Oh, I didn't realize it was points.
This made me think it was an HEI distributor.
Seems as if setting the total on a points distributor to 32-36º would result in the initial being in the 8-12º range.

 

Yeah, it's kinda wild.. lol

At this point I'm hoping the issue is simply a vacuum leak at the baseplate.

 

Do you know the old trick of spraying starting fluid at the suspected vacuum leak area and seeing if the engine increases in RPM?

 

Yeah..I had forgotten about it though..ha

 

.

 

Alright, so here is where we're at.

On Friday I tried the aerosol trick both at the carb base and where the intake and head meet and got nothing. I verified that timing is not the issue by timing it via total timing first (34 degrees total put me at 20 degrees initial with vacuum unplugged). Hooked up the vacuum gauge and saw it was now reading between 7-8hg, but idle is back up to 1200 rpm. The engine does have quite the shake which is why I don't want to go lower on the RPM (this has been a consistent issue).

Saturday, I pulled the carb and noticed the base could be tightened another half turn each screw, so I went ahead and did that. While it was off, I tightened every plug and port on the intake as much as I could. I reinstalled the carb and pulled it out of the garage to let it warm up. Once it was warm, I hooked the vacuum gauge back up and was now pulling between 8hg and 9hg of vacuum, but I cannot get more out of it.

I think at this point I'm going to focus on knocking off the winter to-do list, and once its taken care of I'll send it back down to the assembly shop and have him verify it. I do plan on calling later today though to ask if he was able to get more vacuum when he had it on the dyno. If so, that'd tell me its not valve timing and that its something Im doing (or worse, it punched a hole when the plugs were too long). I do know its running pretty rich at the moment, but I'm planning on getting a wideband and putting it in the old exhaust..so I'll get new plugs for that experience (and thats if it doesn't go down to the shop prior to)

The only other big question mark I have would be the amount of times it fired up through the carb when it was 180 out, could it have blown something internally to create an internal vacuum leak? I don't remember my 600 Summit carb being so loud, but that also didn't push as much as a 750 with a spacer either. I don't even know if there's anything in there that could be blown out to create a vacuum leak-let alone one of this size.

 

Called the assembly shop this morning..evidently they don't check vacuum while on the dyno. He is insistent as many others have been that the 228/235 cam is the reason for the low vacuum. I know in multiple conversations with @cutlassefi he is confident I should be pulling more vacuum, so I am currently on the hunt for a Holley style carburetor to stick on there and try to try to eliminate a variable. If the Holley style stays the same, then I'll try to find a Qjet to rule out the adapter/spacer.

If its just got low vacuum due to the cam, then so be it. I'll get an amplifier or something to ensure the HVAC & Booster have what they need without creating issues with the engine/trans.

 

What carburetor is on it now? There are too many pages for me to search to find if you mentioned it previously.

 

Summit 750, so Holley type

 

Was the cam degree’d and do you know where at?

 

his reply was "yeah that was all done and is correct." then proceeded to reflect back at the cam being the cause for lack of vacuum.

 

The older style Holley power valves could (would?) blow out during a backfire. The new design has a check valve to prevent that, but who knows, maybe with so many backfires the power valve is leaky? It should be easy enough to check it and verify if it's intact or not.

 

if the vacuum is what it is, I know I'll need to change the PV anyway. Would the PV leaking fill the cylinder to the point of vacuum loss yet still allow it to run as good as it does?

 

I’ll tell you it wasn’t done…if it was, they would have given you the info. Any half decent engine shop keeps records of that

 

You should send your original 7029251 out for a rebuild.
https://www.sparkyscarbs.com/

 

yeah, the fact that he quickly tried to revert back added to the laundry list of suspicion anyway (180° out, wouldn't rebuild the carb that was sent with it, put the wrong plugs in, etc)

I did go out and come across the intake bolts were snug but i could still turn them. I doubt it did much since I wasn't getting a chance when I sprayed across them during testing, but here's to hoping I found a bit.

