Modifying and custom curving a GM HEI distributor for street performance

[@grr4561]

I have run quite a few distributors on my Sun 504 and I have the same problems you are showing. When you change springs, the mechanical advance comes in way too early and something you didn't mention is that is causes your idle to fluctuate and is frustrating because your idle is going up and down. I always try to have the advance come in at around 1,000 and all in before 3,000. People just don't realize how hard and how much time that takes to actually accomplish. But I am retired and have time to fiddle...Please keep up the videos because I can always learn something....

[@gasandspark]

I have fought the erratic idle issue and I’ve found that changing the shape if the center football has helped; because the weights “rest” more securely. Another thing is to carefully choose your vacuum advance can. Make sure your advance can is completely pulled in at a vacuum reading at least 2” below your engines vacuum reading at idle. For example; if your engine produces 15” of vacuum at idle, make sure your can is all in at 13”. I then limit the rod travel on the can so that it can only pull in 10-12 (crank.) degrees of advance. This keeps the idle from “hunting”.

[@hotrodswoodshed7405]

VERY APPRECIATIVE of your attention to detail of actually teaching about important subjects that gets overlooked. Fantastic channel

[@v1-vr-rotatev2-vy_vx31]

The Ford distributors have a far superior weight advanced system , that work properly, whereas the GM distributors have the far superior breaker point system. Both of these systems were used in the Excel distributor which was previously engineered by champion spark plugs and used in the Can-Am racing back in the day. Mr Art Early that worked for champion spark plugs educated me on this subject matter. He did the Datsun racing team cam science work and porting tech that helped Paul Newman to victory.

[@Badbehavior]

Excel distributor IS spelled ACCEL, say AK, SELL and we will follow your diction!

[@oldschoolcars3318]

It seems a video might be in order: one that shows how ignition timing is related to the hp and torque curves could demonstrate how critical s Distributor set up is to performance. Understanding if you are setting up for torque or power can guide you in choosing where you have what advance, and how much.

[@randyfitz8310]

Thank you for this video. Great info! (Please replace your smoke alarm battery - I started looking for the problem here!)

[@redherring4335]

Same here. Lol

[@michaelgreen7028]

this is very interesting...how expensive is it to get you to tune an hei like you did here?

[@tomstanley7772]

I watched the GTO points distributor. It opened my eyes. It just watched this one. And you helped me answer a question about an idle issue I have with my old 1 ton truck. And now I'm 90% sure it's the distributor. The truck runs good but her idle from time to time is unstable and too low. Thank you.

[@steven13sweet]

Do you sell sbc distributors ready to run?

[@JohnDoesItAll]

I had the same issue with the weights not returning with light springs. I welded the inside of the slot to get 15° mechanical advance. Basically, weights don't fully retract which takes out the slop and makes the initial timing more stable at idle. Full advance comes in before 3k RPM'S. It's important to dial in the phasing at full advance.

[@orbitup]

Very informative video thank you! BTW your smoke detector battery needs changing.

[@brooklynrust2483]

That is a good observation, what I see on this video is that the components assembly has wrong geometry for spring pins location. That must be change to make springs create pulling effect on waits at all time.

[@kloofyroland]

waits? hehehe

[@lordsauto]

Excellent!

[@shoominati23]

I think the Moroso Advance kit looks like it has a better made weight in it

[@timothyemery4258]

What do you use for lubricant when you reassemble the distributor?

[@nicktheasian]

Summit center weight is upside down and there don't appear to be bushings on the weights which might cause binding.

[@Nathan-bz8zt]

Once again another amazing video. We need more like you out there. Very informative and well explained! What brand/model of distributor machine is that??

[@28704joe]

Could your football be on backwards ? According to the MrGasket HEI Advance Curve kit #929 the diagram indicates yours is on backwards for a clockwise rotation distributor. flipping that football changes the geometry greatly and will make weights come in to hug football with any springs chosen and give zero advance at idle. It did for me.

[@Roger-eh7ez]

I question that also. Seems like that would be the reason for the offset holes?

[@28704joe]

On this video he has the football on backwards , that's why he if forced to modify the profile. It's easy to get in on backwards and develop timing issues.@@Roger-eh7ez

[@rotaxtwin]

This is EXACTLY the problem I was having with the inexpensive recurve kits for HEIs from Mr Gasket, Transdapt, Moroso... They're all junk. That centre contoured component is stamped with who knows what design and the car hangs with a bunch of advance and idles at 1500 RPM 'cause the springs can't pull the weights in even when the engine is stopped. Awful junk. And yes, the ignition curve is important for throttle response!

