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advance on my Chevy

7K views 83 replies 8 participants last post by  BuzzLOL 
#1 ·
Hi all.. So been mucking about work my build and finally addressing the advance. My vac can adds ten crank. My dizzy is adding about 22 centrifugal. With 12 initial I'm about home with it all in around 3k right?

My understanding is initial over 16 will cause hot start cranking issues.. .now here I see another story entirely:
"
To really make a trick street set-up you should only have about 10 degrees or so of mechanical advance in the distributor and about 24 - 26 degrees of initial timing on the crank to obtain your total of 34 - 36 degrees of total timing."

Now while I was playing my newly ground hei to give me more than the 16i was getting.. I noticed when I had too much centrifugal 30! The throttle response was insane.. It snapped like a bullet everytime I blipped the throttle however when I follow the 12/20 path the revs climb slower.

Does too much advance give this crazy response but not make power? I didn't drive it.. Just checked timing..it was a whole new animal (rev wise At least)..

So I'm wondering if I should cap the dizzy back to 16 Max and run like 18 initial?

Just felt like the car would be a rocket with that advance in so early.

89 pump gas vortec stock iron heads 214/224Cam on a stock 350..long tube headers and air gap plus qjet. .
 
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#2 · (Edited)
It depends on the build/combo, what the timing reaction will be. 16 will crank hot, 20 will slow.

Do a search for a starter kill, for that first hot revolution.

More initial more power at launch, usually.

Another experience would be,

My 305 with 9:1 / performer cam 3.73's , likes 36 locked always. For start I use a MSD retard. The vacuum can adds for cruise. It will run fine with 18 and 18 at 2400. Locked is better.

My 440 with 9.9:1 292 cam 3.73's , has a short curve again basically just for idle and start. 16-18 and 20 in at 2000 rpm. 12 in the vacuum can.

Both use Edelbrock AVS carbs , 650 and 800 cfm accordingly, pretty much maxed out. Biggest jet, smallest rod, and hardest spring.
 
#4 ·
tx, very informative.. ive always assumed the recipe is about 10-12 initial, 20-24 in the dizzy and about 10-12 in the can which is why i ground my dizzy down, now it seems i was o the wrong path?

My car is a 77 camaro, and my scr is about 8.7 and dcr about 7.2 :( - quite low so im hoping to regain as much power form my lump as is -

I have an odd hot start issue - when its cold no prob, but hot the first 2 swings are almost stuck, then it swings fine..

I had it tested at a battery place with a very fancy gizmo that apparently tests everything, batt, starter and alternator and everything was fine according to this guy.

This was after I had a start issue and eventually my car wouldnt start so i wired in a remote Ford solenoid and replaced my solenoid/starter with an oem one of a 96 tahoe.

Cam is the lunati 10001 flat tappet hydraulic, and i have a 13/4 long tube headers with 2 1/4 true duals not cat..

I really thought id have more power after all this - quite disappointed in myself really. its quite heart wrenching to end up with what feels like a lazy car after so much bloody work and expectations.

Im kinda pi$$ed off about it really - and quite sorely disappointed.
 
#5 ·
That cam and vortec heads in a 8.5:1 350 should make some good power. Lots of power.

Try more timing. lock the distributor at 36 and see if the launch improves. You will have to dial the distributor back to start it then advance it up to 36. It should scream with that combo. Tune the carb for WOT, and figure the curve afterward.

You can try to just shorten up the curve too. Short , try like 22 initail and 14 degrees more in at 2400. Bark up that tree.

The Q Jet vacuum secondary pod should be set to release the secondary with a slight second delay.

Transmission should be recalibrated with springs and weights to shift at 5500 rpms.

Get a locker for the rear to handle the torque or some postive traction system.
 
#6 ·
ok ill try that - im busy licking my wounds. All i know is when my advance was "too much" at almost 50 without the can hooked up, the throttle response was insane - it sounded like a jet rocket - literally.

Ill try those 2moro and see if there is actually something to this DIY engine building - or I just suck. seriously.
 
