72 454 non-ported mapping curve specs and parts

[Robert B.]

I have a 1972 454/270 automatic roadster. It is currently set up bypassing the TCS and set to factory specs. It is timed at 8 degrees and the stock vacuum advance is set up as 0 @ 8 degrees and 20 @ 17 degrees.

In educating myself on the various posts I am starting to learn more about the mapping curves. My question do I need to change my original vacuum can or centrifugal advance weights now that I am running non-ported vs. ported? If so what size vacuum can and weights should I use? I am seeking optimum performance across the range, fuel etc... I am guessing (thinking) this is where some of the changes were made from the 1971 454/365 (285 gross) net to the 1972 454/270 (350 gross) LS5? I also read possibly re-jetting the carb? I was hoping it was possible to pickup some lost hp and torque form the prior year.

Any help would be great!

[Timothy B.]

Re: 72 454 non-ported mapping curve specs and parts

Robert,

Determine stable idle vacuum with approx 25* advance in drive (vacuum advance plugged) and choose a control that gives 15-16* at 2" lower than the vacuum reading you took.

If you do not have access to a distributor machine keep in mind not to exceed total advance (inital and centrifugal) of 34-40*. Install different (lighter)springs and time by the total timing method and let inital advance fall where it will. All trial and error with detenation the limiting factor. Play with springs and total advance in these parameters.

Good to have a dial back light, when I time for total advance I remove the advance springs so the engine does not need to be reved to advance weights in distributor then reinstall springs.

Archives has good info and I believe using manifold vacuum for the advance will make a improvement, keep all the original parts in case you ever want to go back to original curve.

[Tom L.]

Re: 72 454 non-ported mapping curve specs and parts

Hi rob, I also have a '72BB and love it. I can't help you with the mapping and tuning of the distributor curve but it seems correct for stock. As far as your concern about re-gaining lost HP and tourqe, don't worry, there was little change aside from the method used to record it.

Do you have an AIM? If you do look at sheet F1, page M297. The gross and net HP for that engine is listed and quite different from the 270HP that is accepted by all of us. If you don't have the AIM I'll scan the page later and post it.

[James W.]

Re: 72 454 non-ported mapping curve specs and parts

You can contact Chuck or Dave Anderson at Performance Automotive (817) 763-8115 or Bill Ford at Precision Engine MAchine at (912) 863-3973. Both are great people and both have a Sun Distributor machine with the charts and specs for all types of distributers. If you call them, tell them Jim White says, "HI".

[Michael W.]

Re: 72 454 non-ported mapping curve specs and parts

now that I am running non-ported vs. ported?

Disabling/bypassing the TCS system is very different than going from ported to non-ported vacuum source on the carb.

Are you sure of which source you are using?

[Robert B.]

Re: 72 454 non-ported mapping curve specs and parts

Thanks for all the info. I love my 72 BB. Good idea to work backwards with a dial up light and try to spec out the appropriate vacuum can and springs.

On another note I did disconnect the TCS and I am pulling vacuum from the non-ported source on the front lower right (drivers side of the carb). It is t'ed into the vacuum line that connects the main vacuum tank. I am guessing this is an appropriate source?

[Duke W.]

Re: 72 454 non-ported mapping curve specs and parts

This has been discussed a zillion times - archive search - VC-1765.

Duke

[Clem Z.]

Re: 72 454 non-ported mapping curve specs and parts

Thanks for all the info. I love my 72 BB. Good idea to work backwards with a dial up light and try to spec out the appropriate vacuum can and springs.

On another note I did disconnect the TCS and I am pulling vacuum from the non-ported source on the front lower right (drivers side of the carb). It is t'ed into the vacuum line that connects the main vacuum tank. I am guessing this is an appropriate source?

you want a source of vacuum that goes away when you go full throttle so i would think the vacuum tank would NOT allow this to happen. JMHO

[Robert B.]

Re: 72 454 non-ported mapping curve specs and parts

Thanks Duke for the NAPA part number, I need to reread the archive posts as see which relate to my engine. Where is the best place to tap into "t" into the carb for my vacuum source? I am new at this and trying to do it right and learn what I am doing. Rob

[Clem Z.]

Re: 72 454 non-ported mapping curve specs and parts

Thanks Duke for the NAPA part number, I need to reread the archive posts as see which relate to my engine. Where is the best place to tap into "t" into the carb for my vacuum source? I am new at this and trying to do it right and learn what I am doing. Rob

put a "T"in the vacuum line going to the vacuum break also called the choke pull off on the side of the carb

[Robert B.]

Re: 72 454 non-ported mapping curve specs and parts

Thanks Clem. Will do!

[Duke W.]

Re: 72 454 non-ported mapping curve specs and parts

First check the manifold vacuum idling in Drive. Then select a VAC that complies with the Two-Inch Rule. An auto trans might require the 15" VAC.

Duke

[Robert B.]

Re: 72 454 non-ported mapping curve specs and parts

Duke,

If I understand the 2 inch rule I should have 17'' of manifold vacuum or higher when in drive? Thanks

[Duke W.]

Re: 72 454 non-ported mapping curve specs and parts

I don't know what the vacuum will be in Drive - probably in the range of 12-15". You need reread the 2" rule. To apply it you must know the idle vacuum - in Drive for automatics.

Duke

[Robert B.]

Re: 72 454 non-ported mapping curve specs and parts

Duke,

I tested my vacuum in drive. The vacuum is 17'' to 17.5' in drive. It pulls 19' to 19.5'' in park. I took the reading from the manifold.

Idle is set at 600 rpm's in drive and 900 rpm's in park. So based on the information and the 2'' rule would a 15" can would be appropriate? Would you know the the Napa can equivalent? Would you know the full specs for this can? Any recommendations would be great.

Also my current vacuum can as measured on my vacuum pump tester starts advancing at 8" and is fully advanced at 17.5" Not exactly sure what I have currently have.

I also "t"ed off the choke at the carb - base timing is set at 10 degrees.

I truly appreciate the advise.
Rob