Thoughts/help on fueling for a 68 w/454 block - Page 2 - Chevelle Tech
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post #16 of 27 (permalink) Old Jul 1st, 20, 11:36 AM
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Re: Thoughts/help on fueling for a 68 w/454 block

Airflow formula. (Air Flow)
VE is Volumetric Efficiency expressed as a decimal. For example:

90% = .9
85% = .85
110% = 1.10

RPM is max RPM for horsepower.

AF = Cubic Inches x RPM x VE / 3456

Chas

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post #17 of 27 (permalink) Old Jul 1st, 20, 6:32 PM Thread Starter
James
 
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Re: Thoughts/help on fueling for a 68 w/454 block

Quote:
Originally Posted by Kirk's67SS View Post
Is your Gas Peddle opening the Carb all the way when at/on the Floor

I had that problem and it only showed up because my Mechanic/Pro Racer
said I should be seeing Higher MPH at the end of the 1/4
turned out the Rod on the Gas Peddle Mechanism was not Bent right so it would not interfere with the Air Cleaner
Yessir, verified everything is flowing freely!

Quote:
Originally Posted by chasmalo View Post
On two different cars I've worked on over the years I found the carburetor was not opening completely with accelerator on the floor. It's always worth checking. Get a friend to stand on it - (engine off ) check that all bbls are fully open.

> Watch out for floor mats that get in the way as well.

Chas

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Quote:
Originally Posted by chasmalo View Post
Airflow formula. (Air Flow)
VE is Volumetric Efficiency expressed as a decimal. For example:

90% = .9
85% = .85
110% = 1.10

RPM is max RPM for horsepower.

AF = Cubic Inches x RPM x VE / 3456

Chas

Sent from my SM-G950U using Tapatalk
Chas- Checked it and it is definitely opening with the pedal. Appreciate the formula my friend, i'll write that down!

Ok, so got some new data from today's tinkering.

I put the plain spring in to give it the 8Hg step up, confirmed timing at 16 idle 35-36 total, and pulling a steady 13-14 InHg at a 750ish idle. Went for a little cruise and from the butt dyno and seat feel, it definitely woke up in the lower range. Even straight spun the tires in 2nd gear when going WOT from 3k, which it hasn't done before. I'm still getting that big switch between 80-90 and WOT, but honestly, at this point I have a feeling this is my inexperience with vac secondaries. All my previous carb experience has been with mechanical secondaries. Got back and pulled some plugs which told an interesting story (pics attached).

1-2 ran dead rich, 3-8 looked pretty identical. 3-8 definitely showed signs of being richer, but nothing that would overly freak me out. 1-2 being what they are I think speaks to how poor the distribution is with the Torkker II...and that is with the 4 hole phenolic spacer. Perhaps for now, should I settle on the pink 7Hg step up spring, return to stock rod and the 8Hg step up, or return to stock 5Hg step up and just go 4% more on rod? It def liked more fuel.

Probably what this is coming down to is an intake with not so great distribution and a carb that needed a little tuning. This might be the time to switch her over to the RPM AG2 since 95% of the time, this is staying under 5800
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post #18 of 27 (permalink) Old Jul 1st, 20, 7:09 PM
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Gene
 
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Re: Thoughts/help on fueling for a 68 w/454 block

Methinks you done figured it all out James! The Eddie will respond differently to a dual plane, for sure. With a stick, I just dont think you can ever mimic the "hit" of a double pumper. Why tis a classic combo.

Gene
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post #19 of 27 (permalink) Old Jul 1st, 20, 7:39 PM Thread Starter
James
 
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Quote:
Originally Posted by 427L88 View Post
Methinks you done figured it all out James! The Eddie will respond differently to a dual plane, for sure. With a stick, I just dont think you can ever mimic the "hit" of a double pumper. Why tis a classic combo.
I may be blonde, but I’ll eventually get there! Lol. And definitely agreed. I’ll build up something fun in the future since I’m not worried about it being a true 138 car

General feedback I’ve seen seems to be that the AG2 will fit under the 68 hood as long as you have the drop base and a 3 inch filter?
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post #20 of 27 (permalink) Old Jul 1st, 20, 8:43 PM
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Re: Thoughts/help on fueling for a 68 w/454 block

