1968 Chevy K10 SWB Overlander

[cobra_4]

Very awesome truck! As for the dual manifold, we recently sold a 69 C10 with a dual manifold and a four barrel, of course the internals had been built a little too but it ran just like a V8. The install should be easy, just have to run new pipes if you want duals or run it together if you want singles.

 

[bjowett]

Unfortunately, I do not have any dyno numbers, but I can tell you the basic physics behind it (this is over simplified). Firing order is 153624... when the number 1 exhaust valve opens, it releases it's energy into the single exhaust manifold. Number 5 fires next, but number 1 has not yet left the building, and may even be waiting at number 5's door (valve) when it opens. As one can guess, number 5 has no where to go until number 1 is turned around and heading in the proper direction. This continues all the way through the firing order until we are back at the beginning. By splitting the manifold into 123 and 456, then running duals, number 1 will no longer meet number 5. When number 3 fires into the 123 split manifold, number 1 has had time to clear out while number 5 is firing over in the 456 manifold. If the two manifolds are merged via a Y pipe into a single exhaust, number 1 can meet 5, but 1 won't be at the door. Again, very over simplified here. Best bet, before laying out any money, would be to hit some of the forums that deal with the engine. Also check out the Chevy Inline Six Power Manual... good book with lots of info.

 

[snekvasil]

Unfortunately, I do not have any dyno numbers, but I can tell you the basic physics behind it (this is over simplified). Firing order is 153624... when the number 1 exhaust valve opens, it releases it's energy into the single exhaust manifold. Number 5 fires next, but number 1 has not yet left the building, and may even be waiting at number 5's door (valve) when it opens. As one can guess, number 5 has no where to go until number 1 is turned around and heading in the proper direction. This continues all the way through the firing order until we are back at the beginning. By splitting the manifold into 123 and 456, then running duals, number 1 will no longer meet number 5. When number 3 fires into the 123 split manifold, number 1 has had time to clear out while number 5 is firing over in the 456 manifold. If the two manifolds are merged via a Y pipe into a single exhaust, number 1 can meet 5, but 1 won't be at the door. Again, very over simplified here. Best bet, before laying out any money, would be to hit some of the forums that deal with the engine. Also check out the Chevy Inline Six Power Manual... good book with lots of info.

Ok, I think I'm following the logic. Thanks for explaining. Are you suggesting a dual exhaust would be better then merging it via a Y pipe into a single exhaust? Or does it matter? I'm not a huge fan of dual exhaust...especially on a 6...so I was hoping to keep it a single exhaust.

 

[bjowett]

No, you can run single, but the Y pipe needs to be a certain length before it merges.

Also, more info on your efi? Pics?

 

[east_tn_81]

http://www.cliffordperformance.net/...?Screen=CTGY&Store_Code=CP&Category_Code=C250

Check this website. They have all kinds of stuff for a straight 6. Including headers.

 

[snekvasil]

No, you can run single, but the Y pipe needs to be a certain length before it merges.

Also, more info on your efi? Pics?

If I stuck with dual, would it have enough back pressure if I ran the exhaust in front of the rear tires?

 

[snekvasil]

http://www.cliffordperformance.net/...?Screen=CTGY&Store_Code=CP&Category_Code=C250

Check this website. They have all kinds of stuff for a straight 6. Including headers.

Thank you!

 

[bjowett]

Yes, you just need to keep the tube diameter small. A dual 2" would likely work well. Running a short system will require more sound control, so a large muffler should be utilized.

Headers can offer gains, but their longevity and sealing abilities can be questioned... My brother in law runs the Langdon Manifolds and has no issues.

 

[snekvasil]

EFI

Ok, so for the EFI:

1st of all, I'll try to explain this as well as I can. The truth is, although the install seemed somewhat complicated and took a while to do, I highly recommend it. If I can do it (with help from my buddy, David) anyone can do it. Just as a reminder, I'll start out with what the engine bay used to look like. If you're familiar with older engines, it's fairly easy to locate the air intake and carburetor. That's where the vast majority of the work will be done. As you can see in the picture below, the truck originally had the old-school intake with the tunnel opening. Under the intake sat the Rochester Monojet. Yes, a single-barrel carb. Boy was that thing finicky. I can't say I miss it much. Furthermore, the intake had a hose that attached to the top of the engine. If you have absolutely no idea what I'm talking about or describing, PM me and I'll gladly help more with the details.

