Head welding

[ShionS14]

I have read and heard of people welding extra metal to the top of a cylinder head to raise compression... is this true? can it be done to our heads? would it raise the compression much or just a little? believe it is called cylinder shaping or something like that

[NateDogg]

yesyesdepends how much metal you weld inwelding the combustion chamber

[ShionS14]

has anyone here had this done? i know it increases the quench area and forces the air fuel mixture towards the center for a more complete burn but is it that beneficial? and will it increase compression significantly or just a little?

[PandaS14]

Yes it can be done. It works great as detonation suppression, in addition to the added compression. Large quench areas are how honduh motors run such high compression on relatively low octane gas. For your application, it all depends on how wild you want to go. The more you do, the more potential detonation suppression it could generate. The amount it will up compression is also porportional to how much you do. Whoever you have do it for you will be able to calculate what compression ratio it will yield for different amounts of addition done (and if they can't tell you exactly how much, find someone different.) but the main reason is for the more complete burn and detonation suppression. So if you are planning on running some crazy compression, I recommend it.

[Ubernoober]

I don't know what the smog requirements are in your area, but increased quench will generally raise your HC output while lowering the NOx.I doubt it matters, but I thought you might want to know.

[TrunkMonkey]

head welding has pretty much become a thing of the past. these days, almost all cylinder heads (especially imports...not just hondas) have well designed combustion chambers with quench areas that will take a lot more abuse than it's stock right off the factory floor engine performance will ever give it.

head welding was used back in the day when combustion chambers were just a big space with 2 valves. to top it off, piston design has come a long way too. a well designed piston can help prevent detonation and raise the compression ratio at the same time.

unless you can find someone who actually still practices head welding, i'd steer clear of it.

-demetrius

[ShionS14]

ya i need to find someone to do it know. i am going to use it as an alternative to raising my compression, bump from 9.5:1 stock to a 10:1 or maybe a hare more. i did find i good article on head welding in one of the links you gave me panda, they did theirs on an sr20de motor from a 98 sentra se-r. they were impressed with the results so i am going to have to try it thanks for you guys helping me out

[PandaS14]

I don't think it's a thing of the past at all. It's just that now there's less to do, volume wise, but there are still large gains to be had. Like the article said, it is one of the few mods that truly loses no bottom end with a gain in top end.

[ShionS14]

word!!!

[Xero]

totally, which one of these would you rather have

the stock modern DOHC pent-roof head or the clover-leaf head? (I'd take the clover-leaf every time)

cleaned up Subaru EJ20 head

clover-leaf shaped Nissan head (most likely an SR20)

all images are from http://www.dprracing.com they do some serious head work. Very impressive

[RexAtHighSpeed]

There are a few things you should know about welded heads. When you weld heads, especially aluminum, they warp. If you keep the heat under control, you can control the amount of distortion that takes place in the head to a certain extent. Either way, you're going to apply a tremendous amount of heat (enough to melt aluminum) right next to the valve seats. They guy that does your head will have to sink the valves to get the 45 degree valve seat to clean up all the way around. The welded areas will also be much softer than the unwelded areas - soft right where the head gasket seals. If you're going to turbocharge or add Nitrous I'd advise you not to weld the heads. To do it right, you need to have the head heat treated (like all factory heads) but that is expensive and again, the head will be warped and will need to be surfaced and valve jobbed. Here's what you're looking at:

1. Weld the head2. grind the weld to shape the chambers to be reasonably symmetrical3. Valve job (which includes grinding the tips of the valves since we have non-adjustable valvetrain)4. Surface the heads

Put a dollar figure on all that, add it up and compare it to the cost of a new set of pistons and rings. Call any reputable head shop and they'll tell you the same thing. It's going to cost you big to do it right.

Just my two cents worth.

[ShionS14]

well that was a pretty good amount of insight, but dpr has done a sr20de head before and if i am not mistaking that is aluminum and they didnt have any problems. but i will take that into consideration

[RexAtHighSpeed]

I'm just saying it's alot of work and alot of money. If it's what you want and if it's worth it to you then that's all that matters. I never meant to say that dpr does not do good work - on the contrary. The pictures posted above are top notch. They have definitely been heat treated. When heads that have been welded are surfaced, the soft areas turns light gray and very dull. After heat treating, machining leaves the deck surface nice and shiny (like new). Usually you can see the welds after it's been machined. Especially if someone uses the wrong aluminum rod to weld with but those pictures say a thousand words. Nice job! The price on their website is about right for that amount of work. It's alot of money but you're getting alot of work done. It looks like quality work. Just welding the chambers is not worth it to me but if you add all the work they quote (port work, nice valve job, cc, surface the deck), I'd go for it! You'll definitely get more out of all that than just changing the compression ratio.

[silencer.1]

Why bother welding? Slap some KA24E sohc pistons into a KA24DE and it instantly has a 11.1:1 CR.

[PandaS14]

^^^^

Improved detonation resistance, as well as better air/gas flow. SOHC pistons don't do that.

[ShionS14]

and doing head work is a lot easier to do because i dont have the equipment to do pistons or the money that would be involved in doing it since i am already going for the p and p valve job etc.

