Rebuild #2- Fixing my previous mistakes & Avoid New Ones

[Snap]

pression blue.
Won't the valve height make a differance when CC'ing the head if they are at differant heights?
I am thinking about having a three angle valve grind done on the heads.

Prussian blue is good for shiny new parts. You will see just fine with your old parts what is carbon gunk versus shiny old contact surfaces.
Yes, combustion chamber volume changes as valve profile in combustion chamber changes. Do not worry about it until after valve work is complete.
A three-angle grind is mandatory if you give half a damn. It allows you to set valve depth/seat contact depth and width.
Make sure you supply all the numbers from your Bentley. If exhaust calls for 2.5mm contact width, DO IT. If intake calls for 2mm contact width, DO IT! Valve margin, face, stem diameter, 22*/23* interference on the intake angles, DO IT, the Germans had their reasons!
Colin

Thanks so much!!! I have found a reputable machine shop that will to a three angle grind for $78 for both heads. Did stock mexican heads run SS valves? If not, I am going to replace them also just so I have some longevity.

[Amskeptic]

pression blue.
Won't the valve height make a differance when CC'ing the head if they are at differant heights?
I am thinking about having a three angle valve grind done on the heads.

Prussian blue is good for shiny new parts. You will see just fine with your old parts what is carbon gunk versus shiny old contact surfaces.
Yes, combustion chamber volume changes as valve profile in combustion chamber changes. Do not worry about it until after valve work is complete.
A three-angle grind is mandatory if you give half a damn. It allows you to set valve depth/seat contact depth and width.
Make sure you supply all the numbers from your Bentley. If exhaust calls for 2.5mm contact width, DO IT. If intake calls for 2mm contact width, DO IT! Valve margin, face, stem diameter, 22*/23* interference on the intake angles, DO IT, the Germans had their reasons!
Colin

Thanks so much!!! I have found a reputable machine shop that will to a three angle grind for $78 for both haeds. Did stock mexican heads run SS valves? If not, I am going to replace them also just so I have some longevity.

Stock factory heads should have decent valves that know all about emissions lean heat.
Aftermarket AMC heads from Spain or Auto Linea from Brazil, or the new stuff from China I would not trust the hardware.
Colin

[Snap]

I have never felt I was able to get the carb completely tuned. It seem to have both rich and lean characters. I would have a hard time accelerating from 45-50mph, die while rolling to a stop and pop after I shut it off. I had always thought that that the idle screw was backing out of adjustment. The carb did not have any idle jets (only adjustment screw), air correction circuits to fill in that empty void between idle and main jet circuits. To remedy that problem, I have purchased and plan to install a remanufactured Solex 34 Pict 3.

I also felt that since the PO had removed the thermostat and never drilled the heat riser passage on the header, this was also partially to blame for the poor running characteristics as well as fuel dropping out before it got to the cylinders. I pulled the plugs to read them and was kind of baffled from what I discovered. It looks like 1 and 3 were running lean and hot as 2 & 4 were running rich. I also noticed I could have an excess of blow by as the breather tube is very oily and there seems to be oil leaking past the crank pulley and a small leak at the output seal. I am assuming that the rings never got to seated correctly from day one, even with correcting all the other problems I am still going to have blow-by in 2 & 4. The other possibility that I can think of is that the fuel is droping out so that by the time it reaches 3 & 1 its mostly air and no fuel and all the fuel is running is making it to 2 & 4 never getting up to temp and never fully expanding causing blow by. -Update( with the engine out of the car I was able do a by-hand compression test and only #1 would hold pressure as the rest of the cylenders would quickly bleed off. I got problems...

I finially got the heads torn apart and fiigured out why it had both symptoms of lean running/low power and always smelling like fuel with a pop at shut off. All the cylinders had enough compression to fire, however 1 & 3 were the strongest. On the other hand, 2 and 4 had just enough to run. I found carbon trapped under the seat on the high valve and an intake with carbon on the inside of the runner (bypassing the valve). No matter what I did to adjust the carb, it did not matter if there was not enough compression to burn all the fuel in the week two cylinders. Unburnt fuel was passing by into the exhaust system, building up enough to produce a pop after shut down. By leaning that carb, I just heated the strong cylinders up making no effect on the pop or smell.



I also realized that I only have 11,000 miles on this engine and not 25k.

Exhaust Valve Seat Pics












Are these valves seats slavagable enough for a 3 angle grind? Are they too soft and should be replaced with a better quality seat for miles of trouble free opperation?

