Author Topic: anyone running the gm 350/260 crate motor  (Read 4074 times)

Offline cstiles

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anyone running the gm 350/260 crate motor
« on: November 26, 2015, 03:54:57 PM »
Want opinions on that motor I know it's more like 195 hp and comes from mexico. i wanna yank the 327 out of the 81 short bed i just got and make it a good daily. Just wondering how people like em power wise. Mine is just a short bed 2wd .would have headers and and maybe a e fan and a new dual plane intake & 600 edelbrock
« Last Edit: November 27, 2015, 12:29:30 PM by bd »

Offline Stewart G Griffin

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Re: anyone running the gm 350/260 crate motor
« Reply #1 on: November 26, 2015, 04:24:40 PM »
i had one until the motor hydrauliced.  i don't think it was the engine---i think either the p.o. overheated it or i may have installed one of the heads wrong---some of the bolts go into the water jacket and i may have forgot to put sealant on them.   i took one of the heads off for an unrelated reason.

Anyways with gas so cheap nowadays and it forcasted to stay cheap for a long while i wouldn't hesitate to use one again.

i was able to turn a 16.8 sec 1/4 mile time.  This was with a 2.56 rear diff gear and stock, cheap off brand WesternAuto tires.  Stock intake and quadrajet, no headers.

i think it's a good engine.


Offline Stewart G Griffin

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Re: anyone running the gm 350/260 crate motor
« Reply #2 on: November 26, 2015, 04:30:39 PM »
P.S.
i actually spun the right rear tire a little when making the run.

Offline cstiles

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Re: anyone running the gm 350/260 crate motor
« Reply #3 on: November 26, 2015, 05:03:32 PM »
Nice .I'm use to crap gas mileage .this truck a probably get better with the new motor than the 4x4 tahoe with mudders I had

Offline fitz

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Re: anyone running the gm 350/260 crate motor
« Reply #4 on: November 27, 2015, 12:10:03 PM »
Rich Weyand figured out how to make these motors run good.  I'm sure he will chime in here soon.  He's done his homework to set this motor up right.

Offline rich weyand

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Re: anyone running the gm 350/260 crate motor
« Reply #5 on: November 27, 2015, 07:30:46 PM »
Right out of the box, swap the cam.  You won't need new lifters, but you want the Comp Cams springs if you are going with the 12-235-2 or 12-230-2.  Stock springs are fine foe the 12-300-4.

================

A word on cams for you.

12-230-2 will work fine. With dual-plane and long-tube headers, 290hp/420lbft. Lift is .432/.444. RPM range is 600-4600.

12-235-2 will wind a bit tighter. With dual-plane and long-tube headers, 290hp/415lbft. Lift is .421/.451. RPM range is 1000-5200.

12-300-4 is what I am running. With dual-plane and long-tube headers, 275hp/420lbft. Lift is .390/.390. RPM range is 600-4600.

So all of these are in the same ball park. 12-230-2 has the same hp and torque as the 12-235-2, but will run out of pull at 4600 rpm. 12-235-2 will match that, and pull to 5200, which is a better fit with stock shift points. 12-300-4 gives up some hp on top, matches the torque in the bottom, but keeps the stock .390/.390 lift, which is easier on the valve train (and cam lobes). That's why I picked the 12-300-4, for engine lifetime sake, since they are so similar in performance.

All three cams will work with stock lifters and springs. Note: NEW stock lifters and springs.

For the 12-230-2 and 12-300-4, you should replace one weight in the TH350 governor with the next bigger weight to bring the stock shift points down 500 RPM. If it's a stick (sorry, I don't remember and it's a lot of posts back!), then you will time the shifts yourself, so no worries.

The cam that's in there is an old cam design. In an ideal world, valves would be open or shut, with no in-between. That would maximize flow while giving you an earlier intake closing for more dynamic compression and a later exhaust opening for longer pressure on the exhaust stroke. Unfortunately, we can't do that -- cams are ramped. You can tell how long the ramps are by subtracting the .050 duration from the advertised duration.

The cam that's in there has ramps in the mid- 70-degree range. All three Comp Cams have modern computer-aided designs with ramps in the mid- 40-degree range. That's 30 degrees less dead space in both the intake and exhaust cycles. The difference that makes in the ability to tune the other cam parameters cannot be overstated.

I think you will be very happy with whichever of those three cams you pick. Not a bad choice among them, really.

=====================

Subtract the .050 duration from the advertised duration for that Summit cam. It has 74 degrees of ramps, so it's an old grind. Not necessarily a "bad" cam, but just much less capable than a modern design.

A note about lope. Everybody thinks they want it, but what it means is that the engine doesn't want to run at 700 rpm. So how much torque do you think you're going to get at 1000, or 1500? An engine that's going to generate torque at low rpm is going to LIKE running at low rpm, so it will idle really smooth.

