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Good day guys,

Have a '75 w/250 6 cyl w/automatic that will be getting a new 350/385 crate motor and street/strip TH350 trans installed.

What troubles should I look out for in advance and what has been you'se guys' experiance as I go thru the process.

It'll help with the $$$$ planning to have a few mention what they went thru in similar upgrades.

Thanks Guys!!!
 

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all it really needs is new frame mounts and motor mounts.
that should already have a th350 in it. and if so just rebuild it with v8 rebuild kit.
even the radiator should be ok.
 

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You will need different brackets for the engine side of the mounts. The frame side are the same for both 6 and 8. The engine side brackets are still available new from GM. They are Nova specific even though they look similiar to other Chevy models.
The GM part number for the engine brackets is 10213125 and available from GM parts direct for $21.05 each + shipping or can be purchased at any Chevy dealer for around $35 - $40 each. Left and right are the same. If you decide to go with poly motor mounts the metal shell is not included. You have to drill out the spot welds and change the insert.



Two different size radiators were used in 4th gen Novas. One was the standard cool and the other was HD colling. The HD could be ordered seperatly but was included on all factory AC cars. The core support is different for each type but the small radiator model can be modified for the bigger radiator.

Standard cool core support



HD cooling core support



Here is a photo of where it needs to be cut and the holes the end pice needs to be moved to.

 

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Driveshaft will work and the 75 should already have an 8.5" rear end under it. You will need a shroud if your car didn't have one. The 75 non AC car only had a guard plate. If your car had AC or HD cool the 6 cylinder shroud and fan may work. I have not checked to see if the fan is at the same height for 6 and 8. The hole in the shroud is smaller so you must also use the smaller 6 cyl clutch fan. I can post photos of the differences between the 6 cyl shroud and fan and the V8 parts if you want to see them.
 

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Discussion Starter #5
Yes please, if you don't mind postin' them.
 

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Not too many problems came up with my swap. The smalls ones that came up where the basic ones like forgetting to buy a certian part at the parts store lol. The frame mounts were the same on my 79 nova. If you want you could go to the yard and get a set of motor mounts from a mids 80's truck and it will bolt right up( isay trucks cuz they are plenyiful in the yards lol. The only thing to watch for is the power steering......if you are reusing the one from the 6 it will work fine BUT you need the brackets from a sbc otherwise it will not bolt up. Other than that everything else is cake walk. The swap wouldnt even take you a day with some help. Oh you need the throtle and kickdown bracket for the carb. But one from your local parts store and it will have ajustable hook ups to ease everything. I used the stock one from my truck and it works for the throtle but not the kickdown, it sits too far forward, otherwise the throtle cable hooks right up.

Hey phillip thanks for posting those pics I didnt know the difference before on the supports!! Now I know that I will have to cut mine. ........... I was wondering why the v8 rad looked a bit bigger than the support:rolleyes:.... LOL
 

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If you want you could go to the yard and get a set of motor mounts from a mids 80's truck and it will bolt right up(
No they won't. I had a set and tried them. If you use them with the truck frame mount they will physically bolt the engine in but the motor will set to high and throw off drive shaft angles.
Look at the photo I posted. The tabs sticking out the side of the frame mount have to set into the recess on either side of the engine bracket where the thru bolt installs. The bolt only retains the mount, the tabs support the weight of the engine. This is where the mounts and brackets are most different. If mount and bracket are mismatched the thru bolt will not go in. Then if you measure the height of the bracket from where it bolts to the block to the center of the thru hole you will again find it different. Interesting that the poly mounts I bought from energy suspension fit a little different than the stock ones. If using poly make sure they are installed in the metal housing properly or the mount will not work. I think they were designed to fit more than one application.

I'll post some photos of the shrouds later, I just now got home from work.
 

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Philip is 100% right. I have swapped probably in the neighbor hood of 8 SBC's into 4th gens, and they have to be X-body specific engine side motor mounts in order for them to work. A G-Body mount will work with some grinding, but that isn't always the best when putting more power into a car that was never intended for it and is 30+years old. Save yourself the hassle!!
 

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Mike here are the photos. I did this in the dark, but this weekend I may be able to take better shots. The position of the fans seem to be the same for 6 and 8 but the 8 uses a deeper shroud. I have never seen a std cool V8 so I am assuming that a clutch fan was not used like on the 6 cyl models.

Here are the three top plates used, top is a six cylinder standard cool, it may also be used with the V8 standard cool.
Middle is the six with AC or HD cooling
Bottom is the V8 with AC or HD.



These are the six (right) and V8 (left) clutch fans. Std cool did not get a clutch fan, just the standard 4 blade fixed on the six, not sure on V8 std. Six clutch fan is 17.25" in dia, V8 is 18.5".



The V8 shroud.



six cylinder shroud



And here is a shot of the 6 cyl HD cool installed. This car had no AC but was ordered with the HD cooling option.

