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chiphead · 07-09-2018, 11:49 PM

Is that with manifold vacuum advance? I was thinking 14" was really good for a 9:1 combo with that cam, then I remembered you might be running the vacuum advance to manifold vacuum??

footjoy · 07-10-2018, 12:04 AM

That is manifold vacuum at idle

Thanks

chiphead · 07-10-2018, 07:21 AM

What is idle vacuum with manifold advance disconnected? Adding vacuum timing at idle can help crutch a combination that has a large cam for the compression ratio and engine size. If cam is installed straight up, then advancing it 4* may help low end torque and idle vacuum. That may help overall efficiency, since your cruise RPM is at the bottom of that cam's powerband.

How is power from idle to 2500 RPM?

footjoy · 07-10-2018, 09:26 AM

Quote:

Originally Posted by chiphead

What is idle vacuum with manifold advance disconnected? Adding vacuum timing at idle can help crutch a combination that has a large cam for the compression ratio and engine size. If cam is installed straight up, then advancing it 4* may help low end torque and idle vacuum. That may help overall efficiency, since your cruise RPM is at the bottom of that cam's powerband.

How is power from idle to 2500 RPM?

Ok so I get this right disconnect the vacuum advance, then do I take ported or manifold vacuum reading?

tom s · 07-10-2018, 11:33 AM

We pumped it today.When in straight it pumped 150-155.Today it pumped 165-170.It did exactly what I was told it would do.Should be no issue with our 91 CA gas.Tom

chiphead · 07-10-2018, 12:34 PM

Quote:

Originally Posted by footjoy

Ok so I get this right disconnect the vacuum advance, then do I take ported or manifold vacuum reading?

With engine warmed up and idling, take manifold vacuum reading with advance disconnected from vacuum. You could disconnect the vacuum source to the advance, and then just connect the vacuum gauge to that manifold vacuum source. Verify base timing too if you have a timing light. I would expect that idle will be rougher and vacuum will drop to 8-12 inches at idle.

Do you have any paperwork from the builder saying how the cam was installed relative to the cam card's ICL? Cliff or one of the pro builders with experience with those Crower cams, can likely recommend the optimum ICL for your engine. Then you would have to degree the cam to achieve that desired Intake Centerline.

footjoy · 07-10-2018, 01:53 PM

Quote:

Originally Posted by chiphead

What is idle vacuum with manifold advance disconnected? Adding vacuum timing at idle can help crutch a combination that has a large cam for the compression ratio and engine size. If cam is installed straight up, then advancing it 4* may help low end torque and idle vacuum. That may help overall efficiency, since your cruise RPM is at the bottom of that cam's powerband.

How is power from idle to 2500 RPM?

15 inches straight manifold vacuum
0 inched ported at idle with vacuum advance disconnected

Bruce Meyer · 07-10-2018, 03:02 PM

footjoy- Are you running the sheetmetal spacer that is required to seal a square bore carb to that performer manifold? Also have you tried jetting down some? I know out of the box Holley 4150,s are jetted on the rich side. I usually go down 1-2 sizes on the primary jets. Not sure on your brand though.

chiphead · 07-10-2018, 05:00 PM

Quote:

Originally Posted by footjoy

15 inches straight manifold vacuum
0 inched ported at idle with vacuum advance disconnected

Is that manifold vacuum reading taken with the vac advance disconnected? What RPM does this engine idle at? If you're getting that much manifold vacuum at 800 RPM or less, with no vacuum advance, then you may not need to advance the cam.

The 0 ported at idle usually means the carb is rich enough at idle. If it was going lean, or needed bypass air, the throttle blades get opened into the transition slots, which uncovers the ported vacuum passage. That's when you start seeing ported vacuum signal at idle, which is often not a good thing.

It sounds like the engine isn't struggling at low RPMs.

Leaning the carb out may be a place to start. What is PN, or holley list number for the carb?

How do the plugs look after a cruise? Are the insulators black or fairly white/light tan? Modern fuel doesn't color the plugs much. If mixture is in the ballpark, color may be hard to see, unless you cut the threads off and look at the fuel ring at the base of the insulator.

400 Lemans · 07-10-2018, 05:24 PM

http://forums.maxperformanceinc.com/...d.php?t=809226 Looking back in this older thread Footjoy stated that he had Crower 60240 and not the 60243 installed. That would make sense, with the higher vac reading he is getting. Maybe just a typo.

footjoy · 08:13 PM

Quote:

Originally Posted by 400 Lemans

http://forums.maxperformanceinc.com/...d.php?t=809226 Looking back in this older thread Footjoy stated that he had Crower 60240 and not the 60243 installed. That would make sense, with the higher vac reading he is getting. Maybe just a typo.

