|
Valve unshrouding question
Hello guys,
I´m going to build myself BP4W head using +1mm intake and exhaust valves and some high lift cams. I would like to ask about valve unshrouding. My question is if it is ok to use head gasket as a template to "mark" how much I can take of the head. I´m asking this because I see this a lot on the internet but it seems not correct to me, since I think doing this with stock head gasket which have like 85mm? bore vs 83mm actual bore of cylinders. I wonder if this doesnt do anything bad to a squish ? I know it is best to use engine block for this but that is not an option for me sadly. It will be N/A car 10.3:1 CR runing on 91octane tune. Thanks for your answers. |
Originally Posted by AndrewG
(Post 1385369)
Hello guys,
I´m going to build myself BP4W head using +1mm intake and exhaust valves and some high lift cams. I would like to ask about valve unshrouding. My question is if it is ok to use head gasket as a template to "mark" how much I can take of the head. I´m asking this because I see this a lot on the internet but it seems not correct to me, since I think doing this with stock head gasket which have like 85mm? bore vs 83mm actual bore of cylinders. I wonder if this doesnt do anything bad to a squish ? I know it is best to use engine block for this but that is not an option for me sadly. It will be N/A car 10.3:1 CR runing on 91octane tune. Thanks for your answers. |
Generally the cutter that does the valve job is what unshrouds the valve, that is if the machine that does the valve job is a serdi or sunnen type machine that uses a single profile cutter. A Newen machine can be programed to do whatever contour you want.
That being said, yes you can use the bore diameter as reference, your head gasket is typically bigger than the bore, so you wouldn't want to go to the edge of that. I would not go grab your die grinder and start going to down, do it right on the seat machine |
Thank you for your answers guys.
the problem is that valve job will be done with just hand tools like this one http://images.esellerpro.com/2386/I/147/62/68346.jpg I think I will redraw the head gasket in Catia and make bores same as the bore of the engine and then cut it out laser and go from there . Thank you again |
Deshroud by hand is a pretty major undertaking. I didn't keep track of the amount of time I spent on my head, but would estimate it in the 100 hour area. That wasn't all on the combustion chambers, but a lot of the time was spent there. I will think twice about doing it again.
my 2 centavos Edit: Napkin calcs indicate ~7% flow improvement over stock with everything I did. 5 angle/port/1 mm OS intake/deshroud |
Do you already own the Newway seat tools (the link you posted)? Honestly i would not touch one of my heads with those tools. They do not hold seat concentricity like a seat and guide machine, you are not going to get good seal with it. In the long run your better paying for a machine shop to do the valve job.
When i worked at the engine shop the only thing we used those for was for flathead lawnmower engines. Any overhead valve motor went in the sunnen vsg and flathead fords were done with stones. You may want to be able to say you did it yourself, you may be trying to save some money, but in the long run you get what you pay for, and if you want a good performing engine that will last, i suggest taking it to the people with the correct tools for the job. |
I did it carefully with a dremel. Basically just smoothed and polished, light unshrowding as to not sacrifice quench. Power is a good bit better but I did cams at the same time
|
well valve job will be performed by my friend who have build more than few race engines and they do valve jobs by hand tools (not actually the one I posted, I posted that picture just to show the tool type).
I have got quote from top builder in my country for head work with double the price of same work done by my friend (no friend price). I will think about it again and if I will have money at the moment, I will go with that shop. I will ask them for deshrouding too as they have rottler machine in the shop. Thanks again, much aprreciate it I already did BP head from my NA8 engine in last winter and it worked really nice ! I do not have any numbers but I do not really care about that when I know car performs great ! I also did 4.625 final swap so that helped a lot I guess :skid: few pictures, I´m far from "builder" this is my first car in my life and I learning everything as I felt deep in love with motorsport... port pictures are from exhaust side, I didn ´t know what to do with so much "meat" on divider in time so I leave it more or less how it was from factory...well minus all the carbon deposit :-D https://cimg2.ibsrv.net/gimg/www.mia...c00a03cf2e.jpg https://cimg3.ibsrv.net/gimg/www.mia...c328123e5c.jpg https://cimg4.ibsrv.net/gimg/www.mia...f3aecd0fce.jpg https://cimg5.ibsrv.net/gimg/www.mia...6c495be844.jpg https://cimg6.ibsrv.net/gimg/www.mia...0684d1e197.jpg https://cimg7.ibsrv.net/gimg/www.mia...3d970cdc83.jpg |
Originally Posted by ctdrftna
(Post 1385484)
Do you already own the Newway seat tools (the link you posted)? Honestly i would not touch one of my heads with those tools. They do not hold seat concentricity like a seat and guide machine, you are not going to get good seal with it. In the long run your better paying for a machine shop to do the valve job.
When i worked at the engine shop the only thing we used those for was for flathead lawnmower engines. Any overhead valve motor went in the sunnen vsg and flathead fords were done with stones. You may want to be able to say you did it yourself, you may be trying to save some money, but in the long run you get what you pay for, and if you want a good performing engine that will last, i suggest taking it to the people with the correct tools for the job. |
| All times are GMT -4. The time now is 01:25 AM. |
© 2024 MH Sub I, LLC dba Internet Brands