinlines.com/IgnitionTiming.aspSome folks add in vacuum advance to total advance and that is incorrect. Total advance is initial+mechanical and the vacuum advance allows the timing to vary based on engine load within those paramters. That's why it is pretty important to have on every street driven car as it affects power, performance and gas mileage.Barnett made mention of comparing cam specs, so here's mine. It's a special grind Crower mechanical roller.Only difference is that my rockers are Crane gold aluminum rollers @ 1.57 lift so my lift at the head is a bit more than stock 1.5 ratio. (actual intake is .575 inches and exhaust is .587")Part Number/Work Order Number E11855 Engine Application PONTIAC V-8 Grind Number SPECIAL ADVERTISED CAMSHAFT SPECIFICATIONS: INTAKE:Duration: 279ºLift: .549Clearance Hot: .020EXHAUST:Duration: 282ºLift: .560Clearance Hot: .022The specifications listed above are based on a rocker arm ratio of 1.50 IN1.50 EXcamcard The information below is for degreeing cam only. Correct only at .050" tappet lift.INTAKEOpens: 18.0 BTDCCloses: 50.0 ABDCEXHAUSTOpens: 60.0 BBDCCloses: 12.0 ATDCLOBE SEPERATION 110ºDuration at .050"Intake: 248ºExhaust: 252ºLOBE LIFTIntake: .366Exhaust: .3734 degrees of advance have been ground into this Camshaft.If using "Lobe Center" method of degreeing, cam should be installed on an intake centerline of: 106º When I degreed this cam in, I ended up retarding the crank and additional 4 degrees to get the numbers to come in.Static compression calculates out to 11.4:1 and dynamic rolls in around 9.5:1.
chris my71 - can you tell chris what type of dist you use hiw it is set up and the total advance?chris you can plug my71's specs into your sym and see what advance it recomends.thanks
Distributor is a pertronix flame thrower 3 w/ignitor 3 elctronic module, internal rev limiter set @ 6500RPM. Multi spark to 7500 RPM. With vacuum advance and 60,000 volt HV coil. Mixed advance springs to get me all in by 2800 RPM. Had to modify to advance limits to allow 24 total mechanical. They supply 3 different advance stops of 12, 16 and 20 degrees.
hello my71 thanks for the info. as a last item can you tell us which vacuum port it is hooked up to and why and which port you think chris should use for his cam and street use. thanks again for the info