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K-jet head build for NA

esmth

esmth

The member
Joined
Jul 13, 2016
Location
MA/NH
Hello guys, I have a 1979 K-Jet 398 casting BCP head i've been thinking about getting work done on for a couple months now. The gist is that I want to modify this head to be more fun on the street than my bone stock B230F with B cam. After some reasearch here, I think some reasonable budget work for this head would be 46/38mm valves on cut stock seats, skimmed for more compression, along with a K cam and B21F intake I already have. I also want to stick with my current lh24/ez116k with a raised rev limit.

I have a couple of questions for those more experienced than I:

1.) Do the big coolant passages limit how much I can skim the head? What is a reasonable height to remove and static compression ratio to go for running premium gas?
2.) What is a reasonable valve spring setup for this cam (and an upgrade down the line) and an RPM my bottom end can handle? I currently have the "large" 32mm OD valve spring setup. I think I need new retainers for aftermarket springs?
3.) How practical are physically stock sized injectors in the K-jet head holes? I see its been done here before and I personally mocked up a fuel rail there with seemingly no problems. Though the ID of the injector holes at the bottom seems a bit too narrow.

I put together a cart on kl-racing with the above in mind, please critique it:
4x 46mm stainless intake valve
4x 38mm stainless exhause valve
4x valve stem seals
8x lower spring retainer
8x upper spring retainer
8x valve spring 39kg

Thanks for any input.
 
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Sorry, yes I should have added more info about my car in the post!

It’s a 1991 244 with a B230f and M46. I have LH2.4 with a 561 computer and 175 ezk. It has a B cam, adjustable gear (but set straight up) and a 421 tube header into a custom 2.5 exhaust. Otherwise the engine is factory.

I wanted to use the B21F manifold as the heresy is that it is better than the b230f intake manifold. And I already have it. Adapting LH injectors for Kjet holes doesn’t seem that hard, unless i’m overlooking something
 
Ah, gotcha. Give the machine shop an injector (with new oring) with the head, tell them I want to fit this in there. I don't like giving a good machine shop numbers, they are better at measuring stuff than I will ever be.
 
After thinking about this, that would be like direct injection, which may not be a real good idea. There must be a reason why direct injection is very high fuel pressures. And pretty sure the pintle caps will not stand up to the heat and pressure. Plus you lose the mixing effect with gas and air in the intake runner. How about having injector bungs welded to the B21 manifold, I forget who is doing that but it isn't hard to find. Pretty sure that is a better idea.

IDK, maybe someone else who knows more will comment.
 
I don't know about that head, but I've used a 530 K-jet head & B21 manifold. I was using the Siemens Deka 630cc injectors & wanted to get their pintles as close to the runner as possible.
I used a couple of drill bits (16mm & 14mm) in a hand held drill to enlarge the existing holes so that the injectors fit. I don't think you could do this with the standard shaped injectors as they're fatter. I think there are later volvo injectors that you could do this with that are closer to the standard spray rates. This is not direct injection as you are still spraying into the intake runner/back of valve. Obviously you need to be very careful while drilling but it wasn't difficult.
The fuel rail fit without problem, just need to make up some brackets that use the K-jet injector hold down bolt holes. The Fuel pressure regulator was a problem- you would need to mount one remotely or as I did, adjust the mounting tabs on the rail & regulator to fit.
It's been done a few times on here - I was following a couple of threads. I was also worried about heat initially but had no problems for the 2years I used that head.
Tim
 
Thank you two for your input.
The injectors will still be before the valve itself, only about 30mm closer. I grabbed some pictures this morning to better describe the situation with the fuel rail. I thought I had the later ev6-style injectors for a mockup, but I recently gave them to a friend so the photos are with the ev1-style, which turn out to fit better than expected.

Here is where the rail will sit


Injectors poking though, before the valve


Close up of injector tip near valve stem. The injector is about 2.5mm from the close side of the port wall, and 20mm from the far side.


ev1 injector is too fat, but the taper almost looks like it was meant for this, haha



tight fit, but it might work
 
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VB242 said:
I drilled the plastic injector holders out when I did this. ^
Click to expand...

Did that work well? Seems like a fellow could get some of those STS plugs linked above, and drill them. Or maybe STS would supply them with the proper I.D. shape. :oogle:

2turbotoys said:
I hope it doesn't puddle when it sprays the back of the valve head.
Click to expand...

If that was a problem do you think they would have put the Kjet injectors in that location, spraying continuously?
 
Harry Tuttle said:
If that was a problem do you think they would have put the Kjet injectors in that location, spraying continuously?
Click to expand...

Well K Jet is not a great example of fuel injection,. Maybe good for 40+ years ago, but the reason they moved them off the head is for better atomization. And pretty much every injection system since then has had them in the intake runner, it is just a better idea. But it will probably be fine, just not ideal.

