84' GMC 350 motor rebuild

[Highsierra84]

Apologize for the lengthy thread, this will be my first rebuild.

1984 k2500 High Sierra, long bed
350 motor
sm465
np208
10 bolt auto-lock hubs front axle (someday soon I'm installing warns hubs, don't worry)
14 bolt semi-float rear 3.73
235/85r16 tires

Cherry truck for a k2500, old man used it for a hunting rig, 94k original miles. Rear main seal is slowly going out, got some sticking lifters, valve cover leaks, plus my throw-out bearing on the clutch side is starting to squeal here and there. The time to rebuild the motor is approaching.

I don't care about anyone else's youtube big cam 350 build using daddy's or girlfriends money. Hence why I'm posting this thread. A rebuild that is backdoor, behind the shed, just want to rebuild it right. Close to stock, close to cheap, but throw the money where I can maybe get a little more torque out of this 350 cause this is a work truck.

I've been bouncing around the web, youtube to all the forums of peoples rigs. I've finally got a list going. What you think???

Stock Vortec heads (nothing fancy just junkyard heads with a valve job)
Summit 1787 cam/quality lifters
Summit dual plane vortec intake
Summit 600 cfm vacuum secondary Carburetor (Already on the truck)
Maybe! some shorty headers but the stock manifold fit and will do fine for a torque motor kinda build. What you think. stock manifold vs. shorty headers?

The rest I'll keep stock and salvage everything I can. Won't know entirely until I tear down the block, but I'm hoping to keep the crank and pistons.
I'll replace seals, bearings, timing gear/chain, oil pump, etc...

Planning on having a shop prep the block for assembly(clean,deck, honed,cam bearings,freeze plugs)
I'll have the head shop do a resurface and valve job
The rest of the assembling will be me, my friends, the old man across the street, with some added beers.

Any suggestions and opinions on the build please reply. My goal is to be cheap, but add a couple good parts to give this 350 a new lease on life. I'm going to get my general contractor license soon, and this rig would be sweet on any jobsite.


Summity 1787 cam spec
Basic Operating RPM Range:800-4,500

Intake Duration at 050 inch Lift:204

Exhaust Duration at 050 inch Lift:204

Duration at 050 inch Lift:204 int./204 exh.

Advertised Intake Duration:260

Advertised Exhaust Duration:260

Advertised Duration:260 int./260 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.427 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.427 in.

Valve Lift with Factory Rocker Arm Ratio:0.427 int./0.427 exh.

Lobe Separation (degrees):110

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[El Perdido]

I was going to have a shop in Vegas rebuild the 350 on my '85 K20 Suburban, SM465, same rear diff as you, but 4.10 gears, back in 2008. Original engine had 325,000 on it. He talked me into a Goodwrench crate engine instead since it was a less expensive alternative. It basically duplicated my original stock engine. Have over 100K since. No regrets.

 

[Bextreme04]

I have to agree. It is very unlikely that you will get away with not having to bore it and new pistons. You will likely need at least new pistons and a balance. Heads would likely need a service. You'll be pretty close to the cost of a new goodwrench long block at that point. You're going to hate the vortec's on a carbureted engine in any kind of cold weather also. They were intended for fuel injected engines and dont have a heat crossover.

 

[Highsierra84]

Thanks for mentioning about the vortecs in cold climates. I'm up in 3500ft elevation below Lake Tahoe, California and planning on moving more north to cooler states, so the vortec might not be for me.

I'm now thinking more the lines of just doing a straight rebuild and installing a towing cam like that summit 1787. I want to rebuild what is in it, not for originally purposes, but for learning and knowing what's inside. I'm a stubborn misfit who would rather wrench on my own versus slapping everything together, but that's me.

Are there better intake manifolds with a heat crossover out there versus stock. Would I gain anything from a performance intake, or for what it is, stick with stock?

 

[peats]

RV cam, long tube hedders, and an aluminum intake on a stock build should work just fine. No vortec.

