i have a 355 sbc, 200cc 202/1.60 valves edelbrock performer cam 480/510 lift. edl-7102 ref number of cam, air gap intake, msd ignition, accell dist w/o vac advance and 670 street avenger. i can only get around 8.5-9 hgi of manifold vaccum. i have the base at 14* and total of 36 around 3000. it makes my brake pedal hard, and stopping a joke. should i go with a vac reservoir canister? or is it something else?

 

Whats duration on the cam? Whats your idle fuel mixture like and what rpm?

I think that cam is small being the performer series. It should have good vacuum. Sounds like a vacuum leak.

Check for leaks and if none present, make base timing 20-22 deg and see what happens. Play with idle fuel mix screws and tune for max vacuum at idle. Check plugs to see what fuel mix looks like

 

i used carb cleaner around everything and no idle increase. i have the fuel mixtures screws out 2 turns so far. the plugs are carbon covered (rich). would bringing the base timing up that high make the car run hot? cam specs:
Intake Duration at 050 inch Lift: 234

Exhaust Duration at 050 inch Lift: 244

Duration at 050 inch Lift: 234 int./244 exh.

Advertised Intake Duration: 308

Advertised Exhaust Duration: 318

Advertised Duration: 308 int./318 exh.

Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.

Valve Lift with Factory Rocker Arm Ratio: 0.488 int./0.510 exh.

Lobe Separation (degrees): 112

Computer-Controlled Compatible: No

Lifters Included: Yes

Lifter Style: Hydraulic flat tappet

 

id say thats about the normal vacuum for a cam that big. you should have decent brakes with your 2,800 stall. maybe your brake booster is leaking?
i set the mixture screws with a vacuum gauge. shoot for the highest vacuum reading possible. might help?

 

Ok thats the rpm cam and its a big cam with lazy lobes that will bleed off compression. You need alot more timing to gain vacuum.

Efi cars can run 20-30 deg at idle no problem. Carb car can to, as some lock timing out at 30-36 deg on wild combos. It shouldnt overheat if mixture is right.

Plugs should be tan around the porcelain and just have a dark ring around the base threads for idle. That should be closer to stoich air fuel. Lean it out will help give some vacuum back but timing should make the biggest difference

Even with all that, the cam and heads will have somewhat slower velocity thru port and intake and just wont make alot of vacuum. However i think with timing mods and fuel mix changes you should see 2-3 more inches Hg and that may be enough to make pedal feel better.

Still may want a vacuum canister for braking with multiple pedal presses since vacuum bleeds off quick with multiple pedal presses. Reserve canister will give better first pedal press feel and should help alittle with multiple presses in a row

 

if i set the timing to 20-22 i get a total timing around 43.the pedal feels normal, do i need to mess with the weight and springs to lock it out at 36? i believe thats why i had an overheating problem was do to to much advance timing? im new to this tuning stuff, so sorry if i sound kinda stupid

 

No you can have overheating from too much advance but i dont consider 20 deg alot of advance for a cam head motor like that. I know stock efi cars are 20 deg from factory with stock cams. Why cant a carb run the same or more? I never understood that from the oldschool guys but maybe i am wrong here. I never mess with carbs, just efi but tuning is tuning, give motor what it wants. Timing and proper fueling will raise idle vacuum

You can try it and see. Raise idle rpm up some if needed too.

You will need to recalibrate the distributor so that its 20-22 or whatever degs you need at idle, and then 34-36 at 3000-3500 or whatever it wants

 

ok so i put new srings in to limit the advance to 36 degrees by 3000 rom correct? ill get a tune kit after work and try it.

 

Yeah should have to adjust the springs and such to get the advance curve to do what you want it to do.

For now you can set base and test drive part throttle and see if the pedal feels good. Find the timing it wants and see if it overheats or changes anything about how it drives in general. It should wake up and feel stronger off idle. Just dont go wot with 43 degs advance. Once you know what timin it needs at idle you can then change springs.

If it doesnt help dont change it. I would get a better cam or vacuum canister and try that

 

it seemed to run a hell of alot better with the base at 20, but the total at 43 kinda made me wonder and thats why i dropped it down to run in the 36 degree range

 

ok i bought new weights and springs. the bad part is the pin that holds the middle "bar" busted cause they were rusted and seized together. is that mechanism replaceable or am i screwed and gotta buy new dizzy?

 

ok i had to purchase a new dizzy installed and at 12* base i get 36 total timing. if i go higher on the timing the total raises to about 40* total. and the car get hard to start when its at 16* and above. when its at 12* to me it feels sluggish but it throws you back in the seat. should i go higher and leave it at 40*? i got springs but are unsure which ones to use

 

No you dont want to go over 36 deg at full throttle

 

ok so leave her where shes at then?

 

What kind of distributor is it? Does your distributor have a vacuum advance can on it?

Also the car should not be hard to start at 16 deg. There might be other problems also.

 

its a normal distributor without vac avance. proform model.so if i want to raise the timing to say 18-20 do i put the heavy springs in it and ill be fine or?

 

no they just make the total timing come in faster. They don't change the amount of advance. Although the light spring might make more timing at idle due to them actually advancing at the low rpm.
The heavy springs are a bad idea. They will still be advancing at over 4500 rpm. So if you set timing at 36 at 3000. Think how high it will be at 4500.
Try the light springs. If that doesn't work the only way to reduce the amount of total advance to have more at idle is to weld a stop on the distributor or buy an msd or malory.

 

so basically im stuck at 12* base until i buy a msd distributor? and how do u kno where to weld a stop at? id like more base timing but total gets to high

 

Try the light springs. If they start advancing at 500 and your idling at 900 you will probably get a couple more degrees at idle. Although it may have an adverse affect by not keeping a stable timing number at idle and it might fluctuate between at idle.
I have no idea how to weld a stop.
I always recommend a non hei msd or malory dist for cars with any decent size cam so i can custom tailor the amount of mechanical advance to get the best idle. I also always recomend a dist with a vacuum advance. It has no effect on performance and will allow the car to run smother and get better mileage at cruise. And will also increase timing at idle when it's hooked up to full vacuum.