1983 K20 350 SBC Upgrade Opinions

Catbox said:

Those would be the already upgraded heads.
I would check to be 100% sure, a quick call to Summit should find out what you want to know.

Click to expand...

Thanks for the advice! I actually made the call this weekend and talked to Summit. A fella there assured me that the heads would work as is. Thanks again for the reassurance!

1987 GMC Jimmy said:

If you just hate the Quadrajet, assuming it still has it, go Holley.

Click to expand...

To be honest, I didn't know what a QJ was! I mean, I had HEARD of them, and how some folks hated them, but due to your post, I've delved DEEP into QJ history and performance. Personally, I love the idea of vacuum controlled secondaries. It seems that if I rebuild the Quadrajet correctly, AND get it tuned, it will adjust my CFM based on engine need. No worries with 'over carbing', right?

I don't really have much in the way of an update, as I don't have her in my possession as of yet. I've been doing a ton of research in preparation though!


So here's my first week's plan:

1. Get her home
2. Change fluids (oil, coolant, brake, trans, diff, transfer)
3. Perform leak down
4. Change (and inspect) plugs
5. Desmog (TBH, I don't really know what she has in this department though...)
6. Rebuild QJ
7. Replace dizzy and wires

I'm still looking at vortec heads (and intake that will mate with it) as well as a slightly more aggressive cam (XE256H). It seems if I can get her going well mostly stock, the transition to better intake, heads, and cam should be a smoother operation.

Thanks again for your replies, again, sorry for the late response from me. Thirteen hour nights just suck. Especially when I'm old enough to need to a bunch of 'ologists' on speed dial. Cardiologist. Urologist. Endocrinologist. Ophthalmologist... Well, you get the point.

Stay safe y'all!

Glad you took the carburetor red pill, if you will. At least with respect to GM. I’m sure Mopar guys say the same about the Carter TQ. Ford guys are too busy calling a tow truck to have anything else to say. I kid, but I still prefer the ole General. Keep us posted!

In answer to the question in post 14, I used an Edelbrock performer intake and Quadrajet with Blueprint aluminum heads. My stock iron intake is long gone.

Another tip I got from the forum was to use the Mahle 5746 .026” thick head gasket instead of the stock .039” gasket. I assume it also works with iron heads, but you would have to verify. These engines need all the help they can get to increase compression.

Bruce

Nice rig and pup! I'm in a similar situation with my 84 K20. I ordered a set of summit 165cc iron heads and Lunati Barebones 10120102LK cam kit to go with the current Elderbrock RPM intake, Brawler 670 carbm (on 1" open spacer), and Flowtech long tube headers exiting into 2.5" duals with 23" Jones glasspacks. I'll let you know how the combo works on the stock short block.

Jake

75gmck25 said:

These engines need all the help they can get to increase compression.

Click to expand...

You can make em run MUCH better simply adding compression ratio.

You could save $1500 if youd simply change head gaskets and rebuild the quadrajet.
It certainly wouldnt cause NEAR as much headache as your proposal. It seems fraught with issues and plagued with problems .
Planned headaches and unnecessary expense. You'll take the reliability and fun out of it that way.

Thats all ive got to say about that.

75gmck25 said:

I am surprised the video you saw shows only 12” of vacuum with the xe256h 212/218 @ .050 cam. I have a Howard’s cam with 213/217 @ .050 and 112 LSA, and I show about 19” of vacuum at idle. I use 15 degrees BTDC initial timing and 20 degrees mechanical, and it idles and accelerates very smoothly.

I used Blueprint aluminum heads instead of Vortecs. By the time I would have purchased Vortecs and then swapped to a new Vortec intake, the total cost was very close to the $899 for the Blueprint heads.

Bruce

Click to expand...

The comp cam is on a 110 lsa your Howard's cam was probably a little better choice.

Old60Driver said:

1987 GMC Jimmy - Thanks for the reply! I do, however, have a question regarding the following statement:



You mention the stock spring .450 lift threshold. In the heads I'm looking at from Summit, the maximum valve lift is 0.520 in. Is 'lift threshold' and 'maximum valve lift' the same?

