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Discussion Starter #1
http://www.holley.com/data/Products/Technical/199R8219-2.pdf

I am going to get the secondary spring kit so I can play around and see which one responds best. On the second page on that link, there is a chart that shows approximate RPMS for a given spring and it appears that as cubic inches go down, the RPMS go up. Given that I have a 327, I can assume that the RPMS will be higher than the ones listed for the 350. However, what does higher gearing do to it... anything? I have a 2.73 final drive and I have an M20 wide ratio (2.52 1st).

I know, the gearing is not exactly set up for high performance, yet... But, how does that react with the secondary spring? Should I use a slightly stiffer spring because I have a higher final drive or a more compliant spring? The street avenger came with the plain spring installed and I have swapped that out for the yellow spring just yesterday. It seems like it accelerates earlier, as expected, but perhaps it's a little too early because I get a backfire sometimes when it's around 1.5k RPMS and I smoothly mash the gas pedal.

According to the Holley tech videos, that backfire indicates that I possibly need a bigger squirter. I'm not sure what came with the 670 street avenger as far as squirter size, so I will go check that out and get a bigger one 3 sizes above it...
 

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I had to to do primary jets & larger squirter to get rid of the lean off idle problem. I'd fix that first, then play with the springs if you still are not happy. With your gearing, I would not think making the secondaries open sooner would be a good thing.
Scott
 

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Discussion Starter #5
Would a backfire occur in a rich condition or only in a lean condition? I swapped the silver spring back in and it hardly pops at all, except when cold. A couple other comments: I watched the carb tuning videos on Holleys site. I learned that the power valve should be half of the idle vacuum. The 670 SA comes with a 65 but I'm only pulling 9-10" of vacuum (can't get it any higher than that at my 800RPM idle speed), which indicates I should swap the 65 power valve out for a 45. I'm still new to Holleys so I don't know exactly what the power valve does except that they refer to it as the power enrichment system. Maybe I need to do that swap and/or jet up a little bit.

But first I need to get a grip on what's going on, so would an engine backfire occasionally under a rich condition or just in a lean off-idle condition?
 

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Backfire=lean(or timing)
I don't follow holley's divide/2 rule
I subtract 2-3 from idle
That's some low vacuum-What cam & timing
The gearing is gonna make it tough if your cam is big enough to really cause such low vac.
 

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Discussion Starter #7
It's the Edelbrock 7102 - part of the top-end kit I got from them. Here are the specs from their site:

Duration at 0.006" Lift: Intake: 308° Exhaust: 318°
Duration at 0.050" Lift: Intake: 234° Exhaust: 244°
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Timing at 0.050" lift: Open Close
Intake: 10° BTDC 44° ABDC
Exhaust: 59° BBDC 5° ATDC
Centerlines: Lobe Separation - 112° Intake Centerline - 107°

I currently have it at 16° initial, 36° total with vac advance plugged. At idle vac advance adds about 17-18°. It is hooked up to full manifold vacuum.
 

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I think you need to put some bigger jets in there man. With that lift thats sort of a breather I'm not sure your getting enough fuel in there.
 

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Discussion Starter #9
My headers are getting installed today and I'm sure that will change something somehow. :) I didn't want to do the cam break-in with new ceramic-coated headers. So, my stock manifolds have been on there up until now...

In any case, the 670 SA ships with a 65 primary and 68 secondary... Stock squirter is a 31. With my high rear-end gearing, that 31 squirter should be good enough right? If I changed the jets, what should I try? Jump two sizes (min. jump that Holley recommends) on both jets or do I need a bigger jump?
 

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Thats alot of cam for a 327-I see no real issue with yor timing
What pump cam are you running now?
I've seen headers do some crazy things to motors-GOOD and BAD
In your case I think they may help.
I personaly start with pump cams before shooters.
 

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Discussion Starter #11
Indeed, it's a lot of cam. But it's paired up nicely with Performer RPM aluminum heads (64cc chambers and 185cc) and an RPM Air Gap (dual plane of course) on the top end. As far as the pump cam goes, I'm not sure. I'll have to look when I go pick the car up this afternoon (hopefully). It's the stock 670 SA pump cam (black I think?) - probably running in hole 1. I can verify that later. If that's the case, what color and hole should I switch to, if at all? I imagine with the low rear-end gearing, I probably don't want a pump cam that squirts it out too much faster... right?
 

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pop the dist cap and the code will be visible on the frame of the vac can
I like the blue on hole 2 & green on hole 1 cams in the front.
 

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Discussion Starter #16
So I guess I shouldn't be too surprised that the Holley tech service wasn't very helpful at all. I described my issues that I've outlined in this thread and his only response was to up the squirter from the stock 31 to a 35. I pried a bit to see if he would expound a bit on that. His only comment was basically if that doesn't completely solve it, up the jets by two numbers (from a 65 to a 67).

He didn't really have a comment about the pump cam except to maybe try the pink cam in hole 1 if I want to fine-tune it a bit after changing the squirter and/or the jets. But he wasn't interested in what cam specs or other top-end specs I have on the motor...

Should I just try what he suggested (one thing at a time, of course)? Or should I try getting the pump cam kit and mess around with that?
 

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Thats exactly the sizes I used on my 670. I did the squirters first. It takes like 10 minutes & nothing has to come apart except for the choke shaft. There was an immediate improvement in throttle response. I still had a very slight hesitation, and it would still backfire, but only in certain situations. Went up & the jets & all was fixed. U can still play with the cam after that. I was told it could have been done with the cam and/or different power valve. I have FI now & I will never go back to carb. ;)
Scott
 

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Discussion Starter #18
Squirters plural? Did you have a DP?

Fair enough. I'll get the 35 and try that. LOL I never thought to remove the choke shaft to make access to the squirter easier. I saw the one end was staked and wasn't going to bother with it. It would certainly make it easier with the choke plate/shaft out of the way... Do you just undo it at the linkage and then unscrew the plate from the shaft?
 

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Jeff....before you go with a bigger pump squirt, make sure the "squirt" is happening as soon as the throttle is cracked. Move the linkage by hand and take a look at the squirter. Is it squirting right away? If not, try a different pump cam and make sure it has direct contact with the linkage that it's trying to move.
 

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Discussion Starter #20
Yeah, I have checked to be sure that there is squirt as soon as the throttle moves. The only thing I haven't checked is the 0.015" feeler guage test at WOT per Holley's instructions.

My 35 squirter set should arrive today and I plan on getting the pump cam kit today as well.

So, I will have some things to play with this afternoon/evening. Speaking of that, yesterday after my drive home I decided to get the vacuum gauge out and mess with the idle settings to make sure they are set okay. Since I had just driven home, of course everything was up to temp. Here's the interesting thing: I couldn't get it to idle any less than 900 rpm. So I turned the car off, checked the idle mixture screws. One was set at about 1.75 turns out and the other was 2.25 turns out. So, I set them both at 1.25 turns out and fired it back up.

I'm pulling 11" of vacuum - pretty steady. There's a little bouncing to the needle but not more than 1/2" of vacuum, assuming the gauge is accurate - but that might be due to the cam? If I turn in either of the idle mixture screws 1/4 turn, the vacuum starts to drop and if I go further, it idles pretty rough. If I turn either one out, I can turn it past two turns, even towards three turns and the vacuum doesn't change - still steady around 11". So, what does that mean?

Also, with both idle mixture screws between 1 and 2 turns out (both identical, of course), I am able to get the idle to drop to around 700RPM or so still with 10.5 - 11" of vacuum. Although, after warming it up this morning and driving to work, when I parked in the lot, it was idling at 900 again...
 
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