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Discussion Starter · #1 ·
Gents,

I have seen that people in the past have had the same problem. I have replaced a skanky leaky SBC305 for a stroked SBC 383.
When I was installing the motor last May, I noticed that the motor mounts were not lining up (clamshell with polyurethane mounts).
After reading threads in different forums (incomplete stories that are never followed up, you guys know that feeling), decided to proceed, partially slot the existing frame holes to get to line up the motor.
I have been successful, got to install the remaining components of the car.
Little did I know of the following:

1) Having the engine 3/4 high throws off the drive line angles.

2) I put engine into drive and there’s a mechanical noise (one clunk).

3) I’m not sure if I will be able to compensate for the change of angle out of transmission. I will shim the transmission and try to reduce the angle diffferwnce between transmission-driveshaft and driveshaft-rearend. (I have double adjustables).

This is my horror story, I will continue and see if I can overcome these fitup issues.

Now that being said, if I hit a dead end, can anyone tell why in the bloody hell the f*ck f*ck clamshell motor mounts are not lining up? Is there a discernible part number for the left and right motor mount? Believe me, I have done some researching but there is no clarification.

I appreciate all the help gentlemen. Go Chevy!!!!!
 

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Just going off the picture. Could the urethane insert be installed upside down? There are two different ways it can go.
And only one way works. It's kind of hard to see the driver's side, because the red mark of the circle is right over the metal tabs that stick out of the end of the urethane insert. From what I can tell, the passenger side looks to be correct.

Hopefully this makes sense, it's kind of hard for me to explain...
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Did the part of the engine mount that bolts to the block come off of the 305? They don't look like the factory original. Measure from the center of the bolt hole on the bracket to the mounting surface of the block. For a G body mount, you want 2.5." I suspect you are going to find those are the 3" mounts.
 

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As mentioned, are there shorted clam shell you can use, or can the ones you have be modified by drilling new holes and trimming some extra material away?

Just some ciphering on the computer below.
3/4" over approximately 10' is .358°


Rectangle Parallel Font Diagram Logo
 
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Discussion Starter · #5 ·
Did the part of the engine mount that bolts to the block come off of the 305? They don't look like the factory original. Measure from the center of the bolt hole on the bracket to the mounting surface of the block. For a G body mount, you want 2.5." I suspect you are going to find those are the 3" mounts.
thanks for the info. I will take those dimensions because I truly think this could have been the problem all along. Btw, inMay I had bought new brackets and they sent me the same garbage, same fit up issues etc...

I’ll keep you posted brother. Any tips where to get some of these brackets?I’m afraid to buy from EBay because people are posting stuff without knowing at a 100%. Afraid there isn’t many other options…
 

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Discussion Starter · #6 ·
As mentioned, are there shorted clam shell you can use, or can the ones you have be modified by drilling new holes and trimming some extra material away?

Just some ciphering on the computer below.
3/4" over approximately 10' is .358°


View attachment 622062
I ended up slotting the chasis holes to get the mounts in. I have lost 3/4” clearance with the hood, and yea, angle changes about 0.8 degrees. From engine mount to transmission support I guesstimate is about 4’ (48”). But you are right, it’s not a huge driveline angle change.

you know anything about difference engine mount bracket sizes?

thx!!
 

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Discussion Starter · #8 ·
Did the part of the engine mount that bolts to the block come off of the 305? They don't look like the factory original. Measure from the center of the bolt hole on the bracket to the mounting surface of the block. For a G body mount, you want 2.5." I suspect you are going to find those are the 3" mounts.
I suspect that the original mount was gone long time ago since this car when I got it, the previous owner had put a new motor in. It would love to have the mount. It’s hard to track these part numbers.

Any tips where to get an OEM mount?
 

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This right here is why I like biscuit(bolt through) mounts so much. Easily adjust the angle with shims(washers) .

I have had this happen twice with clamshell mounts. With all the "this fits" sites out it is really easy to get the wrong stuff. Before you break out the welder grab your junk or now junk mount and a tape measure. If I was doing this on the weekend and could not wait I would break out the grinder and welder to modify those. But most sites like Rock Auto or Amazon can get you the correct parts within 3 days.

Amazon offers free (often next day) shipping with prime or on orders over $25. But you need to double check your part numbers cross refrencing and such to make sure your getting the correct part.

Rock auto has been great to me as far as the correct fitting parts at great prices. But shipping can get expensive and it often takes 3 to 10 days at the not so cheap cheapest rate.

Polyurethane is overrated in my book especially for motor mounts. Some good quality rubber mounts will probally last you 30k to 60k, 3 to 5 years, or 2 clutch changes. Rubber being cheaper and stock your going to find replacments easier and be less reluctant to replace those mounts as a preventive measure.
 

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Discussion Starter · #10 ·
Just going off the picture. Could the urethane insert be installed upside down? There are two different ways it can go.
And only one way works. It's kind of hard to see the driver's side, because the red mark of the circle is right over the metal tabs that stick out of the end of the urethane insert. From what I can tell, the passenger side looks to be correct.

Hopefully this makes sense, it's kind of hard for me to explain...
Urethane ridges facing up, else clamps he’ll won’t be able to close and installation would be been triple sloppy! I though the same at the beginning, urethane brackets facing correct way as well.

what a pain in the ass. This monster really bit me
 

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thanks for the info. I will take those dimensions because I truly think this could have been the problem all along. Btw, inMay I had bought new brackets and they sent me the same garbage, same fit up issues etc...

