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Just Got My Head Back - Should I Be P****d??

9K views 63 replies 12 participants last post by  ant_8u 
#1 ·
Hi Guys

I've just got my cylinder head back from being worked on and I'm a little uncertain on a few things

I've taken some (bad) pictures and I need your input

Here goes......

The first six pictures are of the chambers, and show how close the inlet and exhaust valves are to each other

Notice how on some of the chambers the seats actually overlap each other.....Is this ok or should I be worried?

(the head is cast iron and it has had inserts fitted to the exhaust to allow the engine to be run on unleaded fuel)














The next five pictures hopefully show the varying depths the seats have been cut into the head

Should they all be flush with the chamber, or does it not matter that some are recessed?












The next picture shows the original inlet valve next to the new (mismatched) valve

The original valves are 65g in weight even when covered in carbon
The new valves are 70g and have a different shape to them

Note - he has only replaced two of the inlet valves with these heavier valves

The new valves have been fitted into the chambers which have had their seats cut deeper than the others

I'm thinking he's obviously fitted these valves because he's cut the seats too deep?




The last two pictures are both of the same chamber
I have taken one picture with one of the original valves in it, and then another picture with the new (heavier & different shaped) valve in it

I don't know if you cam make it out from the picture, but the original valve sits further into the seats than the new valve does






How right am I to be worried about any of this?

I'm pretty pissed that the head came back covered in old paint and carbon, but I can sort that out myself


What I really need help with is knowing whether the machining is good or not, and why are there different valves in the chambers with the recessed seats?

(I can't contact the guy until tomorrow, so I need your input before then so I know what to say to him - if it's even a problem)
 
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#4 ·
hcompton - the valves are all the same length and diameter

It's just the shape of them that's different


The guy told me the valves I had are terrible and that he would throw them all away and replace them with new/better flowing ones

But now I find I've got my original valves with only two replacement ones which don't match


My original valves are readily available
Should I do a leak test assuggested, and if all is well, replace the mismatched valves with the same ones I had to begin with?
 
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#5 ·
Hi Guys

I've just got my cylinder head back from being worked on and I'm a little uncertain on a few things

I've taken some (bad) pictures and I need your input

Here goes......

The first six pictures are of the chambers, and show how close the inlet and exhaust valves are to each other

Notice how on some of the chambers the seats actually overlap each other.....Is this ok or should I be worried?
The following is my opinion. I am not a machinist, but this ain't the first time I've seen a set of small valve heads w/big valves fitted.

The seat overlap is normal.

The next five pictures hopefully show the varying depths the seats have been cut into the head

Should they all be flush with the chamber, or does it not matter that some are recessed?
You'd like every seat to be the exact same height. But in the real world this doesn't always happen. I do not see anything that will effect the flow, though. This does mean you are going to have to pay attention to the valve spring installed height- but measuring the installed height is SOP anyway.

By mocking up the valves using a light checking spring or even just holding them closed w/your hand you can measure the spring height between the spring seat of the head and the underside of the retainer w/a snap gauge and caliper to see how much the heights actually vary. This gives a direct indication of what the seat placement really is; the chamber volume is not how you judge the seat placement.

If your valves are made to have a stock spec 1.7" spring installed height (they're not +0.100" valves, in other words), compare the measured installed height to 1.7" to see if the seats are sunken or not.

If the installed height is too much for the springs you're going to use, add shims under the springs. Keep the valve seat, valves and shims together once you measure the installed height. Try different valves on different seats to get the best match.

The next picture shows the original inlet valve next to the new (mismatched) valve

The original valves are 65g in weight even when covered in carbon
The new valves are 70g and have a different shape to them

Note - he has only replaced two of the inlet valves with these heavier valves

The new valves have been fitted into the chambers which have had their seats cut deeper than the others

I'm thinking he's obviously fitted these valves because he's cut the seats too deep?

The last two pictures are both of the same chamber
I have taken one picture with one of the original valves in it, and then another picture with the new (heavier & different shaped) valve in it

I don't know if you cam make it out from the picture, but the original valve sits further into the seats than the new valve does
The valves he used are better than the ones you have IMO. The reason the old valve looks to sit deeper in the seat is because they're used up and the margin is too thin.

How right am I to be worried about any of this?

I'm pretty pissed that the head came back covered in old paint and carbon, but I can sort that out myself


What I really need help with is knowing whether the machining is good or not, and why are there different valves in the chambers with the recessed seats?