 

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u should have no problem with the swap i did it in my 78 nova custom that came with a 250 inline six and all i had to do was use the brackets that bolt to the motor every thing else was the same and my car was a non ac car as
well the only problem u run it to is the leaf springs will need to be replaced. because after i did my swap i drove it for like 2 months and then broke the passenger side leaf spring due to to much power. my motor is a 355 small block with 460 hp at the crank. i shoud have thought about that before i drove it. oh well.
 

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well mine is a 77 inline6 turbo350 tranny
l swaped to
79 small block 400turbo OUT OF A TRUCK

My problems
DriveShaft Length
Tranny Mount "longer tranny cut stock mount off"
drive motor mount Too wide??? metal tabs tobe cut off so it drops in
Fan shroud Heigh and Coverage
My HEI dizzy is 2mm from the firewall "great thing l changed cap/roter befor motor went in"
and exhaust manifolds had to go on After motor went in and its a PITA to get them on and then off again without dammagin anything

other then that hell the 4MPG is gona Suck Thank God its only 1mile to school and back again
 

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Discussion Starter #12
Thanks for all the posts guys!
Hoping to make it easier on the garage doing the install by having info and parts needed on hand when the day comes in about a month.

Geesh fella's, I haven't had a real car since I sold my '67 plymouth sport satellite (big block) so we could buy our house. That was 17+ years ago.
It's going to feel good to get behind the wheel of a SB Chevy powered machine again. That's where my heart lies.
That 385 horse crate motor should rock!
 

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well mine is a 77 inline6 turbo350 tranny
l swaped to
79 small block 400turbo OUT OF A TRUCK


other then that hell the 4MPG is gona Suck Thank God its only 1mile to school and back again
You realize that all SBC's are the same physical size, right? A 283 is gonna measure the same outside dimensions as your 400 that is "out of a truck". Have you cut the tabs off yet to get the motor to sit in? And why are you only getting 4mpg? Or is that what the truck with that motor was getting? You should have no problems getting 13+...easy. Not intending to sound condescending, but just trying to clarify a few things.
 

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should l have cut the tabs off on the passenger side also????? cause the passenger side just droped in but the drive side l ground the tabs off so itd Drop in but it cant.

and yes 4mpg l'm using a rochester 4MV 4bbl carb l know for a fact the vacume lines Arnt correct my main secondarry's Dont open And also my idle arm vac coontroller Dosnt actuate and my motor idels barly at 1,500Rpm

l wish l had a camera and video camera still so l could show what problems l'm having.
m bigest headach so far is just finding an Drive shaft to fit everything things elss thats wrong is just little finky crap
 

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Did you get the engine mounts in then? Or are you running it without the engine bolted down? As for the carb issues, it sounds like you should set your timing (with the vac advance disconnected and the vacuum source plugged) first (I'd start at 8 or 9 degrees initial). Then, make sure the carb is sealing to the manifold. Do that by spraying a carb cleaner all around the base of the carb while it is running. If the engine changes RPM at all, you have a vacuum leak. I'd also hook up my vacuum advance from the distributor to full a full vacuum source. Set your idle down to 800, and get a vacuum guage. Set the idle screws for max vacuum, and then readjust your idle speed. Of course there is much much more to it than that, but that's a basic start. Oh yeah...do all of your adjustments to the car with the vacuum advance disconnected...that should be your source of vacuum for the guage. I'm at work so this post may be a tad out of order...sorry!

As for your driveshaft, you can use your factory one as a donor (especially if you swap out to an 8.5" rear end...which I'd reccomend). You can get a conversion U-joint to adapt the TH400's larger and finer spline count (use a TH 400 slip yoke), and join it to your driveshaft, make measurements, and get yours cut and balanced.

One question though...how are you getting MPG numbers without the driveshaft hooked up??:confused::eek:

Kent
 

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hey kent

tried again tonight drive mount Wont go in the tranny side of the motor mount is sitting on the frame. l'm just gona half *** it put the motor on a tilt like it was a slap a bolt thrrew the Top on the mount where orginaly when it was sitting on the clips it worked.

Gona make a tranny mount in cupple days when l have some spair time then get my driveshaft made so l can drive it 2blocks away and haev my friend weld up my mount and bumper.


how l know l's getting 4mpg l jimmi riged a clunk of steel between my 2 shafts so it could rolll up/down the drive so l can access the garage to work on the dodge
 

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if your getting 4 mpg something is seriously wrong even big blocks built get like 11 mpg
 

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yeah my built 355 is getting coles to 11 mpg and its almost fully built so there is no way in hell that ur car is running right
u might want to look in to that and i cant understand how u can not get the motor to just dropin and bolt up i think u might have the wrong motor mounts because i have done to inline 6 to v8 swaps and both of them just droped right in. ohya one swap was on a 77 the other was on a 78. both were 2 doors.
 
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