I was looking at an Elgin valve kit. An oversized 1.560 option is available. Can they be installed in 8BA stock hardened valve seats? If so, it seems like a good option as intend to be at 275-285 CI displacement, porting and perhaps relieving etc. My seats appear in decent condition, but will naturally be sunk a bit after a regrind.
Oversized valves in factory guides.
- Thread starter fenders53
- Start date
I have read enough to know there is not agreement on relieving a block. What I haven't seen is much measurable data on the subject. (i.e. dyno or flowbench testing).
Can you explain to me how relieving would reduce power output if it is not done at the expense of static compression ratio? If I relieved, it would not be without choosing a head with appropriate combustion chamber volume. So where else is the power loss coming from when you relieve?
And thanks for the valve info.
Can you explain to me how relieving would reduce power output if it is not done at the expense of static compression ratio? If I relieved, it would not be without choosing a head with appropriate combustion chamber volume. So where else is the power loss coming from when you relieve?
And thanks for the valve info.
Now I'm busted.
That's a good question. You see I have this addiction to building engines. They don't always have a purpose up front, so sometimes I have to wait on cam and inducton choices. My Mustang stroker SBF drag car already has a spare engine waiting. My 53 F100 is a little heavy with creature comforts and has a low mileage SBF in it. Here is the best answer I can give to the question now. Not going into a 32 coupe. I can envision a later 30s sedan, perhaps an F1. Stick ******, Spirited streetdriving. It will it see the strip a few times but it isn't another a race car so we aren't building a race flatty here.
Block is just now heading to the machineshop but I envision this if I ordered the parts today. 285 CI, traditional dual carb intake, Edelbrock heads. 8.5 - 9 CR. An engine with a very high likelihood of exceeding 150HP. It will be ported. I have ported my race engines with success and it is something I enjoy very much. I will also tread lightly with the die grinder on the flatty until I get guidance because this is not 7000RPM 347 stroker. I know the flathead rules are very different, and that is why I am asking questions here.
I know that is way more info than you asked for Jack. Thanks if you are still reading.
Ol' Ron
Well-known member
If you red my book you'll noticed I ran flow tests on relieved and non relived blocks and found little difference in flow. However I did find an improvement in relieving the heads.
This is a MOO point ( Cows opinion) for a street engine, However having see the inside of several Bonneville engines, including mu own and none were relieved. One of the many myths of Flathead building.
This is a MOO point ( Cows opinion) for a street engine, However having see the inside of several Bonneville engines, including mu own and none were relieved. One of the many myths of Flathead building.
Thanks Ron. I haven't read any flatty books yet because I don't know which ones are full of myths, and which back their facts up with some real data. Just internet internet reading for me so far. What is your book titled? And which other books do you consider factual?
Back to relieving blocks. You said did not find any real difference in the practice. Did you find a reduction in flow from relieving a block? Or just no measurable improvement? Asking because I am reading posts on the net that imply that it reduces power, and I am curious why.
Back to relieving blocks. You said did not find any real difference in the practice. Did you find a reduction in flow from relieving a block? Or just no measurable improvement? Asking because I am reading posts on the net that imply that it reduces power, and I am curious why.
Ron Halloran's Book
Cost including postage is
$27.25 to USA ,
$23.50 to Canada and
$34.50 to the rest of the world.
paypal to me email address is fine but do not forget your postal address is needed as well. I will be shipping once a week.
For info please email billboomer@accesscomm.ca
For JWL's book Flathead Facts, the link is
http://www.flatheadv8.org/jwl.htm
Both are great books.
Lonnie
Cost including postage is
$27.25 to USA ,
$23.50 to Canada and
$34.50 to the rest of the world.
paypal to me email address is fine but do not forget your postal address is needed as well. I will be shipping once a week.
For info please email billboomer@accesscomm.ca
For JWL's book Flathead Facts, the link is
http://www.flatheadv8.org/jwl.htm
Both are great books.
Lonnie
Just my personal opinon: Air going into an engine through the ports does not like to turn corners, especially sharp turns. So the air flowing in past the intake valve is heaed upward, toward the cylinder head which then guides it in a "U" turn down into the cyklinder as the piston descends. So most of trhe air flow is against the head, and very litte, comparatively speaking, flows along the block deck surface. So grinding down into the block (thereby increasing combustion chamber volume and decreasing compression) is counterproductive unless you have a blower.
Picture yourself pushing a heavy load and someone straps your chin to your chest. Can you breathe freely? Now get your chin up in the air. Can you breathe better? Same with a flathead. When you relieve the block and leave the heads untouched, you are forcing the air into an unnatural path. If you want to grind, grind up in the head and provide a nice smooth arc from the valve to the cylinder.
An all-out race engine that doesn't have to make power under 5,000 or so RPM may benefit from relieving at the expnse of compression, but I think a street engine needs compresison more than relieving.
Picture yourself pushing a heavy load and someone straps your chin to your chest. Can you breathe freely? Now get your chin up in the air. Can you breathe better? Same with a flathead. When you relieve the block and leave the heads untouched, you are forcing the air into an unnatural path. If you want to grind, grind up in the head and provide a nice smooth arc from the valve to the cylinder.
An all-out race engine that doesn't have to make power under 5,000 or so RPM may benefit from relieving at the expnse of compression, but I think a street engine needs compresison more than relieving.
BILL WZOREK
Well-known member
40 Deluxe
Thanks Very nice simple explanation and a lite went off in my head / makes a lot of sense.
I for one get very confused when reading,
I am more Hands on type of person 
& your thread was more Hands on type of reading.
