Motor Mounts on '86 Truck/Sub/Blazer

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Do the V8 mounts line up with a straight six or is it a different mount altogether? If they needed to be changed, would cutting and/or welding be required?
~jp
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wrote:

Interesting question but since a 86 still was powered by a old SB the frame mounts should allow either to bolt in. The difference will be in the mount design that bolt to engine, not where they attach to frame. ----------------- TheSnoMan.com
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Well cool... I'm assuming that'd be for a 250ci or smaller, as from what I've read the passenger-side mount for a 292ci sits a little further back...?
I wish I could find a junked truck that had a 292ci around here. It'd be easier to grab parts off that.
~jp
SnoMan wrote:

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Where the pads mount on the frame crossmember are different for the L-6 and the V-8. The holes for the different locations should already be there
Whitelightning
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Gotcha... good to know, thanks...
~jp
Whitelightning wrote:

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Back in the late 60's when I did a 6cyl to V8 swap on a Plymouth, I wound up have to cut old frame mounts out and then cut mounts out of one in a bone yard and then weld them in. GM was always a lot easier to work with on engine swaps and usually the six uses same location on frame. Where it can get confussing though is that GM mounts the engine differently in some models in a 2wd vs 4wd truck. (in the past anyway) I have not done a GM 6 to v8 swap for a very long time but I do not recall any problems with swap bolting it up. I would not mind finding and restoring a old 67 to 72 GM truck with a 6 cyl if it was in good shape and it had not lived in a rusty area.They are few and far between today.
wrote:

----------------- TheSnoMan.com
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Well, I found a running 250 w/ 3 speed from a truck for a good price, but I don't want or need the 3 speed. That, and I'd much rather hold out for a 292. From what I understand the passenger-side mount is further back on the frame when using a 292.
As long as it's a bolt-on affair, I'm cool with that. I want to keep my 700R4 (for now) and I figure most of the other stuff (smog equipment, radiator, etc...) is reusable. Although I'll probably spend a few bucks here and there hunting down accessory brackets for the A/C compressor and all--I doubt the small-block V8 brackets will work.
LMC Truck lists the part numbers for the motor mounts as being the same for both 6cyl and V8 applications...so would I just need to relocate the existing ones to the other location?
When I get this going, I'll probably use a 4-barrel manifold from Clifford topped with a V6 TBI unit and ECM. Apparently, GM Mexico made a TBI intake for the 'sixes' but I've only heard of it, and not actually seen it. Luckily Holley makes a TBI to squarebore adapter.
~jp
SnoMan wrote:

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wrote:

A few months ago I looked at a restored 67 chevy 2wd with a 292 in it that was for sale. It was pretty clean and really basically all metal too with very little body work. I do not recall motor mounts being different on that one. I knew a guy that ran 3 small 2 bbl's on a 250 once in early 70's (one for each port) and they throttled at same time. It was on a engine that was really built up and had a radical cam and headers too. That thing ran really well but had no classic low end 6cyl torque at all. I do not recall who made the intake. ----------------- TheSnoMan.com
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suited for higher-RPM driving. That amount of flow would be less than ideal for low-end torque.
The throttle bracket does have me a bit concerned. Mainly because I'll have to find the proper way to interface the tranny's TV cable with it. The carb/throttle body will be mounted sideways, so some more sophisticated linkage will be required.
~jp
SnoMan wrote:

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wrote:

This is true but the cam did not help matters either and it would not of had much torque even with a 1bbl and a stock intake on it. It did run strong enough that it took a warmed up 327 or 350 to beat it. Other than the unusual exhaust note, it was hard to tell it was a six performance wise. It pulled right up the about 7000 RPM (valve float) ----------------- TheSnoMan.com
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Whitelightning wrote:

Yep, The 250 mounts will be bolted to the front set of holes and the Small block uses the rear set of holes. The 292 uses a mix. The 292 mounts are set up with the left mount in the forward spot and the right side in the back spot. For the TV cable you should be able to use a universal mount for it. Use a cable for the throttle as well. Most of the mounting brackets from a 250 will fit a 292. The belts will be different though for anything using a mount on the head.
--
Steve W.
Near Cooperstown, New York
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Yep, back in the '70's I had to do a overnight motor swap in my roach coach yanking a 292 out and dropping in a 250 to get it on the road back to work. Pass mounts are in different location but everything else swapped over OK. If your gonna swap motors don't even waste your time on a 292. Just go V8. I've had them all.
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Repairman wrote:

Thanks for that... it's nice that Chevy made things so modular.