#8 ·
not to drag it out - and yes I will, but my first pile ogf mistakes was a kent 1600 in a 74 cortina mk3 whick i destroyed 5 times learnign the hard way about pvc and all. i now realize the importance of crank polishing and piston weight and how it can kill performance. Everytime taking out drive shaft, removing trans and picking the motor out with chains and a friend by hand.

I guess oneday ill yank it out and do it over again. Now ive tried with a chevy and seriously short on power.. im just stumped. I guess im a litte 5 yr old kid who wants a blast on the wheels. After installing exhausts in driveways, replacing rearends i picked off the yards, breaking skin, installing the 200-4r by had alone, bolting on heads after redoing all the valves with the comp tool, and im still slow as a turd. I have an absolute love for machines but ive never reached anywhere near what I wanted. Its beyond pride - just pure bloody hard experience. I had noone to show me ropes growing up and working tis stuff out on the budget in a backyard aint easy with only the internet and forums to guide you.

Ill muscle up soon and carry on the road.. just sick of bum results thats all.

Rant over. Will see what 2moro holds..

Fyi my stock is stall - looking at getting a 2400-2600. Lockup so cruise rpm isnt an issue with the 200-4r.
 
#10 ·
Im going to setup the hei like it was with the mad throttle response and take it round the block and report back..

ill try 18 initial and see what i does.. not sure about locking the dizzy out - i couldnt be turning dizzies about when starting my car every time or did i misunderstand that?

I have an oem mini starter.. ill first try get the most brute low/mid end, then see what happens after.

I ground my weight terminals down on the centre plate to move the centrifugal margin back, and went over board, now the pins line up too staight with the weight posts and the light springs dont pull them back enough so ill have to bush it back or something so i can try a light and medium spring.

Im beginning to think perhaps more early advance is the way to go..

ill try 18/18 today and see. I dont have a tach so just kinda guess.. the centrifugal only kicks in about 300 rpms above idle which is about right..


Ill report back - plz stick around chaps, i really want to figure this out. its the last straw - if i dont get this figured ill really be stumped. maybe im just round the corner to unleashing the power in my ride!!
 
#11 ·
ok so i just played around with a few combos and took her round the block a few times. Power is similar to before.

I have 12 initial, about 24 in the dizzy and ten on the vac.. i tried 12-22 initial and didnt notice too much of a difference in the wheels.


Im wondering if perhaps my trans/tc is slipping from being worn out? I think my advance curve is near enough to being very good - and still no great improvements.

Ideas?

I checked my damper inner/outer ring for slippage, still good - it didnt budge at all ....
 
#12 ·
Your low, low compression ratio is really hurting things as far as low end response and power. Low as it is, it will generally respond to the 20-24° initial, 36-38° total plus 12 or so in the vacuum can at cruise, or locked at 36-38° with an ignition cut-out switch to get it rolling over to start, and the added vacuum at cruise

A piston swap that gets you to 9.7-1 compression or so would really help a bunch more than anything you could ever do with the timing.

I think you are just expecting too much from a low compression engine.

I know I've said this a million times now...but ere to the HIGH side on the stall converter rpm or you will end up unhappy with your results there also. 9 times out of 10, with unhappy stall converter people I've helped around my little locality, is when they see how a stall converter really works, usually after they have bought one that is really too low a stall as they were "afraid" to go too big after reading too many BS magazine stories or listening to too many "online magazine story reposters/Mullet heads" who believe everything they read in the trash mags.

Listen to those of us like Myself and F-Bird...go too big on the stall if anything, as you have lock-up to cover any slight too high mistake. I can guarantee you, 3000 rpm stall is not too high for you, and anything less will just be a disappointment to an educated, experienced guy.

I was in the same place you are now, 30 years ago,... bought a 2200 rpm stall, put it behind a low compression 350 with ported heads and a 221° @ .050" .447" lift 114° lobe separation 350 HP 327 cam (GM "151" cam, the mild hotrod "standard" of the day) 350 trans 3.23 gear in a 70 Chevelle. What all the mags said was a "Great street/strip combo"...and was bitterly disappointed when it really only stalled 1900 rpm due to the low comp engine not making enough torque to get the "rated" stall.

