8rt flathead rebuild

[Plaintoast]

I'm about to do a rebuild on an 8rt flathead for a personal project (post war style t bucket). Not looking for a ton of extra out of it, planning to use mostly stock components as was done back then. I do have an erson cam picked out to use, then just your pretty basic rebuild. I'm wondering though, since the cams are pretty low lift, and low rpm motors, what are guys doing for valve seat angles? I see stock listed two ways, but most references refer to 45 on both seats. I'll likely use a modern undercut Chevy valve, but I'm wondering if there's a benefit to using 30 degree seats on both valves?
Any pointers is appreciated. I've done some other old stuff (model t 4 banger) Crosley's etc but not one of these.

[Kahuna]

All Flathead Fords had seats @ 45 degrees.
In an effort to determine what was best, or better, I took a protractor and a head and set the head offset to the block and checked the angle of the valve to the chamber (stock Ford head). My deduction was/is that Henry had it as good as it's gonna get, as the 45 angle pretty much matches the area where the gas ought to go and hit the transfer area in the head.
People that like 30 degree seat angles always talk about low lift flow. Who cares?
Meaningless to me
JMO
Jim

[Plaintoast]

I guess my thought was, there's never really any high lift, I think the cam is only .360" or so lift, so I was wondering if doing a 30 degree valve job would help in an instance like this.

[Olefud]

I believe you want the flow to attach to the head –the old relieving was pretty much counterproductive. 45° would, as a guess be better. Overhead valves also want to attach to the head but the valve is in the head and may benefit from the valve being parallel to the head.

[twl]

I consider .360" lift to be in the territory of 45 degree seat angle.

Flatheads have heavy shrouding around the valves, so I would suggest some roller lifters or radiused lifters, or something to get the lift up higher. I would focus more on lift, and less on valve seat angle.

[Kahuna]

Most ALL stock flathead cams were less than .330" lift. As TWL mentioned, more is better, and really helps a flathead perform (for a flathead).

[Speedbump]

Never seen any roller anything for a flathead and they are lift limited by the top of the combustion chamber. One can raise the combustion chamber ht. for more lift but then the compression goes down and it all becomes counter productive. IMO, best money spent is; adjustable lifters on the new cam and make sure you use a modern 3 ring piston if it doesn't already have them. Best machining tip; Drill small holes in the tops of the lifter bores so you can easily hold the lifters when adjusting the valves with the adjustable lifters. Worst machining; take as little off the deck as you can, or none, as the deck is pretty thin already and making it thinner can cause head gasket problems. DO NOT let someone put the block in a "block thru" or similar block machining fixture unless they REALLY know what they're doing. Henry didn't put the crank in the center of the block. Also, there is a "flathead forum" website with some pretty smart people on it that you can join and ask questions.

[PackardV8]

And have the block pressure tested and magnafluxed. I've never seen one which didn't have a few cracks. Some don't hurt anything, some are repairable and some make the block cost more to fix than it's worth. You'll need someone who's done a few to tell you which is which.

[Plaintoast]

Got it torn down and besides being nasty inside like I've heard they all are, it looks pretty good. Still std bore and std crank sizes, ford stamps on the bearings and valves. Cleaning everything up now then I'll mag it and see if I've got a decent candidate to rebuild. I appreciate all the help so far, if anyone has any more pointers, I'm all ears, this is all new to me here.

[Plaintoast]

One more thing, I noticed this block isn't relieved, I thought I read that was done on the truck motors but mine isn't, pretty sure its a 49, anyone else come across this? I read varying accounts on if its good or not, I'll not waste my time with it if it isn't going to help me.

[Speedbump]

Only done a few for people but never saw one relieved from the factory. You know what opinions are like....mine is that relieving is more work that it's worth, other than a small radius at the edge of the bore. You fight the same compression/flow battle with relieving the block. It did make nice words for the "Deuce Coup" song though. There's a guy on the flathead forum that was working with "aero" guides where he put an inverse radius of sorts on the top of the intake guides to help direct the intake up toward the port/valve. He was doing A-B dyno work which is the only way to see if a lot of the old fairy tales work. Very sharp guy. I bought his book on flatheads. If you're interested, I'll find it and give you the info to see if it's still available.

