10 Bolt BOP Identification and Question

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guller
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10 Bolt BOP Identification and Question

Post by guller » Thu Feb 06, 2020 12:59 pm

Wondering what I have here.

This came out of a 1966 Lemans. At some point someone put a 1975 - Firebird 350 in it, so I'm not sure what other work has been done.

Looks like a standard BOP 8.2 but I can't find the WD code anywhere in 1966. Inside is an open diff.

Can you tell if this is an 8.2 with 2.93 gears?
Diff Overall.jpg
Diff Casting.jpg
axle stamp.jpg
I recently upgraded to a built 406 with a TH350 trans. The cam in the built 406 recommends a 3.90 - 4.11 axle ratio. I think I want to be around 3.55 for a bit of highway cruising.

Can I upgrade this to a 3.55 posi without too much trouble, should I go to 3.91? What parts would I need and what could I re-use?

Had new bearing pressed on last year. Using for street only, no strip.

Thanks!

Jeremy

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monzaz
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Re: 10 Bolt BOP Identification and Question

Post by monzaz » Fri Feb 14, 2020 8:00 pm

I guess the first thing I would wonder is the recommended gearing being Sooooo steep. What is the duration of this came at .050 on your came card?

What stall converter is in the transmission? Stall speed and diameter of the converter.

WD is a 1967 and newer code. 2.93 Open.... G186 or G188 (G is July 18 is the 18th day and the last digit is year 6 -1966 or 8 - 1968. ) But we always recommend opening the cover and reading the ring gear edge outer diameter to confirm. The ring gear will also be date coded which could possibly help dating this rear.
The rear will be 55.25 from flange to flange or 61" over all.

What is the purpose of this car for you?... What will it be doing...I read freeway some so that concerns me if your cam card recommends 3.90 - 4.10 gears which will be outrageous on the freeway.
BUT if you use a 3.55 gear you may not have the low end you will need as the cam has WAY too much over lap.

We need more info on this engine to see the build ...Heads Compression Carb intake etc.

Jim
JD Race
J D Race

guller
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Re: 10 Bolt BOP Identification and Question

Post by guller » Sat Feb 15, 2020 10:21 pm

Cam Info:
RPM-Range 2500-6800
1.5:1 Rocker Ratio
Grind No./Type 280-Mega Hydraulic
High Performance Use
Bracket Racing
Lopey Idle
2500 Stall
9.5-10.5:1 Compression
3.90-4.11 Axle Ratio
Up To 780 CFM Carb
Mega Racing Cam
Hyd.
Valve Lift Int/Ext. 0.485
Valve Lash Hot Int/Ext. 0.000
ADV Duration Int/Ext. 280
0.050 Duration Int/Ext. 232
Lobe Center 108

The converter is a Hughes 2500 stall - 12"

I'll be using it as a recreational weekend driver / street use only. Nice weather only car. Maybe a short hop on the interstate once per year for less than 200 miles.

Engine Specs:
1967 Pontiac 400 ys bored 0.030
1969 Pontiac 428 intake manifold
1969 Pontiac 428 #46 heads
Compression 9.4:1
750cfm quadrajet
350hp estimated

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monzaz
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Re: 10 Bolt BOP Identification and Question

Post by monzaz » Wed Feb 19, 2020 12:41 am

PLEASE do not take any of this personally...I am just evaluating the parts and combo your giving.


any reason for such a big cam. It says BRACKET racing? Your not doing that? correct?
Your cam starts to make power at 2500 RPM...You only have a 2500 converter that is extremely big in diameter which will take a load to get moving.
so from idle 500-1000 rpm to 2500.....so for 1500 + rpms your at low power and non responsive motor output.

When we race we use the stall converter to blow by dead motor output to get into the meat of the power... Your stalling into just the very beginning of the good power....

Your going to need 3.90 at the very least to keep that car in the power band to make it feel throttle responsive.

Did you pick this cam or did a engine builder?

Your motor has just barely enough compression to run that cam properly.
At least you kept the stock heads with smaller valves and intake with stock runners to help keep the velocity of the intake charge up at low motor speeds.

High 260, low 270 advertised duration would have been a good choice for street engine. Would have had Gobs of low end torque.

Are you going to shift at 6800 -7000? If not you will never use the potential of your camshaft.