The STS plugs would hold the injector pretty far away from the intake runner if drilled out.
 
Harry Tuttle said:
Did that work well? Seems like a fellow could get some of those STS plugs linked above, and drill them. Or maybe STS would supply them with the proper I.D. shape. :oogle:



If that was a problem do you think they would have put the Kjet injectors in that location, spraying continuously?
Click to expand...
It worked fine but I had to put the thicker k-jet injector O-rings on the electronic injectors. I'm now using a 530 head with regular intake manifold for the smaller cooling ports, I would like to convert a B21 intake though it did seem more torquey on the butt dyno.
 
Big coolant ports are fine for NA. You can easily cut the head .100” or more and still be fine.
For springs, KL racing single springs will be fine.
For machine work, you’ll want to have the ID of the seats opened up to ~85% if valve diameter, and then have the bowl area blended into the port. Special attention should be paid to the short turn radius (sharp inside corner) on the exhaust and intake... but mostly the exhaust.
 
I ordered the parts listed in the OP from KL last night!

culberro said:
Big coolant ports are fine for NA. You can easily cut the head .100? or more and still be fine.
For springs, KL racing single springs will be fine.
For machine work, you?ll want to have the ID of the seats opened up to ~85% if valve diameter, and then have the bowl area blended into the port. Special attention should be paid to the short turn radius (sharp inside corner) on the exhaust and intake... but mostly the exhaust.
Click to expand...

Thank you! I was most worried about how much I could cut the head. Good to know it can be a ton without issues atleast for NA.
 
I got my order in and am almost ready to send it to the machine shop. Just need to remove two snapped studs.

I am trying to do research with how much I should take off the head and what static compression ratio to go for to run 91/93. This http://www.turbobricks.com/specs/sohc_heads.php says the it should be around 4.3cc of combustion chmaber volume per milimeter of head removed. If I remove 1mm/0.040in and run a 0.036in gasket, that should net me 10.65:1 theoretically. I'm not sure If i should attempt to run a thinner gasket and remove less material. Or if I should go for more compression, but it seems like more than that would be rough for lh24.

Theoretical SCR with 0.036in gasket on b230f bottom end and head shaved:
(assuming piston dish is <strike>6</strike> 8 cc and head started at 51.7cc...)
0.020in: <strike>10.32:1</strike> 10.03:1
0.040in: <strike>10.65:1</strike> 10.34:1
0.060in: <strike>11.00:1</strike> 10.67:1
0.080in: <strike>11.38:1</strike> 11.03:1
0.100in: <strike>11.80:1</strike> 11.42:1

Also I got some ev14 210cc cone-spray injectors from the boneyard and they fit much better than the ev1's. The pintle ends without the plastic retainer go in almost as deep as the original k-jet injectors. I think they will work nicely in the head. :)
 
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0.040" and a thin gasket is a great setup for lh2.4 when running premium (91/93) with the B-cam.
 
culberro said:
0.040" and a thin gasket is a great setup for lh2.4 when running premium (91/93) with the B-cam.
Click to expand...

Thanks! Though I'm planning on running the K cam I've held on to a bit. Could I go for more SCR with the K you think?

shoestring said:
Dish on a B230F piston is 8cc. Our 530 head cut 0.103" measures 44.5cc.
Click to expand...

Thanks! I had a hell of a time trying to find information about the -f piston dish. I ordered some plexiglass tiles to measure the volume of the head and pistons, but apparently that stuff is in high demand right now.
I adjusted the numbers in my previous post, do they look accurate to you? What about the volume of the 398? (I assume its the same as 530) I read somewhere that the head volumes could be as high as 54cc.
 
esmth said:
Thanks! Though I'm planning on running the K cam I've held on to a bit. Could I go for more SCR with the K you think?



Thanks! I had a hell of a time trying to find information about the -f piston dish. I ordered some plexiglass tiles to measure the volume of the head and pistons, but apparently that stuff is in high demand right now.
I adjusted the numbers in my previous post, do they look accurate to you? What about the volume of the 398? (I assume its the same as 530) I read somewhere that the head volumes could be as high as 54cc.
Click to expand...

The K-cam should be fine as is. Both the B and K cam are pretty mild cams.

Chamber volume is all over the map, but somewhat consistent across a single head.

Dish volume is pretty consistent as well, but deck height is not. Which will have a decent impact on final SCR calculations.
 
culberro said:
The K-cam should be fine as is. Both the B and K cam are pretty mild cams.

Chamber volume is all over the map, but somewhat consistent across a single head.

Dish volume is pretty consistent as well, but deck height is not. Which will have a decent impact on final SCR calculations.
Click to expand...

Oh OK, TY again for your input. i'll let y'all know what I get for volume when the plexi comes in:)
 
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