[@DesertRatFabrication]

Great video, I agree if the distributor isn’t performing correctly it’s easy to blame the carburetor, did you end up with the lighter springs , and would you use a stop bushing or the advance canister to limit the 20degrees of advance, thanks much😀😀

[@kloofyroland]

At 2:53 you're saying you have 22° of advance but where you're pointing shows 12° total advance???

[@scottalvarez8870]

True

[@tmsnyder1971]

I assumed the machine was measuring degrees at the distributor, whereas we are used to degrees at the crank. He's just so used to reading it he automatically doubles the number so it's in crank degrees. My opinion.

[@MechanicForGMCCars]

Hello sir great video . I do similar testing but due to lack of parts and mashineri Im limited down . How ever if you use potenciometers,different type capacitors and variabel resistors that might phase shift or increase your spark out put. How ever I did experiment with magnets litel bitt the spark was lot greater be just moveing ceramic magnet close to that metal part you mentioning in your video. So prhaps mounting small electro magnet wuld help you out. The electro magnet shuld be bariabel in frequency and you mounte it inside the distributor cap . The springs have centrain play . But after years I learned that metalic springs stiffnes is effected if you for some reasom get arcing relays ,back charging alternator or simply magnetised engine. Evry thing that has metalic spring stiffens or get softer. I do have some videos that I experimented on HEI ignition system. The problem is not the pick up coil or advance mechanism . The 4 pin GM ignition module has 8pin MC or LD 3334 ic chip it is limited how much volage it can recive true pick up coil it has cirrent limiter and ignition module operates at specific frequency range 33-333hz. So be haveing home made variabel ic chip set you culd probably advance/retard ignition timing lot bether. And that 4 pin gm ignition module stop working at low rpm. The magneto/magnetron ignition look more promesing tought. Pick Up Coil+capacitor/variabel resistor+darlington transistor +ignition coil. That system wuld be lot bether and cheaper solution. And I suspect the ignition coil saturation is to late the spark is to weak so I belive be constantly charging ignition coil via seperate grounding system wuld always provide 100% coil saturation . I belive ordinary buzz relay culd do that task easely. After all that system is mearly identical to magneto/magnetron ignition system. I belive even the alternator culd be modified and add extra constant power to the ignition coil. Those stock Hei systems are to weak to be used for winter weather states and have their limitations. And on the stock HEI is missing zener clamping diode so reverse voltage protection it does not have after some time wire harnest starts to suffer in some cases engine refuse to stop . So I sugest you try to build your own variabel circuet or mechanicaly to control that distributor housing similar to Cadilac 1930 advance/retard lever or try out that pick up coil tuning methode to trick the ignition module that engine run at higher rpm range or externali control sping tension with electro magnet. Perhaps different capacitor types banks culd probably advance retard ignition timing as well in line with the ignition coil probably high speed switching relay culd perform that tack via crank position sensor so most likely DPDT switches might come in handy or similar who do not have resistance in their circuet. Tungsten spark plugs wuld be great and high perfomance low resistance spark plug leads wuld be great to have. Useing longer periods of time plasma/amplifier ignition might result in greater wearing of parts. Thats how much I culd gather information regarding that ignotion system . For the MC3334 ic chip or LD 3334 the chematic can be found and PDF file that describes rpm to frequency relation chip . I hope this info helps you some what.

[@capzstyt]

Can you do a video on how this effect tune port injection engine?

[@shane9883]

It's been my experience that a lot of the problem lays with the vacuum advance rod hanging up on the base of the distributor housing and causing intermittent drivability problems or a bad diaphragm that won't hold vacuum at all. I also like to use an adjustable vacuum advance and vacuum tester when recurving an HEI distributor. And there are a lot of little plastic bits inside that wear out and excessive pin wear with a performance recurved HEI it wakes up your engine

[@sharkcitywarrior5485]

Would re curving the the distributor help with acceleration? My friends truck is kind of a dog down low and it starts to pickup after 3k rpm. It’s has a small cam and a performer intake and has an MSD HEI

[@thedobermangang3503]

Good video my brother

[@juniorwhelchel6337]

Love your videos teaching me a lot I race oval dirt track in South Carolina we have to run completely stock 350 HEI distributor can u help me or possibly build me a good for racing distributor also where are you located

[@gasandspark]

Hi Junior. Check out my website at www.gasandspark.com. My phone number is at the bottom of the “contact me” tab. Give me a call and let’s discuss what RPM range your running on the track and build a distributor that gives you an edge!

[@960wattoffgridrv]

with the extra time to modify the middle piece of the timing advance, keeping the total advance at around 36°. what is your base timing and vacuum advance at low idle? I think you took an extra step that wasn't necessary.

[@mikealdag7309]

gotta ask , what does it cost to have someone like you tune a distributor ?