 

[Bextreme04]

The intake isn't going to help you any. Headers and cam will get you some good power gains. Heads will be the biggest power increase. I'd just get a set of these summit cast iron heads. Fully assembled and ready to run a decent sized cam for $350/ea. They will be similar power wise to double hump fuelie heads and get you WAY more power than you have now. Between the heads, cam, and headers you can probably have it running around 300/300 hp/tq. At $700 for the new heads you'll be right around what it would cost you to buy vortecs and have them rebuilt anyways. Between those heads, a Summit SUM-K1102 cam/lifters kit, and some basic flowtech long tube headers, you'll be all in for less than $1000 and WAY more power and driveability than stock. I'd keep the stock intake and rebuild the factory quadrajet too.

Edit: Adding the links I forgot to add

https://www.summitracing.com/parts/sum-k1102
https://www.summitracing.com/parts/sum-152123/make/chevrolet

 

[Highsierra84]

Funny you mention that summit 1102 cam. The Melling MTC-1 caught my eye, but for the price for the lifters alone, the summit kit is a go. I'll have to see what my local head shop charges for a valve job for my current heads. If it turns out that my current heads need a ton of work, then I'll grab a new pair from summit. Truck only has 94k original miles, so likely my heads are good to go. Trying to save money everywhere I can.
My current quadrajet is junk, primary and secondary throttle linkage rods are worn out. Ton of play, ton of vacuum leaks. Hence why I bought that summit 600 cfm vacuum secondary carburetor. I'm with you though, nothing beats a nicely rebuilt quadrajet. I'm hoping soon to grab a decent quadrajet core to rebuilt and sell that summit carb to someone who can run it a real street/strip car/truck.
I'm currently saving the money to start tearing it down by christmas of this year. Everything stock besides that summit 1102 cam plus a pair of long tube headers would be just right, and cheap(if my current core of an engine isn't **** inside)

 

[Bextreme04]

Funny you mention that summit 1102 cam. The Melling MTC-1 caught my eye, but for the price for the lifters alone, the summit kit is a go. I'll have to see what my local head shop charges for a valve job for my current heads. If it turns out that my current heads need a ton of work, then I'll grab a new pair from summit. Truck only has 94k original miles, so likely my heads are good to go. Trying to save money everywhere I can.
My current quadrajet is junk, primary and secondary throttle linkage rods are worn out. Ton of play, ton of vacuum leaks. Hence why I bought that summit 600 cfm vacuum secondary carburetor. I'm with you though, nothing beats a nicely rebuilt quadrajet. I'm hoping soon to grab a decent quadrajet core to rebuilt and sell that summit carb to someone who can run it a real street/strip car/truck.
I'm currently saving the money to start tearing it down by christmas of this year. Everything stock besides that summit 1102 cam plus a pair of long tube headers would be just right, and cheap(if my current core of an engine isn't **** inside)

To have it done right, and in california, you will likely be pretty close to the price of those new heads. Your current head has 100k miles and almost 40 years of use. You will likely need cleaning, valve job, new guides, and I'd have them machined for positive lock viton stem seals too. Your valve springs and retainers are also likely original and you might want to think about replacing them also. All of that on my 454 L29 heads cost $600 here in Oregon.

 

[Bextreme04]

Also, it should be noted I had my L29 heads rebuilt because they are awesome heads and I wasn't going to get anything better for less than about $2000. 80's truck heads on the other hand are "not great" to put it nicely and "hot garbage" to be a little more honest. If you are going to be anywhere close to that cost, it would be well worth it to upgrade.

 

[45acp]

I was going to have a shop in Vegas rebuild the 350 on my '85 K20 Suburban, SM465, same rear diff as you, but 4.10 gears, back in 2008. Original engine had 325,000 on it. He talked me into a Goodwrench crate engine instead since it was a less expensive alternative. It basically duplicated my original stock engine. Have over 100K since. No regrets.

x2 on the Goodwrench engine. I'm a retired GM partsman if you have a shop install it you get a 3 year 100,000 miles parts and labor warranty. Believe it or not I bought mine from Jegs performance parts they had the best price and drop shipped it to the shop that was doing the install ( they also paid the freight ). I bought mine about 3 years ago and at that time they didn't charge tax, but that may have changed. There is nothing hp about this engine,it's just a brand new 350!

