Big block conversion done - Impala Tech
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post #1 of 11 (permalink) Old 03-17-2020, 11:03 PM Thread Starter
 
 
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Big block conversion done

Well, it took me about 2 months worth of evenings and weekends, but I got it done....

Before....

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After....

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62BillT, BA. and badrad like this.
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post #2 of 11 (permalink) Old 03-17-2020, 11:34 PM
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Nice job!

Big Dave
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post #3 of 11 (permalink) Old 03-17-2020, 11:39 PM Thread Starter
 
 
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Quote:
Originally Posted by Big Dave View Post
Nice job!
Thank you Big Dave. I hope my hood fits
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post #4 of 11 (permalink) Old 03-18-2020, 12:26 PM
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The 396 and the 427 were both options from the factory so it should have plenty of room under the hood.

Big Dave
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post #5 of 11 (permalink) Old 03-18-2020, 01:58 PM
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Any details on the installation:

What issues did you run into?

What carb did you use? Did it fit the pedal linkage?

What transmission did you use? 4 speed Manual?

What could you use from the Small block engine?

What exhaust and Headers did you use?

Did you use a stock radiator, fan, shroud?

Any issues with Engine mounts or oil pan fitment?

Did you change brakes?

Ted
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post #6 of 11 (permalink) Old 03-18-2020, 06:57 PM
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Quote:
Originally Posted by brickwhite View Post
Any details on the installation:
What issues did you run into?
What carb did you use? Did it fit the pedal linkage?
What transmission did you use? 4 speed Manual?
What could you use from the Small block engine?
What exhaust and Headers did you use?
Did you use a stock radiator, fan, shroud?
Any issues with Engine mounts or oil pan fitment?
Did you change brakes?
What issues did you run into?
Looking at his pictures I would say he has finished the install and used aftermarket parts instead of factory parts to do it.

What carb did you use? Did it fit the pedal linkage?
He is using a Holley 4150 or 4160 dual feed Holley. Don't know if it is a vacuum secondary or mechanical. nor can I tell the cfm rating from the picture. Factory stock was a 780 cfm Rochester QuadraJet, with a steel fixed rod from the bell crank to the carb (last year, as in 1969 they went to a throttle cable).

What transmission did you use? 4 speed Manual?
No Idea as I can not see a an automatic dipstick tube sticking up behind the air cleaner, but that doesn't mean it isn't there. If an automatic; then I hope it was the factory recommended TH400 (TH350 was not available in 1968) as your other choice would have been a PowerGlide if he wanted to keep it period correct. If he wanted a strong OD automatic capable of handling a BBC in heavy car I would have gone to a 4L80e transmission.

What could you use from the Small block engine?
Everything except the radiator (undersized in terms of BTUs in cooling) or the transmission as even a Muncie really isn't strong enough for a BBC which is why GM dropped it in favor of the Borg-Warner Super T10 after introducing the 454 in 1970.

What exhaust and Headers did you use?
Once again picture doesn't show much. I think He might have retained the factory cast iron manifolds as there are no fitment issues with them and an Impala is an improbable drag car that doesn't need tubular headers. I suspect he has dual exhaust with matching mufflers, but without the factory resonators as most are not aware that was the BBC dual exhaust option.

Did you use a stock radiator, fan, shroud?
Picture shows an aftermarket fabricated aluminum radiator (probably a Be-Cool) with an aftermarket fan shroud.

Any issues with Engine mounts or oil pan fitment?
Most BBC donor engines come out of a light truck/van as they were not installed in passenger cars after 1973. Light truck oil pans won't fit in a passenger car as the sump is located too far forward and the sump will interfere with the cross-member under the motor. For that reason you need a reproduction passenger car pan to fit the crankshaft (one piece or two piece rear main seal), or an aftermarket oil pan that holds more oil. Motor mounts are the same between a BBC and a SBC assuming you buy an interlocking motor mount used by all Chevy engines rated over 300 horsepower. A BBC will rip a stock base engine Chevy motor mount apart.

Did you change brakes?
Hope so as the car was designed in 1963 ( talking about the 1965-'70 series of B-body cars) for an average road speed of only 45 mph. With a two ton car traveling at today's interstate speeds you are seriously over driving your braking capacity.

Big Dave
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post #7 of 11 (permalink) Old 03-19-2020, 12:48 AM Thread Starter
 
 
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Quote:
Originally Posted by brickwhite View Post
Any details on the installation:

What issues did you run into?