(I can't contact the guy until tomorrow, so I need your input before then so I know what to say to him - if it's even a problem)
The exhaust seat looks a little thin. But again, hard to say just from a photo. You can take some machinist blue or even some grease and lap the valves to see where the seats are located as to how far out towards the edge of the valve the seat is, as well as how wide they are.

For a street engine, you'd like the intake seats to be >/= 0.060" wide and the exhausts to be >/= 0.080" wide. I wouldn't want to go much more than that, and no less. This is a compromise for durability vs. flow.

You need to blend the lip below the seat's last cut into the bowl. You can lap the valves in if you find they're not sealing as well as they should.

Were the valve guides done on these heads?
 
#6 ·
post the bill? did the machinist do the "cheapest" job possible or best? was he informed the application? what is the application?( not engine size but actual intent for the engine,IE hot rod or grocery getter? How do you know what valves go in which hole? were the guides replaced?
 
#8 ·
Not knowing what the original casting looked like. I can see that it has had some guide work. That means the original seat was worn. So some of the depth variance can be due to having to cut the seat a bit more to get a clean seat after the guide work was done.

The exhaust seat depth does vary a bit, but all chambers are not cast in exactly the same height/cc.

The actual seat area looks good for a maintainance valve job. Seat runout and width looks very good. Cut with a profile cutter I would assume.

If this head has an adjustable valve train. Some varience of stem height is allowed. The nominal height/stem protrusion is usually published in the engine rebuild specs.

The aftermkt valves were probably used to get the stem height/chamber volume closer to spec.. A common practice on re-builds.

All told it looks like an acceptable stock replacement valve job with hard seats.


While I'm here. I will tell you of an example I had this past summer.

Two years ago. A customer brings a set of BBC heads in. val port c-chamber early heads. Wants them "rebuilt" going on his hotrod 454. Wants all the best stuff.

By the time they are disassembled (2 weeks) and checked. Like so many people in Michigan. He lost his job.

Now it turns into a "budget job" so he can sell the engine.

The heads needed guides and had at least three/four valve jobs previously. Intake seats were sunk at least .090".

Customer wants them repaired a cheaply as possible. So I knurled the existing guides, something I rarely do. Two of the intake seats were just junk. So I installed new ones. But I had to set them close to the sunken height of the others to maintain some chamber vol. and stem height.

Long story short. The customer comes in last august. "You ruined my heads!" Being two years ago I didn't remember the heads. Of course he didn't have the heads or the original billing. Wants the heads replaced. My bookeeper went back and found all the paper work. No way guy! You got what you paid for.

Seems he had just got the engine running after two years and had a cooling problem. One of his buddies removed the heads (not the cooling problem). Saw the sunken intakes and the stuff hit the fan. Of course its the machinest fault.. I screwed him etc. yada yada yada.. Let no good deed go unpunished.
 
#9 ·
vinnie - I don't have a bill, this was done by a retired individual that came highly recommended for these engines

The car will be used as a weekend toy, he was told to do the best job he can
(parts are so cheap on these engines it really doesn't matter about the cost)

He received the head in July, and I got it back yesterday

He's written 1-12 on the valves in marker so I know their location

I asked for new guides to be fitted, but he left the old ones in place
I'd heard brass ones are better but he said the ones fitted are fine

If I put my finger over the guide and push/pull the valve it sucks my finger
 
#10 ·
Thanks Bob

From yours, and everyone else's comments though, it sounds like I'm good to go


My concern now is the shape and weight variance of the valves

My "original" valves as well as the two replacement ones are both aftermarket

Should I replace them so they all match?
 
#12 ·
BOBCRMAN posted a very good account of what I was leading into. We all have a different idea as to what perfect is.Not just what you think is perfect,also the machinist. Was he trying to make the best results for the least costs? were you hoping for the best headswith no worry of costs?

Bronze guides are good but do not last long. Knurled guides used to be quite common when I was young and poor. Sinking the valves was a quick way to make a chamber bigger,an so on,,,,
 
#15 ·
Oh. almost forgot

The engine is....

1998cc (122cu)
6 cylinder
12 valve
pushrod
All cast iron

Original output was 104hp I believe!!

