Timing frustrations

[c9zx]

I have had very good luck with Taylor wires. I buy the universal fit and cut to length and routing. I've also used MSD, Accel, and Mallory in the past with success. If you want a near stock look the Pertronix wires work well, I wish I could say the same for their ignition modules, the coils are fine just get the right resistance one for the application. I'd use dielectric grease and check resistance of each wire before installing. Chuck

 

[Big Red Mach 1]

Well, for better or worse, I went with these.

https://www.summitracing.com/parts/MSD-31389

I liked what I read here.

"MSD 8.5mm Super Conductor spark plug wire sets feature a special helically wound core that has just 40-50 ohms of resistance per foot—but with an RFI suppression equal to a 1,500 ohm wire. In fact, each foot of finished wire includes 40 ft. of tightly wound copper for superior conductivity".

I would have preferred black, and the Pertronix would have fit the bill, but their resistance was close to 10x higher. Probably fine, just wasn't as jazzed by them.

I also agree that around the valve covers looks super clean, and I do like the dist. hidden at the back like GM does. super clean.

That will be the way the wife's 69 Camaro 396 SS will be setup once we get it here from Indiana, and start working on it.

 

[Big Red Mach 1]

Well, finally got some time to get back to the car. The final answer on vacuum is 11Hg. That's it's consistent vacuum at idle fully warmed. Before this that number was 9. So a little improvement, but not huge.

Here's the buggar though. After all of that, the car still spits out excess gas at idle. And that's after installing a Summit fuel pressure regulator set at 6.5lbs.

So while it was good to correct the intake gasket, rocker arms, studs, valve cover gaskets, add the FP regulator, new plugs, cap and wires, I'm still in the same place really, just with 2 more Hg in vacuum to show for it. All of that stuff certainly needed corrected, but I'd still like to be rid of this raw fuel issue.

I don't think I have a choice but turn my attention back at the carb. This Street Avenger 770 that so many seem to loathe. Stanglover, I definitely need more info on those 3/32 holes your speed shop guy drilled in your butterflies that cured you of the same issue. : ) I'm also definitely taking the power valve back down From the 8.5 at this point. I also need to confirm the original jet sizes and squinter that came with this carb. I think those were swapped also.

In the meantime, I'm also going carb shopping on the web. ;-)

 

[Big Red Mach 1]

So check this out. I decided the take the carb back off and do a couple things. I decided I would open the secondaries a little more instead of drilling butterflies. More air is more and some of that air, albeit a little does come from the secondaries at idle. I also decided to go 5.5 Power Valve based on my 11Hg reading.

First thing I notice yet again is that the gasket above the spacer is once again SOAKED. Last time we thought I may have over-torqued it. but I straight edged the base of the carb and the top of the manifold and all looked good. So why does this thing drink down gas faster than I drink beer?

So I take off the float housing and the metering block. Hmm. not 8.5 as suspected (to be honest Eddie couldn't really remember, but he did throw out 8.5) Turns out it's 6.5. Not what I expected to see, but okay. Here's where the surprise comes. I pull the 6.5 and it's double gasketed!!! And it's hard to see in the photo, but the bottom half of the gasket on the metering block is soaked!! So fuel has been bypassing the power valve the whole time!

The kicker is, that if you go all the way back, I mentioned that I took the carb to "the best carb place in town". I told them I was fighting a rich condition and had raw fuel smell and I paid them over $200 to go through it and rebuild it and get it right. Brought the carb back home and had the same condition. So either Eddie doubled them up and the shop never bothered to pull the PV. Or the shop did it. I'm guessing they never pulled the old PV as the condition existed before and after. All of this for a doubled up gasket.

 

[jpaz]

Sure hope that solves the problem! I did think you would have more vacuum though. Anyway good catch.

 

[Big Red Mach 1]

Thanks! I was hoping for at least 14. But it's apparently not in the cards.

 

[midlife]

Thanks! I was hoping for at least 14. But it's apparently not in the carb.

Fixed it for you.

 

[Big Red Mach 1]

Thanks! I was hoping for at least 14. But it's apparently not in the carb.

Fixed it for you.

Nice one!! lollerz

 

[71coop]

I wouldn't be too surprised if your vacuum improves after this. Any internal leakage is going to effect how much fuel and air is getting into the intake, which in turn could affect how the carb was tuned and how the engine behaves.

 

[boilermaster]

Big red mach 1,

I have seen many times, the power valve gasket come apart in 2 pieces and give the ( impression) that it was double gasketed.

However, that means that there would be a half stuck to both sides, one on the power valve and one on the metering block.

That is NOT what your picture was showing.

Last night, I was going to suggest taking a dial caliper and measuring each half and adding the two to compare that to a new (uncrushed) gasket, however I could not find a new one.

I do have a cup that fits Holley power valves to actually measure the amount of vacuum required to open the valve.

Not an exact science but a useful tool.

I would suggest looking up your list number and find the correct primary metering block gasket.