Inline 6, 292 cu. in., 4.8 L engine. Air intake and carburetor are on the right-ish side of the engine (looking at it from this perspective).



Another pic from the left side of the I-6:



From the right side (here you can clearly see the air intake). Remember, the intake sits directly on the carb.



The first thing I did was research carb-to-EFI conversions. Larry (the same one on this site who has the 78 K10) was extremely patient, helpful, and informative in this process. He steered me toward Howell Engine Development which is located in the great state of Michigan. This company is amazing--I highly recommend. My ONLY complaint is the fuel pump (more on that later). Howell's main customers hail from Jeep world, and not 1968 K10s. However, the systems aren't all that different. After I talked with the owner of the company (I think his name is Brett), we figured out the exact kit I would need. The only thing I needed in addition to the Howell kit was an adapter plate to go from a Monojet (single barrel) to a double barrel injection. That part was tricky. Basically, I needed a metal funnel where the top was for a double barrel and the bottom was for a single barrel (I did not want to change the manifold). I found an adapter online that is actually used for carburetors instead of EFI conversions. However, I was able to make it work. I welded the mounting plate from Howell to the adapter plate. Unfortunately, I don't have any pics of JUST the plates welded together. In the picture below, if you look BELOW the injector, you can see the metal platform it sits on.



After that, the fun stuff happened. I was getting discouraged with the first process because it did take some fab work just to mount the EFI. However, that was the hardest part. Howell does such a good job with their wiring--I've read some complaints, but for me, it worked really well. It was so easy to tell where all the plugs went. The 2nd challenge was the oxygen sensor (pictured below). Getting that set up is all thanks to Dave--I couldn't have done that part without him. I also included a pic of the plugs and connection points.





The next picture shows the "breather." It's the chrome cylinder-shaped item. I'm not sure if "breather" is the technical term or not, but if you look up at the original pictures, you can see the hoses connected to the original air intake. Those hoses were replaced with this Edelbrock breather.



I replaced the old air intake with a K&N filter. I got it 75% off because some of the pleats were a little bent and distorted--fine by me! I'm not a huge fan of chrome, but the cover worked for me. I guess it fits the classic truck look.



So about the fuel pump: Howell didn't include a very high-end pump. At the time, I appreciated this because I wasn't wanted to add to the already expensive investment. However, I should've dropped the extra $200 for an insulated pump. The one I have now is quite loud. It's a whiny noise that's constantly in the background--not that big of a deal when I've got the tunes going and the windows down, but it could get annoying pretty soon.

Now, when I want to drive, all I do is hop in and fire her up! No more choking, no more praying to God that she starts on a cold morning. PLUS, I won't have to hesitate about driving it in higher elevations. Here's the finished product look:



And one of the first times I took it out after getting everything installed (I know the photo is doctored, but I love the colors):

 

[Bojak]

Great truck, you ABSOLUTELY went the right direction with your choices regarding what to and more importantly not to do to that truck. I bet you get approached by someone every time your out and about in it wanting to talk to you about your truck. Old school cool.

 

[Bojak]

Here is some inspiration for you, and it's just good truck porn.

 

[snekvasil]

Here is some inspiration for you, and it's just good truck porn. View attachment 250025View attachment 250026

STEVE MCQUEEN IS MY HERO. Yeah, that truck has been my inspiration since Day 1. I love the stance. I'll add some bumpers and call it a day!

And it's funny what you said about getting approached all the time. It's now a running joke between me and my wife. I try to avoid people because I get sick of talking about it (seems backward, right?) So far, I've gotten 11 offers from guys wanting to buy the truck. Three of those offers have been in the form of a sticky note left on my windshield while I've been at the grocery store, on three separate occasions.

 

[dwh]

Headers all eventually leak past the exhaust gaskets - unless you make re-torquing them a regular maintenance checklist item. Cast iron doesn't have that problem.

Generally, headers will improve top end horsepower more than they'll improve bottom end torque, whereas cast iron manifolds usually have the opposite effect. That has to do with the scavenging effect - the (usually) smaller exhaust runners of a cast iron manifold will usually do a better job of scavenging at lower RPM.

Splitting the exhaust on a 6-banger will absolutely help all across the power band, because it improves scavenging - well, actually it fixes an existing scavenging problem.

