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Discussion Starter · #21 ·
I didnt see anything about drive shafts? I just bought a 454 with a turbo 400 and plan on putting it in my 73 nova. I know i will need a different crossmember and i think a shorter drive shaft? I just got it so i not measured anything.
TH400 is a bigger version of the TH350 (which is a 4/5th scale model of the TH400). It is longer which requires a shorter drive shaft. You also have to change the output yoke because the out put shaft of a TH400 is bigger and stronger (higher spline count).

Big Dave
 

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Discussion Starter · #23 ·
This is a common question and the answer lies in how correct you want your obvious up grade to be (the factory never put a BBC in a '73 Nova so your not going to be able to slide it by the white glove inspection judges at a car show as original).

In 1967 and '68 the factory was fat and happy and operated under the premise that what is good for GM was good for the country. Unfortunately we have lawyers like Ralph Nadir who was trying to get rich by suing the pants off GM for safety issues. (you know those guys on the evening TV who are always asking if you have ever taken or used this product to call us now because we want 2/3rds of the proceeds of a class action lawsuit so we can retire to a third world country). Anyway in 1968 GM was the first company in commercial history to loose a class action court case that resulted in a nation wide recall of a product (in this case it was every Chevrolet V-8 made from 1958 to 1968. The reason the motor mounts failed in service allowing the engine to roll over to the passenger side and jam the throttle open because they used to use a solid steel rod to open the throttle before 1969.

In 1969 GM issued a new design on all motor mounts that will not fit the earlier frame stands. This was to force you to buy new motor mounts of the recently designed interlocking style. (They were not a new design or even a new product. Prior to 1969 all engines over 300 horsepower used different frame stands and motor mounts to keep the vulcanized rubber biscuits used on six cylinders and small base engine V-8's from separating).

Because of this there are four different motor mounts for all Chevy V-8's. Two mounts that fit 1958-'68 cars divided into regular rubber biscuit and interlocking on the high horse engines; and another pair of motor mounts that fit 1969-'72 cars (in 1973 the factory introduced the final solution "clam Shell" motor mount that is still used today on all engines regardless of horse power.

These four motor mounts have different heights and widths and the bolt centerline hole for the grade eight engine mount bolt is different on all four. Because of this many people run into parts mismatch where the motor will not fit (B73nova Moroso: makes three different sized Chevy solid motor mounts (three different part numbers) to fit from 1958 to 1972 and each motor mount has different widths between the tangs, distance from the base to the bolt hole and the tang length is different on each one to match the frame stands the factory used over the years).

The factory is all about interchangeability but there are different parts for different applications (based upon GVW among others factors such as horsepower, even the speed rating of the original equipment tire affects the parts you have on the car: whether you are aware of it or not). Motor mounts are one of these black holes that information falls into and never gets out of (are you paying attention Dr Hawking?)

To answer your question (if I put this up front would you have read this monolog?) the 1969 kit is what you want. The 1967-'68 kit uses the very rare odd-ball size motor mount that is not sold at any corner auto parts store like the 1969 version is.

Big Dave
 

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Discussion Starter · #25 ·
I look at it this way. I'm not getting any younger; and if I don't share what I know while I can still remember it, it will all be lost when I go. I didn't spend as much time in a dealership as you did, (only about two to three hours a day while waiting for my friend to get off work as he was the lead mechanic on the service line), but it was productive spent roaming the entire dealership from the parts stacks to the dumpster (a lot of old catalogs got tossed every year). My full time job was as an industrial engineer making the parts that went into if not Chevrolet parts bins some bodies as I was involved in heavy industry for 17 years before it all folded shop and was sent overseas. I designed and maintained dies and punches, castings (sand and investment) weldments(working with shears brakes and punch presses) and stampings (deep drawn to a depth of 14”), even making my own fasteners from bar stock with automated screw machines to make rockets, transformers, dishwashers, and electrical cabinets and enclosures for heavy power distribution. So I have played with every machine tool, and made every form of part imaginable over a career that spanned less than thirty years (I made a mistake and allowed myself to get promoted into management).

