Building for Torque Porting Question

[Scotty's 52 F3]

I'm getting ready to pull my 52 F3 down for body and paint as well as engine build. I'm gathering parts and got hold of a Merc crank, EAB cam and EAB heads. I'd like to run 3 ring pistons with a more modern ring pack. The only cast versions I see is EGGE in .125 over which I may do if the block will handle it. I don't mind spending the money on Ross pistons if they are less trouble with domes vs heads. I have a 49 block and my still running 52. I'll use whichever is best. I'm already running a modified Accel dual point with a vacuum advance and advance curve as recommended by JWL a while back for my stock 8RT engine. My engine runs well considering all the blow-by it has.

I have JWL's book as a guide so I was also considering an Offenhauser 4 bbl. intake with the 465 Holley. My exhaust manifolds are cracked so I was going to fabricate some center dump type headers and run through some 1 3/4" duals. I have more time than money so I fab as much as I can. Part of the fun anyway.

My question is about porting.......or not, for this build. Do I need to do more than gasket match, blend bowls and radius the sharp edges? If so, does anybody have some specific info or pics for an engine being built for low RPM torque? Would a center port divider benefit me in this case? Any build advice would be greatly appreciated.

[flatheadmurre]

For a F3 with EAB cam and aiming for torque and not more revs i would say compression is what you want instead of large ports.
If you use it for hauling running it hard the higher compression can be an issue...so depends on what you want it to do.
Cleaning up the intake and exhaust ports never hurts...but any serious porting isn´t what you need in my opinion.

[drolston]

Looks like you will end up with 270 or so cubic inches. The 390 CFM Holly might be better suited than the 465. Relieving the area between the valves and cylinder is worth the time and effort. Porting the intakes is much less return on time and effort, but you can get some of that type benefit from cut down valve guides and power-flo valves.

The EAB cam is good for low-end torque; other than that, it is cubic inches, especially from stroke.

I have no personal experience, but the consensus on this board has been that center port dividers do not benefit performance.

[Kahuna]

IMO
Make the engine as large as you can.
Balance the engine
Ross pistons with the metric ring pack are excellent
Do the mild cleaning up of the ports
Do not waste your time relieving the engine
I believe the Offy manifold has the fan mount offset. May be a a consideration.
Maybe the Edelbrock is a better option
Get a cam, maybe the L100 from Krylon. It'll work well
Raise the compression at least 8:1. More if possible
You'll have a great engine
Jim

[tubman]

When I built my latest 258" engine, I used a set of 1/8" over pistons I got from Speedway's "Garage Sale" for about $100 (including pins, clips, and rings). These were 4 ring pistons that i installed without the bottom ring on the advice of a lot of people who should know. I only have break-in time on the engine, but so far I have been very satisfied. I know the juries not in yet, but from all indications this is going to be a good one. See for yourself : https://www.youtube.com/watch?v=deAgpVmvjhU

[flatjack9]

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I'm with Kahuna.

[Frank Miller]

I think porting only benefits at high rpm. It may not be necessary.

[JWL]

There is no harm in porting the rough areas. Low speed torque will not be impacted. However there is harm to be done with relieving. Do not do it. As for a cam, the EAB is a great choice. Almost anything else will reduce power in the RPM range your truck is likely to see.

In the old days I was not in favor of using the Forgedtrue pistons on the street. However, I have adjusted my thinking with Ross pistons. I think they can be set at the minimum clearance and work fine on the street. Do not pay extra for special ring groove machining as you will never see any benefit in your use.

Set the combustion chamber clearances as reasonably close as possible and have fun.

[19Fordy]

Kahuna is correct. The OFFY 4 barrel intake has a 7/8 inch generator/fan mounting offset towards the driver side. Go with something that's centered.

[51 MERC-CT]

Originally Posted by 19Fordy

Kahuna is correct. The OFFY 4 barrel intake has a 7/8 inch generator/fan mounting offset towards the driver side. Go with something that's centered.

I agree that a center mounted bracket mount may be a slightly better choice BUT unless there is fan interference with a fan shroud or any other
component, I nor anyone else will know the difference.