Another plus of the cast iron, is that is adds a bit of stiffening to the block - not as much as 4-bolt main bearing caps, but as someone who has broken a couple of crankshafts due to block flexing (one in a built Ford 460 and another in a built Mopar 440 wedge), I'll take all I can get.

I would absolutely go with those Stovebolt cast iron splits.

You'll have to re-do the oxygen sensor though.


If it was me, when I had the manifolds off, I'd also pull the head and do a new gasket and at the least, valve seals. That would also be the time to do a bit of port matching:




If you do the port matching, you do both the head, and the manifolds.

 

[snekvasil]

Headers all eventually leak past the exhaust gaskets - unless you make re-torquing them a regular maintenance checklist item. Cast iron doesn't have that problem.

Generally, headers will improve top end horsepower more than they'll improve bottom end torque, whereas cast iron manifolds usually have the opposite effect. That has to do with the scavenging effect - the (usually) smaller exhaust runners of a cast iron manifold will usually do a better job of scavenging at lower RPM.

Splitting the exhaust on a 6-banger will absolutely help all across the power band, because it improves scavenging - well, actually it fixes an existing scavenging problem.

Another plus of the cast iron, is that is adds a bit of stiffening to the block - not as much as 4-bolt main bearing caps, but as someone who has broken a couple of crankshafts due to block flexing (one in a built Ford 460 and another in a built Mopar 440 wedge), I'll take all I can get.

I would absolutely go with those Stovebolt cast iron splits.

You'll have to re-do the oxygen sensor though.


If it was me, when I had the manifolds off, I'd also pull the head and do a new gasket and at the least, valve seals. That would also be the time to do a bit of port matching:


If you do the port matching, you do both the head, and the manifolds.

What would be the advantage of port matching? I know the vid said more air, but what would that actually look like in performance of the truck?

After reading quite a bit, I definitely agree that the split exhaust manifold is the way to go. It's not that expensive of a mod either...

 

[dwh]

Well, doing it on the exhaust side improves scavenging, which basically means sucking ALL of the burnt gases out of the cylinder to make room for the next fuel/air charge. (The venturi effect of a smaller exhaust runner also helps this at lower RPM by creating a vacuum which literally sucks the exhaust out of the cylinder as soon as the valve opens, which is what I was talking about earlier - headers don't usually do that because they usually have big runners.)

Doing it on the intake side makes the incoming fuel/air charge move easier (faster) into the cylinder, getting the max charge into the cylinder per stroke of the piston, so each burn produces more power.

Another plus is that since each piston stroke is producing more power per droplet of fuel, you'll probably end up with a measurable miles per gallon improvement. (That's NOT true if you build the engine hot rod, but for a stock bottom end, it will almost always improve the mileage.)


If you had a shop do the head, you could have them do "porting and polishing". What happens there is they do a port matching like in the video, then they use the grinder to open the intake and exhaust runners in the head up a little (make them bigger and smooth out any bumps and humps (impediments)), and then they polish the interior surface of the exhaust runners to increase the speed that the exhaust gases move out, and roughen the interior surface of the intake runners to help "stir" the incoming fuel/air charge a bit to get the best mixing of fuel and air and thus the most efficient burn when the spark plug fires.

They'll also usually do a bit of work on the side that faces the piston - the combustion chamber - to make sure it's all smooth and pretty there. A real hi-po job will include "CCing" or "profiling", which is where they make all the combustion chambers exactly the same volume in cubic centimeters.

Since the shop has the head already, it's normal to also install new valves and seats if needed (or grind and bed them if that's all that's needed), and also new valve seals. That's also the time to check the valve springs to make sure they all have approximately equal spring rates.

I do my own porting and polishing - it's really not that hard. You just have to be VERY aware of the gotcha of taking off too much and opening a breach that might lead to a water jacket, or making a hole in your manifold. You don't have to worry much about that for a simple port matching. For bottom end torque, I DON'T open up the exhaust runners in the head to make them bigger (I want that venturi effect), I just smooth them out and port match them to the manifold.

It doesn't cost that much to have a shop do it. A "Stage 1" port and polish job on a pair of V-8 heads usually runs around 150 bucks + whatever else needs doing, like a valve job + a bit more if they also port match the manifolds for you. 6-banger should be a bit less. Stage 1 is all you need unless you are gonna build a hot rod engine.