T da dos aprietes diferentes???? O uno es pa C20XE y el otro...
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T da dos aprietes diferentes???? O uno es pa C20XE y el otro...
Buenas
Paco: lo de los dos aprietes :shock: ummmmmm
Oye algo, las Kolven de sugunda generación sufrían no de poros, sinó de que se les aflojaban los tornillos de la culata. (es lo que he leído). Y la explicación es que las primeras Kolben tenían un material de 380 y las kolven de segunda generación 220, osea que las del 93 en adelante vienen con el material más blandito. Por el contrario todas las coscast vienen a 350.
Será por eso que vienen dos aprientes??? :roll: el 25kpm+90+90+90+15 para las kolven más blanditas y menos apriete para las coscast más duras de 25kpm+65+65+65, ó será al reves. :?
Saludos y espero ayudarte con eso.
Mira la tabla de topbuss (creo que fuíste tú quién la encontró hace mucho)
(Coscast) Cosworth 1987-1989 KADETT-E. C20XE 350N/mm² No Problem! .
-(KS)Kolben Schmidt 1989-1991 KADETT-E .C20XE 380N/mm² Water damage possible .
-(KS)Kolben Schmidt 1989-1993 ASTRA-F/VECTRA-A/CALIBRA. C20XE y
C20LET 380N/mm² Water damage possible .
-(Coscast) Cosworth 1993-199x ASTRA-F/VECTRA-A/CALIBRA. C20XE y
C20LET 350N/mm² No Problem! .
-(KS)Kolben Schmidt 1993-199x ASTRA-F/VECTRA-A/CALIBRA. C20XE y
C20LET 220N/mm² Material too soft! Head screws come loose!!!! :!: :!: :!: :!: :!:
Saludos
Cita:
Iniciado por K_V6
Cuando leí el post me puse a pensar en eso y primero pensé que talvez sea para el 8valvulas??, pero me fijé que arriba especifica que es para C20XE del 93, entonces pensé en lo de los dos tipos de culatas. Quizás no sea un error del TIS, sinó que no especifica bien para que será cada apriete.
Saludos
Por lo que llevo deducido hasta el momento, parece ser que el tipo de apriete está relacionado directamente con la longitud de los tornillos:
Para tornillos de 110mm: las 3 tandas de 65º
Para tornillos de 105mm: las 3 tandas de 90º
Parece lógico pensar que ha tornillos más cortos, necesitarán más apriete para sujetar lo mismo ¿No os parece?
Lo que no está claro es el tema del reapriete:
-En el TIS dice que no es necesario en ninguno de los casos.
-En el manual de la junta(AJUSA) dice que 30 grados para el primer caso y que no es necesario en el segundo.
En la teoría del reapriete están de acuerdo la mayoría de mecánicos, pero ¿Cuando grados le doy? ¿ A cuántos kms el reapriete?1500-4000....
Bueno esta tarde he asentado culata, he lijado bien la junta del bloque con lija P-1200 y sin apretar mucho para no marcar, de momento le he dado sólo el apriete en kpm:2,5 a la espera que Alex(Kilm3r) me comente lo que le dice un amigo que tiene en Opel, además lel apriete de 2,5 se lo he dado en 6 u 8 tandas, para que luego no digan que no ha asentado uniformemente, además el apriete angular en pensado dárselo con una hora de intervalo entre uno y otro :D .
Ahora estoy rallado con el tema de los taqués: tengo dos tocados de la Kolben que son lo que llevaba actualmente, los de la Coscat no me fueron bien en su día, pero estoy pensando en volverlos a probar, por cierto los he limpiado según el método que comento Corsa220HP.
Saludos
La logica de los tornillos no es mala.
Respeto a lo q dices de los takes, bueno el take siempre podras sakarlo sin tener q desmontar culata no? A muy malas se prueba aunke t lleve otra tarde el abrirlo pa kitarlos. Pero bueno...
Na, es cuestión de 1/2 hora: lo que tardas en levantar arboles y volver a calar distribución.Cita:
Iniciado por K_V6
Date cuenta que para probar no pongo correa de accesorios, y eli filtro de aire,caudalímetro y demás lo pongo un poco superpuesto y a correr... :D
No te olvides de decirnos como apretastes la culata. Mi culata es la misma que la tuya, y le dí los tres aprietes de 65º mas los 30 de reaprite. Llevo los tornillos cortos, asi que estaré atento.
Hola:
Aqui les dejo algunos datos mas que e encontrado en un foro ingles.
Siento que este en ingles pero para el que no entienda, con cualquier traductor es suficiente.
"This is by no means meant to be a definitive guide to the Cosworth produced 20XE cylinder heads, i'm just collating all the stuff i know into one pile and hopefully it should go some ways to dispelling a few myths and answering a few questions about the illustrious chunks of metal! The main two points of discussion seem to be that the head produces more power than the GM variant, the other discussion banded about is that Coscast heads are not prone to the infamous 20XE porosity issue.
So the story starts back in 1987/1988 when Vauxhall decided to develop a range topping 2 litre 16v double over head cam engine for the forthcoming Astra GTE16v. It was based on the current range topping 2.0 8v family-2 engine block with changes to the crank, rods and pistons. The first major point is that Cosworth did not design the cylinder head. To my knowledge they had no involvement in the design process at all. The 20XE cylinder head was penned by Opel advanced engine development, lead by german born chief engineer Dr Fritz Indra. I think the confusion was fueled by the fact that Cosworth had previously designed and produced heads for the 70/80s CIH engines, most notably motorsport and road going heads for the 2.4 manta 400 power plant.