IMHO the bottom half of this gasket should never be wet (unless the power valve is ruptured or the power valve gasket is loose, damaged or missing)

Paying good money for poor workmanship is all too common these days.

Wish I could swap carbs with you for a day

Boilermaster

 

[Stanglover]

I don't think I have a choice but turn my attention back at the carb.  This Street Avenger 770 that so many seem to loathe. Stanglover, I definitely need more info on those 3/32 holes your speed shop guy drilled in your butterflies that cured you of the same issue. : ) I'm also definitely taking the power valve back down From the 8.5 at this point. I also need to confirm the original jet sizes and squinter that came with this carb. I think those were swapped also.

In the meantime, I'm also going carb shopping on the web. ;-)

 Hi Big Red, Not that it matters, earlier I thought you said you had a S/A 670, now you mention S/A 770.

As I have said many many times, I'm no expert on carbs, but in my case with the Holley S/A 670 I have that was over rich at idle, the speed shop carb tuner guy, went straight to drilling the 3/32" hole in each primary plate AFTER test driving the car and letting it settle into a steady idle, the gas smell was horrendous . He removed the carb and saw right away that I had the transfer slots way to far open, just to keep the motor idling. The idle screws were the usual 1 1/2 out. Now, is this guy a super expert? I don't know, but he knows more than do I and he does it for a living. Also, you mentioned opening the secondary's for more air, that I had done also, so he reset them correctly too. The 3/32' dia. was a start point, but it worked in my case, so I never enlarged them. These hole are drilled pretty much in the center of the forward part of the plate i.e. forward of the shaft. 

This notion has caused much discussion, mostly negative, but trust me it worked. I have very little gas smell around the car or in the garage, which in the past was enough to choke a horse (mustang?) I'm NOT saying go head and do this, but it might be worth a try especially if you're thinking about a different carb anyway. If you do remove the plates, make sure you loc-tite them or peen the screws so they never come lose, but you're a mechanic, you know that anyway.

It was not just about loosing the gas smell and over rich idle, but about getting my motor to run better than it ever did in the past. To recap, my motor is pretty much stock with just a small increase in cam lift. I did borrow an AFR meter, I already had O2 bungs in the exhaust from an earlier run on a dyno, so running the AFR was simple. (I have a video of that I may post if I can find it and think it relative).

You may also have looked at my post on Edelbrock carbs and a bunch of amusing videos, yeah well, I'm not convinced on that brand for MY car. For me if I ever decide to replace my 670, I lean toward the Quick Fuel HR 735, or possibly the Summit series in that cfm range. I just fell the 670 does not provide quite enough air at wot.

Hope that dose not confuse the issue even more.

EDTIT: before anyone jumps on " the holes will have no effect once the throttle plates open past idle" that was not what I meant. but Just part of setting the entire carb up for better performance. The curb idle could not be correctly set until other changes were made. It all goes hand in hand.

 

[71coop]

Big Red - just my .02 cents.

Your build isn't so radical it should need anything like holes drilled in the secondary butterflies. I'm also running flattop pistons with smaller cc chambers.Your runners are larger, so that has an effect on airflow, but I believe we are probably running similar compression.

You cam is a little more conservative than mine, I'm running what I'm told is the roller version of a Boss cam (272/280 ; Duration @ .050 (Int/Exh): 221/229 ; Gross Valve Lift (Int/Exh): .593/.611 ; LSA/ICL: 112/106 ). Not really much more aggressive than the one you describe,mostly more lift and probably acts bigger given the aggresive lobes.

These builds aren't identical, but I don't see them being all that far apart.

My carb is a basic 750 cfm Holley (this one):

https://www.jegs.com/i/Holley/510/0-80459SA/10002/-1

The only thing I needed to do was play with float and mixture settings. I usually associate doing things like drilling holes in primaries (corrected) as something suitable for more radical builds.

I am pulling about 16 inches of mercury. Before you spend too much, I would just try correcting the issues with your carb and re-tuning.

After that,I would not be afraid to try 12, 14 degrees or so initial timing either - my engine really like more advance (15 degrees ), in addition to using manifold vacuum advance, and doesn't ping. You may just need to try a few different carb/timing adjustments to see what your engine likes.

 

[jpaz]

I had the same issues with my 770. Very rich at idle, stumbles off the line, not very responsive and then lean when at speed. I just couldn’t get it tuned right. I got fed up with it and got a Quick Fuel HR 735. Now I can tune this carb to match my engine needs. I am by no means a carb guru or anything, but for whatever reason I just couldn’t get that Street Avenger tuned correct. I’m not saying the QF is the best carb out there, there’s some others too, but SA carb is not so good imop.

 

[71coop]

QF carbs are good - I run their 850 SS on my vette's 427 SBC...

 

[Stanglover]

Big Red - just ky .02 cents.

Your build isn't so radical it should need anything like holes drilled in the secondary butterflies.  I'm also running flattop pistons with smaller cc chambers.Your runners are larger, so that has an effect on airflow, but I believe we are probably running similar compression.