I'm actually going the opposite direction with this one. Started with the stock 305, then put in a crate 350. That mistake cost a lot, but taught me a lot, and I've come to realize that HP is not what I need in my application--I need low-end torque. My driving style rarely exceeds 2000rpm in my Blazer (my Saab is a different story ;-) ) and I consistently hear about the pulling power of the 6cyl motors, especially the 292.
While the selection is limited as compared to V8s, there are quite a few performance parts available for the 'sixes'. However, most will not apply in my situation, as they are for building upper RPM HP, and are by nature, not so great for low-end torque.
I'm tired of screwing with that 350. It's not "faulty", it's just not right for a truck, and I don't feel like changing the cam, replacing the heads to bump up compression, etc... I'm going to sell it and start from scratch with a clean 292. I found someone who sells them re-man'd for about a grand plus shipping and core (close to what I paid for the 350).
It'll satisfy my undying need to tinker. With a little forethought, it should make good low-end torque, and hopefully it'll restore my MPG to what it was before the 305 went belly-up. A lot of folks suggested a big-block, but if I wanted my K5 to be like every other built 4x4 on the road, I wouldn't be doing this ;-)
Thanks,
~jp
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wrote:

I have driven a lot of 292 in the past that were per emission era and it is a very strong motor stock. 73 and later 292's are a lot weaker and should not be used as to what a 292 can do. those engine can pull strongly from less than 1000 RPM which most V8's will not do unless they are a LOT bigger than a 350. . ----------------- TheSnoMan.com
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Precisely my reasoning behind this swap... Still, I'm interested in what can be done to increase the low-speed output even further than stock. There seems to be a lack of material on the subject. Everybody sells something to help you go faster...
~jp
SnoMan wrote:

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wrote:

Simple, supercharge it. ----------------- TheSnoMan.com
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That *is* an option, or turbocharging...
~jp
SnoMan wrote:

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wrote:

A turbo will not give you quick crisp low RPM torque. To change gears for a moment, consider this, GM made some V6's for truck in 60 through early 70's that made it into GMC P/U's in 60's (never seen one in a Chevy stock) There was a 305, a 351, 401 and a 478. They all appeared to share the same basic block. Never seen bigger than a 351 in a P/U but a 401 or 478 should fit too. The bigger ones made some serious torque at low RPM with the 478 making over 440 ft lbs at 1400 RPM. I drove a GMC tandum dump truck a few times with a 478 and it was a stump puller right off a idle. They are all low compression too so supercharging them would be viable and with a 6 PSI or so bost 600 to 700 FT lbs of torque would be quite possible with a 401 or 478 with 450 to 500 or more possible with a 351. These engines had massive cranks and bearings and were built for severe duty. They will not rev up much though because they were not designed for that. The link below has specs on some of these old forgotten motors.
http://forum.snoman.com/viewtopic.php?t ----------------- TheSnoMan.com
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Yeah, true, but... What I'm wanting to do is have great low-end torque, right off idle. Keep in mind, this wouldn't be used for racing or anything--more like quickly accelerating on the street for when I'm fighting the idiots in Atlanta traffic, and great pulling power without having to re-gear the diffs (which would raise RPM and hurt MPG). With my 31" tires, the 3.08 seemed a bit high, and the 3.73's seemed good, although I'm curious how a 3.42 would do. Apparently 3.42 was common with the L6 engines.
Since building an engine to do one thing well makes it suffer in another area, I'd focus all my attention on making the most power on the low-end as possible, naturally aspirated. In my mind, where a turbo would be useful would be in increasing the usefulness of the engine above 2000rpm. I stick to that number because at 80mph in top gear, I'm turning less than 2000rpm.
~jp
SnoMan wrote:

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wrote:

Al the more reason to maybe consider a 351 V6. It would shame a 292 in low speed torque and they will pull down to 500 RPM's or less too. They were purely a truck motor from day one. Personally I would stay away from too tall a gears if you want best traction too. ----------------- TheSnoMan.com
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