TH400 mpg with 455 and 200-4r horror stories?

[Canon_Mutant]

Sorry if I missed it but what do you intend to do with this? Will it live on a drag strip? Just want a nice street rod?

 

[QS442]

Sorry if I missed it but what do you intend to do with this? Will it live on a drag strip? Just want a nice street rod?

99% street car.

 

[olds307 and 403]

Try that GN 2004R. I would buy a pressure gauge, it needs to have high pressure to have any chance to live.

 

[454GrandPrix]

Depending on conditions, I usually get around 8-12 mpg with my 455/TH-400/3:73

Could you share some info on your RPM readings with your combo?

It's been a while since I've driven it and my memory isn't 100%... but I'm pretty sure it spins around 2500 rpm at 55 mph... That's with a 255/60R15 rear tire... not much taller than stock.

For the curious, there are many online gear ratio/engine rpm calculators (such as this one). Plugging in the pertinent info, at the listed road speeds Blake's car turns the following rpm:

55 MPH = 2550 rpm
65 MPH = 3020 rpm
75 MPH = 3480 rpm

(These figures assume no converter slippage. If Blake doesn't have a lockup converter, his actual rpm will be higher than the figures shown.)

FYI

 

[UNGN]

I am putting a 200 4r behind my built 67 buick 400. It has dual 4s 10.25 compression rato, ..30 over engine.. Factory it had 440 ft torque at 3200 rpm. The olds 455 had 500 ft lbs at 3200.

Pre '72 factory "gross" Hp and Torque readings have almost no bearing on reality. A modern car that weighs the same, with the same "Net" HP torque ratings as the old Gross ratings will be 1.5 - 2 seconds quicker and 10 mph faster in the 1/4 mile... and it isn't just "modern tires".

Factory gross HP and Torque numbers were not in the least bit scientific.

 

[Rus]

Pre '72 factory "gross" Hp and Torque readings have almost no bearing on reality. A modern car that weighs the same, with the same "Net" HP torque ratings as the old Gross ratings will be 1.5 - 2 seconds quicker and 10 mph faster in the 1/4 mile... and it isn't just "modern tires".

Factory gross HP and Torque numbers were not in the least bit scientific.

Totally agree, I was just comparing apples to apples for this post. I like rwhp numbers myself. I plan to dyno mine once completed.

 

[84GP455]

How much hp/tq is your Pontiac 455 putting out? I have a "unproven" stock rebuilt BRF 200-4r that I got to use as a core. I thought about running it as is until... the trans needed overhaul.

I am guessing my hp/torque ratings to be about 400/380lb-ft. It is a crate engine with 10:1 compression I have a BRF tag off a 87 G/N which is the best 200-4r to get from what I read. It is a stock transmission and converter and I did nothing to it but it seems to be pretty strong as is.....so far.

 

[QS442]

That's good to know and thanks. I wouldn't of even believed a stock BRF would handle anything close to that amount of power.

 

[olds307 and 403]

I am guessing my hp/torque ratings to be about 400/380lb-ft. It is a crate engine with 10:1 compression I have a BRF tag off a 87 G/N which is the best 200-4r to get from what I read. It is a stock transmission and converter and I did nothing to it but it seems to be pretty strong as is.....so far.

That's good to know and thanks. I wouldn't of even believed a stock BRF would handle anything close to that amount of power.

I assume that is power to the wheels? It would have 480 ft/lbs of torque easy.

 

[el camino ss 84]

If you can't get ahold of a gn 2004r the next best one is out of a late 88 or 89 caprice since it had all the upgrades like the gn version but a lot cheaper.