[@joe-hp4nk]

The system's perfect. the springs are too long when closed, get shorter springs.

[@DIESELMAN8V92]

Amazing! Can I send you one?

[@LarryHinkle-ir7sh]

do you work on distributors

[@Raysandfamily]

So I'm building a street fire msd hei for my 355 sbc and balancer make is jumping around like 8°back and forth

[@28704joe]

I believe football in video was laid down backwards. Review MrGasket #929 HEI Advance Curve Kit diagram football compare it to video.

[@lordsauto]

Do you agree with ported or manifold vac?

[@gasandspark]

Hi Rob. I find that Manifold vacuum seems to work best on most street engines with mild / moderate cams.

[@lordsauto]

@@gasandspark I have a stock cam . It seems to run well smoothly 👌

[@mikef-gi2dg]

This is the first time I have actually seen a distributor machine in use, and it shows me I have no idea what my advance curve is for my GM crate basic 350 engine. I thought I had a good understanding of the weights and the FOOTBALL.....wrong again. After all these years, I must enroll on HEI 101 school again. Any suggestions?

[@Trump985]

I find just locking out the advance and running fixed timing is the best thing to do. If you have a separate starter and ignition switch you can just spin it up with the starter and then switch on the ignition. It will light right off without kicking back and breaking the starters nose off. You can always add a start retard module if you want. An engine with fixed timing really seems to be responsive to the throttle. It idles a lot better with fixed timing and will idle at a lower speed without fouling plugs.

[@flinch622]

A locked distributor pretty much needs an ECM to manage advance. An engine just needs help to idle easily - softening advance at low rpms does that. I look at it this way: idle [and its compromises] is something we put up with, but its not where we or the engine want to be.

[@tonywalker2334]

What state are you located in???

[@gasandspark]

I am in Southern Oregon. I can be reached at [e-mail].

[@yurimodin7333]

since HEI was created to satiate EPA requirements wouldn't it stand to reason that its designed for engine vacuum to pull the advance back down. Might be interesting to see what it does with 15 inches of vacuum.

[@lowellhalsteadjr4832]

Seems like adding heavier weights instead of subtracting spring would solve the problem

[@Thumperr6]

What machine is that

[@lordsauto]

Have a question for ya hoping u can help me. I have an hei sbc stock cam. I have a performance curve initial is 12. All in 3000 @36 total. Good power seems fine. But my exhaust smells very strong sharp acidic smell. I have no idea any ideas

[@gasandspark]

Do you have a catalytic converter? A failing cat can produce a sulfur / rotten egg smell.

[@lordsauto]

No cat. Duels doesn't smell like sulfur at all just strong acidy smell more when I get on it then after a bit at idle that when I smell it. 1405 edelbrock

[@gasandspark]

I haven’t experienced a smell like that…I’m sorry. I wish I could help.

[@lordsauto]

@@gasandspark someone said it could be nox

[@ralphfeuerborn3487]

Can you redo a boat one

[@bobnob1130]

I know I'm almost a year late, Hope you changed the smoke detector battery. I'll be hearing the chirp for the rest of the day.

[@borismcfinnigan3430]

But you never explained how go fix the fact that those weighs still kinda flop around unless they are at their "flung" position. Its kinda odd how the geometry of the spring allows this, it will make it inconsistent. i wish i knew how to fix it because i cannot seem to get a repeatable initial due to that issue..I set the total at 3k but dependi g how fast you back off depends how far those weights return..this is on a brand new msd

[@gasandspark]

The weights do flop around freely until centrifugal force takes over and causes the weights to act upon the center cam and advance it. I’ve experienced weights that do not fully return, resulting in inconsistent idle, when very light springs are used. I have to add heavier weights and modify the center cam to overcome this. The other issue than can cause inconsistent idle is a vacuum can (attached to a manifold source) whose pull in point is near or above the vacuum that the engine is producing at idle. For example. If your engine is pulling in 15” of vacuum at idle and your vacuum can does not act until 14” of idle, you will likely experience an erratic idle as it gets pulled in and released based on vacuum pulses. If your vacuum can is hooked to a manifold source, makes sure it pulls in at least 2” below the vacuum that the engine produces at idle.

[@borismcfinnigan3430]

@@gasandspark Thanks a lot for your reply mate. I dont have a vac canister at all. My distributor advance is purely mechanical, i was horrified to find that it takes between 3 to 5 seconds for the advance to settle down to initial settings after i give it a blip, and as i mentioned the idle sometimes settles back to 1100, sometines stays up around 1250. I took the distributor out, had a look and nothing at all is interfering with the weights returning to the initial position, so in my opinion the only thing that coukd be causing this is that sloppiness in the weights due to the fact that (because of the geometry) here is no spring pressure until the weights have flung at least 3/16ths away from the "football" . This would surely cause issues wouldn't you say? I was almost thinking of adding some material to the weights to move their resting position so that they are always under some kind of spring tension. This would reduce my total advance though if all else was left untouched..however i only need 8 or 10 degrees maximum.. Would you think that is a worthy fix? Thanks again.

