JTNKTZ

iTrader: (10)

Alright I am still working some kinks out. I am running the following:
Edelbrock Performer RPM
MSD Streetfire HEI Vacuum Advance Dizzy
Holley 650 Double Pumper (4777 - 4150 model)

First, base setting is set at about 12 degrees. But when I rev it at high RPM's, it goes passed 60 degrees... This cannot be right. Whats wrong and how do I fix it?

Second, It still needs to be tuned. When tuning the 2 corner idle mixture screws, I have been told many ways to do it.
One was keep turning clockwise till it bogs down and move out 3/4 turns. The other was to find maximum vacuum than avg the 2 screws.
How should I be doing it?

Third, I need to rejet it. I have seen many different ways to do it. I read the holley tuning sticky but don't understand the "jet stepping" process.

Anyhelp is greatly appreciated.

one92rs

iTrader: (5)

ok is this a stock engine? 650 double pumper if it is is to much. i thought a double pumper had four corner idle screws. you set them with a vacuum gauge. still need to know more engine specs.

Blown84Bird

Disconnect vacuum line from dis then retest total timing. Had same problem awhile back I left vacuum advance off works fine.

JTNKTZ

iTrader: (10)

It's a stock 350 for what I know. Yes it is a little too much, but it should work fine till I possible get a cam swap.

All the 4777 carbs I have seen have 2 corner idle mixture screws cause I thought the same thing. Some examples:
http://cgi.ebay.com/ebaymotors/HOLLE...Q5fAccessories
http://cgi.ebay.com/ebaymotors/HOLLE...Q5fAccessories

I have a vacuum gauge I'm just not sure how to use it.

Did that.

JTNKTZ

iTrader: (10)

Alright so I went out to play.
In neutral my vacuum is 20
In Drive it fluctuates from 16.5-17.
Turning it in only makes the vacuum go down after 1/4 turn.
Turning it out doesn't do anything to the vacuum
Also, I unplugged the dizzy from the carb and noticed that the timing is bouncing around? I have the base set at 13 but when it bounces around it could go up to 15. At idle about 900 rpms...
When the dizzy is plugged into the carb the timing could go anywhere up to 50 degrees at wot!

Blown84Bird

Total timing w/o vacuum was still 50°+ put new weights/springs in distributor should lower total timing and limit some of the jumping at idle

one92rs

iTrader: (5)

first off idle it down to 750 rpm's and check the timing. if it is still bouncing then there is a problem in the distributor. did you put stock weights and springs on it. are you sure you dont have a missfire? i to have the msd distributor and it is rock solid. your timing jumping around is the first problem that needs to be tracked down and fixed. my rs is a 305. someone or you changed the engine if it is a 350. the only other thing i can think of is a timing chain problem. how did it run before the carb swap?

JTNKTZ

iTrader: (10)

My cars tach is off I think. Cause it runs at about 900 RPMs and any lower it pretty much shuts down.

There is a hole in the coil cap could that be causing the problem? It's a new dizzy so there shouldn't be anything wrong with it.

Also the secondary side vent tube is missing. Could that be causing a problem?
The PO did the swap. It has a 638 block in it (roller, 350 4 bolt main 1 piece RMS)

onebad82z

iTrader: (7)

Before you attempt to tune any part of the carb fix any and all mechanical problems. Be positive fuel pressure is sufficient and timing is correct.

It is possible it is going past 60. Disconnect vacuum advance and note idle timing and total (rev it till the timing no longer raises. Note these on paper. Then connect vacuum advance and not how much it added to idle. You need to get this set 1st.

You can do it either way really. Find what works best for you. I normally only add 1/4 to at max 1/2 turn out if done like the first idea. Either way average it out when done.

Why do you need to rejet it? Once you have the timing set right start with the carb at Holley spec and then tune it to your combo.

Answered above.

Timing should not bounce with a cam that mild. You may need to dig in deeper. The 350 was swapped in with how many miles? Sounds like a bad chain or something in the dizzy. Does the advance mechanism advance smoothly and have a postive stop to it?

onebad82z

iTrader: (7)

Fix it!

Air_Adam

Won't idle below 900rpm, timing wanders around... suggests to me either a vacuum leak or a worn out (stretched) timing chain.

JTNKTZ

iTrader: (10)

No vacuum leak because I sprayed around the motor with carb cleaner and it didn't try to bog down.

