I have a 68 350 rocket block with 69heads can't remember the number they are the high compression ones. I think 6a or so.

Also has a cam machine shop didn't give me the card so uncertain of lift supposed to be mild.

Edelbrock performer rpm intake 7111 I believe and edelbrock 1406 carb I believe

Msd hei ignition.

Having a hell of a time tuning it.

Timing was set via vacuum gauge for max vacuum which max I could get was 19 and backed off 2.

Attempted to set idle mix screws the same issue is the motor itself has a pretty serious shake to it like it's missing very hard.

The vacuum gauge doesnt do steady if fluctates and almost vibrates in a range of about 2-3.

Checked for vacuum leaks all over none were found the idle lowest I've gotten it without it dying shows 1300 in park can drop it to 1100 in gear.

When you jab the gas just a quick stab most times it will bog and almost die though since I've turned the idle screws in a bit it will catch it self but if you stab it sometimes it will spit some gas out of the carb.

Sorry I know it's all over the place but I'm losing my mind here trying to get the idle where it needs to be and actually make it driveable.

 

I would start by setting the timing with a timing light, then progress to carb tuning. Trying to get max vacuum with a messed up carb doesn't sound productive.

 

That would be base timing of what 12 degrees btdc?

We set it once via timing light problem was it ran horribly and wouldn't stay running so it was very confusing that's why we went to vacuum gauge.

 

You've got an Edelbrock economy carb on a high performance manifold. You may spend a long long time dialing it in to never get it right. That's how my car came when I bought it, and even with the anemic low comp 72 350, It couldn't be tuned right. I will say, I was able to get it to run fantastic only at WOT. Other than that it would spit, sputter, flood, etc. I assumed the previous owner knew what they were doing. I was wrong.

I swapped to a 1405 and I'm not really happy with Edelbrock.


As far as the fuel spitting, check the fuel pressure. It should be no more than 5 1/2psi max. Edelbrocks are pretty sensitive to fuel pressure.

With HEI you're going to need more than 12* initial/base timing. It'd bump that up a few more degrees and see if you fair better. All the HEI equipped 350's I've seen, the base timing has been bumped up around or past the high mark on the balancer. I don't know why, but they run better.

If your max vacuum is 19, I wouldn't consider that a mild cam. That's a pretty stock cam.

Is there a vacuum leak? Try spraying carb cleaner or penetrating oil, something, around the base of the carb and listen to the motor. Are all the vacuum lines tight? Check the plug on the Edelbrock port (either times or manifold) depending on which your Vacuum advance is hooked up to. A lot of times they crack/split. Put your thumb over the cap and see if anything sounds different.

 

New vacuum lines. Wasn't able to get any idle change with spraying around for vacuum leaks and don't notice any cracks. And ok so about 16 btdc then?

Yea I can get almost to 19 but this is a complete fresh from machine shop build and the dang builder only said mild cam. Not the best experience.

And so you think the 1406 is going to continue having issues on the 7111 anyone else with similar experience?

 

I have the 1406 paired to the 7111 intake and I don't have those sorts of problems. In fact, I recently added a fuel pressure regulator and my 72 350 runs damn well.

I think you definitely also need to set your timing with a light and not vacuum. On my 350 with HEI ignition, it likes about 18 degrees initial timing.

One thing with the Edelbrock 1406; make SURE your floats are set to factory, F/A screws are clean and free of debris, make sure your needles and seats are absolutely clean and make sure to check your fuel pressure. The 1406 HATES anything above 4psi from my experience, and it WILL KEEP FLOODING, so I keep it around 2.5 with the use of a regulator.

 

From what I've found wth the 7111 and a small cam and around 10 compression they suggest the 1407 a 750 cfm carb will that be too much fuel?

 

You should not have any problem getting that carb to idle. Top end performance may be an issue, but idling should not. If its running like it has a miss, check your firing order and make sure all your spark plug wires are secure at both ends. You possibly could have a bad spark plug or wire. As stated above you need a bit more advance.