I’ll keep you posted brother. Any tips where to get some of these brackets?I’m afraid to buy from EBay because people are posting stuff without knowing at a 100%. Afraid there isn’t many other options…
Buy this kit

Loosen the bolts on the frame mounts to allow for fine adjustment. Just enough to be able to move them a little if you need to. Problem solved.

Frankly, you can skip the measurement part. I know what they are by the picture.
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Glove Snout Personal protective equipment Helmet Auto part


The factory mount is on the left. What you have is on the right. It shows the 1/2" difference pretty well.
 

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This might sound strange. But compare and swap sides. Drivers to the passenger side etc. Unless you pull both out of the boxes at the same time you may not notice one is slightly diffrent or offset from the other. Its easy to do on some "universal" fit parts that have elongated holes. If one is not a diffrent part then the other or you were suspisto get a left and right using the mounts to offset the engine and actually recieved two lefts.
 

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I'll relate a quick story just in case it may apply...

Friend got a 350 and swapped it into his 4.3L V6 equipped stick shift 88 0r 90 Chevy truck. He got past everything except the second engine mount through bolt just would not go in and it ended up sitting for months.

One day it occurred to me that the frame's engine crossmember might be sagging. So I jacked it up in the center and the bolt went right in. Because the distance between holes changes with frame sag. Which is fairly normal especially with lots of years and miles done.
 

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The polyurethane mount that bolts to the frame could be left to right specific. The ones I've seen like that are pretty clearly labeled. You could measure to make sure the hole for the bolt is centered between the distance between the bolts. Sometimes left to right, front to back is a bit of trial and error. How much did you slot the holes on the chassis and which ones?

The metal brackets to the engine are just plain wrong. The correct ones will restore the height of the engine to factory spec. The Rock Auto option Cerial mentioned may be the cheaper way to go. Any G body 305 stock replacements will do. The factory G body brackets are the same left to right.

The overall offset of the drivetrain on all G body cars is built in at 1/2" to the passenger side. You won't notice it in the engine cradle, the driveshaft will ride in the middle of the tunnel. If you measure the pinion offset at the rear end, you'll find that same 1/2". I don't know if they were clearing room for the steering shaft or sneaking a little extra room in the driver side or making something universal across different platforms. Who knows. Just know that it is that way if you find it in your measurements.

The "clunk" going into drive can be a number of or combination of things. If that mount is not attached it would clunk. U-joints are a common culprit. Excessive backlash in a rear end or shift linkage hitting custom exhaust. Sometimes the way a transmission is built can cause harsh engagement into drive or reverse and even though it's a highly unlikely cause, there is literally a part in there called an "anti-clunk spring" depending on the transmission.

Get the engine mounted correctly and we can go from there. I bought the G body Malibu in my garage in 1989. I have touched every nut, bolt and washer on that car AT LEAST twice. Most of the folks on this forum know a lot more than I do and, as a group, we can sort out any of this "horror story" stuff.
 

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View attachment 622065

The factory mount is on the left. What you have is on the right. It shows the 1/2" difference pretty well.
This^^^^

Passenger car cup on the left....Truck/Van cup on the right.

Trying to use truck cups in a car chassis doesn't work. you get the very fit-up issue the OP is having.

This usually happens in a g-body swap from a Buick/Olds engine or V-6 engine to a SBC or BBC.
Guy gets his swap SBC from a truck and never realizes the cups are different, or buys used cups and gets the tall ones not knowing there is a difference.
 

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In my previous post I forgot to add another somewhat common "clunker" area after a fresh install. It's pretty easy to forget to really tighten the flex plate to torque converter bolts when washers/shims are going in and out for torque converter spacing and checking starter depth. The same can be said for just snugging up the flex plate to crank bolts while on the engine stand and forgetting to torque them. I have missed those things more than once. Tight enough not to clatter, but not tight enough to avoid movement within the holes.
 

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Discussion Starter · #19 ·
This^^^^

Passenger car cup on the left....Truck/Van cup on the right.

Trying to use truck cups in a car chassis doesn't work. you get the very fit-up issue the OP is having.

This usually happens in a g-body swap from a Buick/Olds engine or V-6 engine to a SBC or BBC.
Guy gets his swap SBC from a truck and never realizes the cups are different, or buys used cups and gets the tall ones not knowing there is a difference.
It seems this car had the incorrect cups all along since I bought it back 8 years ago for 5k.

here’s a pic!

hopefully she’ll be running soon!
 

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Discussion Starter · #20 ·
In my previous post I forgot to add another somewhat common "clunker" area after a fresh install. It's pretty easy to forget to really tighten the flex plate to torque converter bolts when washers/shims are going in and out for torque converter spacing and checking starter depth. The same can be said for just snugging up the flex plate to crank bolts while on the engine stand and forgetting to torque them. I have missed those things more than once. Tight enough not to clatter, but not tight enough to avoid movement within the holes.
thanks for the tips! And yes, I did check and verify the float between torque converter and flexplate, 1/8”, right on the money!

I did torque them bolts and tomorrow, I will try to get the rearend readjusted a bit more, let’s see how it goes!

thanks to everyone for the clarifications! It means a lot!
 
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