I want to share what I have learned over the decades; I learned a lot of it the hard way but I am a degreed mechanical engineer and I am willing to teach others what I can remember. By the way my misspent youth hanging around the dealership for my friend to get off was so we could go to the shop we shared and build race cars all night until we got up and started over again the next day. It wasn’t all textbook learn’en.

Big Dave
 

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Thanks Big Dave for the info! Yes i would have read it if you put the answer up top! That info is helpful to know for future projects. I'm young so I pick at guys brains at work who restore cars! (I learn better by doing than that text book stuff)
 

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Hello, Wow Dave, you really know you stuff!:thumbsup: My Nova is a 68 with a 454 from a 74? Motor mounts are in great shape with very low miles. However the factory rubber mounts still allow the engine to torque under heavy load. Last owner fixed this by using a cable bolted from the frame around the upper control arm shaft to a bolt on the head. Hard launch and the cable snapped the end off by the head, engine rocked and stuck at wide open like you said. Turned off with the key and nothing was damaged other than the end of the cable was snapped off. Have saw many big blocks with the engine chained or cabled and even the solid plate bolted across the front of the engine. Would solid motor mounts be better than the chain or cable or would it be better to have solid mounts and a cable? Would I need the Moroso solid mouns for the 68? Would it be smart to convert it to a cable throtle? If so is, What would need to be switched? Thanks, Dennis.
 

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Discussion Starter · #29 ·
That cable was all that was left of the original GM recall kit.

What you are talking about is a torque limiter. I do not recommend solid motor mounts for the street not because of the engine vibrations they transfer into the car (on a poorly balanced motor it will rattle your teeth), but because of the stress it places upon your aluminum transmission case. A better solution is a plastic motor AND a plastic transmission mount.

http://www.energysuspensionparts.com/proddetail.asp?prod=3.1129

Whatever style of mount system you use, you must use the same type mount at all attachment points. If you go with solid Moroso motor mounts then buy the solid steel tranny mount (Moroso part number 62600); and be sure to use a lot of red Loctite because of the vibration. If you use a plastic interlocking motor mount use the transmission mount made of plastic as well or you will crack the case of the tranny with time.

As to chains and cables. There are two issues. First it can not be mounted to an aluminum head. A single bolt will transmit enough force to pull the aluminum head apart. If you have aluminum heads you will need a steel plate to attach it to the head (such as the A/C front mounting plate on the big block that bolts to the front of the head and part of the block to distribute the load). Second is where you attach the other end. It will be under stress and by definition it will be bending (stress is synonymous with deflection in engineering). So if you are attaching it to your front suspension expect your steering to change when the cable/chain pulls on it.

Race cars all use a front and mid mounting plate to attach the motor solidly to the frame. Your car doesn't have a frame (a sub frame yeas but that gets bolted to sheet metal unless you have sub frame connectors and a roll cage to make a frame). As such I do not recommend a mid mount front mount system for the street.

Big Dave
 

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My son bought a '73 SS 350 Nova for his son (my grandson) and we are building a '69 BBC (long water pump) to put in it. Big Dave's list is lengthy (and discouraging). We will be using a built 700R4 tranny, stock BBC Nova exhaust manifolds, new Nova BBC frame mounts and oil pan.

The Nova has factory A/C and the evaporator box clears the SBC valve cover by about 2 inches. With the new frame mounts, will the BBC valve cover clear the A/C evaporator box??
 

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Discussion Starter · #31 ·
A BBC is 2 inches taller (with stock low rise manifolds), and wider and 2.3 inches longer than a SBC (this assumes it is the standard height block, a tall deck truck block makes it nearly 3.4 inches wider than a small block).

You could order A/C with a big block back in 1968-'70 (just not with the 375 horse solid lifter 396 version of it), so I know it can be done with factory parts that are no longer available from your Chevy parts counter. The BBC has different heater cores and heater core covers than a small block uses to move the hose outlets away from those big heads rammed up against the fire wall.

I suspect that the A/C air handler box is unique to the big block as well, and you know it won't be a high demand part for the reproduction companies to mold; but they are making parts for the first gen Camaro and most of the firewall is the same. So see if that part can be modified to fit.