[Plaintoast]

Yes, very interested in that info and any more. I can find lots of info on various sites from lots of people, but frankly I don't know what to believe and don't want to try to wade through the bs, that's why I figured I'd ask here where there's lots of knowledge.

[Speedbump]

Book is called "FLATHEAD FACTS" , by John W. Lawson. The copyright date is 2008. I think he might still hang out on the FORD BARN, but I haven't contacted him in a few years. He could be a little un-popular with the old flathead guys on the flathead forum as his dyno studies seemed to kill much of the old, revered flathead legend, especially where street engines are concerned. The book is a good read if you can still get it.

Just checked. The book is available from VANPELT SALES, along with lots of other flathead stuff.

[Truckedup]

People who know say a well done and expensive street flat head of around 280 cubic inches might make 180 HP .

[GOSFAST]

Here is a general list of a decent build, there are more options, but this will get it done.

Block:
(01) Pressure test block, DO NOT rely on magnafluxing only (OK to do both)
There are areas where only the pressure testing will assure accuracy.
(02) Drill the lifter bores to help with adjusting valves.
(03) Finish hone w/block plate.
(04) If possible use ONLY "moly" rings.
(05) Use ONLY teflon coated cam brgs. This is an important area with respect to oil clearances.
Measure and record the clearance between the cam and the brgs.
(06) Use the Melling M-19 oil pump, it will be your best choice.
(07) Deck the block but remove minimal material.
(08) Also if possible, we recommend "pinning" the heads and gaskets to the block with some SBC (5/16") dowels.
(09) I would use ONLY bronze guides, this avoids any "hanging-valves" during longer periods of storage. This has
always been a major issue on the Flatheads. I would also stay with the 1.500" valves, in most applications it is
all that's really required.
(10) Stay with "Johnson" for the tappets, avoid ANY off-shore lifters for these builds.
(11) Use an ARP main stud kit (recommended), toss the old bolts.
(12) I assume you are building the original 239", if you are looking for any higher HP numbers (80 HP on the 239 is
nominal) I would use a 4.000" (or longer) OEM or aftermarket crank.
(13) Change the wrist-pin bushings, resize the big ends, and use some ARP rod nuts or some new OEM "Marsden"
nuts. The factory rods will be fine, if a stroker is in the program we recommend an Eagle crank with Scat rods.
Do not use the Eagle Flathead rods, they are a tough "fit". The Scats pretty much go right in.
(14) Use "moly" on the cam lobes.
(15) Set up the block for the 95% oil filtration deal using a remote filter. Recommended but optional.
(16) Make certain there are inserts for the valve seats. (Some blocks are already equipped)

Heads:
(1) Maganflux or pressure test, the latter recommended.
(2) Mill flat only,
(3) Measure chambers (optional).
(4) Check piston/head clearance. One method is turn it over without any head gasket.

If you are looking for some power gains over stock, your best bet would be some pistons set up with a "metric" ring pack. We use Ross with our stroker kits! The ring pack is 1.5mm, 1.5mm, 3.0mm. Almost all our "stocking" kits are the 4.250" stroke.

I would also highly recommend breaking these "Flatties" in on a dyno or at least on a "test-stand". We use the dyno here.

I can only give you HP estimates on the strokers, this is mostly the ones we build. We see anywhere from 150 to 170 HP on the 1/4" Merc builds (4.250"). These are all nominal numbers.

Staying N/A it takes some "deeper-pockets" to get past 150 HP, not to mention 180!! Increasing the stroke helps here.

(Add) If you stay with the iron heads the factory fasteners will be fine, with aluminuim heads go to ARP studs/washers/nuts!

Thanks, Gary in N.Y.

P.S. Here's a link to the Flathead site! http://www.fordbarn.com/