Colin, You stated that as long as these were VW heads, more than likely, they were made with quality parts. I identifeid that the intake valves were made by TRW, which I think is a reputable brand, but who made these exhaust valves? .... does CB performance make a better SS valve for $8 a piece to go with new seats?


TRW is printed but not quite visable


The Diammond

Here is what I am thinking. I already have the engine pulled to install the thermostat assembly, and now going to replace the output seal and flywheel o-ring.

I read the thread to make sure my next front main seals this time!!!



I have decided that since I have this thing apart this far, and I know I did not break the rings in correctly the first go around, I am going to follow Slugo's lead by honing and replacing the rings, following with the Bob Hover cleaning method.

[ruckman101]

Looks like you're on track to getting it done right.


neal

[Snap]

Looks like you're on track to getting it done right.


neal

I sure hope so.

[Amskeptic]

I also realized that I only have 11,000 miles on this engine and not 25k.

Those photographs look weird. You might have weak valve springs. I do not see adequate contact pressure in the lack of shiny. Your questions at this point must be answered by a competent machinist actually looking at the parts.

Good work, diving in like this.
Colin

[Snap]

I cleaned some stuff up and the dirt carried away with the solvent may have covered up the shinny spots (I did not lap them yet either). I will probably have them check the spring pressures also.

[Amskeptic]

I cleaned some stuff up and the dirt carried away with the solvent may have covered up the shinny spots (I did not lap them yet either). I will probably have them check the spring pressures also.

Without a doubt, they best will should had better have checked the spring pressures and heights without your even had occasion to have had to having ever asked.
ColinFunWithConjugation

[Snap]

I dropped the heads off to the machine shop last night and sounds like the exhasut seats are too far gone to be reground and fixed, so they are going to be replace. I am kinda of learly of the seats dropping out in the future now that they are going to be replaced. Is this mainly a problem with the Type VI heads or all Aircooled heads? I am having the height and spring tension checked also.

[Amskeptic]

I dropped the heads off to the machine shop last night and sounds like the exhasut seats are too far gone to be reground and fixed, so they are going to be replace. I am kinda of learly of the seats dropping out in the future now that they are going to be replaced. Is this mainly a problem with the Type VI heads or all Aircooled heads? I am having the height and spring tension checked also.

The problem is less with the heads and more with the installers and the drivers once it is all back together. The installer *must* follow the directions to the letter. There are some tricks to help keep them in the heads, sweging the aluminum over the seat edges a little, making sure the heads are heated to installation temps + a little and making sure the seats are chilled so that the interference will be greater than any environmental condition you are likely to experience . . . and that is where the driver has some responsibility to not overheat the heads.
Colin

[hambone]

I was under the ASSumption that dropped seats meant the death of a head due to the machinist's required skill.

[Snap]

I was under the ASSumption that dropped seats meant the death of a head due to the machinist's required skill.

No, I am just leary that they may eventually drop out after the replacement. I just order a head temp sendor so I can keep an eye on temps and preserve all this work. I trust that the machinist knows what he is doing but I am going to check his work just to be on the safe side.

[chitwnvw]

Has anyone seen a dropped seat? I've seen lots of recessed valves, but never a dropped seat.

[Snap]

I dropped the heads off to the machine shop last night and sounds like the exhasut seats are too far gone to be reground and fixed, so they are going to be replace. I am kinda of learly of the seats dropping out in the future now that they are going to be replaced. Is this mainly a problem with the Type VI heads or all Aircooled heads? I am having the height and spring tension checked also.

The problem is less with the heads and more with the installers and the drivers once it is all back together. The installer *must* follow the directions to the letter. There are some tricks to help keep them in the heads, sweging the aluminum over the seat edges a little, making sure the heads are heated to installation temps + a little and making sure the seats are chilled so that the interference will be greater than any environmental condition you are likely to experience . . . and that is where the driver has some responsibility to not overheat the heads.
Colin

Good to hear, I feel much better now. This guy seems to know what he is doing, been around a while, I cannot find any bad reviews, and I got a head temp sendor.

[Amskeptic]

Has anyone seen a dropped seat? I've seen lots of recessed valves, but never a dropped seat.

Yes, some are subtle where they just move a little and get hammered by the valve. You can see a space opening up between the seat and the head material. When they let go, they can land cocked and stick a valve into the piston, grenade city with hardened metal fragments.
Colin