[Fidelity101]

w

Why bother welding? Slap some KA24E sohc pistons into a KA24DE and it instantly has a 11.1:1 CR.

why not do both?

[Bigvinnie]

Well really good professionals are the only ones that still weld heads...The averagage Joe usually keeps it simple and just gets the head milled.....Down side to welding is that a head can warp from the intense heat of the new compression, and the downside to milling is that you can deal with valve clearance issues. You can bend a rod if you mill to much.I saw an show on the speed channel, it is pretty informative.It states that you should look for a company that does casting.There is always a company out there that can cast you a head.......Or you can do what a bunch of old schoolers do and modify heads from other engines such as implementing a 1970's V8 Dodge HEMI head on to a datsun/nissan L series engine........I think that the clover leaf weld is very interesting though and I would like to try it some day.............

[eddiec]

you can avoid valve clearance issues by getting the piston tops "flycut" or whatever they call it. basically little pockets are cut int the piston tops to allow the valve to open fully and not hit hte piston.

any welding will be expensive unless you do it or have a good friend who can. the modern head design is quite efficiet compared to its old school bretheren, but its still has its faults. so if this is just an exercise to have something different then go for it. junk heads can be had cheap. try it out and let us know. if your looking for more power from increased compression or just some slightly beneficail gains from welding, then address other larger problems before this. the gains will be there, but i believe they will be of little notice compared to other possible mods.

[Bigvinnie]

Flycuts aren't that great if you are trying to achieve really high compression, fly cut's will drop compression. Personally I don't like flycut'sGood reliable method of achieving higher compressions is destroking in my opinion.It allows for better use of the power band, and allows more high rev......I think if people want good compression just drop the SOHC KA pistons into the DE, and use thinner headgaskets......Advancing the BTDC through adjustable cam gears, and shifting the power band a bit is a good way of maximizing efficiency when changing to a higher compression............

[PandaS14]

^^^^^

However, with really high lift cams sometimes you can't avoid flycuts.

[deviousKA]

Modified by deviousKA at 5:01 AM 9/17/2005

[Bigvinnie]

Devious KA this question is mostly for you since you are more knowledgable in the NAPS-Z/KA department.........I'm looking for a good compression for a destroked KA/NAPS-z frankenstein....Instead of dropping sleeves into the KA block I will be using a NAPS-Z front sump block found on the 82-83 200sx, and a SOHC KA head for a much easier conversion, the internals will be forged and the crank bearing's will be KA not naps-z bearings......The SOHC head will be using a solid lifter assembly which I noticed that your company is one in a few that sells the solid lifters....I understand that NAPS-z had dropped dish piston volumes. What would my compression be with a milled KA head at .020......I'm looking for a compression of 9:1, plan on boosting with atleast 10PSI for a 510 project that I am starting........Is this setup possible?????Or would it be easier to drop sleeves into the KA block?????I also understand that the NAPS-Z block had poor cooling that was later redesigned better for KA, how can I improve the cooling of the NAPS-Z block also, if this project is possible.........
Modified by Bigvinnie at 7:54 AM 5/8/2005

[deviousKA]

Modified by deviousKA at 5:04 AM 9/17/2005

[Bigvinnie]

Thats great devious....That is what I was looking for........I'll do a cloverleaf to the head "no milling" I know the head shop Rebello Racing sources there work too, use a z20/22e block and head bolts, 2.2 bored .040 over, use naps z timing cam sprocket, use a z18et turbo manifold "with small modifications to the mani ports to make them round not square", or I'll pick up a NIZZX turbo mani for KAe "which ever one I can get first", "silvia/240sx intercooler"One little kick *** 510, with no smog emissions.........I can get a NAPS-Z block for under $300 at the wrecking yards, my cheapest performance build to date.............I'll follow John Ropers install adendum on mounting into 510...........

[SSS]

I had the chambers welded to decrease their volume about 3 years ago, in an effort to increase compression to around 9.2:1 on my SOHC.It's still going strong, but i was never 100% happy with how i finished the chambers. It was my first time doing this sort of work to a head. Big step i know, but i was trying to pull out all the stops to get as much power from this head as i could.In hindsight, i would have been far better off just getting the chambers ceramic coated.

[Bigvinnie]

My bad that is the sohc.........Was there clearance issues with the spark plugs, and any hot spots??????

[SSS]

No plug interference problems at all, and with upto 7degs advance (via distributor), has not pinged once in 3 years.Although the advance has been altered via my smt6 piggyback ecu until i can tune a decent rom, and i always run it on 98 octane.I was hoping the large quench area that was added as a result of welding would perform.

[Bigvinnie]

You should check out http://www.nizzx.com. They now carry modifiied forged pistons for sohc and dohc for the KA, head welding will not be necessary.They offer the pistons in 8.1 all the way up to 13.1.Here is the link http://nizzx.com/engine%20build%20up.asp

[SSS]

I plan on using coated CP forged pistons with a stock combustion chamber volume head, then swap to a DE head when i hit a brick wall with the E head.

I wouldn't bother with the Mahle pistons they have listed, they are probably no better than the ACL hypereutectic pistons i can get here for $350 a set including rings.