What were you looking at when choosing this cam combo? HP, Idle, Price?
INFO
Low compression motors with BIG duration cams (over 280 advertised or .230 at .050 will have sluggish low end with out a 3000- 3500 stall converter.)
This is the reason all performance cars back in the day used STANDARD shift transmissions to dump the clutch up higher in the power band needed to move the car correctly. Plus they had higher compression motors to handle the long duration of the camshaft to rev and get the HP at higher engine speeds.

Please do not overlook ignition.... Aftermarket multi spark ignition boxes create excellent efficiency and will get your engine the best performance in all RPM ranges.

Jim
JD Race
J D Race

guller
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Re: 10 Bolt BOP Identification and Question

Post by guller » Wed Feb 19, 2020 10:49 am

Admittedly I don't know anything about this stuff; however, I am learning as I go.

No, not bracket racing. Street driving only.

I just purchased the complete engine and trans combo for a great deal to get rid of my mid 70's 350 smog dog with ST300. The ST300 went out in the fall so I jumped on this deal so I can get going in the spring. The 350 that is presently in there is pathetically slow and leaks everywhere.

The engine builder, whom I don't know personally chose all of the parts. The ad said lopey idle with great street drivability on 91 pump gas. I figured I could make something work out of it.

Should I move up to a 3000 or 3500 converter?

Can the existing 8.2 rear be built to make this more streetable or should I just bite the bullet and move up to the 9-in? I guess I can give up the highway if needed.

Thanks for the help.

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monzaz
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Re: 10 Bolt BOP Identification and Question

Post by monzaz » Thu Feb 20, 2020 1:16 pm

Tell you truthfully ...Drive the car first... Even with the gear ratio you have. Then evaluate the car.
Just get a BASE LINE first.
I still say with the compression of the motor and that cam combo it will be doggy off the line until 3500 RPM
If it were me I would have the came smaller and get more lowend and mid range torque back to the motor so you do not need to go nutty on ratio and still have plenty of burn out instant torque and freeway cruise.

Since drag race ET slips are not your thing.

JUST remember....NO MATTER what anyone suggests, even us... It is YOUR car and you make the final decisions of the changing, if any parts at all. :)

We are not here to boss you around and make you spend more money if you do not have it.

THE car will move and drive as is...It is how far you want to go to make it do what you want it to do and money cap...

THIS is why I say Drive the car first. See where your at...Compare to the old 350 setup etc.

More cubes is always going to help in fun low end torque area... BUT i do not think it is going to be enough to over come that cam duration you have.
We all normally buy Muscle cars for the low end torque and snappy take off of the cubic inches. What happens is we get caught up in the bigger better combo again and again... PLUS mismatch combos like you have here low compression motor and bigger over lap duration are just a bad combo for low end snappy torque out of the hole...So we try to adjust it with torque converters and gears and timing etc. Band aiding the works till we are out of money and fed up...

3000-3500 stall will be pretty high and you will need a trans cooler for the slippage your going to get with around town regular driving or any freeway driving.
J D Race

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monzaz
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Re: 10 Bolt BOP Identification and Question

Post by monzaz » Thu Feb 20, 2020 1:25 pm

Tell you truthfully ...Drive the car first... Even with the gear ratio you have. Then evaluate the car.
Just get a BASE LINE first.
I still say with the compression of the motor and that cam combo it will be doggy off the line until 3500 RPM
If it were me I would have the came smaller and get more lowend and mid range torque back to the motor so you do not need to go nutty on ratio and still have plenty of burn out instant torque and freeway cruise.

Since drag race ET slips are not your thing.

JUST remember....NO MATTER what anyone suggests, even us... It is YOUR car and you make the final decisions of the changing, if any parts at all. :)

We are not here to boss you around and make you spend more money if you do not have it.

THE car will move and drive as is...It is how far you want to go to make it do what you want it to do and money cap...

THIS is why I say Drive the car first. See where your at...Compare to the old 350 setup etc.

More cubes is always going to help in fun low end torque area... BUT i do not think it is going to be enough to over come that cam duration you have.
We all normally buy Muscle cars for the low end torque and snappy take off of the cubic inches. What happens is we get caught up in the bigger better combo again and again... PLUS mismatch combos like you have here low compression motor and bigger over lap duration are just a bad combo for low end snappy torque out of the hole...So we try to adjust it with torque converters and gears and timing etc. Band aiding the works till we are out of money and fed up...

3000-3500 stall will be pretty high and you will need a trans cooler for the slippage your going to get with around town regular driving or any freeway driving.
Last edited by monzaz on Thu Feb 20, 2020 1:26 pm, edited 1 time in total.
Reason: doubled it
J D Race

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