You might not notice it fully, having never used a stall converter, but I would be instantly disappointed on my very first ride in your car with a 22-2400 rpm stall.

I drive a 4000 stall on the street 75 miles one way to the track and back, run mid-11's in 1/4, and have no problems with converter slip at highway speed 3000 rpm cruise (because it doesn't "stall" unless you are down hard on the gas, and only makes heat when stalling up). I use a single cooler, 8"x11"x1-1/2" thick stacked plate type, and can barely get trans to 180° in the heat of the summer after 5 or so passes at the track, does 140°-160° on the highway(sender in trans pan).

Just a few words from someone who has been there and done that, got all the logo T-shirts to prove it. ;)
 
#13 · (Edited)
Ericnova thats prob about the most helpful post ive read. ur right - u will be SORELY disappointed in my ride.

Right then - saving toward a piston swap. U recommended the claimer ones before. Ill budget for a deck as well to get a tight squish then.

Ill keep the cam/heads/intake/carb then.

And save for a 3000-3500 stall.

My trans is a 200-4r, and I will be maxed out for budget, but whats the cheapest upgrade I can do on it to shift/perform nicely with these next upgrades?

Will a shift kit be ok, or should I look at a $350 rebuild kit and do some more parts?

Just a daily driver / cruiser - no dragging / racing.

thanks again - I will see if some freelance work comes in and nail this puppy once and for all.




Something like this?

http://www.summitracing.com/int/parts/ape-4840hd/overview/
 
#15 ·
Ericnova thats prob about the most helpful post ive read. ur right - u will be SORELY disappointed in my ride.

Something like this?

http://www.summitracing.com/int/parts/ape-4840hd/overview/
Nope, that's just a 12" POS stocker with the fins bent over, won't multiply torque worth a hoot, just slip to get you that stall rating.

Look for 10" core size to get good converter efficiency, maybe 11" at biggest diameter with the lock-up.

ACC "Boss Hog" was my mistake 30 years ago, never again - JUNK!!
 
#14 ·
Eric what do you think of the split case stalls that have a 12" case and 10" turbine?

Everybody errs low on the stall the first time.

I would think a cam with that lift and 8.5:1 compression would do fair. Sure it would crank soft. It will still hit 300 hp and make for some joyrides.

There is a screw hole to lock the HEI it is easy. You put a screw in it.
 
#16 ·
Eric what do you think of the split case stalls that have a 12" case and 10" turbine?

Everybody errs low on the stall the first time.
.
Never tried one, but can't believe it would be anywhere near as efficient as a true 10" case model...just off what I've learned from converter makers and my race trans builder...there are no shortcuts worth taking in converter manufacturing.

You're right, virtually everyone on the street goes too low on their converter, all those years of magazine fools warning about "slip" at cruise speeds and burning up the trans baloney...if you burn up a trans, it is because of a low quality converter, or you just didn't buy enough cooler for the job in the first place.

I've seen 5000-6500 rpm stalls on the street just fine, cars driven 50 miles or more at a time and 8" race converters.
 
#17 ·
Eric, could u recommend something at the LOW end of a cash supply?? thanks. Ive read of chaps putting in the 'pricey' stuff and not noticing much difference - so i was dubious at best..

tx

Im up in seattle, ive heard of oregon performance or something up here..
 
#18 ·
So the stall units with a 10" body and 12" clutch are just bent fin 12's , ok. Didn't know.

I use poor terminology too.

A stall upgrade is commonly reported to improve 1/4 miles by .5 seconds or more. After the ones I installed that is an accurate claim.
 
#19 ·
So the stall units with a 10" body and 12" clutch are just bent fin 12's , ok. Didn't know.
I can't say that for sure about the 10/12" units, but the pure 12" are just bent fin stockers. There is only so much you can do "right" on a certain core size, then you are out of range.

I'd have to see/ask the builder exactly how he does his 10/12" hybrid...is it all 10" internal except got the clutch part, or 1/2-3/4 10" and 1/4 12" plus the converter clutch?? Is what I'd want to know.
 
