“Cliffs Notes” First Recipe to Full first recipe

[theraymondguy]

I have successfully rebuilt and modified my 17085580 to the “Cliffs Notes” standard (idle circuit mods only - as found in the “meat” of early chapter 6 in the good book.) and have enjoyed the car for an entire summer.  My wife marvelled that she didn’t have to pump the gas before hot starting the car (we’re both Gen Xers, last of the carburetor kids).

It’s an ‘85 LG4 Firebird 9.5:1 305
204/214 112LSA cam,
Edelbrock 2101 intake, Hedman headers into a stock replacement Dynomax +1 diameter exhaust.
416 heads (185 cfm intake 150 exhaust iirc.

It idles at 600 rpm making 18”Hg, 10* of initial and 35 all in at 2800rpm, pulls like it means it 3500 to 5000 but I think it could be better 2500 to 3500.

I’m ready to commit to the carb at this point, I believe there’s more power in it and I’m looking at extracting it.  I’m looking for help with my shopping list to complete the full “first recipe”.

It currently has stock secondary hanger and rods installed, “G” and “CH”. I have a “K” hanger available.
It has stock “stepped” primary rods and jets (72 I believe). I have completed the APT mod as well.

[theraymondguy]

There is of course the consideration that the first recipe might be a bit much for a bolt on 305…

[Cliff Ruggles]

Are you looking for more power in the 2500-3500rpm range at FULL throttle?.....

[theraymondguy]

I’ll be honest and say that I’m greedy, I want it everywhere.

However, WOT while accelerating it certainly pulls harder 3500 - 5000 than it does 2500-3500.

Edit:  I’ve not touched the secondary air door spring, to my knowledge everything but the idle circuit and apt setup is stock.

[Cliff Ruggles]

If you want more power at every RPM increase the compression ratio about a full point and keep the same camshaft.

A 305 cid built with 416 heads at 9.5 to 1 compression just doesn't make a lot of power in terms of torque production and for sure with that much cam in it the good power will start past 3000rpm's and it should pull really hard to at least 5000rpms depending on where the cam was installed at.

Even with all that said it still should have plenty of "grunt" for a small engine and do a good job of moving the car around with decent authority.

When it comes to making strong low end power there is simply no replacement for displacement and compression.  Compression is your friend with these things and sadly there is a LOT of miss-information about these engine builds on the Forums. 

Whoever came up with the proverbial "brick wall" of 9.5 to 1 compression for pump gas should have been banned from the Internet FOREVER.  For my pump gas street/strip engines here I like to see at least 10 to 1 compression and prefer 10.5-10.6 for SBC builds.  I've built, dyno'd, street and track tested a LOT of engines here and have always found that low compression builds are "lazy" below 3000rpm's or so if you try to put a lot of cam in them to salvage some decent upper mid-range and top end power.

Even so I've been watching folks lower compression or running lower compression with these engines for decades now.  Many also follow the advice of installing camshafts with tight LSA and short seat timing events with the unrealistic expectations that you really can have a low compression engine and make great power with it.

Since lowering compression and installing a smaller cam completely defies the laws of physics with these things the end user should NOT be surprised that their new engine build is somewhat lacking at low RPM's and runs out of steam early in the RPM range when they follow that advice.....FWIW......

[theraymondguy]

Thanks for the words and a chuckle.  I’m stuck with the 5.0L unless a windfall finds me and provides better accommodation than my current one car garage.  I’ve been meaning to spend an afternoon at the junkyard hunting a crack free set of Vortec heads, they’ll need to be decked regardless and perhaps I can pick up a little compression.

As far as my q jet parts list, maybe just the tapered primary rods and finish the remainder of the first recipe (sans secondary rods and hanger) until such time as the heads are done?

[Cliff Ruggles]

Vortec heads are NOT a bargain for SBC builds.  They are paper thin and will crack if you stare at them too long!

The require a "custom" or special intake manifold which costs more money, and they lack screw in studs and guide plates so you have to buy self centering rocker arms which is another additional cost.

They also lack a heat crossover since the later Vortec engines used a dry intake.  All wet flow systems require a heated intake for best efficiency and I don't care what all the resident "experts" tell you about blocking off the heat crossovers to make more power, that's another regurgitated statement we see all over the NET that just passes on more poor advice.

IF you lived down by the equator you'd probably be OK with a cold intake.  Even up here they will eventually warm up anyhow, but all you do is cost yourself efficiency till some heat gets in it. 

I've had quite a few customers try the Vortec heads on later SBC's because they are dirt cheap compared to far superior aftermarket heads like World Products SR's and they are fine until the temps get cool/cold outside.  Then the phone rings off the hook and they are complaining about hesitation/stumble/bog, surging at light engine load and asking me about buying different jets and rods to fatten things up so they can effectively plow snow in Wisconsin or run around the Mountains of Colorado on their hunting trips. 

I even had one customer rig up a coolant hose system to heat his aluminum Vortec intake because thing worked very poorly in the cold Winters in the Rocky Mountains where he uses the truck......FWIW....

[Mudsport96]

What are the "G" codes on your rpo list? It is also possible that your rear gear ratio is causing the car to be sluggish in the lower revs. An 85 fbody could have had anything from a 2.73 to a 3.42 gear 3.73s were possible with higher option cars. And no amount of tuning will really help if you have 2.73s and a 305.

[lightning boy]

I agree, up the compression. Keep in mind 305's make good torque, but they are RPM limited due to the small bore size. I think the factory tuned port motors made 200hp.