Big Dave
 

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Thank you very much for your quick reply, Dave.

FYI, I had the block rebuilt by Lamar Walden of Atlanta (home of the world's fastest W-Block). I pick it up today.

The engine is (now) a 30 over 396 with rectangular port heads and 17 cc crowned pistons for a streetable 9 to 1 CR. On the surface, the part numbers look like it's a 375, but milder cam and CR will drop the peformance considerably. I have a totally outfitted '67 427 435HP Tri-power Corvette engine (actual 351 block casting) that I want to put in my living room under a glass table top (lol). On this engine, I installed aluminum open chambered heads, so I have the original cast iron closed chamber tri-power heads which I'm using on the 396. (These are the same heads as used on the 375-396 engines).

On the Nova, the A/C air box has a straight vertical side (against the engine) so that makes engine extraction less complicated. We'll probably pull off the front end so we have straight in access to the engine bay. We are going to have to do a "fitting" to see what the clearances are (or are not) to determine what surgery needs to be conducted.

As an aside, Lamar said that the new motor oils do not support flat tappet cams and suggests to all who have older flat tappet engines to use a zinc additive (available through Summit Racing). Lamar said he gets a large number of customers each month with wiped cams.

I really appreciate your valued input, Dave . . . Thanks! Jack
 

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Great post but i have to ask.... Why? Why does the big block need to be moved to the right? I had a small block and am switching to a big block the trans cross member that i have is aftermarket and does not claim to be big block or small block so why can i have it centered?
 

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If not moved to the right there are clearance issues with the steering gear.
Not sure on the AC box shape being different between BB and sb cars, but it may be possible.

Starting in 75 all the engines were moved to the right and the AC box had a recessed area in it. Not completely sure why the change was made but it may have been to clear the steering shaft with the front steer set up.

AC box change



Cross member change to an offset mounting position



Frame change, the yellow marks show the difference between the frame rail edge and the engine cross member position.


 

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Discussion Starter · #35 · (Edited)
There has been a question raise to the frame stand for a 1968-'70 Nova BBC frame stand so I wrote this reply:

If you need the dimensions of the big block engine stands there are two different sets because of the 1968 motor mount recall. The 1968 frame stand dimensions are :

Driver's side: 2- 9/16" tall; distance from engine mount hole to centerline of outer 2 mounting bolts- 2-3/16" (this is the same for both frame stands).
Pass side is 2- 3/4" tall.

http://www.rickscamaros.com/camaro-e...1967-1968.html

Rick's EP-6 is concours correct and is dimensionally accurate copy of the OEM part. Rick's EP-199 is a cheaper knock off made off shore and they make no claims as to dimensions; only that it should allow a motor to bolt up.

In 1969 the frame stands changed to represent the tall and narrow interlocking motor mount then in use for the first time (NDP sells a rubber reproduction under part number TRU 31-2308HD that is made by Westar their part # is EM-2285). The dimensions are:

Driver's side: 2-1/2" tall; distance from engine mount hole to centerline of outer 2 mounting bolts- 1-3/4" (this is the same for both frame stands).
Pass side is 2" tall.

The shorter frame mount should be on the passenger side. The taller frame mount is on the driver's side. The original Chevy part numbers (discontinued part) where 3950113 (left), 3950114(right). You may be able to find a replacement in the reproduction houses such as Rick's Camaro that offers an installation kit that includes BBC frame stands, alternator brackets for BBC and a Long Water pump, and a BBC power steering pump mounting brackets:

http://www.rickscamaros.com/camaro-e...lock-1969.html.

If you want just the 1969-'70 motor mount frame stands then Rick's EP-7 is concours correct and is dimensionally accurate copy of the 1969 OEM part. Rick's EP-200 is the cheaper knock off made off shore and they make no claims as to dimensions; only that it should allow a motor to bolt up.

In 1973 the factory went to a clam shell motor mount which consists of a solid steel motor mount (similar to the Moroso solid steel mount) the difference being the factory solid steel motor mount bolted to a captured on the frame rubber mount. The captured rubber mount can be replaced with a polyurethane mount, but it requires that you remove the rubber mounts outer shell (you will need a spot weld cutter) and reuse it. Philip wrote a great post covering this issue. This is good info; but unfortunately it is irrelevant. If you are putting a BBC into a 1973-'74 rear steer Nova you will still need to use a 1968 or a 1969-'70 motor mount and matching frame stand to offset the motor away from the steering gear box.