#23 ·
I remember my first hot rod build (ok it was last year). I did everything right, paid attention to all the details, read, researched, posted here, googled, etc. I was really disappointed in my lack luster engine performance :embarrass . Finally I realized that I had not adjusted the throttle linkage properly on my carb. The secondaries were *barley* and I mean barely opening. I was essentially running on half throttle at best. After properly adjusting it, the first time I stabbed the pedal I was grinning ear to ear :D then I had to wrestle the steering wheel to keep the truck out of the ditch since the rear end was going crazy!

It helps to have someone in the car pushing on the pedal while you watch the primary and secondary butterflies open. Just keep in mind that on a cold engine the carb will lock out the secondaries from opening, so you need to defeat that with a booger hook before your partner presses the gas pedal.
 
#24 ·
I'll check that out on the qjet. .I tend to believe I've done a pretty good job rebuilding mine.. Everything seems fine except I've never made it to the secondaries.. Not sure why.. Vac can stays tight no matter what rpm.. . I've been told it won't open on idle.. Ie motor must be under load. This I don't understand since its vacuum controlled right? Load is ambiguous anyway.

I'll take a spin on freeway without the can hooked up and see.. I'm 99 percent sure the primaries are opening but I'll double check with a friend just now..
 
#25 ·
The qjets vacuum pod will open the secondary under throttle, at temp, and when vacuum falls under a determined amount. Watch the pod with a hand held vacuum gauge and pump. You don't want it to flop open, it is a spread bore. There are good books on q jets, Cliff's for one is top notch.

FYI - I think you want to modify an intermediated orifice( drilled golf tee in between in pod hose) to release the blade slowly over 1-2 seconds.
 
#26 ·
Yeah I've bought all those books.. I don't have a drill bit small enough.. One article suggested about 0.011 to 0.012 and checking that.. Maybe I'll try a .25mm from hardware store 0.010 and try that.

So u are saying it will open on idle/ie revving in neutral?
 
#28 ·
Ok - thats interesting. Could U perhaps explain that to me? Im curious - my understanding is the vacuum gets "absorbed" since the air is being moved. I can only see engine load (ie actually moving the car) adding to friction and using some rpms - but surely a vacuum operated can responds to vacuum. It doesnt 'see' engine load?

Ive never grasped this and would be really interested to know why - Im just applying a monkeys logic here - so forgive me :pimp:
 
#29 ·
Eric is right about what he is saying, Plus i will add this, "DO NOT" buy an e-bay converter, You need a good quality piece form a reputable source, I myself always use PTC, There prices are fare also, & all of his perf. converters come with ballooning plates for nitrous.

Its not just the stall your looking at, Its the "flash" stall, does it have a good stater, If not, it'll be a POS on the street & most likely have too much slippage, Thats just part of it though, be careful what you buy.

I'd call Kenny at PTC & talk with him.

Performance Torque Converters - Performance Torque Converters
 
#30 ·
I think it also comes down to the torque multiplication right? I think anywhere deom 2+ is acceptable.. alot of the bent ones are 1.5-1.7 and they suck. I think its a fair question/spec to ask from a TC builder. btw those on ebay look good. theyre 9.5" US made and list ALOT of specs on the add. Not everything on ebay is junk.
 
#42 ·
Theres alot of questionable stuff on e-bay, don't always buy into the "made in the USA", some will use it as a hype for selling a product, i'v run into this, & trying to return a product can also be a pain.

You'd be better off buying one from Jegs or Summit, they have an excellent return policy, they stand behind what they sell.

If i was going to buy a converter off e-bay for 399.00, I'd rather spend a little extra & get one custom made.

PTC builds them for "your" application, even there 300.00 converters are custom built for the stall you want.
 
#32 · (Edited)
yes but its load is air, and whether the air moving thru is in neutral or pushing a car - either way its moving, the can doesnt 'see' engine load, it sees air pressure. I dont 'logically' understand why ppl say the engine has to be under load, ie driving instead of idling, for the can to release. Surely revving the motor in neutral will cause the vac to also drop - and thus let the can release?

:confused:

Im just being politely firm until proven otherwise :)
 
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