66 GTO; Change Rear End Ratio vs Overdrive

[Marty Roth]

Our 1930 Packard 7-Passenger Touring has a 5.08:1 differential since it was intended to be used between Paris and Monaco, crossing the Alps.

That is fine for city driving, but the 0.70 Overdrive gives the equivalent of a 3.556:1 for country roads. We don't need higher speeds - just fewer engine revs, and it is a pleasure to have both ratios.

 

The intermediate-sized Pontiacwith the "honkin' V-8 has more than enough torque to get moving without slipping the clutch.

 

Enjoy it every day that you can, and smile all the way to the ice cream stand with your bride and grandsons.

[padgett]

My notes from a while ago for the T-5 was "both world class and non-world class, were rated at 265-lbs.ft. of torque. 1990-’93s were rated at 300-lbs.ft., and the ’93-’96 Cobra “Z-Spec” T-5 was rated at 330-lbs.ft." and why I decided not to bolt my T5 to the GTO RA 400. It may have held it or may need a performance rebuild but been sitting there for about a decade now. Guess I should dig out and see which one it is.

[Pfeil]

2 hours ago, carbking said:

 

Tests often show what the tester wishes to show; and that is certainly true with the tripower.

 

Pontiac paid Carter to sabotage the AFB on the mid-60's Pontiacs in order that the standard 4-barrel engine would not out run the more expensive tripower!

 

Of course, the tripower wins the "open hood racing" contests until such time as one looks at a dual quad  

 

As far as the original gear question; not my ballpark, no comment.

 

Jon.

 

 

   The second test I saw was a 400 with a 041 cam Rhoads lifters with a Q-jet on a RA4 intake vs the same car with a 1966 Tri-Power- large center 2GC on the floor dyno-real RW hp. The Tri-Power got it in HP and Torque. That test must have been all of ten years ago. Maybe 15.  

Edited September 15, 2019 by Pfeil (see edit history)

[carbking]

Wasn't questioning your mention of the test; I knew of its existence. Questioning the test itself.

 

Pontiac Super Duty Division also tested the tripower, and didn't care for the results. For racing, Pontiac opted for single quad (AFB) and dual quads (AFB).

 

Pontiac sales continued to advertise and sell the tripower, after the street AFB was modified to allow the tripower to outrun the AFB.

 

Pretty conclusive results.

 

Jon.

[C Carl]

Man, you just don't know who to trust anymore !       -    CC 

[padgett]

Ask Jon about the Carter-Pontiac three barrel carbs. AFAIR the rules of the race organizations restricted the number/size of the carbs and the dual quad NHRA manifold flowed A Lot More than the tripower. Also those A93C triple pots limited the tripower CFM, the single ginormous Air Cleaner for B-body tripowers flowed  much better than the little ones.

 

Which has nothing to do with a good tranny for a GTO. Did find the specs on my T-5 and is a 1352-210 with 3.75 2.19 1.41 1.00 0.72 ratios and a 305 lb-ft torque rating that I was always told was too weak for a RA 400.

[Robert G. Smits]

Again thanks for all the replies.  I continue to be amazed at the knowledge on this forum.  I already have 15 inch Rally II's.  Never  heard of the Hone O Drive.  Anyone have any experience?  I think the viable options will begin with a rear end change.  I have found a couple of LeMans rear ends here in Texas but haven't determined the ratio yet.  I can do this in my own shop for not much money.  If unsatisfactory I may add the Tremec or Richmond 4+1 route although the Tremec required major tunnel work.  There are always  trade offs.  May be simpler to just drive my 64 Bonnie with the 421HO and automatic but it is not a convert.  BTW where I grew up in Iowa these were always "GOATS" and proud of it.  A classmate and I drove his new 64 from Iowa City to Houston for interviews and I have been in love with them ever since.

Padgett, didn't they use the later T-5's in Mustangs and Camero"s and isn't there a NWC and  WC class?

