mid 80's 250ci engine mounts vs. 305 mounts

[R72K5]

ok mid 80s pickups(2wd) with 250ci, were the rubber engine mounts same exact thing as 305 ones or ?

need to know

for sure

not guess

the engine mounts in the '84 c-10 are letting the '76 350 engine i put in it rock side to side real bad but they are not broken or rotted, the truck was originally a 250ci truck,

if you wedge a railroad bar inbetween exhaust manifold and top of frame rail then engine sits perfectly still nice like its supposed to

engine runs perfectly smooth


something funny is going on ?


thanks

 

[tarussell]

The BBC motor mounts have a different durometer rating than the SBC ones do , so maybe the 2WD 250 mounts are even softer than the SBC mounts ????? Just a thought .

Tom

 

[R72K5]

humm this is pretty interesting

ok i looked on napa and compared numbers and they are identical numbers

however that doesnt mean that napa just grouped them to same mount, as replacement that is

doesnt mean gm originally used different/softer mounts for 250

dunno why they would when im pretty sure 250 have more bottom torque output than the v8 of that year(305)

so i am really confused here


does anyone know what the real deal is with mounts, in 84 that is


remember no 350 in early mid 80s in 1/2 ton 2wd's anyways, not available from factory



thanks

 

[diesel4me]

Mine are the same

When I recently installed an 86 305 in my 79 C10 in place of the 250 six,I used the same pads,just had to move them to the other set of holes in the frame(and those 3 bolts suck to get at!)--another thing that can make the engine sit low in the front is the steel brackets that bolt to the block--they make at least 2 versions of them,one has the hole for the thru bolt 1 inch closer to the block than the other style,usually used in passenger cars--the other style has the hole 1 inch farther away from the block,usually theese are used in trucks(but I have seen both,but who knows if GM put them in??)--using the car ones will make the motor tilt down in front,I had a truck that someone swapped a motor in with it that way,didnt seem to bother anything--but having it right is always better...my 86 motor was from a van (G10) and the plates on the block were evidenly van only,they offset the motor to one side,and had weird angles to the mounts,no way they'ed work in a pickup--lukily I had a pair from a 73 chevelle 307 I put in my van that had the right hole location,and the motor sits nice and level(guess it pays to be a pack rat sometimes!)...

 

[R72K5]

yep there are different metal mount bracket cups yes everyone knows that, ive come across this quite a few times, most recently with the van 350 i put in the 82 trans am, those block mounted brackets were big time different cross bolt hole location/distance, also gm sometimes used triangle 1/8" plate steel spacer between block and block mounted bracket, it seems to be extremely random too, some vehicles and years used the spacers and some didnt, and some only used one on one side and none on other, its a motherf*cker trying to get the long horizontal cross bolt through engine mount and bracket hole when you dont have right block bracket and/or are or are not using the 1/8" triangle spacer when you should or shouldnt be, it just plain sucks big time alot of times trying to figure out what exactly to use to get the freaking horizontal bolt hole to line up all way across thropugh the mount

if you dont know what im talking about then you have little experience with 60s 70s 80s gm RWD vehicles then, cars trucks vans


im still trying to find answer about the rubber mounts themselves,

i guess no one knows or has come across this 250 vs sbc mount thing


not the brackets!

thanks anyway

 

[diesel4me]

I know what you are talking about!!

I know you asked about the motor MOUNTS,not the steel brackets,just thought I'd mention them in case you didnt know...

As far as I know,there are only 2 types of motor mount pads,(aftermarket anyway)one has 3 bolts,the other uses 4 bolts,and both have the same rubber cushion and location,maybe GM OEM ones have different specs,but as far as Doan,Anchor,and other "parts store" brands,they only have those 2 choices AFAIK...

The 86 305 I put in my truck had 1 of those triangle plates on the drivers side only--I never saw one before,and I've swapped dozens of chevy motors--I didnt use it in my truck,the bolts went right in with no sweat once I bolted the motor mounts into the V8 set of holes in the crossmember..Have no idea why its used at all....

 

[R72K5]

i dont know either, another one of those GM assembly secrets we will never find out about and i dont knwo why not ?



thanks