So, where do Cosworth come into the equation ? Well simply, Vauxhall commissioned Cosworth to produce the original astra cylinder heads at much cost I might add. Infact, Dr Fritz Indra’s approach to whole engine was one of complete perfection with little regard to cost. How he managed to convince the number crunchers at opel is beyond me. It bares testament to the units over-engineering, the fact there are thousands still going strong and being tuned further, 10-15 years later.
Quote:
Designs built in large numbers are often spoiled by insufficient attention to detail, he says - a four-valve head is wasted unless every other part of the engine is carefully optimised to exploit its breathing potential and combustion efficiency. "You must have the best induction system, the best injection system, the best exhaust system, the best ignition system and proper knock control." In some rival four-valve engines, he says, the potential for free breathing is thrown away by the use of an intake air cleaner of the same size as for the two-valve variant
The trade mark “Coscast” is a licensed method to produce quality castings, molten aluminium is pumped into an inverted high quality mould made from a grade of zircon sand, via a sealed crucible. Crucially the same grade of aluminium was used for both the later Kolbenschmidt (see below) produced heads as the Cosworth heads (LM25TF with the TF being the brinnel hardness range). So the only difference was down to Cosworths comprehensive casting method.
Now, this is where my info gets a little vague as I don’t know the exact reason, but, late in 1989 GM dropped the contract with Cosworth and farmed the production of the cylinder heads out to the german engine manufacturer Kolbenschmidt. Using the same design as the original Opel head but utilising their own inferior casting process, they then pumped out heads in their thousands between 1989 and 1993, so basically late GTE’s, and mk3 Atras/Cavaliers. A second run from cosworth was produced later in 1993, and cars from that date onwards had either type fitted.
So what is porosity? well, despite what the name suggests its nothing to do with the metal becoming porous (allowing water to seep through its microscopic structure), it is infact a physical crack between the main oil channel in the front centre of the cylinder head (between exhaust ports 2+3) and the coolant gallery above cylinders 2+3. In the Kolbenschmidt produced heads, the cast was too thin in this area, in some cases critically, and the alloy was slightly harder and thus brittle, a combination of concentrated pressure from the front centre head bolt and the extreme cylinder heat below, this forms a crack in the alloy allowing oil to enter the coolant passages. Then you get the trade mark mayonnaise in the coolant system as oil and water mix together with resulting confusion that its a head gasket failure. On this premise alone it is still possible for a coscast head to go "porous" but its infinitely less likely due to the casting being thicker at the key point and the alloy itself being physically stronger. Vauxhall never admitted liability for the failures and there was never a proper recall for the fault, but, any car that came in with this fault under the manufacturers warrantee was fitted with a tube repair in the oil gallery or an exchange Coscast head. Aparently post 1993 Kolbenschmidt heads had softer alloy structure, added to the porosity issue, its rumoured this is why Vauxhall altered the method of tightening down the XE/LET head bolts from the earlier 5 stage sequence to the later 4 stage sequence. Later engines also were fitted with short head bolts from the factory.
Whats the difference between Kolbenschmidt and Coscast heads and how can I tell which one I have ? Apart from the porosity issue described, the heads are virtually identical. There is an exception however, the early astra heads between 1988-1989 had hand finished inlet ports from the chamber all the way to inlet manifold, they also had 2mm bigger valve guides, and slightly deeper valve seats, they also used dish shaped valve springs seats as opposed to the later flat disk. The later coscast heads after 1993 were same in specification as the interim Kolbenschmidt heads, basic machining around the valve throat is all they got. The port finish was just left from the cast, almost like the complexion of orange peel. As mentioned earlier, the early pre catalysed 20XE engines made 156bhp from the factory, purely by coincidence the Kolbenschmidt cylinder heads were introduced at the same time as factory fitted catalysts and the power dropped to 150bhp. Needless to say ever since rumours are bound that the power difference was due to Coascast heads being better, this simply isn’t the case! The catalyst sapped the power.
The most definitive way to tell if you have a Coscast head is to look under the 2nd exhaust port along from the cam belt end of the engine and you will see the coscast oval. Clearly visible if the head is on the bench, or its still possible to see with a small vanity mirror held under the exhaust manifold…
http://www.astra-mk2.com/0ddball/cos/cos.jpg
Alternatively there are distinct casting differences such as the posts that the engine lifting rings bolt to, and the exhaust heat shield bolt to, these are U shaped on Coscast heads and just round posts on Kolbenschmidt heads…
http://www.astra-mk2.com/0ddball/cos/cos2.jpg
Also on the distributor end of the head you will see a tapered hole and a distinct Z shaped ledge along the side of Coscast heads…
http://www.astra-mk2.com/0ddball/cos/cos3.jpg
Note also in the above picture the head is plain cast at the distributor end. On Kolbenschmidt and post 1993 Coscast heads it will have a GM stamp and GM part number there in raised lettering. So this particular picture is the nicer early gte head.
The following chart is a guide to the production dates and types of head fitted to different types of car. Kadett-E being mk2 Astra, Astra-F being mk3 Astra, Vectra-A being mk3 Cavalier. Note this is just a guide to the heads produced during those periods, its been nearly 15 years since the engines were first produced and the amount of mixing and matching will be widespread by now. So some cars made after 1989 can and do have Coscast heads."
http://www.astra-mk2.com/0ddball/cos/cos4.jpg
Espero que les sea de ayuda.
Saludos
Antes de ayer, asenté la culata y le dí los 2,5Kpm en 8- 10 tantas proporcionales, ayer le dí las tres tandas de 90º dejando un intervalo de una hora entre tanda y tanda para que se fuera asentando bien.
Ahora la duda que me queda es si darle 15-30º despues de hacer 1500 kms.
Saludos