Thanks Very nice simple explanation and a lite went off in my head / makes a lot of sense.
I for one get very confused when reading,
I am more Hands on type of person & your thread was more Hands on type of reading.My confusion lies in that the block surface appears to in effect be an extension of the short side radius coming out of the port. The SS radius is usually the obstruction in a port if it isn't designed really well. If it is proven that relieving is of no benefit I can accept it, but I still desire to understand why. Please don't take my persistence here as defiance. I KNOW the people who were kind enough to post this thread are FAR more experienced on flatties.
The anatomical reference would work if placing your chin on your chest merely changed the "port shape" but it almost closes the port off completely. Of course it's harder to breath.
In any event, I found some good Flatty books to buy.
The anatomical reference would work if placing your chin on your chest merely changed the "port shape" but it almost closes the port off completely. Of course it's harder to breath.
In any event, I found some good Flatty books to buy.
fenders53, Interesting comments about the block deck being the short side radius. Flow no doubt could be enhanced with some creative grinding here. But in a flathead there is always the lost compression trade-off. Which do you need-airflow or compression? Are you building for the street or a race only engine? My thinking is that, since air wants to go in a straight line, it will flow along the roof of the chamber (the head) and only "leftover" air will be forced to follow the deck surface. I imagine port work upstream of the intake valve could be done to set the airflow up to more easily make the turn to follow the block relief. Don't ask me how! I'm just bench racing here.
Also, any change in airflow direction has to be done smoothly or you get turbulence, which will block airflow. (Turbulence is good on the compression stroke, but not on the intake stroke!) Another point: What is the worst restriction to airflow in a flathead? Is it the intake port? Upstream or downstream of the valve? Valve size? The sharp turn after coming through the valve? The turn down into the cylinder?
Something to think about with airflow: Air is not "pulled" into the cylinder, it is pushed! You can't pull air.
Also, any change in airflow direction has to be done smoothly or you get turbulence, which will block airflow. (Turbulence is good on the compression stroke, but not on the intake stroke!) Another point: What is the worst restriction to airflow in a flathead? Is it the intake port? Upstream or downstream of the valve? Valve size? The sharp turn after coming through the valve? The turn down into the cylinder?
Something to think about with airflow: Air is not "pulled" into the cylinder, it is pushed! You can't pull air.
lowandratty
Member
40 Deluxe
What are you talking about, all air in a natural breathing engine is pulled into the cylinder with the vacuum created by the piston moving down into the cylinder, the only way to push air into the cylinder is to use a blower / supercharger / ect. and force the air in under pressure. (Forced air induction) ring any bells.
The answer about cutting into the block is when you cut into the bloc to give more room around the valve, you do have a compression loss, but it also disrupts the flow, as the air flows past the valve it is drawn to the roof of the head and past the valves into the cylinder. If you cut the block, the air will go up to the roof of the head and try to fall back into the area you cut from the valve area and disturb the flow, kinda like the air moving of the roof of a car and seamlessly down the trunk and off the back, versus the air moving over the roof of a pickup truck and down into the bed and then back up over the tailgate, it creates a vortex effect. the vortex is great for a overhead valve engine but not a flatty.
What are you talking about, all air in a natural breathing engine is pulled into the cylinder with the vacuum created by the piston moving down into the cylinder, the only way to push air into the cylinder is to use a blower / supercharger / ect. and force the air in under pressure. (Forced air induction) ring any bells.
The answer about cutting into the block is when you cut into the bloc to give more room around the valve, you do have a compression loss, but it also disrupts the flow, as the air flows past the valve it is drawn to the roof of the head and past the valves into the cylinder. If you cut the block, the air will go up to the roof of the head and try to fall back into the area you cut from the valve area and disturb the flow, kinda like the air moving of the roof of a car and seamlessly down the trunk and off the back, versus the air moving over the roof of a pickup truck and down into the bed and then back up over the tailgate, it creates a vortex effect. the vortex is great for a overhead valve engine but not a flatty.
lowandratty, Whether naturally aspirated or forced induction, the only way to get air into an engine is to push it. In the case of naturally aspirated, atmospheric pressure does the pushing. Remember high school physics: Air flows from an area of high pressure to an area of low pressure. Again, how can you 'pull' air? There are not hooks on a piston that grip the air to pull it in, are there? Air is like a liquid in this respect. You can't pull water through a pipe, either. Consider the old-time watertower most small towns had, and many still do. Watrer pressure is generated by the height of the tower and the weight of the water, so water is pushed through pipes into your house and out the faucet. With air, we have the height of the atmosphere and the weight of the air pushing everywhere at the rate of 14.7 PSI at sea level. This weight is the pressure pushing air into your engine. The descending piston on the intake stroke is creating an area of low pressure that is filled when the intake valve opens, letting atmospheric pressure push air into the cylinder as it attempts to equalize the pressure. Simple, no?
Karl Wolf
Well-known member
I hava block that has seats cut out for 1 13/16" intake valves... Sure looks big... And, I don't think it's worth it... The block/head/valve area is pretty tight anyway- You give up something to get something, after all.
I try to maintain a perspective- a box stock 1955 ohv engine with a 2 barrel carb can beat out most flatheads, cept for the fun factor.
Karl
Ol' Ron
Well-known member
Here is what I did to improve flow by relieving the head. For a street engine I machine the trans fer area at an 8 degree angle, on a race or hi output engine I cut this at an 11 degree angle. both heads have a 45 degree or better exit from the transfer area. I tried several differant angles and found that some heads are very thin in this area and you can break through. And yes the air is still PUSHED into the cylinder. You can also change the CR by the length of the transfer area.