[HO LEMANS]

Ok this may or may not be a dumb question so here goes
I have a 428 large valve #16 heads w/a R/A IV cam and the Crane version of the anti-pump ... Rhoads lifters (sorry for the life of me cannot come up with correct name for them)
The car it's going in is a 67 Tempest with an M-20 and 3.55 gears
question is with those lifters giving me some of my low end back is this going to be a decent/spirited driver or will those gears make it sluggish?

I apologize if this is stupid but the car previously had a similar 400 but had 4.10 gears

Thanks in advance ......... don't be too harsh

[tom s]

Close too 9-1 final first gear,should not be bad.My 62 GP with a 9-1 final first and a 068 cam and Tunnel ram with a pair of 750 AFB is no issue,just change feet,no need to feather the clutch.I know I have less cam but I think i have more weight on you.Tom

[steve25]

I will venture a guess that due to the 428s greater 4.00” stroke over the 400 and the bleed down of those veritable lifters once the oil warms up that your low end power and throttle response will be 7% better at minimum.

Have you been running vacuum advance with the 400?
If not be sure to do that and get 8 to 10 degrees of it into the 428.

[HO LEMANS]

Originally Posted by tom s

Close too 9-1 final first gear,should not be bad.My 62 GP with a 9-1 final first and a 068 cam and Tunnel ram with a pair of 750 AFB is no issue,just change feet,no need to feather the clutch.I know I have less cam but I think i have more weight on you.Tom

that sounds like that is fun to drive!!
thank you for the response it's good to hear real world similar comparisons
I appreciate it Tom

[HO LEMANS]

Originally Posted by steve25

I will venture a guess that due to the 428s greater 4.00” stroke over the 400 and the bleed down of those veritable lifters once the oil warms up that your low end power and throttle response will be 7% better at minimum.

Have you been running vacuum advance with the 400?
If not be sure to do that and get 8 to 10 degrees of it into the 428.

Steve, yes I was running the vac advance on the 400 as it was not being used as a race car or anything just some fun street stuff and that engine went in to my brothers 67 GTO so in goes the 428 but the gear change had me curious and when curious I come here for the real answers from the people that KNOW

I appreciate the response

[b-man]

Seems like a good combo to me. The bleed down lifters will help bottom end and make the 3.55 gears pretty nice for city driving.

Rear tire size (height) is a substantial part of the gearing equation. A shorter tire can be used if you feel the gears are too tall. All within reason of course so the tire doesn’t look ‘lost’ in the wheel opening from being too short.

What size tires do you plan to use ?

[tom s]

My 62 GP is a 421-30 over 63 421 HO block.9.5 CR.Tom

[oldman66gto]

The bleed down lifters will help bottom end and make the 3.55 gears pretty nice for city driving.


Not trying to upset, nor steal this thread, but I have a 428 in my '66 GTO, with a 3.55, P275R/15 BFG's, and am curious about the "bleed down lifters". What are they, and how do they work/help, and without pulling the engine apart, is there a way to tell? And sadly, I don't know what cam is in it! But it has a nice rumpity, rump sound and decent pressure from exhaust . Doesn't tell much does it? Seems to have decent low end power with an Edelbrock & Torker. But, as we speak, I am having a brand new tri-power set-up installed, new distributor, along with a Tremec TKX 5 spd.
My Christmas present to myself!
Only had the car about 7 months. Sadly a previous owner's "ex" trashed all documentation, pictures, etc, of the restoration, which is about now 12 years old.

You guys are great with suggestions, ideas, sharing of experience, etc. And any advice is appreciated!

Allan

PS: All of my previous experience is with Chevy engines!

[steve25]

You should start a new thread about your motor so that when folks reply they don’t have to preface it as being to you and not the OP of this thread.

[Half-Inch Stud]

I would suggest an overdrive ratio or/and highway gears, to open up the use-ability and enjoyment.

[JLMounce]

How much driving above 50mph are you going to be doing? How sure are you that performance is the number one desire from the car? I have found that performance as a priority, for most people, isn't in sync with how the car is actually used. The reality for a street car is that 90% of the time you're tooling around. Having the performance is great, until you have to deal with the effects of that 90% of the time.

Your engine is going to produce plenty of torque at a reasonable enough rpm that you don't need steep gears. Unless you're running a pretty tall tire, that gear ratio on the highway is probably gonna get old, fast. Costs are always a concern, but if it was me, I'd either be looking for a TKX conversion and keeping the 3.55's, or dropping the 3.55 for a more highway friendly gear like a 3.08.

The TKX is the best option for performance and efficiency. You cut out a good bit of conversion cost since you've already got a trans in the car. Still not "cheap" though.

