90 K1500 V6 to V8 swap. MOUNTS

volfan72

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Hey Guys,

I could not find this information anywhere in a manner that I trusted. I’m replacing my 4.3 V6 for a 383 V8.
Do I need frame mounts and motor mounts? Can the frame mounts be purchased new? What is needed just in regards to the motor being mounted?
 

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Schurkey

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Do I need frame mounts and motor mounts?
I have not done this. I expect you need both the rubber cushions (bolted to the frame) and the steel brackets (bolted to the engine) from a 305 or 350--I think they're the same. GM used steel brackets mounted to the engine on many different body styles--passenger cars, trucks, vans, etc. Be sure to get the ones for your application, 'cause they're NOT all the same.

As I recall, the frame mounts bolt to different holes in the frame than the V6 mounts.

Can the frame mounts be purchased new?
Effectively, no. They're available in the aftermarket, but they're hateful cheap Chinese junk using thin steel shells and questionable rubber.

There are Polyurethane cushion inserts available from at least two suppliers; I couldn't make the Poly cushions fit into the original steel shells. The design is totally different from OEM, yet both suppliers product looks the same.

The OEM mounts were discontinued years ago. OEM mounts are Treasure-Yard Only at this point.

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Energy Suspension Poly mount cushion vs. OEM rubber. Poly is wider, and has steel reinforcements at the wrong angle.
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What is needed just in regards to the motor being mounted?
I would not expect the V-6 mounts to work on a Small-Block, even if you move them to the proper holes in the frame.

Good luck getting the rubber cushions. When it was me in 2018, I put my 300,000-mile worn-out rubber mounts back in, and returned the Chinese crap to the store, and the Poly inserts to Summit. I was not happy about that.
 
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volfan72

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THANK YOU SO MUCH !!! This is great information! What are your thoughts on a GM part?
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Schurkey

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The first one is a mount bracket, that bolts to the engine. They're essentially non-wearing parts in normal use.

You can pay $30 new for one side, or $10 for both sides at a Treasure Yard. I vote for the Treasure Yard, as long as you assure that you get the correct items, not something from a 1980s car or some other application.

I can't tell what the second item is. Doesn't look like the other engine bracket, or the frame cushions. If it's a frame cushion, I thought they were discontinued from GM. So I can't help you with that.
 

Nick_R_23

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Just grab the block mounts from someone parting out an 88-98 truck or the junkyard. Don’t forget the “spacers” that fit between the engine block and mounts. These provided a place for the bracing/torque rods to bolt to that also bolted to the transmission’s inspection cover. Even if these rods are not used, the spacers need to be in place or you will have a hell of a time lining the engine up with the rubber frame mounts.

As far as the rubber frame mounts, just get parts store replacements. Napa offers an HD version with thicker metal, I’m sure the others do as well. While not OEM, I have yet to have a set fail.
 

7thdarkangel

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All i did on my v6 to v8 swap was change the frame side mounts. Dont forget the v8 fan shroud as well.
 

volfan72

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Thanks to everyone that has responded.
Does this illustration help?
I have identified part #2 as something that GM still offers (15719194) as well as #1 GM part number (15529450) and available aftermarket.
It appears that #7, #3, and #8 are no longer available.

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Schurkey

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All i did on my v6 to v8 swap was change the frame side mounts. Dont forget the v8 fan shroud as well.
The Voice of Experience speaks, and should be respected.

I totally forgot about the spacers and the trans support rods. But if they're re-usable along with the engine brackets, all you need is the frame mounts (rubber cushions) and as said--the fan shroud. Amazon has the GM part number frame cushions for about $60. (The Amazon description says they're made in China.) I'd have sworn those were discontinued.

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Note that one review from Canada says this mount is for 2wd not 4wd. He had to cut this mount apart to salvage the rubber insert, modify the rubber insert, and put it into his original steel clamshell. [Later edit] I can confirm that the steel housing is not the same as the ones for my '88 K1500.[/Later edit]


I assume the wire harness is the same. Perhaps you need to extend some wires.

As far as the rubber frame mounts, just get parts store replacements. Napa offers an HD version with thicker metal, I’m sure the others do as well.
News to me. No-one offered me a "HD version" when I was looking.

Do you have a part number for the HD version? I checked www.napaonline.com and they're only listing one mount for my '88 K1500 5.7L; and it's the same thin-steel-shell Chinese junk as I got from O'Reillys.
 
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volfan72

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Sorry…just to clarify. Regarding the engine mounting I just need 2 of these?
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Schurkey

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Sorry…just to clarify. Regarding the engine mounting I just need 2 of these?
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NO. The 4wd rubber cushion clamshell assembly is different. The steel is formed differently.

See how the attachment to the frame is different--one side has a step up, where the mount you've pictured is flat on the bottom.

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