The way they get launches at the drag strips out of engines with a lot of lope is to run high-rpm lockup torque converters so they can wind the engine up to where the hp is. High-rpm torque converters are great for the drags, but a PITA to drive around on the street, and they're hard on transmissions.
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline mcintyrederek

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Re: anyone running the gm 350/260 crate motor
« Reply #6 on: December 01, 2015, 08:29:58 PM »
I'm running the 350 Goodwrench in my '86 C10 with no problems, driving a TH400 to a 2.73.  Works great.  I have no idea what type of HP numbers I'm running and really don't care.  It pulls a dual axle trailer fine with a modest load.  I'm running a stock iron intake with an Edelbrock 1405 (600 CFM I think).  With the stock cam that comes with the 350 crate engine, it almost seems like the jets may be a tad too big.  Opening the secondaries will definitely give it a heck of a run, but it almost seems a tad too rich.  A better cam as suggested would probably do a world of good, especially if you want more performance.

I'm going to buy another one for another project car.  For the price, including delivery, you can't beat it. 

Mack.
1986 C-10 Silverado 350 CI 260 HP, Edelbrock 1405, TH400, 2.73's - rescued from the junkyard - Farm Truck, daily driver!

Offline 76LongBox

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Re: anyone running the gm 350/260 crate motor
« Reply #7 on: December 02, 2015, 03:09:05 PM »
I am running one of these in my '76 paired with a TCI StreetRodder TH350 transmission.  I had never done anything as significant as change an engine/trans before, but thanks to a buddy of mine helping with the actual swap, and then thanks to people on this site (especialy Rich), I have it running like a champ now.

I'm running an Edelbrock intake and carb, but everything is pretty well stock - even have factory A/C (converted several years ago to R-134a).  I don't do a lot of pulling or hauling (have another truck that does that kind of work), but wouldn't hesitate to do so if I needed to.

Like Mack, I have no idea what the HP #'s are, but it certainly works for me as is.

Offline cstiles

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Re: anyone running the gm 350/260 crate motor
« Reply #8 on: December 06, 2015, 02:21:58 PM »
Appreciate the suggestions on the cam .May do that in the future.right now I'd just like to get a tamer motor in it were I can drive it everyday and fix it up when I have the funds. Doing other thangs to the truck right now .mainly cosmetically.slow progress but getting there slowly

Offline rich weyand

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Re: anyone running the gm 350/260 crate motor
« Reply #9 on: December 06, 2015, 03:20:49 PM »
Appreciate the suggestions on the cam .May do that in the future.right now I'd just like to get a tamer motor in it were I can drive it everyday and fix it up when I have the funds. Doing other thangs to the truck right now .mainly cosmetically.slow progress but getting there slowly

The 350/260 is perfect.

I have some hints for tuning the Edelbrock too.  Basically, use the 8" step-up springs after stretching them 1/4" or so.  Put in smaller main jets, and choose the right rods.  62/52 in 092 jets should be right for your setup, or a bit leaner with 65/57 in 092s.  65/57 might be your best summer jets, with 62/52 winter, or leave the 62/52 in all year.
https://www.google.com/?gws_rd=ssl#q=%22weyand%22+edelbrock+tuning
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline cstiles

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Re: anyone running the gm 350/260 crate motor
« Reply #10 on: December 06, 2015, 04:10:23 PM »
Good information . thanks rich. Still learning about fully tunning carbs.that a come in handy.I have heard people say the edelbrock 600s seem a little rich on a stock 350 in the past

Offline rich weyand

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Re: anyone running the gm 350/260 crate motor
« Reply #11 on: December 06, 2015, 08:02:13 PM »
They do that on purpose, because people don't tune the dang things, and if you run lean all the time, you'll burn the valves.

So split it before you put it on, and downsize those jets two notches.  Also check the float adjustment.  They are *always* wrong, from the factory.  Get the gasket for putting it back together tight.

All the part numbers are in the first thread or two of that google lookup above.
Rich

"Working Girl": 1978 K-10 RCSB 350/TH350/NP203 +2/+3 Tuff Country lift

Offline cstiles

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Re: anyone running the gm 350/260 crate motor
« Reply #12 on: December 07, 2015, 09:22:17 PM »
I should get a book and rebuild the Holley for a learning experience amd to get familiar wit all the parts I. A carb..not for sure much Bout it.it was there when I got the truck. I know it leaks down some when I turn the truck off .it smokes a little and smells a little rich to me but it runs fine.I  Believe it's a 4160 model.

Offline mcintyrederek

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Re: anyone running the gm 350/260 crate motor
« Reply #13 on: December 08, 2015, 09:04:11 AM »
Thank you for posting that about the Edelbrock tuning.  I knew it was running too rich all along but wasn't sure what rods and jets to use.  In the spring I'm going to do just that..

Mack.
1986 C-10 Silverado 350 CI 260 HP, Edelbrock 1405, TH400, 2.73's - rescued from the junkyard - Farm Truck, daily driver!

Offline cstiles

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Re: anyone running the gm 350/260 crate motor
« Reply #14 on: December 18, 2015, 10:19:35 PM »
Rich .just a thought the 1404 or 500 cfm would be right on the money for a stock 350 then .it's got the exact jets u we're saying to use on it from the factory for all round year

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