What carb did you use? Did it fit the pedal linkage?

What transmission did you use? 4 speed Manual?

What could you use from the Small block engine?

What exhaust and Headers did you use?

Did you use a stock radiator, fan, shroud?

Any issues with Engine mounts or oil pan fitment?

Did you change brakes?

It’s amazing how close Big Dave described my conversion, it definitely shows the years of experience he has with the Chevys.

No issues really to speak of other than it can be time consuming depending on how nice you want the end result to be.
I was going for a somewhat stock look so it would look like it maybe could have been a real SS with the 427 option. It’s really a ‘73 pickup 454 and like Dave mentioned I had to get a passenger car 5qt pan.
Probably the most difficult decision I had to make was to go short water pump like a ‘68 should have or long water pump like 69 and later, but where I had all the pulleys from the pickup I opted to go long water pump. Then came the whole AC thing. I didn’t want to use the original style compressor so I bought a Sanden compressor and used Alan Grove brackets for the compressor, alternator and power steering pump. Which are very nice and align perfectly and I highly recommend.
Originally I thought by going with a long water pump and the 4 row radiator I would need to remove the filler panel between the core support and the radiator (like the factory did from ‘69 on) but with the new 6 blade steel fan with no spacer I left it in and I have about 3/4” between the fan and radiator.

The Carb is exactly as Big Dave described, a 4160 Holley 750cfm dual feed with electric choke and vacuum secondaries. A trip to the hardware store gave me what I needed for throttle linkage. Heim joints, 1/4” brass rod and some bushings.
[IMG][/IMG]

When I bought this car it had a ‘69 327 and a Saginaw 4 speed from a 82ish Camaro as reverse was left and back as opposed to left and forward like I’ve been used to. I was baffled by that until I researched it and discovered the later Saginaw 4 speeds patterns were that way.
Now with the big block I installed a Muncie M20 that I had. I’m confident it will hold up fine where this car is just a cruiser.
[IMG][/IMG]
[IMG][/IMG]

As far as using stuff from the small block, I did use the starter and fuel pump, distributor, alternator, sending units and bell housing. Also, I retained the original cast iron exhaust manifolds from the pickup. They fit perfect and had the indentation to clear the steering box.

Prior to the BBC conversion I did do a complete suspension, brake and steering rebuild and installed Wilwood disc brakes up front and retained the drum brakes in back. I got a reman booster from Napa and a disc/drum master cylinder and proportioning valve from Summit.
[IMG][/IMG]
[IMG][/IMG]

Hope this info helps. If you need more details just ask. Doug
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post #8 of 11 (permalink) Old 03-19-2020, 11:02 AM
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Thanks for the details on your build, Doug.

More details on person builds always help, more details the better on technical forums....

I am in the process with my 66 impala and have run into situations that required some knowledge on what fits and what doesn't when you swap in a BBC into a SBC car.

- Power steering bracket choices OE or Aftermarket, small block does not fit big block
- Power steering lines, SB are not long enough
- Pulley's on SBs do not fit BBCs
- Making sure you have the correct driveshaft, crossmember, and flexplate, when coverting transmissions
- Carb choices and fuel lines, I also am using a 4 bbl holley type 750, but one could use different 4 barrels, edlebrock etc.
- Going from Single Brake master to Dual brake master, using a proportiong valve etc.
- Short Water pump vs Long water pump and what pulleys need to be used
- Engine mount towers and engine mounts. Tall and skinny or short and wide.


Hearing what others have had to deal with I'm sure would help anyone down the line that searches these posts.

Ted
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post #9 of 11 (permalink) Old 03-19-2020, 12:54 PM
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Quote:
- Going from Single Brake master to Dual brake master, using a proportiong valve etc.
You only use a Proportioning Valve if you are running disc brakes. This is because disc brakes require 1,500, to 3,000 psi to operate: but drum brakes only need 850 pounds to operate. Without a Proportioning Valve the rear brakes would lock up instantly at the first tap of the brake pedal. I recommend an adjustable one to get the ratio correct for your car's brakes, weight and suspension.

Quote:
- Power steering bracket choices OE or Aftermarket, small block does not fit big block
- Power steering lines, SB are not long enough
BBC is a truck engine. It is much bigger than a SBC. Every other GM car engine, and all other car makes use the same size engine for a small block and a big block.