Edited September 16, 2019 by Robert G. Smits
Addition (see edit history)

[carbking]

Robert - since you mentioned "Bonnie" in your last post, see if you can find a video of the "Bonnie & Clyde" GTO commercial. You will be glad you did.

 

Other monikers other than GOAT for the GTO were "gas, tires, oil; give ticket officer; and girls take over (that was the name of another interesting Pontiac commercial).

 

My solution to the gear issue was to use a lower numeric rear gear with an ultra wide ratio 4-speed. The problem with this is trying to use first gear for WOT. The rear tires object.

 

Padgett - the Carter AFB 3-barrel flowed 939 CFM when flowed on the 4-barrel scale; and 1128 CFM when flowed on the 2-barrel scale.

 

Jon.

[padgett]

a) more than you ever wanted to know about B-W T5s (now Tremec)

http://www.britishv8.org/Articles/Borg-Warner-T5-ID-Tags.htm

Who said you could use a T5 with a 455 ?

 

b) What Jon is referring to is that 2bbls are measured differently than 4bbls. On the flow bench a 2 bbl is measured at 3" of Hg back pressure. However when 4bbls came along most benches could not manage 3" so they are measured at half that or 1.5" Hg. However a three barrel is neither but flowed 1128 cfb at 3" of Hg and  939 at 1.5".  Isn't linear but not going to get into compressible gas flow theory. Holly also had a 3 bbl but was later. I understand that some thermoquads exceeded 1,000 cfm.

[Pfeil]

2 hours ago, padgett said:

Ask Jon about the Carter-Pontiac three barrel carbs. AFAIR the rules of the race organizations restricted the number/size of the carbs and the dual quad NHRA manifold flowed A Lot More than the tripower. Also those A93C triple pots limited the tripower CFM, the single ginormous Air Cleaner for B-body tripowers flowed  much better than the little ones.

 

Which has nothing to do with a good tranny for a GTO. Did find the specs on my T-5 and is a 1352-210 with 3.75 2.19 1.41 1.00 0.72 ratios and a 305 lb-ft torque rating that I was always told was too weak for a RA 400.

 

You mentioned the 421 "B" body cars with Tri-Power. I think starting with the 64 ( maybe 63) cars the 350HP Tri Power used the large air cleaner while the 370 H-O engine used the three pot air cleaners, same true for the 65-66 cars of 356hp using the large single and the 376HP H-O engines using the three pot air cleaners. 

[Pfeil]

8 minutes ago, padgett said:

a) more than you ever wanted to know about B-W T5s (now Tremec)

http://www.britishv8.org/Articles/Borg-Warner-T5-ID-Tags.htm

Who said you could use a T5 with a 455 ?

 

b) What Jon is referring to is that 2bbls are measured differently than 4bbls. On the flow bench a 2 bbl is measured at 3" of Hg back pressure. However when 4bbls came along most benches could not manage 3" so they are measured at half that or 1.5" Hg. However a three barrel is neither but flowed 1128 cfb at 3" of Hg and  939 at 1.5".  Isn't linear but not going to get into compressible gas flow theory. Holly also had a 3 bbl but was later. I understand that some thermoquads exceeded 1,000 cfm.

 

I had a chance to buy one of those Pontiac 3bbl NASCAR carbs. Sorry I didn't. Also a aluminum 389 complete engine that M/T got from Pontiac engineering.😢 

[carbking]

9 hours ago, Pfeil said:

 

I had a chance to buy one of those Pontiac 3bbl NASCAR carbs. Sorry I didn't. Also a aluminum 389 complete engine that M/T got from Pontiac engineering.😢 

How sorry are you?

 

I know where there are two looking for a new home.

 

Jon.

[Pfeil]

2 hours ago, carbking said:

How sorry are you?

 

I know where there are two looking for a new home.

 

Jon.

 

About 20 years back very sorry,  and that carburetor ( 1963) I forgot to mention came with the special aluminum intake manifold that was the forerunner in basic design of the manifold on later Q-Jet equipped Pontiac engines.