The actual shift is a half inch, but because the motor is tilted up as well as shifted to one side the distance as measured from the centerline of the hood is an inch to the carburetor air cleaner bolt. The shift is obvious when you look at the transmission mount location on the BBC cross-member which is of course different from the SBC cross-member in your car now.


The BBC cross-member is on the bottom.

Big Dave
 

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Discussion Starter · #36 ·
The factory frame stands that are no longer sold by Chevrolet moved the motor a half inch to the passenger side and raised on the drivers side (so there is a left and right part that has to be installed correctly). To identify the two parts you need only place them side by side and you will see one of them is taller (the drivers side). If you compare the SBC stands to the BBC you will note that the motor mount holes do not line up with each other. Neither BBC stand has the hole in the same place though both SBC stands are duplicate of each other that have the holes at the same height.



Restoration parts are of questionable quality. They are not all bad but you have to examine the part closely to see that they match the factory dimensions. Most are formed out of a thinner gage metal as thicker steel is harder to bend into the correct shape and requires not only a very powerful punch press but a complex (expensive) progressive die that has to be well maintained by a tool and die maker. Chevrolet had thousands of highly skilled machinists and press operators in their foundry and more punch press machines than they could fit under the roof of the plant at any one time. The same can not be said for the country of origin.



Team Camaro has talked this question to death and they will refer you to David Pozzi's home page

http://www.pozziracing.com/

to read all there is to know about your sub frame (the same sub-frame as was used under the first generation Camaro was also used beneath the Nova from 1968-'74). He talks about the steering geometry problems and lays out all of the fixes, the frame stands and everything else such as quick ratio steering boxes, brakes suspension parts and everything that bolts onto to the sub-frame.

Here is some information I have collected that is related to the frame stands.

The first thing is that the motor mounts are not all the same there are three different sizes that Chevy has used from 1958-'72. Here are the dimensions according to Moroso:



Energy Suspension sells the two different high performance interlocking variants that Chevy has used over this time frame:



Here is a set of BBC frame stands installed correctly and you can see the difference in the positioning of the motor mount bolt hole.



Big Dave
 

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1969 and 1970 cooling fan is a fixed blade steel 5 blade fan identified by a W stamping and there is no fan spacer, it bolts directly on to the pulley surface. They are very rare and go for around $750 on ebay or original. Repro sells for around $250 I think and they are a nice repro. There is a mistake in the assembly manual that shows a 1 inch spacer. It is wrong. As far as I know it is not the 7772 fan for 68 but it is a clutch fan. I will check my fan collection to see the number. Chevelle used the 7772 fan I believe. I could be mistaken but the 7772 part number does not ring a bell for Nova in 68.
 

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thanks dave for the parts list greatly apre. so it looks like i can use the alt just change the brackets but not the power steering pump,again thanks everyone for all your info
now with the steering bar i gotta try and find headers
 

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Re: SBC to BBC conversion

Lots of great info. I made the swap last year on my 69 that originally came with a small block 350. Pulled the mouse out and dropped the rat in, a 454 big block. Everything went smooth as silk. I used the stock small block frame mounts, and also used moroso solid motor mounts for a small block. Didn't have to change out the heater box, car doesn't have ac as well. Bought cheap flowtech headers from summit racing. I'm running a turbo 350 tranny with a B&M holeshot 3000 converter. Ford 9" with 3.89 gears. Puts a grin on my face every time I drive it. This engine has a massive torque curve.
were you able to use your power steering pump and alt from your small block with differant brackets
 

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Discussion Starter · #40 ·
Alternators interchange and will bolt up with the correct brackets (must fit the water pump). Power steering reservoir on the power steering pumps are different. If you used a SBC pump on a BBC the hoses discharges right into the head of the BBC. The BBC pump reservoir has hoses that enter lower on the pump and are bent at ninety degrees.

Big Dave
 
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