 

[75gmck25]

Considering your relatively modest goals, my recommendation is to use an L31 crate engine like this one. https://www.jegs.com/i/JEGS/059/0282/10002/-1

The L31 crate is sold for 1996 and trucks, but once you add an electric fuel pump and Vortec intake it will work fine with the older trucks. It has a mild cam that will work good right up front, but its a roller cam, so you could easily swap to something better later on if it doesn't have the power you want.

Now for the bad news - these low priced engines are still listed by Jegs and Summit for about $2000-2200, but are not currently available. The ones that can be shipped immediately are official GM crate engines priced at about $3,100 https://www.gmperformancemotor.com/parts/12691673.html

At one time I remember there being an official GM L31 crate that was priced at about $2,200, so I don't know if GM really jacked up the price, discontinued one of the engines, or whatever. This dealer is one of the few places that lists the old lower-priced engine. However, I've never ordered from them. https://www.trailerpartstogo.com/12...evy-gmc-full-size-trucks-3-4-ton-up.html.aspx

Also check with friends that work for any type of GM dealer or associated truck dealer to see if they can get a discount. I got my old Goodwrench 350 crate through a friend who worked at a Peterbilt dealer, and he could order it at near dealer cost.

Bruce

 

[45acp]

Considering your relatively modest goals, my recommendation is to use an L31 crate engine like this one. https://www.jegs.com/i/JEGS/059/0282/10002/-1

The L31 crate is sold for 1996 and trucks, but once you add an electric fuel pump and Vortec intake it will work fine with the older trucks. It has a mild cam that will work good right up front, but its a roller cam, so you could easily swap to something better later on if it doesn't have the power you want.

Now for the bad news - these low priced engines are still listed by Jegs and Summit for about $2000-2200, but are not currently available. The ones that can be shipped immediately are official GM crate engines priced at about $3,100 https://www.gmperformancemotor.com/parts/12691673.html

At one time I remember there being an official GM L31 crate that was priced at about $2,200, so I don't know if GM really jacked up the price, discontinued one of the engines, or whatever. This dealer is one of the few places that lists the old lower-priced engine. However, I've never ordered from them. https://www.trailerpartstogo.com/12...evy-gmc-full-size-trucks-3-4-ton-up.html.aspx

Also check with friends that work for any type of GM dealer or associated truck dealer to see if they can get a discount. I got my old Goodwrench 350 crate through a friend who worked at a Peterbilt dealer, and he could order it at near dealer cost.

Bruce

Bruce you are absolutely correct!!! I just called a buddy of mine that I worked with for years ( he is and I was GM partsman ) I gave have him the old part number and he started laughing! Not only has the price skyrocked it's also a restricted part. There is only one dealer that shows stock ( Coughlin Chevrolet in Ohio ). That will teach me to talk about parts availability after retirement!

 

[Octane]

For a long long time it has been more cost effective to buy long blocks.I still like to occasionally rebuild an old sbc.I've been lucky,every old engine I've done has had 140 to 180k miles on them and only needed a hone and simple head work.A lot to be said for those long blocks and crate engines and warranties tho.But I guess I've been a sucker for punishment. Lol

 

[Highsierra84]

Making a christmas list:
Basic rebuild kit(bearings,gaskets,pistons&rings,timing set, water pump, fuel pump, oil pump,etc)
$500 roughly
New summit heads 152123 cast iron 72cc
$700
Summit k1102 cam kit
$113
Long tube headers
$175

I'll keeping my Original Intake manifold and distributor. Forgot to mention, last owner of the truck deleted the y pipe and installed dual 2 1/4" exhaust, so heads, headers, and a cam would sound so much better than original.

Roughly $1500 in parts alone. Ain't to bad when comparing to a crate. Hopefully I can get a deal on my long block prep at the shop. I'm planning on punching the pistons 0.020" over, but if there isn't any ridges in the bore, I'll take the shops advice to bore it or hone.
I'm confident I can wrap this up for under $2200, which will beat the crate.

 

[75gmck25]

I don’t know much about the Summit 152123 heads, but it seems like you should use 64cc heads instead of 72cc heads if you are going to use something equivalent to stock dished pistons. However, if you use flat top or domed pistons you could get your compression up higher that way.

Bruce