Again, thanks for the feedback; it's much appreciated!

Click to expand...

Yep same thing your not looking at stock vortec heads if they say can run .520

Thank you all for your replies and comments! Again, sorry for the lateness of my replies, but 94 hours or so of night shift is wearing on me a bit. lol

Ricko1966 said:

Yep same thing your not looking at stock vortec heads if they say can run .520

Click to expand...

Sorry if I didn't clarify correctly. When I put down which parts I was looking into, I hyperlinked the part address from Summit, but didn't note it in my description. The vortec heads I'm using are:

https://www.summitracing.com/parts/...QBWExzouDgLB-5PfUVnR1w6Ni1HZvbjhoCUmQQAvD_BwE

They are definitely aftermarket. Still, I'd like to clarify the lift with all y'all!!

Interestingly story, I purchased the Cliff Ruggles book on rebuilding Q-jets. Decided to call his shop to order a kit. Turns out he answered personally, and we got to talking about the build. Man, he is NOT a fan of the vortec heads! lol Says he's never pulled vortec heads off that weren't cracked. In fact, he stated that he's had some come off in two pieces??? Additionally, he thought my cam choice (XE256) was too much, and wouldn't do much in my search for low end grunt. He recommended this:

Camshaft - CS-274 (this was his 'go-to)
Heads - SR Torquer from World Products
Rocker Arms - 1.6 ratio

Told me to stay away from a fancy intake due to the fact that it would take forever to warm up? Something about the 'wet cross', or something like that. I was writing as fast as I could, and still couldn't keep up. Also, didn't want to keep him on the phone for longer than I already had.

Finished up by telling me that if I couldn't roast the tires off the truck, he'd come down personally and figure out why! lol He was fun to talk to, that's for sure!!!

What do y'all think?

Jake_S said:

Nice rig and pup! I'm in a similar situation with my 84 K20. I ordered a set of summit 165cc iron heads and Lunati Barebones 10120102LK cam kit to go with the current Elderbrock RPM intake, Brawler 670 carbm (on 1" open spacer), and Flowtech long tube headers exiting into 2.5" duals with 23" Jones glasspacks. I'll let you know how the combo works on the stock short block.

Click to expand...

Thanks, and please do! Man, glasspacks! Should sound amazing! Are you using Summit for your upgrades?

82sbshortbed said:

Nice dog too. I think you'll be happy with those upgrades. You should gain a good bit of horsees for the money. I did that or in the process of putting them on on my sbc. I got the new Edelbrock performer eps intake and new Quadrajet on and seen a great improvement in the motor. Then I was going to put t he cam and hedders on but, found a BBC 454 that had all that already done to it so I went that route.

Anyways I like the plan you got going forward. I'm sure y'all will enjoy it.

Click to expand...

Im looking at the eps intake for my crate motor.

Im no fan of vortex heads either. That's asking for trouble I dont want!
Of course, I dont like black wheels either ,Trendy.
I can afford good looking ones.


I've bought THREE pairs of cylinder heads in the last two years and never once considered vortex headache. Got nothin to prove lol.

- I DID buy a pair of World Products Torquers though for a 408 SBC that has a Comp Cams 268H camshaft in it.

-Also a pair of GM #416s that KICKED ASS on an LM1

AND

-A pair of GM #113 for an L69 , but I may screw around and set em on the LO5 in my Blazer.

Hope this helps!

The next pair of cylinder heads i'm gonna buy are #083s.
THAT IS the best flowing SBC cast iron head GM ever built.

Old60Driver said:

Thanks, and please do! Man, glasspacks! Should sound amazing! Are you using Summit for your upgrades?

Click to expand...

Oh yeah, the glasspacks are nice, a bit louder than I was expecting for being 23"s, and yup, Summit is the blackhole currently sucking up my fun money.

Parts go on next weekend.

