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Are these valves too big for the street?
https://slantsix.org/forum/viewtopic.php?t=38331		 Page 1 of 3
Author:  Reed [ Thu Dec 17, 2009 10:53 am ]
Post subject:  Are these valves too big for the street?
Purpose of motor being assembled is to power an 83 Dodge van to get best fuel economy and power on the street. Motor rarely turns more than 3000 RPM. Rear gears are 3.2, van weighs in the neighborhood of 33-3500 pounds, used to haul five adults plus band gear regularly.

I am planning on installing a cam reground to the Erson RV-10 specs as follows:

Duration @ .050 lift = 212 intake and exhaust
valve lift = .435 intake and exhaust
valve lash is .012 intake and .012 exhaust

I also have my 1972 198 slant six cylinder head which has been rebuilt with Ford 300 valves. The valve diameters are:

Intake: 1.776 inches
Exhaust: 1.558 inches

I need to get the head CCd and milled to achieve a good dynamic compression ratio, but can anyone tell me if this combination of cam and valves will be too big for a truck motor/daily driver? I am worried about killing low RPM torque with those huge valves.

Any tips are greatly appreciated. Thanks.
Author:  Doc [ Thu Dec 17, 2009 1:18 pm ]
Post subject: 
I think the biggest problem is the exhaust valve diameter...
It is hard to get anything over 1.5 to clear the edge of a 3.4XX bore.
Are you planning to notch the block?
DD
Author:  Reed [ Thu Dec 17, 2009 2:44 pm ]
Post subject: 
Sorry, I forgot to mention that the motor this head would go on has .030 oversize pistons. So, yes, the bores have been enlarged in the block.

Years ago I actually used this head on this block for about 3,000 miles (long story about how the motor and block became separated with neither logging many miles since separation) and I had no interference problems. However, I don't know if the valves were shrouded by the combustion chamber or the cylinder bore.
Author:  terrylittlejohn [ Thu Dec 17, 2009 3:18 pm ]
Post subject: 
with a low lift cam it might work. i use a 1.60ex valve in a .060 over engine and had to notch the block another .030 to make it work, the 1.80 int cleared . my .030 over engine i cut the 1.50 valve to 1.47 to clear the bore. the cam was a .540lift.
Author:  Reed [ Thu Dec 17, 2009 3:32 pm ]
Post subject: 
Here's a picture of the head with the valves:

Image


Hmmm. I think when I had this head put together I just used valves that were too big. If I remember right, the motor ran okay but lacked power down low. However, I discovered after I took this head off the motor that the timing mark had slipped on the dampener and the timing was set 8 degrees too retarded.

The diameter of the valves measured at the widest point of the valve, right? Not somewhere farther up closer to the actual seating surface on the back face of the valve?

Dang it, I wish I could just pull the motor and put it on a stand to trial fit and measure all this, but the van is up at my brother's house and I won't be able to pull the motor. :? I hate trying to figure this sort of thing out by guessing...
Author:  sandy in BC [ Thu Dec 17, 2009 3:48 pm ]
Post subject: 
I am using 1.50 ex V/vs with the Erson 80/270 and enough milling to be at 9.5 to 1.

When I pre assembled everyting I had a look up the bores into the head to see how things cleared. (Thanks for the tip Doug) Even with no head gasket and only a 40 thou overbore there was enough room....I did not say plenty of room,....
Author:  Rug_Trucker [ Thu Dec 17, 2009 4:17 pm ]
Post subject: 
:popcorn:
Author:  Reed [ Thu Dec 17, 2009 4:30 pm ]
Post subject: 
Okay, since I have run this head on this motor before with no interference, lets assume that the valves will clear the cylinder walls and ignore the potential shrouding issues (not a good thing to ignore, I know, but I am working with the parts I have on hand). The question then is will running valves that big hurt low RPM torque? :? Remember, the motor never turns more than 3k, even on the highway. It will spend most of its time in the 1500-2700 RPM band.
Author:  Reed [ Thu Dec 17, 2009 4:34 pm ]
Post subject: 
Quote:
:popcorn:
You mean, Image
Author:  Rug_Trucker [ Thu Dec 17, 2009 4:53 pm ]
Post subject: 
Quote:
Quote:
:popcorn:
You mean, Image
ZACKLY!

:lol:

Have you modified the turbonator for a 2bbl? :roll:
Author:  sandy in BC [ Thu Dec 17, 2009 4:54 pm ]
Post subject: 
You wont lose any low end because of the vaLves.....that what cams are for......
Author:  Rug_Trucker [ Thu Dec 17, 2009 4:55 pm ]
Post subject: 
What type of valve job do you have on the intakes? Enought room for a 5 angle? That is suppossed to help flow at low speed.

Aren't the Ford Valves pretty thick in the stem? Been a while since I held one, and it was for the 240. Same basic engine.
Author:  Reed [ Thu Dec 17, 2009 5:17 pm ]
Post subject: 
Yeah, it took a bunch of extra machine work to get the valves into the guides. I don't have a clue what ind of valve job are on the intakes. THis head was put together about ten years ago and I never got a detailed build sheet from the machinist.

Just for giggles I went out and did some measuring on the head-

General combustion chamber diameter = 3.44 inches
Combustion chamber diameter acros the notches for the valves = 3.47
Image
I also did these same measurements off of a mid 60s head (nonrevised combustion chamber) and an 83 hydraulic head-

early head-
overall diameter = 3.37
notch diameter = 3.47

hydraulic head-

overall diameter = 3.41
notch diameter = 3.48

Allowing for discrepancies in how I was holding the caliper, it looks like my big valve head still has the factory original diameter on the combustion chamber and the clearance notch.

The gap between the intake and exhaust valves is .049 inches.

Sandy- what is the lift on your cam?

Maybe I will try bolting this head to a spare stock block and seeing how tight the clearances are.

P.S. No, no turbinator yet, but I do have a "Hydrocatalyst"that will fit! :D

Image
Image
Image
Author:  Greg Ondayko [ Thu Dec 17, 2009 5:35 pm ]
Post subject: 
Looks like eye candy for the Carb.

G
Author:  carsrme [ Thu Dec 17, 2009 5:45 pm ]
Post subject: 
Quote:
Looks like eye candy for the Carb.

G
Image
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