Because the engine is physically bigger it requires it's own brackets (there are four that fit and three that don't). Despite what I said above you can not use SBC accessory drives on a big block. I think in terms of accessories as going with the engine when I buy it (complete top to bottom and running at point of sale).

I generally use what was on the rebuildable engine core when I buy it out of the junk yard. The only exception to this is V-belts. V-belts are dead. The manufactures no longer routinely make them. They are made only in small batches once a year or once every two years, or not at all as not all belts are being made now. Most of the V-belts sold on line are fractional horsepower belts made for lawn mowers not cars that rev four to five times higher than a lawn mower engine can rev.

I use serpentine belts (two not one) to drive everything. This is because you can not throw a serpentine belt the way you can a V-belt. They also transmit more power without slipping. The more ribs in the belt the more power they will transmit. I use aftermarket billet seven rib aluminum pulleys from March or Zoops along with their brackets to mount them.

There are power steering brackets made for a BBC with a short water pump. (1965-'68)
There are power steering brackets made for a BBC with a long water pump. (1969-'84)
There are power steering brackets made for a BBC with a long water pump and one or two serpentine belts. standard rotation pumps and two serpentine belts where used from mid 1984-'86, starting in 1987 all water pumps are reverse rotation and have one serpentine belts with two or more idler pulleys.

Quote:
- Making sure you have the correct driveshaft, crossmember, and flexplate, when coverting transmissions
This has nothing to do with the engine, it depends upon your choice of transmission. All GM engines use the same transmission dimensions, Chevy is different from BOP trannies, but share some of the overall dimensions but could differ even within the same family of transmissions. The transmission is mounted in the same place (relative to the back of engine), and uses drive shafts that match the transmission (spline count and length).

The transmissions themselves all have different transmission mounting points (distance from the face of the bell back to the mount), and different overall lengths (from bell mouth to rear seal). They also may have different input shaft lengths and spline counts as well as different out put lengths and spline counts depending upon torque rating.

If you used what the factory used originally then parts are available used or as a reproduction part to fit and install it easily. If you don't then you have to buy or make cross-members and adapters to fit the transmission.

You can use a 153 tooth flywheel (or flexplate) on a big block and the engine will crank up and run just as well as it will with a 168 tooth flywheel. The engine could care less what happens to the energy it makes; or what is bolted to the crankshaft flange. If you don't mind your ten and a half inch clutch slipping and burning up you can use it behind the more powerful big block. The engineers designed the eleven inch clutch (and flexplate) to fit behind a BBC to offer more friction area to prevent the clutch slipping.

Quote:
- Engine mount towers and engine mounts. Tall and skinny or short and wide.
Tall and skinny or short and wide is due to a safety recall caused by Ralph Nader to address the problem of broken motor mounts.

The 265 SBC used four mounting points. Two on the front and two attached to the cast iron bell housing that also was where the starter bolted up. Starting in 1958 with the introduction of the X-frame cars the motor mount was bolted to the side of the block and GM made their own three speed (Saginaw) that had a transmission mount on the back of the tranny.

In 1968 the federal courts decided that GM had to change the motor mount to prevent engine torque from pulling them apart. This had been done since the 348 was introduced and all engines that made more than 300 horsepower from the factory required an interlocking engine mount (the Corvette retained the four point engine and tranny mount up until 1965 when the BBC caused them to go to a three point mount). The 275 horse 327 in a heavy car (or if little Johnny borrowed mom's car) had enough torque to break the motor mount, and often did prompting the law suit.

The tall and narrow mount was used from 1958 through 1968. After the recall (and everyone having a five ton steel cable torque strap wrapped around the upper control arm mount) Chevy went to short and wide motor mounts on 1969 through 1972. The two mounts do not interchange, even though you can only buy the correct tall and narrow through a reproduction reseller as the corner auto parts store only sells short and wide motor mounts which as I said won't fit a 1958-'68 car.

Big Dave
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post #10 of 11 (permalink) Old 03-19-2020, 02:31 PM
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Dave I think you took my post out of context. I'm not really sure why you are quoting what I ran into...

I was just stating what "I" have ran into with my build and maybe what Doug had ran into with in his build.

Not really the history of engine mounts regulations nor the preference of transmissions.

Merely what one's personal preference is within their build details.

Ted
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post #11 of 11 (permalink) Old 03-19-2020, 03:31 PM
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OK I understand now. I though Doug was looking for this info.

Big Dave
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