Instructions on how to jet a Holley Street Avenger?

SadbutTrue · Apr 21, 2009

Gonna try to do it tonight/tomorrow when I re-set the floats.

Was planning on jetting it significantly richer (and dialing the idle mixture a bit leaner), as the dyno said it was running about 14.5:1 above 2500 rpm and pretty rich from idle up to 2500. I believe in my 'help me my car runs like ass' thread someone recommended 72 primaries and 80 secondaries... probably a little big but he said that worked for him with his 670 street avenger.

Thanks.

CraigMBA · Apr 21, 2009

What jets are in it now?

SadbutTrue · Apr 21, 2009

CraigMBA said:
What jets are in it now?

Whatever it came with... 65 primary/68 secondary IIRC.

Also am considering removing the choke (i'm in california, hardly think I'm ever going to need it). Any advice there would appreciated too.

CraigMBA · Apr 21, 2009

I doubt it's 65/68.

I'd go two numbers smaller on the primary and up two on the secondary if it was me and recheck the AF ratios.

I take it you figured out you had it timed wrong?

SadbutTrue · Apr 21, 2009

CraigMBA said:
I doubt it's 65/68.

I'd go two numbers smaller on the primary and up two on the secondary if it was me and recheck the AF ratios.

I take it you figured out you had it timed wrong?

I ordered a piston stop from summit but it won't get here until the weekend or monday, so figured i'd try to get something done in the meantime.

When you say two smaller on primary and up two on secondary, do you mean from what i proposed or from what it is now?

CraigMBA · Apr 22, 2009

No - from stock, whatever stock is.

If you're correct, and it has 65/68s stock, going up seven sizes on the primary (which is already too rich) and a dozen on the secondary is just crazy overkill. If you have to move that many jet sizes from stock calibration, you have something wrong in your component selection.

In short, you should only do these changes either on the dyno or if you have an AF meter.

And I wouldn't do any of it before you fix the timing.

SadbutTrue · Apr 22, 2009

CraigMBA said:
No - from stock, whatever stock is.

If you're correct, and it has 65/68s stock, going up seven sizes on the primary (which is already too rich) and a dozen on the secondary is just crazy overkill. If you have to move that many jet sizes from stock calibration, you have something wrong in your component selection.

In short, you should only do these changes either on the dyno or if you have an AF meter.

And I wouldn't do any of it before you fix the timing.

I don't think its currently too rich. Some guy (Marlon, this board knows him well) tried to help me out with a quick carb adjustment... but what he did was simply to turn the idle mixture screw about 3 turns rich before i dynoed it. I've since (after the dyno) adjusted that... I doubt it'll still be nearly as rich off idle, even with fatter jets.

It was running 14-14.5:1 A/F above 2500 rpm... which is really lean (should be 12.5-13). I was told changing jet sizes up 2 at a time probably won't make any noticeable difference.

How do I get at the jets on these carbs? Anyone have a good step by step? Fordmuscle had one but the link on their web page doesn't seem to be working.

SadbutTrue · Apr 22, 2009

Called Holley... after waiting 30-40 minutes on hold finally got in touch with a tech. He said there's not a whole lot to it.. just remove the bowl (removing the 4 bolts) and you'll be staring at the jet. Is there anything else I should know?

As far as removing the choke goes.. he said the only interesting part is plugging up a 'pencil lead' sized hole into the housing. He said you should drive a fishing weight into the hole with a hammer.

This sounds slightly delicate and I'm also fresh out of fishing weights... anyone want to elaborate on this procedure and what else I could use to plug it?

jcode68 · Apr 22, 2009

I am going to rejet my Street Avenger 670 this week as well. The stock jets are 65 primary, 68 secondary. I was told to only change the primary jets and am planning to go to either 68 or 69. Am going to leave the scondary jets alone. Anyone have an opinion on this?

SadbutTrue · Apr 22, 2009

jcode68 said:
I am going to rejet my Street Avenger 670 this week as well. The stock jets are 65 primary, 68 secondary. I was told to only change the primary jets and am planning to go to either 68 or 69. Am going to leave the scondary jets alone. Anyone have an opinion on this?

When i asked about this over summer a guy with a similar build as me said that (and this was before I dynoed it and found he was right) that Street Avengers come pretty lean from the factory. He said he went with 72 in the primaries and 80 in the secondaries (and gained something like 20 hp).

