Just make sure all the ring gaps are on the other side of the piston. It's a ring end that likes to pop out.
Building for Torque Porting Question
- Thread starter Scotty's 52 F3
- Start date
Just make sure all the ring gaps are on the other side of the piston. It's a ring end that likes to pop out.
Henry Floored
Well-known member
Well gang EVERY Flathead block I have ever seen is factory relieved. That big eyebrow cast or machined into the deck around the valves is a flow relief.
If you wish smooth the edges and radius the top edge of the cylinder that is in between the head gasket. I doubt anything more would be of help though I've got no flow numbers to prove it either way.
The idea of the transfer area in a Flathead Ford is to turn the mixture down into the cylinder because the flow wants to go straight up.
This is the plight of any side valve engine.
Ford Flatheads are actually quite sophisticated in this area. Pull the head off any side valve lawnmower engine and you'll see what basic looks like.
The early racers had it right, (remember it took a while and a bunch more cubic inches for the OHV's to start beating the Flatheads on the salt) when they started "popping" the piston up into the head and greatly reducing the impediment to flow without giving up compression.
I can't think of one reason why even a street performance engine couldn't benefit from this other than extra cost.
If you wish smooth the edges and radius the top edge of the cylinder that is in between the head gasket. I doubt anything more would be of help though I've got no flow numbers to prove it either way.
The idea of the transfer area in a Flathead Ford is to turn the mixture down into the cylinder because the flow wants to go straight up.
This is the plight of any side valve engine.
Ford Flatheads are actually quite sophisticated in this area. Pull the head off any side valve lawnmower engine and you'll see what basic looks like.
The early racers had it right, (remember it took a while and a bunch more cubic inches for the OHV's to start beating the Flatheads on the salt) when they started "popping" the piston up into the head and greatly reducing the impediment to flow without giving up compression.
I can't think of one reason why even a street performance engine couldn't benefit from this other than extra cost.
Henry Floored
Well-known member
70mach1
Junior Member
So I have read through all of the posts with interest but my situation is different than the OP. Here is a little background: I have a 28 AV8 Closed Cab Pickup that I am setting out to rebuild the 8BA that I installed into it earlier this year. I bought the engine locally dressed out with some performance items. The engine has Offy .400 heads and a dual carb intake with 2 -97s on it. I have an HEI distributor on it as well. It is supposed to have a Potvin 3/8 cam in it. The truck drives great and feels quick, even with the 3-3/4 stroke and .030 over it currently is. The only real performance issue I have with the truck is torque related. I have an RTS Overdrive behind the engine and 3.78 gears with a 7.00X16 rear tire. That translates to 2000rpm at 70. The truck does not have enough power to pull hills in overdrive at 70-75mph. I have a LOT of blow by and excessive oil consumption, hence the rebuild. I plan to do any porting and relieving myself, I am a toolmaker and have done other engines, this is my first Flathead. I have already purchased a SCAT 4-1/8" stroker kit with the .125 over Ross pistons, bearings and gaskets for a 284" build. Here are my questions:
1. I get that relieving might not be worth the money if you are paying someone to do it, but doing it myself is it a bad idea for any reason? I would think that the main point of this mod is to unshroud the valves to use OHV speak. So, maybe not a full relief, but at least bringing the block down around the low side of the valve and blending with a more gentle slope up to the deck? This would serve most of the benefits of relieving without as much of a compression loss.
2. My performance issue can also be solved by changing my 3.78 gears for an already purchased set of 4.44. But I was hoping to gain enough power with the extra bore and stroke to keep my RPMs in the basement while cruising. I have gotten advice to ditch the Potvin cam for a 1007B Isky. Do y'all concur?
1. I get that relieving might not be worth the money if you are paying someone to do it, but doing it myself is it a bad idea for any reason? I would think that the main point of this mod is to unshroud the valves to use OHV speak. So, maybe not a full relief, but at least bringing the block down around the low side of the valve and blending with a more gentle slope up to the deck? This would serve most of the benefits of relieving without as much of a compression loss.
2. My performance issue can also be solved by changing my 3.78 gears for an already purchased set of 4.44. But I was hoping to gain enough power with the extra bore and stroke to keep my RPMs in the basement while cruising. I have gotten advice to ditch the Potvin cam for a 1007B Isky. Do y'all concur?
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flatjack9
Well-known member
With that cam you are probably down on torque at that rpm compared to a stock cam. Obviously you will pick up torque with the increase in stroke. I would maybe clean up a few of the sharp corners in the ports and forget the relief. It will do you no good in the rpm range you are talking about. Just tell everyone it's ported and relieved. The 1007B is a good choice for a street cam.
Ross now makes pop-up pistons that are about 1/2 the cost of the Arias ones.
Ol' Ron
Well-known member
The cam might have too much overlap. I'm running the EAB cam with the 280 and the torque is fantastic. This business with the relief is not worth the effort. Maybe if you were running Bville.
I went up Weston hill in Vermont (14%) started at the bottom in oD at 50MPH and cleared the top at 43 Engine was turning 1300 RPM. You have to have a reason to make a modification.
I went up Weston hill in Vermont (14%) started at the bottom in oD at 50MPH and cleared the top at 43 Engine was turning 1300 RPM. You have to have a reason to make a modification.
I'll admit that I didn't read your post that closely, but it sounds like your motor is on the decline, so I'm not sure it's fair to judge performance modes done on a weak engine.
Somewhere on the interwebs is Mike Bishop's porting guide. Google it and when found, print two copies. One for your night time reading and one to keep next to you as you are working on the engine in the shop.
Other may know, but I'd do the math of what the O/D will make those 4.44's. That is a steep rear. I also believe that Potvin 3/8ths will wake up a bit with the large CI and stroke.
Ol' Ron
Well-known member
I made a mistake on the 81A head. I think it was the 81s head which is sometimes called the 'Denver head" I learn allot after building many engines and sometimes I get mixed up on just what I did. But I will stand by the piston to head clearance as being a very good mod. As it improves drivability as well as economy, for very little cash.