Looking to rebuild it as best as possible - thinking 160hp would be very optimistic in this car, 130-140hp being more realistic

Quite a beast!! haahaa
 
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#18 ·
I would use a 20b mazda engine ,none bridge port before the Suzuki. I know the motor cycle engine is very popular though. Another good option is a sbf,like the coyote crate engine.
All of the swaps start with more hp than the original 6 could hope to supply.I also thing the 20-b ported sounds nasty,and it has enough rpm to make it sports car like. W/E you decide,its yours and different.Make sure to post some pictures when its close to being finished,and enjoy the project
 
#25 · (Edited)
I've heard people saying they've got 180-200hp out of these engines.....doubtful if you ask me

The engines are the same as the TR6 one....the TR6 has a longer stroke to make it a 2500cc rather than the GT6's 1998cc
The injected TR6's had 150hp

I'll build this one as well as I can, and we'll see what it puts out

I'm trying to find exhaust Vs inlet flow......I want to say it's ~72 to ~75% though
 
#23 ·
For a weekend toy you won't notice any difference from valve weights. If you're running 10 grand then the added weight affects inertia and then you've got to adjust the springs & they're out of balance etc. etc. The seat overlap is no big deal as long as the actual contact areas don't touch.
I fit the valves, turn the head on its side and fill the ports 1/2 way with alcohol then blow around the valve with an air gun. Sometimes all they need is a quick lap to bring them in. Sometimes it's a crappy job. Hopefully your retired machinist has had enough experience to do the job right.
 
#26 ·
For a weekend toy you won't notice any difference from valve weights. If you're running 10 grand then the added weight affects inertia....... Hopefully your retired machinist has had enough experience to do the job right.....
It'll run to around 8K absolute maximum
Most likely 7K though

I'm guessing he's more than experienced enough, my uneducated mind saw the overlapping seats in the head and got scared
 
#31 ·
The mazda is smaller lighter and over 300 hp.I watched the next video on your set there and saw the guy trash that engine,,,The carb noise is quite loud,are you wanting that?If you use a big cam it will be noisey,sounds like they are large gap cams,lash close to 30?
 
#33 ·
.. Instead of building to please others/win trophies, how about just building something YOU would enjoy DRIVING?

.. The 'overlap' of the valve areas is normal for those valve sizes, my new MoTown heads have the same thing... but, I would go in with a powered grinding ball and carefully round over any razor sharp edges to prevent them from glowing red hot when the engine is running and causing engine damaging pre-ignition... being careful to never touch the valve seat in the slightest with the grinder... put old valves in the chamber being worked on to prevent contact with valve sealing area... also remove sharp edges if any on valve heads and backcut the older valves underneath if needed for more lowlift flow...
 
#34 ·
Should I do anything about the carbon in the chambers?
If I remove it will it just return seconds after firing the engine up?


What level of finish do the chambers and ports benefit from?

I've heard mirror polishing is a waste of time, but what level is seen as 'right' ?
 
#36 ·
Remove any sharp edges or casting irregularities that could glow and cause preignition. The area below the seats can be smoothed/blended to help flow. Don't alter the short turn radius.

If you clean all the oily carbon off you can smooth the chambers (if you leave it it'll clog the sanding rolls almost immediately, making them useless), but I wouldn't do much more than what is mentioned in the first paragraph. But it won't hurt anything to smooth the chambers as long as you stay away from the seats and you don't change the basic shapes of anything. I don't know if you have too much compression but if you do, you can work the chambers to lower it some w/o causing any problems as long as you're careful.

The chambers look to be at least partially machined, the scalloped recesses are by the looks of it, and possibly the whole chambers are machined. If that's the case, nothing but touch up needs doing IMHO.

If there are areas left unmachined, use the machined areas as your guide for the finish you want to achieve.

Someone mentioned back cutting the valves. Often this is a cheap and easy way to help flow. GM did this w/the Vortec head- and they do nothing on a whim.

Port matching the manifolds can add a bit of flow, just don't use a gasket and hog out both openings to match the gasket (aka "gasket matching")- that'll create a bulge that will slow the flow when it reaches the bulge, and that'll make for a lot of flow-killing turbulence. You can do some research on port vs. gasket matching (one post: http://www.hotrodders.com/forum/how-difficult-port-intake-manifold-208003.html#post1485231). There's also a little info and some links here.

OT, those chambers have a slight resemblance to the machined chambers of a Pontiac.:cool:
 
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