[tom s]

My 63 421 Lemans has a TKO with I believe the 2.78 first and a 3.64 in the back with the .67 OD.Had a 3.90 in the back and opted to reduce the freeway Rs a little.Tom

[i82much]

i have a 505 with 3.54 gears and an ultra wide muncie, like 2.98 first. freeways suck but that bish makes up for it when you find a straight stretch on a country road!!!

[Radman]

You should be good with that engine and gear combination. I have two 62 Tempest convertibles. The first one still has the 195 4 cylinder with 3:55 gears in the transaxle. It does well for street driving and I am running 3000RPM at 60 MPH. That is the factory setup. The second one has a 1961 389 Tri-Power, 700R4 transmission and a Ford 9 inch with 3:50 gears. Rear tires are Hooser Street Pro 27x9.50x15. 60 foot time at the strip is 2.1 seconds. 70 MPH on the interstate is 2000 RPM.

[Half-Inch Stud]

Ref. Note; we thoroughly enjoyed a 70 GTO stick car with a 2.54:1 posi rear. 1900 rpm on HWY

Any HWY RPM from 1900 to 2500 @ 75 MPH is an eye-opener joy.

[JLMounce]

Originally Posted by Half-Inch Stud

Ref. Note; we thoroughly enjoyed a 70 GTO stick car with a 2.54:1 posi rear. 1900 rpm on HWY

Any HWY RPM from 1900 to 2500 @ 75 MPH is an eye-opener joy.

100% this.

I originally built my firebird with a set of 3.73 rear gears with it's th400. "For the performance." With a 26" tall tire it was terrible to live with at any speed approaching 60mph. 65mph was 3400 rpm. As a result the car only ever got driven around town. Maybe 500-700 miles per year is all.

I got tired of that and wanted a more highway friendly ratio so I put a 3.31 in it because I still wanted the performance. It was better, but still not great on the highway. It didn't really change my driving habits with the car.

Finally I bit the bullet and did the 4l80e conversion. Now I drive the car everywhere, typically around 3000-5000 miles per year. With the overdrive gear I didn't sacrifice any performance, but now the car is absolutely at home at 75mph and a much more relaxing 2200rpm. The value for dollar of that one update is far and away the best thing I ever did to the car.

[VCho455]

I drove my 69 400 T400 GTO for over a decade with 3.55 gears driving 255/60/15's. It Is a perfect combination for the car. With a manual 3.73's will make stop and go traffic easier to deal with as well as launching the car without lighting up the rears. But it comes at the expense of the a higher highway RPM. However different tire diameters can make the two ratios very similar.

The link goes to a great gear ratio calculator which allows a person to make detailed comparisons of drive ratio changes. Have fun!

https://www.blocklayer.com/rpm-gear

With a RAIV cam, Rhodes lifters, home ported 62 heads it ran 12.9 's shifting at 5500 and crossing the line finish at 5700 rpm. I also drove many road trips at 70mph without problems. But I'm not afraid to run 4000 rpm for hours like many folks. The first Pontiac I was around was in high school. My buddy Mark had a 68 GTO, 4.33 geared 4 speed and we drove all over North Idaho in it.

Lots of opinions on subjects like this and mine along with a sawbuck will get you a steaming hot cup of Joe just about anywhere. 🙂

[oldman66gto]

I'm not the "OP", but Thanks for your posts, as they have been quite informative for me.

Hoping the "OP" got the information he needed, as well. And Thanks to him for making the original post!

Happy New Year to ALL! 2026 is going to be a great year!

[HO LEMANS]

Originally Posted by b-man

Seems like a good combo to me. The bleed down lifters will help bottom end and make the 3.55 gears pretty nice for city driving.

Rear tire size (height) is a substantial part of the gearing equation. A shorter tire can be used if you feel the gears are too tall. All within reason of course so the tire doesn’t look ‘lost’ in the wheel opening from being too short.

What size tires do you plan to use ?

B-Man sorry for the delay in my reply I lost an argument with a receiver hitch on my brothers pickup and it's been quite the ordeal ended up with an infection, and a (few now) trips to the wound clinic... blah blah blah .....

Anyway the car has 265-60/14s on the rear so I won't be to tall .... this car won't ever be an interstate cruiser anyway so I think I will run with it the way it is and as always thank you for your input!!

[Formulas]

An important part of your equation is compression ratio. if you have flat tops in a 428 and bleed down lifters under 16 heads you might create to much dynamic compression when at running temp.... the bleed downs on paper will give more low end torque yes but what else is going on then? a reduction of valve duration which is in effect a smaller cam at that time and if octane tolerance is low due to a higher static compression you can be shooting yourself in the foot