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Discussion Starter · #1 ·
My 408ci smallblock mopar last year with twin 61mm p-trims w/ 1.15ar's went 5.65 at 127mph...this was with edelbrock heads flowing roughly 280/210 cfm...565 lift flat tappet @ 3400lbs...no transbrake , just a 2-step leaving on 5lbs..

I've got a new set of Indy 230cc heads with 2.10/1.65 valves that flow 330/245 @ 600lift... newcam is 259/255 .630 lift, also a pair of 67mminducer/99mm exducer,68mm/82mm 1.22 ar turbines...these turbos are gt42 frame size..also going to a 1.80 ati glide...The fuel system is already in place 160lb,belt drive, accel dfi....

I am wanting to run about 140mph 1/8 this year and was contemplating putting 76mm compressor wheels in the turbos or just trying out the 67's first...do you think the 67's will make the power needed to run...

Thanks,
Brian Phillips
72 barracuda
 

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It depends on may things. Both the 67 and 76 can be had in quite a few different combinations.

67 P or Q trim? 76 in P,Q or S? PTE has the HPQ also?
 

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Discussion Starter · #3 ·
The 67's I already have is similar in size to a Q with a slight;y larger turbine inducer.
 

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I was running twin 67mm P-trim with .96 on-center housings on a 289" SBF lasts year and it was spooling pretty well. It struggled a little bit at the SCSN in Vegas but most of that I am sure was due to the altitude and the higher awesome track surface. I'd think that with a 400+" motor you should have no trouble at all even with the 76's.

Then again, not having the transbrake will make it tricky...
 

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Pair of TC76's would do it, and bolt in their place......plus they are priced right.
 

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mfi turbos rule
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My 408ci smallblock mopar last year with twin 61mm p-trims w/ 1.15ar's went 5.65 at 127mph...this was with edelbrock heads flowing roughly 280/210 cfm...565 lift flat tappet @ 3400lbs...no transbrake , just a 2-step leaving on 5lbs..

I've got a new set of Indy 230cc heads with 2.10/1.65 valves that flow 330/245 @ 600lift... newcam is 259/255 .630 lift, also a pair of 67mminducer/99mm exducer,68mm/82mm 1.22 ar turbines...these turbos are gt42 frame size..also going to a 1.80 ati glide...The fuel system is already in place 160lb,belt drive, accel dfi....

I am wanting to run about 140mph 1/8 this year and was contemplating putting 76mm compressor wheels in the turbos or just trying out the 67's first...do you think the 67's will make the power needed to run...

Thanks,
Brian Phillips
72 barracuda
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should be nice combo...

i was always told, just run enough turbo to meet your goals..
the 67's would make 1400hp at the out side.
the 76's will go 1850- 1900 hp
( flywheel hp )

run these figures through a et caculater, and see what hp you need to run 140 mph...
at 408 cubes, the engine will consume the air ( lb's per min ..)fairly quick.

my 358 tt sbc , with twin 66's max's out at 7000 ish rpm...

whats your diff ratio ? and tyres size.... i think you will find the 76's will be a better choose if you want to run 140 mph @ 3400 lbs


ash
 

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Discussion Starter · #10 ·
Thanks for the all the information,

Ash, the rear gear is 3.54's with a 295-65-15 M/T drag radial(29.5" tall)

The turbos I have now are big units, definetlly easier to package the TC units,but I have started on mounting up the 67's...Due to cash flow I think I may just try them out 1st...already paid for....may upgrade the wheel later
 

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Discussion Starter · #11 ·
old 61's vs 67's...the 1.15's spooled fine before so I didn't think the 1.22's would be a problem, especially since I am going with the brake.....I know this a big turbo with fairly small wheels, but will usually a larger housing allow more volume of flow...Yes they are master power...and they have a new 76mm wheel that I may see is uprgadable into my housing..machining and balancing aside.

The turbine wheel inducer is 80% the size of the compressor exducer...much better than the 71% for a p-trim...The turbine wheel should be able to drive the 76mm...right?





 

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Huh, I wonder what my single 67mm P trim T4 turbo is good for on my bone stock 350 chevy? Its got a .68 A/r Turbine and the M24 A/r .70 compressor housing.

Its up and running and makes boost really quick. I have a stock convertor and 2.73 gear with 28" tires...The car moves out with some serious authority. I doubt I have spun the engine over 4,000 rpm yet. (Doesnt need to so far...Its a hoot)

I just bought a Precision Q-trim 76mm T4 with a .96 A/r turbine and a .75 A/r compressor with bigger 3" outlet...

How will it differ? On the same car...

Of course my set-up is single....so would two automatically double the effect? Or could I be a el cheapo and run a 67mm on one bank of cylinders and the 76mm on the other side?

Just for kicks am I asking....I have no desire to run two turbo's
 

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The funny thing about turbos is that bigger is not always better. On the Accufab Cougar, we have tried about four different sizes, up to twin 88's. Our best runs (6.335) have all been with twin 78's. Of course, we do not have a 400-inch engine to feed but we made 2300 HP at 9200 RPM on Westech's engine dyno with the 78's.
 
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