6 cyl to V8 conversion troubles?

[mikeorwan]

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!!!

[KEITH'S75CUSTOM]

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.

[Philip]

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.

http://i80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/engine/motormounts.jpg

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

http://i80.photobucket.com/albums/j199/64elcamino/Aluminum%20radiator/stdcoolcoresupport.jpg

HD cooling core support

http://i80.photobucket.com/albums/j199/64elcamino/Aluminum%20radiator/P7050007.jpg

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

http://i80.photobucket.com/albums/j199/64elcamino/Aluminum%20radiator/modification.jpg

[Philip]

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.

[mikeorwan]

Yes please, if you don't mind postin' them.

[79novaSS4]

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

[Philip]

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.

[mrkent]

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!!

[Philip]

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.

http://i80.photobucket.com/albums/j199/64elcamino/Nova%20stuff/Novatopplate.jpg

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".

http://i80.photobucket.com/albums/j199/64elcamino/Nova%20stuff/Novafans.jpg

The V8 shroud.

http://i80.photobucket.com/albums/j199/64elcamino/Nova%20stuff/NovashroudV8.jpg

six cylinder shroud

http://i80.photobucket.com/albums/j199/64elcamino/Nova%20stuff/NovashroudI6.jpg

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.

http://i80.photobucket.com/albums/j199/64elcamino/Nova%20stuff/4drshroud.jpg

[78novafan]

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.

[Nova_Power4]

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

[mikeorwan]

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!

[mrkent]

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.

[Nova_Power4]

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

[mrkent]

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

[Nova_Power4]

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

[KEITH'S75CUSTOM]

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

[78novafan]

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.

[KEITH'S75CUSTOM]

both were 2 doors.

2 or 4 door they are the same exact front end

[78novafan]

true but arnt the drive shafts dif on the 4 door.

[Green Dragon]

well, my 2 cents, based on limited 4th gen swaps ( most we owned were V8 from GM, so.....

I do know on our 69, the swap from 6 to Big Block was 95% bolt-in, with exception of fabricated throttle linkage and the new TH400 crossmember.

on our 79 ( original 250 inline 6, Auto ( not sure if TH350 or 200metric, my 77 and 76 both had metrics with 305 V8's * sic * ) , anyways we swapped to a V8 from a 74 NOVA and it dropped right in, so guessing the 74 (3rd gen) mounts on the block are same or close enough ?
I'd never heard about the 'ear/ tab' length differences until now, so sounds like lucky coincedence we avoided the problems :rolleyes:
we used the 74's TH350 as well as drive shaft and 10 bolt 8.5" rear end ( now been swapped to a 12 bolt, but still same driveshaft fitment) .
ALso cut the rad support as noted and are running a custom recored ( 4 core of stock end tanks ) "hd width' rad, no cooling issues.

I do know 7.5" rear ends vs 8.5" have differing length driveshafts, unsure if 6 vs V8 has differing ( again, since we swapped rear ends, might've dodges that bullet inadvertently as well ).

more news on the 79 later, maybe.. it;s being torn down to provide donor parts to our 63SS * sic * , but will reemerge ( fingers crossed) down the road mintubbed and 496 powered :)

~ AL

[Philip]

six and V8 engines set in the car at the same mount location. The transmissions that came with the car do also and use the same driveshaft for 3 and 4 speed manual and the th350 and th200 auto transmissions.
The th400 is longer, was never offered in the 4th gens and will require a shorter shaft. There are 2 driveshaft lengths and it was determined by rear differential. The 7.5" has a longer shaft then the 8.5". The difference is 1.5" and could cause problems.

http://i80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/driveshaftlength.jpg

[Philip]

That 385 horse crate motor should rock!

Yes it will. I had a ZZ4 in a 64 Malibu SS and it was awesome. The ZZ4 only has 355 horse, the 385 should put a smile on your face :D

[mrkent]

As for the motor mounts not bolting in, it's because they're out of a truck. We've been saying all along that the mounts are Nova specific.

Nova_power4 said:
"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"



I'd put money on if you got the motor mounts (both of them) with the numbers that have been supplied, it's fall right into place. Even if you have to go to GM to get them, it's better than having an unsafely mounted engine. Good luck!

[KEITH'S75CUSTOM]

true but arnt the drive shafts dif on the 4 door.

no they are the same 4 doors and 2 doors are the exact same size and only 50 pounds different in weight.

look at a 2 door and a 4door the extra door is just cut into the quarter panel
and the front door is longer on the 2 door. but if you look
the back door is right under the window the quarters are the same. so a 2 door quarter skin on a two door makes a quarter skin and door skin on a 4 door:D

[KEITH'S75CUSTOM]

http://i96.photobucket.com/albums/l193/kennanke/IMG013.jpg


http://i96.photobucket.com/albums/l193/kennanke/hgiikf.jpg


see pretty much the same

the 4 door is actually more proportional
and a better looking back window. imo the two door quarter window is just to big if they put the same sail on the two door thats on the 4 door it would look better
jmo though

[Nova_Power4]

AAHHHH it just clued into me now what u'v been saying all along.........NOVA MOTOR BRACKETS is what l need for the reason there slightly Less tall of a bracket?

there goes 4days wondering W.T.H you guys were talking about.

as for my driveshaft yes my Stock th350 driveshaft is TOO LONG by 1/2inch and the wrong yoke also of course.
my mesurment is 53"inches center cap to center cap.