 

The intake manifold could be leaking from the underside of the ports (in the valley). You would not be able to detect that with a starting fluid/gumout spray test on the top of the manifold ports.

 

Fair point.

The daily has to go in for another rear window seal replacement, so I may get thrust into using the Olds to get to/from work out of necessity next week. If I don't get to try it out before, we'll find out then if it helped..ha!

 

Good point.

If this were true, with the engine running you should be able to cover the hole in one valve cover and feel vacuum from the hole on the other side.

 

You're talking like the PCV on one side and the filter looking deal that hooks to the air cleaner on the other side, correct?

The one that hooks to the air cleaner I have yet to connect (to the air cleaner) yet due to continuously removing the air cleaner to make adjustments.

 

Yes.

 

I guess I didn't think that'd have anything to do with vacuum. Since it's just open, would that attribute to the lack of vacuum?

 

If the intake was leaking from the bottom as described in post 337, the crank case would be under vacuum at idle, not neutral or under light pressure. The valve covers are open to the crank case. Yes, it is probable that this would lead to decreased vacuum inside the intake manifold because vacuum is leaking into the crank case.

Don't mean to be repetitive, just trying to be clear.

 

You're good, I'd just never considered that route. Granted, I'd also not gone through such an extensive search for vacuum before either, ha!

 

I agree with rocket guy. Seal one side with good tape and cover the other side with the palm of your hand. Is it sucking on your palm (vacuum leak) or is it pushing air out (normal) or neither (probably normal too).

 

I'll see if I still have the plug for the carb (PCV) and I'll just do it that way (cover the thing on the PS and put my thumb over the PCV hose)

 

PCV valve may close if there is vacuum from the engine, so it may not be a valid test.

 

Ah, okay.

 

Played around a bit with it Friday and Saturday, no real change.

I think at this point, I'm going to go ahead and get a set of jets and power valves for the vacuum it has, and send it down to get dyno'd/tuned. I'll probably also go ahead and look for a vacuum pump/amplifier to make sure all the external draws have enough (brakes/trans/AC). If I get to it ahead of time, I'll also try to verify that my factory tach is correct. I'd hate to think that after all this headache, my 1100 RPM idle is actually like 700 this whole time. Surely that'd effect vacuum readings as well.

I also need to look at the throttle cable again to ensure its allowing full travel. I finally got tired of fighting with the intermittent catching of the throttle cable from not being hooked up correctly, so picked up the Holley 20-38 adapter deal and got everything hooked up right.

 

Had a bit of a revelation this morning due conversation in another thread so I called @cutlassefi to make sure I wasn't talking crazy...

Long story short, I know the block was cut but cannot guarantee the intake was to match. Add to that, the assembler put in the valley pan rather than just simple gaskets..so its quite possible that could be a portion of the leak (internal) and why I cannot find it. I am going to order a set of gaskets and pull the intake (hopefully sooner than later) to measure and replace. Now that I've got a new direction to head on the hunt for vacuum, my goal is to get that squared away so that I can work on the rest of my list..which will culminate in having the car put on a chassis dyno and having it tuned and seeing what kind of numbers we can pull.

 

With the mess around the vacuum issue and now the brakes..I forgot to add the clip from last Friday.
hoping over the next week or two I can get time to yank the intake and fix the brakes.

 

For sure thats not 1100 rpm, more like 750.
I had to calibrate mine with a digital tachometer actually.
Might be a good idea to elimate every vacuum source not in use just to be sure, that motor doesn't sound that unstable.

I walked into the fire chasing low vacuum on my 400 and it was a combination of things.
Had a leak at #5 intake and Q jet throttle shafts.
On the gaskets, I actually caused a problem by using thick paper Moroso gaskets vs the turkey tray gasket.
The thicker gaskets actually raised the intake but it also allowed cam oil splash to coke up and flake on the bottom of the intake crossover that the tray deflects.
Mondelo makes a deflector to keep the splash from burning and coking on the bottom, but that wasn't the only problem
I ended up cutting the ports side .030 to lower the intake for proper alignment with the thicker gaskets.