I might not go that aggressive but it'll be similar. I've never heard that you dont' want to change the secondaries... in fact, even on edelbrocks, I've always heard that if anything you want your secondaries to be the richer of the two (for several reasons... better detonation protection and more power when you're on it, better fuel economy when you're not, etc).

But then again... I'm not an expert...

jcode68 · Apr 22, 2009

The secondaries are 3 steps richer from the factory. It would make sense to me to bump them both up proportionally - Primary bump to 68 and secondary bump to 71. Where is Dhearne when you need him?

SadbutTrue · Apr 22, 2009

jcode68 said:
The secondaries are 3 steps richer from the factory. It would make sense to me to bump them both up proportionally - Primary bump to 68 and secondary bump to 71. Where is Dhearne when you need him?

Well, the other thing I was hearing is that you don't want to just bump it up a couple increments... you might have to do that 3 or 4 times before you get where you want.

did a mini search and... (yes, i've asked this question a couple times and dragged my feet on it... see talk section for why my motivation isn't quite what it normally would be)...

http://forums.stangnet.com/769598-re-jetting-holley-street-avenger.html

blkfrd was the one who recommended the 72/80 combo. Hearne says he would always move up a minimum of 4 jet sizes bcause you wouldn't tell a difference otherwise.

57fairlane · Apr 24, 2009

SadbutTrue said:
As far as removing the choke goes.. he said the only interesting part is plugging up a 'pencil lead' sized hole into the housing. He said you should drive a fishing weight into the hole with a hammer.

if you are going to stay n/a I would just mill that stuff off (after taking everything off the main body) and leave it.

You only need to jb weld the choke rod hole if you are using a hat for a blower/turbo

D.Hearne · Apr 24, 2009

jcode68 said:
The secondaries are 3 steps richer from the factory. It would make sense to me to bump them both up proportionally - Primary bump to 68 and secondary bump to 71. Where is Dhearne when you need him?

Just me, but when I do change jets on a 4 bbl, I only do the primarys. And I go up 4 sizes in one step. Going 2 numbers rarely nets a change in plug color. Never done one with an A/F meter. And screwing with the idle mixture screws does nothing for the main metering circuits. They're not called "idle mixture screws" for nothing. With my 3x2's I went from 58's straight across the board to 60's in the primary carb and 62's in the secondary carbs.
On the 570SA on my Ranger's 5.0 I did nothing to the jets. It was perfect right out of the box. I did change the secondary spring to a lighter one.

jcode68 · Apr 26, 2009

I swapped my jets this weekend and it made a tremendous difference. I swapped the primaries from 65 to 69 and secondaries from 68 to 71. I also swapped my vac secondary spring from the stock silver to the lighter yellow and it kicks in more aggresively (sooner), which is the way I like it. The biggest change I noticed is the car no longer surges while driving steadily at say 45 mph. Very smooth now. SadbutTrue, let us know how you make out with yours. The swap was very simple to do.

SadbutTrue · Apr 27, 2009

jcode68 said:
I swapped my jets this weekend and it made a tremendous difference. I swapped the primaries from 65 to 69 and secondaries from 68 to 71. I also swapped my vac secondary spring from the stock silver to the lighter yellow and it kicks in more aggresively (sooner), which is the way I like it. The biggest change I noticed is the car no longer surges while driving steadily at say 45 mph. Very smooth now. SadbutTrue, let us know how you make out with yours. The swap was very simple to do.

Is that the only combo you tried? If its easy, might be worth jumping them up one more time to see if it helps any more.

Good to hear its that easy, that way i can make a mild jump now and fine-tune it on the dyno at a later time.

57fairlane... could you elaborate on the 'milling'? I was under the impression there'd just be a hole after you remove the assembly, I'm having a hard time visualizing what would need any milling... though it might become more apparent when I actually take the thing apart.

jcode68 · Apr 27, 2009

It is very easy, but rather than just guess at which jets are best, I am going to locate and schedule some time for a test & tune session with a local dyno shop. The carb was so lean before, I didn't want to schedule a session until I got it in the safe zone.

Regarding the reference to "milling" - that simply means to have a machine shop use a milling machine to remove the air/choke horn that sits on top of the carb. This is not a bolt on item for many carbs, so if you want it removed the only option is to have it milled off.

woodsnake · Apr 27, 2009

I think 57fairlane is saying to mill the air horn and choke plate assembly off.

D.Hearne · Apr 28, 2009

Milling it off can be done at home with a hacksaw and a diegrinder.

Instructions on how to jet a Holley Street Avenger?

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