l hope by monday my exhaust manifolds are finished so l can bolt some exhaust up.............Stock manifolds l also have an option for a set of Sanderson ceramic shorties for $200

[captrich]

Guys - I just wanted to say thanks for all of the good info. I just finished swapping my in line 6 in my 77 4 door for a 350 small block which came out of a G series 1987 chevy van. I found enough Junk yard parts and some new stuff to convert this to a carburated engine with vbelts. It runs great but after awhile she heats up to around 200 degrees and does not go back down. I have a new 185 degree thermastat, I cut the front support as shown in the photo and installed a fan shroud I got off of a newer chevy in the bone yard. This seemed to help but it still runs up to 200 eventually. I wrapped the headders and this cut down some of the heat under the hood but after looking at my radiator, It looks like a single row HD cooling for a six. I bought this new for my six about a year ago. If I upgrade to a 3 row hd for the v-8, they come with a heater return line. My heater hoses are connected to the intake and the waterpump. I have the top heater hose routed to the water pump. Any suggestions on if a 3 row radiator may keep this motor a bit cooler and where to route the heater hoses? I got the motor from a neighbor who wanted it out of his garage and after I ran it and checked compression , I put new gaskets on the heads , pan, valve covers, new timeing cover etc.. and put in new lifters. It painted up nice and looks and runs great. I cant quite trust it more than across town until I get the cooling situation conquered so any thoughts are appreciated. PS I have a 5 bladed cluth fan off of a junk yard motor. I'll post the long story in the story section when I get time. I have been putzing with this in my spare time for the past 8 months and its my 1st attempt at anything like this. So far so good except for my painting and body work skills - looks good at night though! :)

[Philip]

A bigger radiator will cool better. The temp is slowly reaching 200 because the it takes awhile for the cooling system to max out. A 3 row core will allow more water to be cooled and keep the temperature closer to your theromstat setting. The extra heater hose nipple in the radiator can just be capped. Most come with a rubber cap that installs with a hose clamp. Make sure your junk yard fan is turning the proper irection, the ones from a serentine set up run the opposite direction of the V belt set up.

[ALLT4]

FWIW, I found a stock 3 row, metal tank radiator at Pep Boys of all places for $125.00 Also came with a return line bung that was threaded and included a plug if you didn't need it. Screwed the plug in, filed it flat and forgot it was there.

I didn't think $125.00 was too bad of a price. Worth a try anyway, I like stock looking but carry a big inch. It works perfectly to cool my 383, 180 rock solid, well actually like 185 w/ a 180 T-stat. Sometimes I wonder why smaller motors than mine take so much radiator to keep the engine cool. They have to be masking a cooling/tuning issue with those 15 row 3 feet thick aluminum jobs. Well, I guess race parts make a race car :rolleyes:

Funny enough, my 77 w/ AC had a two row in it, I'm not sure if it was the original or a replacement. Maybe they just stuck in whatever they had in the good old days.

[captrich]

Thanks Guys - I will shop around for a 3 row Radiator before I take any long rides. I was redoing the gasket on the headder collector as I was hearing an exhaust leak and after fixing that I realized another leak was comeing from under the hood. I tightened the headder bolts - A couple were hard to reach and were a bit loose. I had seen some smokeing and figured it was the high heat paint on the headder wraps still burning off but it was an exhaust leak. Made a big difference in operating temp. Runs between 170 and 185 steady now - at least idleing for 25 minutes with the hood closed. That hot exhaust may have been contributing to the heat under the hood. I checked my fan and it is blowing the proper direction. I'll try posting a picture of some of the swap photos I took.
http://www.fishmeister.com/images/carpics.jpg

[ALLT4]

From your pictures there that looks like a reverse rotation water pump. If you converted it to pulleys I hope you replaced the pump with a normal rotation pump. Otherwise your pump is going backwards

[captrich]

The water pump was bought new as a replacement part for what what listed as a 1977 nova 5.7 liter v-8. The pump that was originally on the 87 engine was different in that it did not have the added bosses for the waterpump and power steering brackets. Both old and new pumps had the discharge holes on the same side of the pump. I'll check to see if there is a rotation arrow cast into the aftermarket pump casting like there is on a Marine pump. I did not think of checking the cooling fins to see if they pointed the same way but I do remember when I started it on the engine stand that some spray shot out of the discharge hole so I am hopeing its right. I guess I assumed all of the pumps turned the same way except on older Marine applications where they had counter rotation on one motor. The fan was off of a diesel junkyard motor. The hole spaceing matched the holes on the replacement pump flange and it blows air towards the motor so I figured it was correct. Here's a basic question, should the pump pull coolant from the motor and feed it back to the bottom hole on the radiator or does it do the opposite? A flow diagram would be nice but they did not have one in the chiltons book I was useing.

[ALLT4]

If you bought a pump for a 77 Nova you're fine. The flow goes from the bottom of the radiator into the pump, then the motor and out of the top radiator hose back into the radiator.

Sounds like you got everything right, what was the problem again? :turn:

[captrich]

It was the engine temp after about 20 minutes of city driveing on a hot day. I believe I have a single row heavey duty 6 cylinder radiator where I need a 3 row v-8 radiator. The one I bought last year was about 27 inches by 17 by 1.5 inches. Aluminum core and plastic tank. It's the same length and width as the v-8 radiator but has less capacity with the single core.