Porting L-35

[Blake]

I'm in the process of porting a set of L-35s. When I disassembled them for cleaning I noticed that in the combustion chamber, on the sparkplug side, there was a "dead spot" on the outermost edge toward the cylinder edge. It was full of carbon. I knocked down the raised seat of both intake and exhaust ever so slightly because they were raised nearly an 1/8th inch. I'm trying to polish these areas out so carbon formation won't be so prevalent(detonation fear)after I get them on my Ty. Does anyone have any idea why these two pockets were left so deep?

Exhaust porting is easy and needed a lot of help due to poor casting on the heads I have. I squared up the exhaust ports a little since they taper inward at the top. Don't know why they did this. Most everything I've read said that most flow is in this area of the port. Easily seen why when looking straight through the exhaust port from the combustion chamber side.

Intake ports left of LOT of room in the "bowl" area for improvement. Not much to do on the intake runner entry since it almost matches the gasket already.

I'm sticking with stock sized valves due to shrouding problems associated with our cylinder size. The bigger valves are supposed to actually become a restriction until higher lifts(over .500)are obtained.I did go ahead and slightly deshroud the combustion around the valves just a little(mainly to take the sharp edge off the "cliff").
Also laid back the edge of the combusion chamber opposite the sparkplug. The top edge actually curled over into the combustion chamber and was razor sharp. Hopefully smoothing it a little helps also.

Like many have said. They is no comparison between the L-35s and the old L-B4s. With the Sonoma GT being available with the Central port injection, I don't know why GM didn't go ahead and use these heads(L-35s) on the SyTys after they went through all the other trouble. Doesn't make any sense. Oh well. Hope this opens some ideas on what to do(or NOT to do)when setting up a setting up a set of heads. These were about $150 with 36K on them. Please give out any ideas on what to do/not to do with the porting techniques.
Thanks,
Blake

 

[nightdiver]

George go and buy Engine blueprinting by Rick Voegelin
i got it from summit
this will answer all of your questions
this is one of the few books i really liked

did you get your seals ?

 

[V6 Kompressor]

Hey George, what year are those heads?? the L35's from the factory had some valve seal issues and caused alot of carbon formation in the egr ports and combustion chambers. Mine would puff smoke everytime I cranked it after it sat for a while. The higher mileage units would also have problems when chunks of carbon would break loose and hang in the egr valve, causing it to stick open, causing little or no vacuum, loss of brakes, idle sucked ect...John Waller has done some work/testing on these heads I believe....

 

[Blake]

Yeah. These were full of carbon. The egr passage was nearly plugged. I think a lot of the problem had to do with the combustion chamber. There are two extremely deep "pockets" on outer edge of the intake and exhaust valves caused by the raised area around the valve seat. These rings around the seats were raised by almost an 1/8th of an inch. The carbon sat in the pockets. The pockets were almost like a "dead space". I have for the most part removed them. Combustion chamber surfaces should be polished as well as exhaust ports. Intake polishing is not recommended since it would hinder atomization of fuel at low temps. The units I have were given to me. The seals were shot. The valve stem seals were hard,shrunken and brittle. They only had 36k on them. There were no valve guide seals on the exhaust side and the ones on the intake side looked like crap. The engine that these came out of appeared to have been somewhat neglected. Baked on oil sludge over a 1/4 inch deep was everywhere. I'm hoping the changes I made help. I've spent a lot of time and took off a lot of metal that the books have recommended. I tried to get some input from real world experience from guys but like old women with their favorite recipes, no one gave any. Like I was supposed to expect anything different? :smile:

I won't be using the egr and the port on the bottom of the intake will actually be plugged with a 3/8" brass plug after it is tapped to accept it.
The only real restriction appears to be the cast iron around the pushrods where it extends into the the intake runners. This makes another "dead space" as I call it right where the push rod cast iron area stops. There was a LOT of metal to be removed on the short side radius of the intake and exhaust.
Both of the valve seals have a hard time in our engines due to the excessive heat being transferred up the exhaust valve. I will send off my valves to have them coated by swain tech coatings. If the exhaust heat can't be transferred up the valve stems, the guides will live longer. I just reused the stock valves in mine so costs are way down and the coating will make me come out about even.
I'll also be running a 160 thermostat. That should help by keeping the heat down in the heads.
I really can't wait to try these out. I'll be keeping the stock turbo for now so I should get a better idea of how well they work. I'm gonna try to just take a stock chip at stock boost levels and work timing and fueling(I have one of the diy wb o2 setups on the way)and see how much more can be factored in at stock boost and then get some times. I use Promgrammer. You can download it at
http://www.chitownsyty.com/tech/p01.jar
Doesn't really do anyone any good if you use new heads and then put on a huge turbo, big injectors, a cam, and air to air ic, and hedders. There is no way to tell how much the heads really helped when they get lost in the mix.
This is a learning experience for me. I wish more guys would be willing to help with the process. If you find out any more useful info let me know. It was nice to hear that it wasn't just my set and they were all that way.

 

[V6 Kompressor]

No Problem, I have some experience with iron and steel Big Block heads, and I was planning on doing a set of L35's. I appreciate you sharing the info on what you have done and Yes, the damn pushrod area just seems to be in the way on both the l35's and the lb4's. I don't have a set of L34's so I don't what those ports look like inside, except they seem to flow the best, but you have to do some major mods to make them work, somewhat like using a BBC truck block, you have to use spacers for the intake, custom distributor ect... I didn't think about coating the valves, I was going to try a set of stainless, and see if I can get some teflon pc seals for our application.
My old lady's 95 L35 blazer has 140,000 on it, and it doesn't puff smoke, but when I drive it on the interstate, 9 out of 10 times I get a chunk of carbon hung in the egr valve....something to do with my right foot...I think you will have less problems with the synthetic oil, because it's not supposed to carbon up, like conventional oils do...I would like to see some pictures of your art work when you are done....Thanks, Steve.

 

[jwaller]

ok....listen up...making the vortecs work is so simple you will kick yourself for not doing it....suck it up...the vortec heads are so much better than the L35's and stockers you will be amazed...if you ever looked at them side by side you will wonder how the hell anybody ever even thought of sing the L35s/stocker

 

[V6 Kompressor]

Hey Blake, I told you John W. had done some work on these...Email him for the straight scoop or look for past threads on the heads, flows, ect...

 

[Blake]

I really appreciate your feedback Steve and John. I'm trying to keep costs down to real world figures. Most of us don't have $1000's to dump into their engines. These heads were given to me and I have seen them side by side with the LB4s. There is no comparison. I will be helping Jesse very soon with his trans and I'll see if he wants to take some pics of these heads when I am done so I can put them on here. I've purchased a couple of books and looked at many sites on the internet and they have all jived together. So these heads will probably make me run very lean with a stock calibration. I'll see if I can CC the before and after of the combustion chambers.
I may use Vortecs in the future but being able to just bolt on the L-35s with some major porting is fine for me right now.I don't have to mod my distributer, buy expensive phenolic spacers or fab up adaptors, or worry about accessories not fitting up just right. Right now I have time available to me and not tons of money :sad: (saving for a 3 years old's college). These are something that anyone could do and *should* be little more than RR.
I used a dremel with carbide bits and the HD flex shaft attachment so I was able to do very detailed changes to the combustion chamber as far as reshaping, deshrouding and smoothing. Took several hours and lots of dustmasks :smile:
I've seen very little discussion on head porting except for multi angle valve jobs, but if you look at the bowls of the ports on the L-35s the money you spent on the valve job is pretty much waisted comparitively. Doing ANYTHING with LB4 heads is waisted time as L-35s become more available at the bone yards.
Sorry so long. I'll try to get these done and put them on and see what kinda changes it makes.
I have one of the diy wb o2 kits on the way so I'll get see some detailed stuff that may give guys a starting point if they want to use stock boost levels with L-35s.

 

[Hu Ryde]

Sure George, we can take as many pis as you like. Let me know what your schedule is so I can come over sometime.