What’s the part number for those spark plugs? They look too cold. I’d consider upping the heat range and going with a projected nose plug.
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post #21 of 27 (permalink) Old Jul 1st, 20, 9:39 PM Thread Starter
James
 
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Re: Thoughts/help on fueling for a 68 w/454 block

Quote:
Originally Posted by Roadknee View Post
What’s the part number for those spark plugs? They look too cold. I’d consider upping the heat range and going with a projected nose plug.
Delco 10. At the time I bought them, figured this was a mild stockish 73 454. Recommendations on brand/part#?
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post #22 of 27 (permalink) Old Jul 1st, 20, 10:37 PM
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Re: Thoughts/help on fueling for a 68 w/454 block

R44TS gapped at 0.035”. Have you run a cranking compression test?
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post #23 of 27 (permalink) Old Jul 2nd, 20, 12:04 AM
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Kerry
 
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Put a projected tip plug in there, NGK UR5 gapped at .040”. No reason to not use a projected tip plug for street driving.

Leave the plain 8” step up springs. They do not make the jetting richer, they allow the enrichment to start sooner. Changing to a lower rating spring and richer rod will not work the same as the enrichment starting sooner.

Bump the timing up 2 more degrees. And hook up the vacuum advance.
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post #24 of 27 (permalink) Old Jul 2nd, 20, 11:00 PM Thread Starter
James
 
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Quote:
Originally Posted by Roadknee View Post
R44TS gapped at 0.035”. Have you run a cranking compression test?
She runs so strong that I haven’t felt a need to run one. Def haven’t seen any smoking under load and the new oil I put in about 700 miles ago is pretty clean.

Quote:
Originally Posted by pockets View Post
Put a projected tip plug in there, NGK UR5 gapped at .040”. No reason to not use a projected tip plug for street driving.

Leave the plain 8” step up springs. They do not make the jetting richer, they allow the enrichment to start sooner. Changing to a lower rating spring and richer rod will not work the same as the enrichment starting sooner.

Bump the timing up 2 more degrees. And hook up the vacuum advance.
Agreed on the plugs. I throw a few more miles on these and then I’ll switch over.

Just for curiosity today, I messed around with a few combos and then took it out on a nice 15 mile loop where I can run it through some paces and different loads. I tried the original stock rod with the 8 step up and it was good, but not great. Used the richer rod with the 7 step up and it ran great, but plugs looked pretty white on the ceramic. I think the winner here is the richer rod with the 8 step up. For some reason it didn’t show rich on the plugs today like it did yesterday. I’ll keep an eye on it. I’ll throw a couple degrees in it and call this closed! RPM AG2 is prob in the works over the next few months
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post #25 of 27 (permalink) Old Jul 3rd, 20, 9:17 AM
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Re: Thoughts/help on fueling for a 68 w/454 block

1) Are all the spark plug wires OK?

2) Wiith the MSD box you could use a larger gap in normally aspirated engine.

Chas

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post #26 of 27 (permalink) Old Jul 3rd, 20, 4:43 PM
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Re: Thoughts/help on fueling for a 68 w/454 block

BTW, Vacuum Advance is for cruising gas mileage.
Under full throttle only the mechanical advance is working

Chas

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post #27 of 27 (permalink) Old Jul 3rd, 20, 9:29 PM Thread Starter
James
 
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Quote:
Originally Posted by chasmalo View Post
1) Are all the spark plug wires OK?

2) Wiith the MSD box you could use a larger gap in normally aspirated engine.
Quote:
Originally Posted by chasmalo View Post
BTW, Vacuum Advance is for cruising gas mileage.
Under full throttle only the mechanical advance is working

Chas
Wires are all good man; fresh set of Summit 8.5mm with only 700ish miles on them. When I get back in town, I’ll throw a couple more degrees in her for 18/37-38.

It has what looks like a nice newer HEI setup and I checked cap, rotor, and all the electronic internals when I replaced the vac advance. Everything looked and checked out fine. I spent two days tracking down that vac leak because the advance was hooked up to ported and not manifold vac...
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