neverendingproject

finally finished my heads, cam, etc install on my new to me 80. i have a whopping 7.5 inches of vacuum @ idle now. car runs great, idle sounds awesome & revs faster than any hydraulic cammed engine i've ever heard. idles at 850rpms.

even though the vacuum is low, the brakes work fine. however, the headlights wont open without help. how much vacuum is actually needed to operate the headlights? do any of you guys know where i can get an electric vacuum pump?

i also have a distributor problem to overcome. i have way too much advance. im getting 35* in the distributor. in other words , if i set it for 12* initial , i have 47* by 3000rpms. not sure whats missing in there, but it has definately been modified.

quick recap of everything i did ... did the performer rpm e-tec package minus edelbrocks heads. i used my own modified vortec heads. also installed the accessory drive system off a 94 chevy truck, which i must say is pretty sweet.

what it had ( i discovered upon tear down). engine had been rebuilt some 30,000 miles ago. found true .030" over flat top pistons and double hump heads. the heads b.t.w. had accessory bracket holes drilled thru them. emphasis on the word "thru". wonder why it had an oil leak or two. :lol:

sorry for the long post. please give me all your comments , advise, etc.


[Modified by neverendingproject, 8:10 PM 3/27/2004]

cardo0

:cheers: Very ingenious of you to use the vortec heads. :thumbs: What mods did you make to the heads? Pocket port? Springs & new spring pockets? Studs?
A tech call to Edelbrock might tell you what kind of vacuum to expect. That RPM cam does have plenty of overlap so I expect low vacuum.
I like your economy of performance parts here though as that combo should make plenty of power to practice your ignition and carb tuning skills. I read nearly every day about a forum member that spends thousands on expensive engine parts and can't set the timing right or tune the advance let alone the carb. Its much better to learn on an economy effort and avoid expensive dissapointments.
Sounds like your total advance is coming in late but hey I'm learning here too.
I think 2,500-2,800 rpm sounds like better numbers - check the C3 tech tips on the tools dop down list above . Have fun and enjoy the performance experience. :thumbs:
Thanks for posting your accessory drive sys upgrade. Man that really sounds like a great idea. Would like to add that to my list with/when a set of electric fans. :lol:

REDRED62

The installation of a simple vacuum canister should solve the problem. The 80 has a vacuum tank installed in the front of the car. This tank could also be used as a reserve supply tank for the headlamp system. The tank has a check valve already made into it. You could mount it under the left fender by the firewall. Earlier cars like the 68-72 cars used this design and the headlamps worked well.

If there is not enough vacuum to operate the headlamp relay’s under the front of the nose, the hose that runs from the headlamp switch to the relay could also be routed through the extra vacuum tank.

The p/n for the round vacuum canister is 14011852 and you should be able to purchase it for around 40.00 from your local GM part’s dealer.

neverendingproject

thanks for the reply.
only mods done to the heads were port matching, spring seats and guide clearance for the larger springs & of course, screw in studs.

the timing rpm was kinda general , as i knew it was too much. im shooting for 12* inital and 34*-36* total by 2800 rpms.

when you do the drive system upgrade, let me know. i can save you a few bucks on mistakes. its really not bad though. i also added 2 electric fans. controlled via relay by a temp switch. switch turns them on at 195*. when i get the a/c lines made up, i'll also be wiring a high press. switch into the control side of the relay.

as far as carb tuning, it really didn't need a lot. mind you , i haven't put 10 miles on it yet. only thing i had to change immediately was the metering plunger springs to 3" springs. its an edelbrock eps 800 carb and, even though most of you guys are for holley, i have always had good luck w/ edelbrock carbs.

if anyone has any tips for smoothing the idle out , id really like to hear them.

neverendingproject

thanks for the info REDRED. that had crossed my mind , wasn't sure if it would help though. the fuel vapor canister is in that fenderwell, but its umm not connected right now. i'll give that a shot.