I'm hoping it's not the timing chain :/

I noticed that the secondary fuel bowl was kinda low. So I corrected the level but now when I take turns hard or hit the breaks hard it bogs and sometimes even shuts off.... Ugh.

onebad82z

iTrader: (7)

See post #10.

JTNKTZ

iTrader: (10)

Did some more work today. I timed the dizzy without the vacuum advance connected. it maxes out at 30 degrees. The timing is fine, my eyes were just playing tricks on me I think.

I pulled the carb off and started dissambling it. There was a lot of dirt in there and I think that is half my problem. I cleaned it out real good shooting a shitton of carb cleaner in ever hole from smallest to biggest and i blew it out with compressed air.

I broke some gaskets so I need to go buy some new ones before I can test it again.

onebad82z

iTrader: (7)

Total is good to know and that it is not fluctuating is also good news.

What is your idle timing with vacuum advance connected? Incorrect setup on idle timing will cause your issue even though total is good.

JTNKTZ

iTrader: (10)

With vacuum advance it is at the same place. But it stops around 50-60 degrees. Couldn't tell you exact atm. Is it possible to make my own vent tubes? Only place I could find is jegs and they want 14 bucks a set.... I just got laid off sooooooo lol.

onebad82z

iTrader: (7)

I do not know of a way to make vents, although I am sure it can be done.

JTNKTZ

iTrader: (10)

Got the carb on today. I also used clamps on all vacuum hoses just in case. I got the idle down to 800-850 RPM's so I'm going to leave it at that for now.
It seems to be running a little better but it still has a choppy idle and wants to shut down and will if I just leave it running for a while.
When I tune the needles, do I go a quarter out after I hear the RPM's drop slightly or wait for a noticable bog?

Also at idle if I give it a little love tap it it bogs a little.

Here's a 0-60 I did.
http://www.youtube.com/watch?v=ydn0WKWA0hA

onebad82z

iTrader: (7)

... go a quarter out after I hear the RPM's drop slightly.

84firebird383

The reason it is bogging or killing is because you have no vent tube and fuel is sloshing out the top and back into the throat of the carb. How are you determining that your floats are set right? Also, when you are setting your mixture screws the engine should be at operating temperature. If I had to guess 1 1/4 turns out should be real close.

JTNKTZ

iTrader: (10)

Just bought these for the vent tubes: http://cgi.ebay.com/ebaymotors/ws/eB...m=160384396305

I am adjusting it so the gas is on the thread but not dribbling out on both the primary and secondary.

Well I need to readjust the idle mixtures because I was doing it until the car bogged down, not at a slight RPM decrease. Hopefully that will fix the choppy idle problem.

JTNKTZ

iTrader: (10)

Well I retuned and they were both exactly a 1 full turn out. Does this sound right?

onebad82z

iTrader: (7)

How does it drive now? Still no vent tube till the ebay ones come in right?

JTNKTZ

iTrader: (10)

Correct. It feels like it is driving a lot better. About time! Haha I am thinking I also had some vacuum leaks cause I put some hose clamps on all the vacuum lines.

It doesn't want to shut off it I give it a love tap. But it does drop to about 500 and come back up.

Also I am running with the vacuum advance disconnected but would like to run with it connected. How do I fix the 60 degree advance problem? Or is that normal?

onebad82z

iTrader: (7)

OK so you now have a car that runs somewhat good. It more than likely will still have issues till you get that vent tube installed during braking. But you can work on timing for now to make it happier.

12 degrees base is a decent start. But more can help from vacuum advance so...

What springs are in the dizzy? You are using the weights that came with it correct? Is this the HEI style streetfire?

UNplug vacuum advance and re-verify you have 12 at idle. Make sure to plug the hose as it will be a vacuum leak. Make sure idle is low(ish), like 500-750 if it will. This ensures you are not into the advance curve which will throw off what you find at idle. Then rev the motor slowly, helps to have someone do this while you watch the timing and see when it stops and how many degrees you find at that point. You watch the timing while they rev it (slowly) and when you say stop let them know to remember what RPM it was at. Then let us know what you have at idle and fully advanced with NO vacuum can attached. Also record this on paper as you will possibly forget it. Easier to keep notes.

JTNKTZ

iTrader: (10)

I bought the dizzy from eBay. It was supposedly a back up for a marine motor. So who knows what is in it spring and weight wise. One thing for sure it was definitely new when I got it. No signs of use on the rotor or cap. Grease was still on it as well.