Today I wouldn't know what to do with it. 

[carbking]

More information:

 

Carter 3 barrel documentation letter

 

Jon.

[Pfeil]

1 hour ago, carbking said:

More information:

 

Carter 3 barrel documentation letter

 

Jon.

 

Jon, do you know much about the Offey, 2X4 Quadra jet intake manifold.  I still use a single Q jet on my Pontiac that I most exclusively use on the street now but I built for the track ( Grand Touring ) and street back in 1992-2012. Today I am many miles from a road course so my car is only driven on the street. I set my car up with a Pontiac/ Buick Q jet and must say for ease and trouble free operation and the ability to go around corners with a high G load the Q-Jet is one of the best carburetors I have ever come across. Just wondering how that manifold and two Q-jets would do on a road course. Probably have to use the Chevy Cadillac rt. side fuel inlet type Q-Jet. I don't even know if they make it anymore.

Edited September 16, 2019 by Pfeil (see edit history)

[Guest]

I just saw this on AmeriCars site and thought it might be of interest here.

[Pfeil]

12 minutes ago, Tinindian said:

I just saw this on AmeriCars site and thought it might be of interest here.

 

Absolutely!  However this dealer applied the GTO junior moniker to a plain Tempest. In reality the Tempest, Tempest Custon, or LeMans could be had with the SPRINT package; a 4bbl Quadra jet OHC six with splitter exhaust iron headers dual exhaust heavy duty suspension like the GTO and was called the GTO Tiger Junior by marketing!

Edited September 16, 2019 by Pfeil (see edit history)

[carbking]

53 minutes ago, Pfeil said:

 

Jon, do you know much about the Offey, 2X4 Quadra jet intake manifold.  I still use a single Q jet on my Pontiac that I most exclusively use on the street now but I built for the track ( Grand Touring ) and street back in 1992-2012. Today I am many miles from a road course so my car is only driven on the street. I set my car up with a Pontiac/ Buick Q jet and must say for ease and trouble free operation and the ability to go around corners with a high G load the Q-Jet is one of the best carburetors I have ever come across. Just wondering how that manifold and two Q-jets would do on a road course. Probably have to use the Chevy Cadillac rt. side fuel inlet type Q-Jet. I don't even know if they make it anymore.

 

[carbking]

That looks like a picture from my website.

 

I would have installed it on my GTO years ago with a pair of Carter thermoquads, but not good enough with sheet metal to convert the dual quad to the shaker.

 

I am not high on the spread-bore design for road-course racing. Drag racing and circle track racing yes, but not road course racing. Difficult to get the secondaries to kick in smoothly enough for the vast number of shifts required on a road-course.

 

For street, the Offy is MUCH better than the other common A/M manifold for use on Pontiac engines.

 

Currently, my Pontiac 350 in the GTO has an 850 CFM Carter thermoquad.

 

We probably should start another thread if we are going to continue talking Pontiac performance carbs and manifolds.

 

Jon.

[Robert G. Smits]

misrerc9:  when I read your post on ESSO I remembered buying this at the indy ad show on my way home from the 2011 Glidden at Cumberland MD.  Took me a while to dig it out of storage but now I will frame and hang it. Thanks. I also have a 4 by 12 ft  cloth one but haven’t found it yet

[Robert G. Smits]

Thank you for all the replies AND the interesting Pontiac literature.  Brought back many memories from the 60's and 70's.

[padgett]

Always liked the QJ but as said few knew how to tune it. Many just backed off the secondary opening spring and created a horrendous bog off the line. I had one on my autocrossing 65 Corsa 140 (rules were a lot looser then) and response was immediate. NP even with blue streak race tires.

 

Now I do like lotsa carbs and keep thinking about either dual quads with AFBs or a factory 66 tripower (big center carb). But really needs a five or six speed. Unfortunately sold my '57 Pontiac FI. Decisions, decisions.