Author Topic: 86 C10 262 to 305 swap  (Read 342 times)

Offline Ccm

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86 C10 262 to 305 swap
« on: August 08, 2017, 05:57:03 PM »
Getting ready to start a project with my son..New to the world of engine swaps..but going for it...Does anyone know if the motor mounts for a 262 will work for the 305?

Online zieg85

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Re: 86 C10 262 to 305 swap
« Reply #1 on: August 08, 2017, 06:29:27 PM »
No the engine frame perches need to be changed as well.  Stewart has done this recently, he will chime in, give it time, I just PM'd him...
« Last Edit: August 08, 2017, 06:35:17 PM by zieg85 »
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Ccm

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Re: 86 C10 262 to 305 swap
« Reply #2 on: August 08, 2017, 08:28:26 PM »
👌

Offline Stewart G Griffin

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Re: 86 C10 262 to 305 swap
« Reply #3 on: August 09, 2017, 07:43:03 AM »
This is right up my alley and i love this engine and swap.  i'll get back to you in much more detail probably this weekend.

Until then, the short answer is that the mounts are different than the v-6 (they are reversed, although looking at it, the mounts SHOULD interchange, but let's do it properly for now with the v-8 mounts).   Also, the frame perches are not the same.   They may look the same, but on closer inspection, they are not.   Photobucket has cancelled all my pictures, so again i'll try to provide examples this weekend.

Also, can i ask why you are going 305?   Do you plan eventually going 350 and larger?

Offline Ccm

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Re: 86 C10 262 to 305 swap
« Reply #4 on: August 09, 2017, 11:29:15 AM »
No..picked up the truck last October, engine has unknown amount of miles and was getting ready to do a tune up on it when I found this 305, also a 1986, but has 30,000 original mile on it..have video of the engine (305 ) running and supposedly it was only used on sunny days, and the owner took his driving test when he was 16 in it...they dropped a 350 bb it their truck. So wasn't really in the market for a upgrade but the price was right

Offline Stewart G Griffin

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Re: 86 C10 262 to 305 swap
« Reply #5 on: August 12, 2017, 08:13:07 AM »
First i want to ascertain why you want to swap and what are your goals?

Because an 86 305 only makes 5lbs more torque and 5hp more than the v-6.   It is also 125 pounds heavier.  Also, based on my and other's tests, the 305 will be down about 2 mpg from the v-6 on average.

So, you're getting very little performance advantage switching to a 305.  i don't think you'd be able to tell the difference.   Ok, the 305 does not vibrate at idle like the 6, but other than that....

i am not trying to talk you out of this because there are advantages:

If you switch to the 305, it's easy if you want to later switch to 350, 383 etc.   BTW a 350 is NOT a big block.  If you DID later want to switch to big block you MIGHT be also be able to use the small block v-8 mounts......?

Offline Ccm

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Re: 86 C10 262 to 305 swap
« Reply #6 on: August 14, 2017, 08:54:19 AM »
Well this truck is going to be my sons first vehicle..soo..I really don't want it to be a rocket..just a dependable, good sound truck...the engine in it is shot..

Offline Stewart G Griffin

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Re: 86 C10 262 to 305 swap
« Reply #7 on: August 14, 2017, 09:44:07 PM »
And you think switching to v-8 would make it easy to be dependable----because of the universalness and popularity of the small block?

That's not a bad strategy, if that is your strategy?  Fair enough.

i also want you keep in mind the possibility of getting a replacement 4.3---at about the same price as a crate v-8.  (at least keep your v-6 parts in case you wanted to switch back someday).

Here we have a v-6 frame perch, driver's side:


Next, a v-8 frame perch, driver's side:


Notice with the 6 perch, it is set back further towards the cab (because the v-6 is about 4.5" inches shorter than a v-8).  AND if you look closely, one of the mounting points of the v-6 perch is on the SIDE of the framerail.   Whereas the 8 perch bolts to the top of the frame rail and the other two bolts, bolt to the crossmember.  (there are two bolts, one is hidden in the picture, but it's there)

So, you need v-8 frame perches and i'm thinking junkyard or maybe someone here can help.  i would give you mine, but i want to keep mine just in case i want to switch back to 8 (not likely, but you never know).

Also, you will need to get v-8 specific mounts;  i'm 99% sure that v-6 and v-8 mounts SHOULD interchange and SHOULD WORK,  and if you look closely, i think you'll agree. But let's do it properly for now. (We can experiment later)
These do not have to be junkyard sourced.  There are plenty of good aftermarket sources for that.

Offline Ccm

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Re: 86 C10 262 to 305 swap
« Reply #8 on: August 17, 2017, 08:08:44 PM »
Wow stew..I am digging this!! Great info..getting ready to pick up starter so I can do a compression test on the new motor..Had a question....This 305 has a 168 tooth flywheel..what would be the advantage of the 168 tooth FW over the 154 tooth? Is there any?...already figured out I need the offset starter for the 168, just wondered why it was on this motor?...

Offline Stewart G Griffin

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Re: 86 C10 262 to 305 swap
« Reply #9 on: August 17, 2017, 10:29:05 PM »
The 4.3's starter should work on the 305.

i'm not sure of any disadvantage or advantage of the 168 tooth flexplate vs. the 153 tooth.  Perhaps someone can chime in?

Also, both the 4.3 and 305 should both use the 168 flexplate and should interchange.

Offline Stewart G Griffin

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Re: 86 C10 262 to 305 swap
« Reply #10 on: August 20, 2017, 10:50:46 AM »
Actually, if i could bug you for a sec.

Can you check for me if the starter on the 4.3 has a front brace like this:
http://nastyz28.com/threads/wtb-starter-brace.272580/