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Max effective Valve size
https://slantsix.org/forum/viewtopic.php?t=35793		 Page 1 of 1
Author:  Greg Ondayko [ Wed Jun 10, 2009 8:33 pm ]
Post subject:  Max effective Valve size
Hello I am getting ideas / Ca$h together for my clunker race car.

I am interested in going with the K1 / Weisco Combo in either the 3.500" or the 3.504" I see theat they have 1.800" Valve notches - What is the largest usuable valvew sizes without notching the head (EDIT - I MEAN BLOCK) that you folks have used??


I know that after a certain point bigger is not better due to valve shrouding.


This would be on a 3.500 or 3.504" bored engine.


Thanks,


Greg
Author:  slantzilla [ Thu Jun 11, 2009 3:33 am ]
Post subject: 
Greg, even at 1.7" you really need to relieve the area around the valve head in the chamber to get the best flow. I don't have a good head off of a motor now or I could send you a picture of what I mean.

At 4.5" bore you should not have to notch the top of the bore at any valve size.

People will tell you that they have used 1.88 intakes and gotten great flow numbers on a flow bench, but you will find that on a motor a valve that big is really restricted by the cylinder wall.

Half the time I think "great" flow numbers are achieved without a spark plug in the head too. :wink:
Author:  Greg Ondayko [ Thu Jun 11, 2009 5:06 am ]
Post subject: 
Quote:
Greg, even at 1.7" you really need to relieve the area around the valve head in the chamber to get the best flow. I don't have a good head off of a motor now or I could send you a picture of what I mean.

At 4.5" bore you should not have to notch the top of the bore at any valve size.
Dennis, Yes well i was going to Unshround the head I did not mention that but it seems like common sense to me. I am asking about The cylinder wall area reducing valve size effectiveness.

and I thinks you mean a 3.5" bore -


Greg
Author:  66aCUDA [ Thu Jun 11, 2009 5:41 am ]
Post subject: 
Greg
I think 1.78 and 1.50 is about the largest your will get to fit in the head.
I have 2 heads with this combination. I dont have a flow bench and have NOT seen any numbers for these.
Frank
Author:  sandy in BC [ Thu Jun 11, 2009 6:20 am ]
Post subject: 
I have 1.72/1.50 valves. I radiused the chamber but left the bore alone. I believe if you mill the block for compression and leave the head "big" it reduces the need to notch. No evidence to support.
Author:  Dart270 [ Thu Jun 11, 2009 6:38 am ]
Post subject: 
From the heavies I've talked to, 1.76/1.50 is the biggest you want to go with a 0.100" over motor. Last time I spoke with Mike, he thought that was even a little big. 1.72/1.50 work very well and are plentiful. I think Ferrea has some nice drop in 1.76/1.50 for 11/32" stem.

The bowl work in the head will have much more impact than a few extra thou of valve size.

Lou
Author:  Greg Ondayko [ Thu Jun 11, 2009 8:33 am ]
Post subject: 
Thanks Guys!

I have some 11/32" stemmed valves that Are 1.838" and 1.543"


Looks like I will get them turned down to 1.76" and 1.50"


Thanks


Greg
Author:  moper [ Thu Jun 11, 2009 8:48 am ]
Post subject: 
The maximum figure I use is 51% of the bore size which for 3.504 is 1.787". However, this assumes the perfect size fits easily. When they don't, I go to the largest easy fit. I'm starting to play with a /6 for myself and it's all new to me although I do have some knowledge of Chevy straight 6s. Can anyone post a pic or two of the two chamber designs? I've never seen a slant chamber and I'm very curious...

Thanks!
Author:  rock [ Thu Jun 11, 2009 11:54 am ]
Post subject:  Here's some pics of my unshrouded valves in a .100 milled he
Greg and all,

Here's the URL to some pics of my head milled to .100, engnbldr valves and unshrouded valves, extensive porting

http://camimenko.com/gallery/v/Lancer/rock/

Thanks again to Menko for the host.

rock
'64d100
Author:  terrylittlejohn [ Thu Jun 11, 2009 6:13 pm ]
Post subject: 
on my 11/1 comp engine with 0.060 over bore and .540lift cam i had 1.80int and 1.60ex, i had to use a cutter to relieve the top of the bore .030 on the ex but the int clear 0.060. this engine gave me my fastest ride N/A at 12.30 109mph. i had 1.78int and 1.47ex on the .080 over blower motor but i am doing a new head with 1.70int and 1.44ex egblder valves for this season have to see if it work better with smaller valves.
Author:  moper [ Fri Jun 12, 2009 4:33 am ]
Post subject: 
Thanks Rock, that's exactly what I was looking for. My valve jobs get a little more relief than that but I think it's more of a minor difference in the cutter shape than anything else. Is there a way to post a picture here without a host? [/img]
Author:  Rust collector [ Fri Jun 12, 2009 4:51 am ]
Post subject: 
No, they have to be hosted somewhere...

I can do it, if you email them to me
Author:  slantvaliant [ Fri Jun 12, 2009 6:10 am ]
Post subject: 
Moper, here's Doug Dutra's article on HEADS. There's some good reading in the articles section of this forum!

For photo hosting, I use Photobucket.com. I can't say it's the best - I haven't tried others - but it works for me. It's also free.
Author:  moper [ Fri Jun 12, 2009 8:43 am ]
Post subject: 
Thanks Slant! I'll do a bit of research. I'm getting the car Sunday from what I'm told so I should have more questions come next week...lol.
Author:  slantvaliant [ Fri Jun 12, 2009 9:19 am ]
Post subject: 
Do yourself - and us - a favor: Take a bunch of photos of the car as found, and as you work on it. Detailed photos make parts ID much easier, and could make a good basis for a build book.

Besides, it's good to see how far you've come.
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