neverendingproject

any other advice? :confused:

litevette

I read somewhere of an electric vaccum booster for use when a hipo engine is built and you need more vaccum. Don't remember where I read it. Try searching "electric vaccum booster". Good luck! :cheers:

rcastor426

is your car auto or manual, i had that cam in an automatic before and it was awful until i put a 2500 converter in it. the engine then really came to life. it was hard to keep traction and pulled hard through 6000

neverendingproject

its an auto. i dont believe the tranny or stall in it are stock though( nothing else has been). i really like the way it runs. i haven't driven it much due to the distributor problem, but i did test it a little. it will jump sideways quickly when you punch it at 35mph. :D

Smokehouse69

There is another alternative, on of the guys here on the forum is marketing some kits to convert your vacuum head lights to electric. It doesn't require permanent modification of any of the actuator parts, and uses off the shelf parts from GM F-Body headlights.
1Bad69 comes to mind as someone who might have some more information on them! Good Luck!

Red73Vert

Not sure which distributor you're running. Most of the GM (points and HE) have a small bushing located on a pin on the underside of the top of the distributor shaft (rotating assembly) where the rotor is attached. This bushing limits the amount of mechanical advance in the distributor - the weights/springs affect only the rate of advance. Sounds like the bushing is gone if you've got that much advance in the distributor. Bushings come in different sizes - effectively changing the amount of mechanical advance available. I know Crane and others offer distributor "tune-up kits" which include this bushing(s). Recommend you try to get a bushing that limits mechanical advance to 20 degrees (crankshaft) and that way you can run 15-18 degrees initial advance and 35-38 degrees total. You might also want to play with the springs (lighter allows a quicker mechanical advance) to achieve as quick a rate of advance of as your engine will tolerate without detonation. The more advance you have at idle/low RPMs (without detonation) the more idle vacuum you'll have and the more torque you'll have down low. The other place to get more vacuum at idle is by tuning the idle mixture screws on the carburator. The best approach is to use a vacuum gauge and to adjust them to best vacuum. Sounds like you have a well thought out combination - should be real strong once you get it tuned. Enjoy!!!

neverendingproject

thanks for the info guys. i think im gonna get after the headlight system w/ a manual vacuum pump before i make a move on that end of it.
you gave me a lot of useful info there Red73vert. now that i think about it, i dont believe i saw a pin in there at all. i was planning on getting another distributor anyway. so you think i would be better off w/ 15 to 18 degrees initial? you think it would run a little cooler w/ that much advance at idle?
i always use a vacuum gauge to set the idle mixture too.

gerry72

You can get a new electric vacuum pump with high-low switch easily from either Stainless Steel Brake Corp. or Master Power Brakes. They're not cheap. You can also go to your local bone yard and try to grab one from a number of early to mid 80's GM cars. Go online and do a search on automotive electric 12V vacuum pumps. You'll see that many folks who build EVs have already done a lot of the research.

As to the timing issue, you're reading the advance with the initial, the centrifugal, and the vacuum advance all kicking in. Total timing that is always referenced is just the initial and centrifugal. Unplug the vacuum advance line and read your total.

The Edelbrock RPM cam is great as long as you can live with no vacuum or bottom end. They use 108-degree LSA which makes for a robust cam with a very lumpy idle but it works well for very few.

Red73Vert

Gerry, you make a good point about vacuum advance - need to make sure that you are checking timing and mechanical advance with vacuum line disconnected from the distributor and plugged.

I'm running an overcammed 30 over 350. I've tried a number of different timing adjustments and it seems to idle best (with the most vacuum) with 18 degrees initial and 20 degrees mechanical advance all in by 2600 rpm for a total of 38 degrees. I also have the vacuum advance (an adjustable Crane unit with 10 degrees additional advance) attached to the manifold vacuum, so that it is functioning at idle (versus using "ported" carb vacuum which is not present at idle). FYI - I've also drilled out my idle circuits on my rochester 4bbl so that it will have enough gas to idle with the throttle plates just opening. If you have to adjust the throttle too far open at idle you'll lose vacuum that way also. Regards and have fun!!!!


[Modified by Red73Vert, 2:28 AM 3/30/2004]


[Modified by Red73Vert, 2:31 AM 3/30/2004]