[@gasandspark]

@@borismcfinnigan3430; I believe that adding material to the center football helps to keep pressure against the weights so that they “rest” more securely. I think it’s a fairly poor design from GM, so we can only improve it so much.

[@28704joe]

I believe football was installed backwards in video. There is a right and wrong way to lay that football down. See MrGasket #929 HEI Advance Curve Kit diagram. Compare diagram football closely to video football.

[@borismcfinnigan3430]

@@28704joe what on earth do you mean? The "football" is welded to the shaft there is only one way it can go

[@jeffreystroman2811]

Would you say 20° total mechanical advance is a good target for most streetable v8 engines? And how much total with vacuum added in with mechanical as I recently discovered there may be an adjustment inside the vacuum diaphragm you access thru where the tube plugs onto it.

[@gasandspark]

Hi Jeffrey. Yes, 20* mechanical seems to work well with most engines. I limit the vacuum can to only pull in an additional 10-12*. I do this by welding up the slot in the vacuum advance can. In total the engine gets about 46-48* advance (16 initial + 20 mechanical +10-12 vacuum can).

[@deanbecker7008]

If you would have started off on an Excel advance curve kit it would have all the bushings in the springs and everything cartoon that HEI distributor perfect.

[@thetriode]

I'll say that the advance weights available in the aftermarket are poor design, and I'd believe they're designed for the least common denominator not to ping. I'm surprised someone hasn't started repopping these with how available CNC water jetting is.

[@1crazypj]

Did well to get the return with such a poor mechanical advantage from the spring post positions. Pretty sure I've ever seen such a bad design on any motorcycle I've worked on in 50+ years, even the Made in Spain stuff in 1970's

[@deanbecker7008]

You got a lot to learn about HEI ignition I'm 65 and I ve built so many HIE SIN MY TIME. And I see your mistakes

[@cuylermayer661]

Giveaway was when he kept calling the cam a football

[@SpeakerKevin]

Time to change the battery on your smoke detector.

[@joe-hp4nk]

Just about every engine on the planet runs best with about 34 to 38 degrees total advance all in by 2500rpm.

[@v8packard]

I rarely find that to be the case. What engine are you running that needs that much advance that early?

[@joe-hp4nk]

@@v8packard Just the most produced engine in the world, the small block chevy. It clear you haven't a clue.

[@v8packard]

@@joe-hp4nk I have spent my career improving the piston to deck clearance, chambers, and compression ratio if nearly every small block Chevy I have worked on, in part so they don't need the crap advance curve you are fond of. But, since you just want to be shitty, you can continue on and miss out on real performance.

[@trailerparkcryptoking5213]

My BBC likes 40* total all in by 2800 rpm. HEI’s give 20* mech advance at best and 20* initial is too much to start my engine so I have to run an MSD starter retard with my Jacob’s Ignition spark box. A company now makes a digital controlled HEI where total, all in and vacuum advance are all entirely programmable with an iPhone and has an anti theft device. $500 and now economically feasible compared to sending your distributor off and paying for a curving service on an already piss poor design that can’t pull weights all the way back in and cause erratic idling and the end user can tune to perfection with total control...!!!

[@v8packard]

@@trailerparkcryptoking5213 Have you used the HEI that is programmable? I wonder how reliable it is.

[@WiSeNhEiMeR-1369]

HOWdy G&S, ... I'm having a terrible time "seeing" what you are calling the total SPARK ADVANCE on your machine DIAL I see zero ( 0 ) just fine / and thought I was seeing / 5 degrees / 10 degrees / 20 degrees / but / when your are telling us 18 degrees = I'm seeing "10" on the dial ... Can you straighten me out please ? ... COOP the WiSeNhEiMeR from Richmond, INDIANA ...

[@gasandspark]

Hi Dave, you bring up a very valid question / point. Every hash mark on the machine equals 1 distributor degree, but 2 crank degrees. For simplicity sake, I always talk in terms of crank degrees. I do this because this is what most people are family with. However, the crank turns twice for every rotation of the cam. When working on a distributor it is proper to communicate in distributor degrees, but I’ve found this creates confusion with the lay person. However; you picked up on it (and I failed to reiterate in my video). What you are seeing is distributor degrees and I am commenting in crank degrees. I hope this helps. Thanks for pointing it out.