1986 Chevy K-20 Exhaust Manifold

[JCM 10,125]

Like many of you I seem to have several projects going on at the same time and that does not include the interior or exterior of the house.This one involves the 86 K-20.Last fall I noticed the dreadful exhaust manifold leak noise,I  really can't complain the only parts under the hood that have been replaced on the engine is the alternator and just last summer the water pump. This truck has the H.D.emission LT9 350 M code engine 4 Speed manual trans with true dual exhaust, no cats and built to run on leaded fuel.I did replace the original aluminized exhaust system because of the age but was still a  very functional system. The truck now has 104000 original and I am looking for professional advice.Truck is used as a pleasure vehicle other than dump and lumber yard runs and is garaged 12 months a year so downtime does not concern me.Any suggestions on the proper way to go about removing the factory original stainless steel exhaust manifold, drivers side without having to remove the head because of a broken stud.I believe the manifolds are NLA from GM and Aftermarket? Because of my job I have had many experiences with removing copper tankless water heater coils in cast iron boilers and have had good and bad luck with the stud removals, I am very mechanically inclined but I am not an auto mechanic by trade and hate to do more harm than good.This truck is in here under vintage trucks.Thanks in advance for your suggestions, help etc.And by the way, I will take no offense at all to any wisecrack comments like just drop in a new GM crate motor etc,which would be nice but not in the budget, but if you know which LS motor would drop in relatively easy thats fine! This engine runs like the day I bought it new and hate to replace it. Thanks

[ebinmaine 71,990]

I'm kind of a fan of the older 350 so I would not replace that one with a new LS for anything.

I've had mixed results with getting broken studs out of Chevy heads in the past. The only really good advice I can give you is to try to tighten it 1/16 of a turn before you try to loosen it.

 

 

@WVHillbilly520H

Or 

@pullstart

 

Perhaps they could weigh in...

[Pullstart 66,178]

If you do snap it, drill all the way through the bolt as to have a path for penetrating oil to the end of the bolt, and to soak from the other side.  Even pressure and back and forth movements are helpful as well.

 

Honestly, the only snapped studs related to GM manifolds I’ve ever dealt with are on my 01 6.0L Vortec.  Any 350 manifold I’ve ever removed I had problems with were the passenger (?) side where there seems to be less oil leaks than drivers side... and it was due to the 9/16” head being part way gone and I was challenged with finding a metric undersized socket to beat on.

[Pullstart 66,178]

Another 2 cents (you’re getting pretty rich here) is that every LS engine I’m aware of is the same physical dimension shy of maybe the monster 8.1L.

[JCM 10,125]

@pullstart   I Think after owning that 70 Chevelle SS 396/402 4 Speed for 22 years I got  Spoiled when I wanted to pass someone,all I had to do was just give it a little more and off it went,the truck is a whole different story.

[WVHillbilly520H 10,376]

25 minutes ago, pullstart said:

Another 2 cents (you’re getting pretty rich here) is that every LS engine I’m aware of is the same physical dimension shy of maybe the monster 8.1L.

You are 100% correct...4.8L-7.0L...then there's the wet sump vs dry sump oil pans...but yes just like the original SBC the outside block dimesions are all the same...the 8.1(496ci) was the last "big block"...now @JCM as far as stainless manifolds that shouldn't matter about the bolt threads in the cast heads but the bolts could have corroded in the manifold flange, if you happen to break anymore of the bolt heads off... after the manifold is completely removed you can weld nuts to the remaining exposed studs/bolts the heat from welding will help with loosening the rust and then the nut will be yours new bolt head for a socket or wrench...that's how I got them out of my aluminum headed Trailblazer I-6... 1st pic cast iron 2cd pic stainless steel manifold.

[JCM 10,125]

@WV Hillbilly I have not got into this project as of yet,and I appreciate all your help, This truck means a lot to me and I just want to approach this  correctly. The last picture looks like  the correct manifold, I am sitting by the woodstove at present and not in the garage, still winter here. Thank you very much.

[JCM 10,125]

@BPEisenhower  Must be nice to have that knowledge on those smallblocks and or motors in general. That looks like that just might slide right into the engine compartment of that K-20? How much HP?

[BPEisenhower 553]

1 minute ago, JCM said:

@BPEisenhower  Must be nice to have that knowledge on those smallblocks and or motors in general. That looks like that just might slide right into the engine compartment of that K-20? How much HP?

It would fit in about anything. 383 stroker. Just a SBC 350 bored .30 over. Full roller, Erson cam, flat top Keith Black Hyper Pistons, heads are made from aluminum stock at my uncles machine shop. Intake 2.29 Exhaust 2.16. Valves made in shop. Edelbrock dual plane intake. Edelbrock 1407 carb. Fabricated valve covers by me and modified HEI ignition. Dyno puts it at 750 HP. Still working on it though. So far we have 170 hours fab and build time and roughly $900 in materials 

[JoeM 8,190]

Patience is always your friend dealing with broken stud or bolts. If I remember correctly there is a lot of  room along side of those manifolds. Of course removing the rest of the bolts unbroken is essential. Like EB says in a little before out has worked. All the suggestions are good. I have seen were the inner fender has been cut (neatly) to gain access through the wheel well.