Ask your builder for the part number of your cam, then get the cam card online with a PN search.

 

Is your 72 motor stock? I assume you at least had to jet/metering rod it up, and use the highest ( steel) springs on the metering rods.

What made you put a regulator on it? What kind of issues were you having?


Can you reach out to the machine shop and ask for what they did? 10:1 compression and an engine that runs at 19" Hg idle seems not possible to me.

I would not buy another edelbrock carb. You'll be much better off with a properly built Q-Jet, or even a holley. If you like the design on the carter/afb, you should go for one of the street demon(I think) variants, and they have carb bodies made from phenolic material which will prevent bogs/hesitations due to fuel getting too hot.

 

It's pretty much all stock. I never changed out the metering rods or the springs. Hell, if I did, would it run even better?!

 

If setting the timing, 20 base is the stock spec on most Olds HEI distributors. Is this the large coil in cap or small body distributor? If that does nothing dump that carb, A LOT people who come on here with poor running motors have that carb. Do you have that gasket and thin plate under the carb? The Qjet and Street Demon, which is basically an all new casting 3 barrel carb heavily based off the Carter Thermoquad, the AFB's replacement with all the problem areas fixed. Around the same price as the Edelbrock but a much more sophisticated design that will yield better mileage, both tunes being equal.

 

Unfortunately have no contact information anymore for the machinist so I'm just guessing on compression based on what I thought I heard him say same with the cam. For arguements sake I know it was recently rebuilt.

I also know it has the performer rpm 7111 intake

So I should be doing 16 btdc initial timing and this carb should support this motor at idle around 1100 rooms without a problem it's later in the power band I should have issues correct?

 

It's actually an msd ready to run distributor with blaster 2 coil.

 

No, the factory points distributor is set to 12º because the mechanical advance has 24º for 36º total. As others have posted, HEI distributors are set up with a higher initial (~20º) and lower mechanical (~14º) to get the same total advance.

Now that I think about it, this shouldn't matter for idle speeds. 12º should be sufficient for the engine to run OK at idle; it just won't have very good throttle response or performance at mid-high RPM.

 

You car doesn't hesitate or sputter if you go WOT? How about if you're moving at say 25mph and you floor it? There's no hesitation or 1/4 second bog?

Whats the wagon got for a rear end in it?

You might be one of the first people that's gotten a high rise manifold to work with a 1406. Just curious, why the high rise manifold on a stock 72 motor?

 

I have a 69 Rocket 350 in my car still with points and ive noticed it likes the timing advanced a fair bit more than setting it at the suggested mark, timing chain is probably stretched, dunno how yours is, mine didnt run bad at the suggested timing but ive noticed it ran a lot better power wise after advancing it a bit more.

Also I had a hell of a similar problem with my car, took me 2 or 3 days of frustration to figure out, ended up being an old wire off the dizzy that had moved out of place and was arcing against the block, I would screw with the timing itd go away and I tink id fixed it then itd come back, finally by pure chance my grandma came out to watch the engine while I cranked it and noticed it arcing. Of course this was after a carb rebuild, a carb swap, new plugs, and new plug wires, it arced out when adjusting the timing before and blew a backfire through the carb and starting running like crap which made me think I had blown the metering rods out or something.

 

First thing is to figure out exactly what you have. Every single 1968 and 1968 Olds 350 came from the factory with No. 5 heads. Chamber volume would be about 64cc, though that tends to vary based on production and manufacturing tolerances and whether or not a valve job has ever been done or the heads milled. Ram Rod and W-31 heads would have larger valves but otherwise used exactly the same castings.

If you really do have 6A heads, those are from a 1980s Canadian-spec Olds 307 without the computerized carb and are small valve and slightly larger chambers (ie, lower compression) than the originals for that motor. If you actually have No. 6 heads, those would be from a 1970 350 and are virtually identical to the stock No. 5 heads.

 

Sorry good call I misremembered the heads are #5

 

#5s are what I have on my 69, they are good heads