My vacuum issues ended with an Edlebrock AVS and have since put on a 455 Performer dual plane intake to match the carb.
I look at the key and it starts now, night and day difference.
If you have a vacuum problem the first thing you will realize is the brakes suck, scary suck.
Lots of maybes, but if you close the choke off and it runs better this points at a vacuum problem effecting the carburetor fuel delivery properly.

Huge thread btw, I hope you get to the bottom of this.

 

Ya know, I wasn't buying the 1100 either..to the point where I'd threatened to get a separate tach, but regardless if its idling where it should and I don't have vacuum, then that's an issue. I had someone offer up letting me their light that also reads RPM (if I understood it correctly), but seeing as without getting the brakes fixed I can't roll it-that's an option for another day.

I need to quit complaining about the cold and go ahead and get the intake off of there. At this point, the two big things (back brakes & intake) need to get done so I can finish the rest of the list to get it able to be dyno'd. Hopefully once we're through the Christmas season I can find the motivation to get things done.

 

Shooting to get the intake off this weekend. Picked up some new bolts and some RTV-never had any luck with end gaskets no matter what engine I'm on.

I'm still not 100% that the intake is leaking underneath causing a vacuum leak of that amount, but A-I've been wrong before and B-if thats what creates the super loud whistle coming from the back of the engine then that'd explain things. It wouldn't explain how it runs so strong with such a leak, unless I've just not gotten anywhere close to its potential yet.

I also picked up an adapter to hook up the throttle cable bracket. Meant to order gaskets last night and forgot, so hopefully the parts store will have one in stock.

My goal is to get this back together as next week (hopefully) it's going in to get the quarter panel fixed.

 

I'll be hoping for you also. Good luck !

 

Holy smokes..its evident I've been spoiled by aluminum.

So, in short..I'm going to take it back off next weekend (hopefully) and with the help of the hoist (unless I can con a friend into helping) try to set it back down without pushing the RTV off the ends and tearing a gasket. I think it "may have been" okay, but I don't want to hook everything up just to find out my suspicions were correct. I did get the distributor swapped around though as well, and am hoping it lines up correct. As careful as I was, it spun around when it let free and in my haste I forgot to mark everything. I believe I've got everything lined up after having to basically reset it, but won't know until its all back together and I can check as it cranks (unless theres another way to verify)

 

LOL...makes you wonder why they didn't make all of them AL

 

Alright, in Friday i got home from work and with the help of the hoist and Pops, we got the intake off and back on again. I went out yesterday and put everything back together (including the new throttle cable bracket for my holley style carb) and can't get it to fire. It'll occasionally backfire, but more often than not it's just cranking. Gonna wait for a second set of hands so i can better verify timing before something gets too messed up. I thought I'd had it a few times, but to no avail.

I did however notice that the carb it's leaking fuel from where the linkage meets the carb body. I'd seen what looked like varnished fuel directly below that on the intake, but just figured it was from the carb being loose/gasket not sealing/the other messes I'd had.. and figured that was fixed. So now in back to questioning carb choice again. Ill make more power with the Holley, and am more experienced with them.. but been the leak and the PITA geometry, I'm half tempted to rebuild the one I've got, increasing jets/rods/whatever and and electric choke in the process.

If it finally gets going and I still have terrible vacuum, I'm gonna lose it..lol

 

Run back through your firing order. Sounds like you may have crossed a few wires.

 

yeah..Im going to reset everything and try again.

I thought I had the firing order right, then thought I was off by 1 so adjusted it and it sounded closer, but then I was maxed out on the dist. So I popped it up and rotated it to allow more space but as I type this I realize I didn't reset the firing order.