[WVHillbilly520H 10,376]

34 minutes ago, BPEisenhower said:

It would fit in about anything. 383 stroker. Just a SBC 350 bored .30 over. Full roller, Erson cam, flat top Keith Black Hyper Pistons, heads are made from aluminum stock at my uncles machine shop. Intake 2.29 Exhaust 2.16. Valves made in shop. Edelbrock dual plane intake. Edelbrock 1407 carb. Fabricated valve covers by me and modified HEI ignition. Dyno puts it at 750 HP. Still working on it though. So far we have 170 hours fab and build time and roughly $900 in materials 

I built a "mild" street/strip 406 SBC for my '78 Malibu Comp full roller cam and billet timing set, Dart Iron Eagle Platinum heads and Eagle rotating assembly with forged I beam rods moving Mahle forged flat tops...

[JCM 10,125]

@OILUJ52  Thanks for the help.About 25 years ago I purchased 2 GM inner fenders from a local dealer should the need arise to replace them, I did install them last spring and when I assemble anything use neverseize on the threads.I remember a neighbor of mine who was a farmer where I grew up and he saw me working on my IH Farmall Super A , so he strolled over to my yard with a Coors Extra Gold and a cigar, great combination by the way and told me that I would have that neverseize in my bed that night, and you know, I think he was right.Those inner fenders would come right back out if needed.    Thanks again.

[ebinmaine 71,990]

Jim I'm a hug fan of the 383 stroker Engines in general.

Seen a few in operation.

Like any other small block they can be built from mild to wild.

 

Summit racing and jegs and many others sell everything to build and even crate street/towing/race Engines can be had.

 

Be sure to keep your low end torque alive for towing. You can yank 350-400 HP or more from modern cams and properly built breathing Engines and still be able to drive around town happily.

 

@WVHillbilly520H are those intake valves or just some spare supper dishes you had laying around???

Wow.

 

[Sarge 3,465]

The bolts may have suffered from a dissimilar metals corrosion from those stainless manifolds, so be aware of that. Most likely the head will have to come off. You can try the regular removal methods if you can remove the inner liners, but I doubt they will work shy of welding a nut to what is left of the bolt shank. I've gotten quite a few out that way and also have had quite a few that just had to be drilled out and re-tapped with the head off. The only way to find out is to get to work on it. There are a ton of various "tricks" to remove broken bolts/studs - sometimes it will take trying every single one of them and still end up with the part at the machine shop. Personally - I've never had to resort to that - but I have had to pull heads off several times. Pulling the head is no biggie - its a SBC, after all.

 

Sarge

[WVHillbilly520H 10,376]

11 hours ago, ebinmaine said:

 

Like any other small block they can be built from mild to wild.

 

Summit racing and jegs and many others sell everything to build and even crate street/race Engines can be had.

 

@WVHillbilly520H are those intake valves or just some spare supper dishes you had laying around???

Wow.

 

Eric, those are the itsie bitsie valves (2.08in 1.60ex) in my lil small block...these heads flow nearly as much as a BBC, but it's hard to even come close to the LS components that's where GM and the aftermarket exploded with goodies.

[diesel cowboy 263]

19 hours ago, WVHillbilly520H said:

You are 100% correct...4.8L-7.0L...then there's the wet sump vs dry sump oil pans...but yes just like the original SBC the outside block dimesions are all the same...the 8.1(496ci) was the last "big block"...now @JCM as far as stainless manifolds that shouldn't matter about the bolt threads in the cast heads but the bolts could have corroded in the manifold flange, if you happen to break anymore of the bolt heads off... after the manifold is completely removed you can weld nuts to the remaining exposed studs/bolts the heat from welding will help with loosening the rust and then the nut will be yours new bolt head for a socket or wrench...that's how I got them out of my aluminum headed Trailblazer I-6... 1st pic cast iron 2cd pic stainless steel manifold.

 

18 hours ago, JCM said:

@WV Hillbilly I have not got into this project as of yet,and I appreciate all your help, This truck means a lot to me and I just want to approach this  correctly. The last picture looks like  the correct manifold, I am sitting by the woodstove at present and not in the garage, still winter here. Thank you very much.

 

I had almost the exact same truck down to the year and almost the same mileage when I had to pull the heads and it had the manifolds in the second picture.  I had a couple of the nuts fight me and was afraid they were going to break and I hate trying to drill broken studs out of heads and blocks.  

Mine were junk so I took the torches with the small cutting tip and heated the nuts up.  The spacers on the manifold itself just kind of melted away cause they were so badly rusted.  With them gone I was able to get at the back side of the nut to spray penetrating fluid on it, but in the end with the spacer gone there was enough room to get a cutoff wheel in there and cut the nuts saving the studs.

 Didn't make much difference in my case cause when I got the heads off I found the cylinder wall on the #6 was cracked so I ended up replacing the whole engine.