I am going to begin my transmission swap tomorrow and I won't be done till Wednesday night because I have school tomorrow and Wednesday. The Vent tubes should be here by than as well.

I'll than start playing with the timing and post back.
Thanks ALOT for all the help, it's greatly appreciated.

onebad82z

iTrader: (7)

Start with a soft and a medium spring, stay with the weights it came with as they should be right for it. Get the vent tubes installed and then get some notes on the timing and I can help you go from there.

No problem! I try to help when I can and know I can give some decent info! It sucks when the hot rod runs like everyone else expects it to. I like to get them sorted out and then they can't believe it can run that nicely.

JTNKTZ

iTrader: (10)

Alright well my car is back to running like crap :/ WEll not crap just sluggish.
I put the new vent tubes in and it still on a rough stop shuts off.
Also When in nuetral and I rev it a few times, there is a backfire in the intake sometimes around 300-5500 rpms...

Any ideas? I am running at 12degrees with the vacuum disconnected for now. Should I run higher?

I'm debating on buying a new edelbrock 600 cfm and see how it goes :/

onebad82z

iTrader: (7)

Play with float levels. Drop them a 1/4 turn and see if it likes it, if not raise them back up that 1/4 and add another 1/4 turn. I have had carbs like em high and some like em low.

Are you running around with the vacuum hooked up? How much does it add at idle?

JTNKTZ

iTrader: (10)

Well I have played with float levels and nothing :/

No lately I've been running with it disconnected

onebad82z

iTrader: (7)

12 degrees is not enough timing. You need to get the timing set before any carb tuning can take place.

Are you running the Streetfire as it cam from MSD? Tell me what has been done with it thus far?

five7kid

iTrader: (14)

Other than actually setting the timing, nothing good can come from not having the vacuum advance hooked up. If you're having problems, they won't be solved by disconnecting the vacuum advance.

JTNKTZ

iTrader: (10)

The streetfire has not been tampered with. What would you suggest I set the timing to at idle with the vacuum hooked up?

onebad82z

iTrader: (7)

Yes I would. But first lets get some data we can use to dial things in...

Here is what I would do and how I typically figure out what my combo likes best. You can leave the vacuum advance disconnected for this...

Start the car and drive it around some to get it nice and warm. Then park it and put the e brake on. Let it idle, make sure fans and such are on as to not overheat it for this test. What is the RPM? Remember this. Record it on paper. Not bad to have a piece and a pen for this.....

Now loosen the bolt for the distributor and rotate it a few degrees. Did the idle RPM raise? If so, good. Turn the idle speed back down to your typical idle RPM you just took note of. Now turn it (distributor) some more. Not talking 1/8 turns here, just give it a bump to advance the timing... CCW. Turn the vacuum advance towards the front of the car. Again if the idle RPM has raised bring it back down to where it was before any turning of the distributor. Keep going in this direction till the idle RPM no longer raises (increases) with advancing the distributor. When idle RPM no longer increases... It is at this point you get a timing light and record what it is at idle. Don't be surprised to see 20+ degrees. NOW... DO NOT drive it like this as more than likely your total timing is way advanced. This is just to figure out what YOUR combo likes at idle.

Record this idle #

At this point drop it back down to where you have it now (12 you said right?) since it should be a safe setting for WOT. From what I have seen on the streetfire's they have a 20 degree or so mechanical curve. Not a bad idea to verify this either. With timing back at 12 degrees at idle and a timing light hooked up, rev the car till the timing no longer advances and take note of that #. Ensure vacuum advance is still unhooked for this test as well. Now... Take this last # and subtracting your 12 at idle tells you how much mechanical advance is in the distributor.

Record this mechanical advance #

Now one more step so we know what we are working with. At idle with your 12 degrees plug in the vacuum advance and with your timing light record what the timing is now with it hooked up. It should raise 12-16 degrees or so.

Vacuum advance #

Get back with these numbers and we can help get the timing closer to better understand the extent of tuning the carb may need.

five7kid

iTrader: (14)

Go ahead and go through those steps. My point was you should keep the vacuum advance hooked up except for while you set/check the timing.

JTNKTZ

iTrader: (10)

Well, I just went out and did that but the idle does increase or decrease unless I give it a little throttle.

onebad82z

iTrader: (7)

You turned the dizzy at idle and it made no difference? Make a bigger move then...