The only thing I needed to do was play with float and mixture settings. I usually associate doing things like drilling holes in secondaries as something suitable for more radical builds.

I am pulling about 16 inches of mercury.  Before you spend too much, I would just try correcting the issues with your carb and re-tuning.

After that,I would not be afraid to try 12, 14 degrees or so initial timing either - my engine really like more advance (15 degrees ), in addition to using manifold vacuum advance, and doesn't ping. You may just need to try a few  different carb/timing adjustments to see what your engine likes.

 The holes I'm am referring to are NOT in the secondary's, but in the PRIMARY"S. Drilling hole in the secondary's would be a no-no as far as my limited knowledge goes.

However, I do agree with setting the float level to just be seen, engine running with the screw out. I don't use plastic sight plugs anymore, they are deceptive.

As for timing absolutely 14-16 degrees with 20 deg. on the cam. Big Red's distributor if I recall is set for about that. I also use ported vacuum, not manifold. That again is a point of discussion.

I was not meaning to be critical of your post, just to correct a miss-quote and no offence meant.

 

[71coop]

None taken - I'm not sure why I typed secondaries, that was simply a brain fart on my part - correct now...

I'm not saying its not warranted in some situations, but it is (in my view) something that is more appropriate for a more radical build than this one. While it might be a viable solution, it would not be one I would jump to unless all other carb adjustments were definitively tried and failed. Then, I may consider it an option.

Right now, there is an obvious issue with his carb that affects fuel flow and possibly mixture. I'm just saying he should correct that first, try it out, then if it doesn't fix the issue, move on to the next thing.

 

[Stanglover]

Just for the heck of it and for what it's worth, which is probably not much, but here is the video of the AFR readings during a test drive. This was sometime after the primary plates were modified and at this point, I was trying to resolve an annoying 'bog" when hitting the loud peddle. At times, I thought the atmospherics could play a part in why it seemed to bog some days and not others. I later changed the squirter one size bigger and that solved the issue for the most part. AS I think we all agree, the SA carb is not one of Holley better offerings. I still may switch to a QF HR735 when the US/CAD exchange is more favorable.

Anyway here is the video. It's a bit shaky, but you'll see the numbers and get to hear the new Flowmaster  FlowFX mufflers.

 

[Stanglover]

None taken - I'm not sure why I typed secondaries, that was simply a brain fart on my part - correct now...

I'm not saying its not warranted in some situations, but it is (in my view) something that is more appropriate for a more radical build than this one. While it might be a viable solution, it would not be one I would jump to unless all other carb adjustments were definitively tried and failed. Then, I may consider it an option.

Right now, there is an obvious issue with his carb that affects fuel flow and possibly mixture. I'm just saying he should correct that first, try it out, then if it doesn't fix the issue, move on to the next thing.

 Yeah, those brain farts! I seem to get them more often these days too.

 Perhaps I did miss mentioning that my carb had been stripped, check, rebuilt and it was still bad. I had also played with different spacer thicknesses and currently run a 1" fiber spacer on a stock manifold (with exhaust cross-over plugged off). not that that was a cause. All I'm saying is that this "trick" worked for my engine configuration, a pretty much stock M code 4 speed.

Holley carbs are notorious for being fat at idle, which is better than being too lean.

 

[Big Red Mach 1]

Big red mach 1,

I have seen many times, the power valve gasket come apart in 2 pieces and give the ( impression) that it was double gasketed.

However, that means that there would be a half stuck to both sides, one on the power valve and one on the metering block.

That is NOT what your picture was showing.

Last night, I was going to suggest taking a dial caliper and measuring each half and adding the two to compare that to a new (uncrushed) gasket, however I could not find a new one.

I do have a cup that fits Holley power valves to actually measure the amount of vacuum required to open the valve.

Not an exact science but a useful tool.

I would suggest looking up your list number and find the correct primary metering block gasket.

IMHO the bottom half of this gasket should never be wet (unless the power valve is ruptured or the power valve gasket is loose, damaged or missing)

Paying good money for poor workmanship is all too common these days.

Wish I could swap carbs with you for a day

Boilermaster

So this morning, I compared both gaskets that came off to a new one, and to the eye, the two halves do in fact equal the thickness of a new one. That is the odd thing though. These don't appear torn in any way, and the one on the PV itself was loose, not stuck to it at all. Also, the lower half of the one that was stuck to the block was visibly soaked mid-way down. Essentially from where the two fuel ports each side of the power valve are, downward. If fuel was in fact bypassing the PV, that fuel would come out below the plates, making it virtually impossible to see, correct? Is there any other part of a carb that would allow fuel to enter below the plates and soak that base plate gasket like that?

 

[Big Red Mach 1]

I have heard many times in many places that a good place to have your plates set to is where you "Box" your transfer slots on your primaries and secondaries, particularly if you have mechanical secondaries. My secondaries were not like this, in fact they seemed very closed off. I went ahead and "boxed them out" and you can see from the old lines around the ports how far I had to go to do that. I had to run the screw in a decent amount before they ever became visible. Hopefully this change in setting may help as well.