[Scotty's 52 F3]

Good to know about the offset on the Offy. I have the stock 6 blade fan and shroud. I think there is room but, I'll look.

The truck is mainly used as just a cool old cruiser but, I do load it up and use it as a truck as well.

I have 32" tall tires, 3.73 gears and the T98 4 speed if it matters.

I was considering the 465 Holley because it fared better in JWL's dyno tests than the 390 did.

It seems the exhaust didn't matter much in this case. However, since I'm building my own exhaust would a 2 into one system run any different than duals other than how it sounds?

Thanks for all the replies and the video.

[Scotty's 52 F3]

Ross (ALBQF1) has had good results with a Rochester two bbl and the 4 bolt Merc manifold. Would this be a better choice than the small 4 bbl?

[40 Deluxe]

Originally Posted by drolston

Looks like you will end up with 270 or so cubic inches. The 390 CFM Holly might be better suited than the 465. Relieving the area between the valves and cylinder is worth the time and effort.

No, do not relieve the block! That is an out-dated "speed trick" that only serves to lower the compression and gives negative results, except maybe in an all-out high RPM race engine. Compression is your friend!
Consider: Air has weight, thus inertia, and so does not like to turn corners. Every bend in the intake tract slows air flow. When the air/fuel mixture flows past the intake valve it is traveling upward, toward the head and is forced down into the cylinder at the transfer area. Since air wants to go straight, following the path of least resistance, very little air will flow through the block relief. It just won't make that sharp turn very effectively. Now, if you're cramming the air/fuel mixture in with a supercharger, relieving may help, but I don't think the relief area is the biggest restriction to intake flow. More likely, it's coming through the intake port, making that sharp bend.
Remember, air is never pulled into the cylinder, it is always pushed in. You can't pull a fluid, you have to push it. Atmospheric pressure does the pushing. We may mistakenly picture the piston pulling air in through that nice relief we just ground into the block, but not so!

[GOSFAST]

If you choose the right parts, all depending on your budget, you can do about 150 HP and 250# Torque. These numbers will move your ride nicely!

Thanks, Gary in N.Y.

P.S. All this with NO porting whatsoever!

[Scotty's 52 F3]

Looks like relieving not going to be in the recipe. Gary I'm all ears to the "right parts".

[drolston]

To relieve or not relieve? A never ending debate.

The engine I just built was factory relieved. The fact that FoMoCo eventually decided it was a good way to improve performance is all the convincing you should need. The loss of about 3cc of combustion chamber volume only costs about .2 to .3 of compression ratio. You can still easily get to 8.5:1 which is the point of diminishing returns for compression on a flathead. Reference article regarding relieving and for dyno test of increasing compression:

http://www.hotrod.com/articles/0905s...lathead-myths/

Look at the cross section showing relief between the valves and cylinder and you can see where it opens the transfer area by a significant amount. If the object is to get the most fuel mixture into the cylinder in the shortest time, that flow restriction has to be important. I will see if I can find dyno tests on before and after block relief.

No offense to those that believe otherwise. Probably none of us could tell the difference of 10 horsepower in every day driving.

[Ol' Ron]

I don't believe in relieving the block, but to each his own. I do believe in a tight piston to head clearance. Mill the head for .045/.050" clearance. it one of the cheapest mods you can make with noticeable results.

[Scotty's 52 F3]

Ol' Ron, after reading all your posts about squish it's definitely in my plan.

I don't mean to spark debate over relieving a block. This is my first Flathead build and most info on the web involves mods for higher revs. I'm all ears for this torque build.

Thanks to all that offer advice. I do appreciate it.

Some pics of basic port work would be nice if anybody has some.

[flatheadmurre]

If the engine will be run as a truck the relieve has a pro widening the flat area between the valves/cylinders preventing cracks from heat.

[JWL]

FoMoCo never decided to broach the transfer area because it was a performance enhancing technique. It was done to help prevent crack formation at the upper level of the eyebrow. The only debate is about whether or not it was helpful in that regard.