Jake

Thanks for all the replies! Definitely a lot to consider, and by my own admission, I will absolutely research something to death before I pull the trigger. That trait DEFINITELY gets on my wife's nerves sometimes.

So here's the plan. Originally, I was going to drive up to KS and pick her up on a trailer, and bring her home, but due to unforeseen circumstances, that isn't an option. Given that she's only running 53,000 miles or so, and she's modestly cared for, I plan to give her a THOROUGH tune-up (me and my son), and drive her the 600 miles back home. I'll have the wife in a trail car behind me just in case, and I have AAA as well. I've ordered a good bit of the hardware I need (noted as ONSITE), and it's all been delivered. Everything else I'll have to buy locally, as noted.

This may be a long winded post, and I apologize up front, but I wanted to put my plan out there, and let you gurus look it over if you have time. How does this sound???

FLUIDS:

ENGINE OIL

• FILTER ONSITE
• PURCHASE OIL LOCALLY (10W30)

DIFFERENTIAL

• GASKET ONSITE
• PURCHASE OIL LOCALLY (75W90)

TRANSFER CASE

• PURCHASE OIL LOCALLY (SAE 30)

TRANSMISSION

• GASKET/FILTER ONSITE
• PURCHASE FLUID LOCALLY (DEX III)

ENGINE COOLANT

• PURCHASE FLUSH KIT LOCALLY
• PURCHASE COOLANT LOCALLY

BRAKE FLUID

• PURCHASE FLUID LOCALLY
• EVALUATE BRAKE LINES
• PURCHASE LOCALLY IF REQUIRED

REBUILD/REPAIR:

ROCHESTER QUADRAJET CARBURETOR

• QUADRAJET POWER REBUILD KIT ONSITE
• PURCHASE CHEM DIP/MINERAL SPIRITS ON SITE
• PURCHASE BRUSHES/PIPE CLEANERS LOCALLY

FRONT BRAKE CALIPERS

• EVALUATE THE NEED FOR REBUILD/REPLACEMENT
• PURCHASE LOCALLY IF NEEDED

REAR BRAKE SLAVE CYLINDERS AND HARDWARE

• EVALUATE THE NEED FOR REBUILD/REPLACEMET
• PURCHASE LOCALLY IF NEEDED

WHEEL BEARINGS

• EVALUATE THE NEED TO REBUILD/REPACK FRONT BEARINGS
• EVALUATE THE CONDITION OF REAR AXLE SEALS
• PURCHASE GREASE/BEARINGS/SEALS LOCALLY

NEW PARTS:

TIRES

• PURCHASE LOCALLY

DISTRIBUTOR

• ONSITE

DISTRIBUTOR CAP

• ONSITE

DISTRIBUTOR ROTOR

• ONSITE

COIL AND IGNITION WIRES

• ONSITE

COIL

• ONSITE

SPARK PLUGS

• ONSITE

TEMPORARY TACHOMETER

• ONSITE

VALVE COVER GASKETS

• ONSITE

BELTS

• PURCHASE LOCALLY

RADIATOR/HEATER HOSES

• PURCHASE LOCALLY

THERMOSTAT

• PURCHASE LOCALLY

FRONT DISC BRAKE PADS

• PURCHASE LOCALLY

REAR DRUM BRAKE PADS

• PURCHASE LOCALLY

AIR FILTER

• PURCHASE LOCALLY

PCV VALVE

• PURCHASE LOCALLY

INLINE FUEL FILTER

• PURCHASE LOCALLY

WIPER BLADES

• PURCHASE LOCALLY

ANY LIGHTS THAT ARE INOP

• PURCHASE LOCALLY

VACUUM HOSES/FUEL LINES

• MOST WILL BE REPLACED DUE TO AGE/CRACKING
• PURCHASE LOCALLY

FUEL TANKS WILL NEED TO BE EVALUATED

Barring any unforeseen issues, all I should need to do once all of that is done, is flip the breather cover for that horsepower boost, and hit the road!

What say you folks??