I checked and it was th 60240 cam

footjoy · 07-10-2018, 08:36 PM

Leaning the carb out may be a place to start. What is PN, or holley list number for the carb?

The carb is a quikfuel 735 cfm HR vacuum secondary.

Its to adjustable.

Thanks

greg

#1965GTO · 07-11-2018, 11:49 AM

My set up is fairly similar to yours. My 65 has a 68 400, .030 0ver with flat tops with 2 valve reliefs. I am using 6X-8 heads and a Voodoo cam. The 200-4R in ours has a lock converter with a B&M controller. The rear gear is 3.55 on and Eaton posi carrier. Performer intake with Edelbrock 600 CFM on top. Exhaust is
2 1/2" Ram Air manifolds with 2 1/2" Flow Master pipes and Walker super turbos out the back. I'm running a 26" tall T/A tire all around. After compensating for the speedometer error it gets and easy 18 MGH going 75 on hilly I-15. When I get to 80 + MPH I can tell the difference in MPG. Running the AC only makes a slight difference. Around town that's another story, I still like to get on it now and then.

footjoy · 07-11-2018, 05:35 PM

Quote:

Originally Posted by #1965GTO

My set up is fairly similar to yours. My 65 has a 68 400, .030 0ver with flat tops with 2 valve reliefs. I am using 6X-8 heads and a Voodoo cam. The 200-4R in ours has a lock converter with a B&M controller. The rear gear is 3.55 on and Eaton posi carrier. Performer intake with Edelbrock 600 CFM on top. Exhaust is
2 1/2" Ram Air manifolds with 2 1/2" Flow Master pipes and Walker super turbos out the back. I'm running a 26" tall T/A tire all around. After compensating for the speedometer error it gets and easy 18 MGH going 75 on hilly I-15. When I get to 80 + MPH I can tell the difference in MPG. Running the AC only makes a slight difference. Around town that's another story, I still like to get on it now and then.

How is your timing set?

Thanks

#1965GTO · 07-12-2018, 10:56 AM

The initial is 12 and 34 all in by 2200 with 10 more on timed port vacuum. I use the Accel blue print HEI with built in super coil and MSD 8mm wires.

footjoy · 07-12-2018, 11:45 AM

Quote:

Originally Posted by #1965GTO

The initial is 12 and 34 all in by 2200 with 10 more on timed port vacuum. I use the Accel blue print HEI with built in super coil and MSD 8mm wires.

What I don't understand is how do you get it all in at such a low rpm. Mine is at I beleive 3000.

Thanks

"QUICK-SILVER" · 07-12-2018, 01:00 PM

Quote:

Originally Posted by footjoy

What I don't understand is how do you get it all in at such a low rpm. Mine is at I beleive 3000.

Lighter/weaker springs on the advance weights lets timing come in sooner.

I don't think using a carb designed for high performance, when you're after fuel economy, is a good idea.
Might try tightening up the spring on the vacuum secondary so you know it's not trying to open at cruise speed. Factory setting would have been set light for the 4BBL to open easy. Fuel doesn't atomize good when throttle blades are barely cracked open. Fuel just dribbles out of the boosters on to the throttle blades.

Clay

#1965GTO · 07-12-2018, 02:39 PM

These Accel distributors and others come with a selection of advance springs for you choosing, Mallory makes an even better one that is a mechanical type of adjustment that is probably as better choice. The Accel and others come with the adjustable vacuum advance installed.

ho428 · 07-12-2018, 02:51 PM

Part of the problem with mileage is it's a Pontiac, and this little gauge tends to stay pegged to the right when the fun peddle stays pegged to the floor.

amcmike · 07-12-2018, 03:58 PM

Quote:

Originally Posted by "QUICK-SILVER"

Lighter/weaker springs on the advance weights lets timing come in sooner.

Initial and centrifugal timing should be set based on what the engine wants for WOT conditions. If you adjust it for really early centrifugal, then you could be losing power, and/or cause detonation (which is not always audible).

Only vacuum should be modified to obtain the optimum fuel economy. Many kits that only adjust by an allen-head in the port are controlling just the rate, so the total is limited by how much vacuum you have) Crane has a kit which adjusts rate of vacuum advance as well as total. That way, you can use a light pre-load to allow it to come in fast, but then stop the travel, so that you don't get too much.

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