Flathead Porting for Dummies...?

http://www.flatheadv8.org/bishop/porting1.htm

 

More please, you can't stop there!

 

Well, Chuck, Flatdog, and some of the others have the experience.
I had the oportunity to sit down and talk with Barney Navarro and Rod Furtado before they p***ed away and Rod actually started the machine work on my current motor....which is going together.

This kind of information really gets my heart working overtime (at my age that's not always good) but port matching/porting is certainly one of the first steps to consider in a street flathead motor. I believe that relieving the block is another, and during my conversation with both Barney and Rod they believed the same thing........just for different reasons.

My question......or maybe we could start another thread about going beyond just port matching/porting and talk about valve pocket work and why or why not to relieve the block, talk about the oiling system and for not a lot of money make it a full pressure system (if there are any advantages), talk about cams/springs.......ignitions............intake manifolds........heads and head design.................but take it one step at a time..............

Don't know if this is practicle, but I would sure like hear from more knowlegeable people than myself.

Just a thought..................this tech is too good to just stop here..........especially for the guys that enjoy our flatmotors.

 

When I built my 8BA, I intoeduced myelf to a crash course flathead porting haha. I read EVERYTHING I could get my hands on re the subject, and then had a go. At this point the block is unrelieved and the heads really should be swapped out for better flowing units (even prepped stockers would allow her to breathe better lol) so the CR is a little high, but we'll get to that a little further down the track.

Heres what I did as porting goes...

1. Concentrate on cleaning up the bowl area under the valve,about an inch into the port.
2. Cleaned up the eyebrow in the runner up the the intake valve seat as mentioned.
3. Ported out the exhaust ports and opened then up as safely as I could while removing
the sharp ridge on the inside of the outer exh ports in the block,all the while blending
and removing anything that could be a hinderance to flow. I was amazed at the
casting wire I found in the exhaust ports and the amount of casting slag..
4. Ground around the valves at the top of the chamber about halfway down the valve
diameter/chamber - to the gasket line to unshroud the valve.
5. Removed all the sharp edges in the head/chamber to prevent preiginition.
6. Port matched the blower intake to the block using the gasket as a template.
the flow and unshroud the valve.

Does all this stuff work? I dunno, but she sure pulls ****** hard to 5K haha.

I wish I could have a done a before and after to compare...maybe a dyno session will tell me what she is doing and allow me to check EGT's at WOT.

 

I have been pondering all this myself. I plan on sourcing a new block for the roadster next year and having a go. All the above info is brilliant, Chuckspeed I await some pics...

Rat when it comes time, i'll be ringing you too

 

Just a note in p***ing....the factory relief in flathead truck engines was done to reduce the thickness of the casting in this area and reduce the tendency for cracks over time in hard-working trucks. Any power increase was incidental.

 

I was told by Rod Furtado and others that the factory relief was done to try and avoid cracks due to overheating in truck and heavy use motors. I believe one of the reasons was to reduce the stress/metal fatigue at the area where the cylinder wall and valve pocket come to a point. The is would be the area most likely to separate/crack when the motor got overheated because the thinness of material.
This is the reason Rod Furtado didn't want any flathead to leave his shop without at least making a relief like the factory.
Barney Navarro said the same thing only talked about the forces exerted on the block in this area (of a non relieved block) as it got hotter.....and also believed it promoted better flow in a non-pop-up pistong design.
When I first talked to Rod, I had read all I could about the Harley Davidson relieving they had done on some of their race motors............and asked about step relieving the block. Rod said he had never done it before and we decided to try it. I relieved .050 on the exhaust and .125 on the intake side. I directed the intake path at the center of the piston.
Would have been nice to have a before and after on a dyno or flow bench to see if this really makes a difference..............we will see.

IMHO

 

In the Mike Davidson book "Flathead Fever" he lists flowbench data. For 20 bucks, why guess?

 

Agree with back-cutting the head helps flow a lot.

Current flow-bench testing by Joe Abbin has proven that a traditional relief results in 7-15% increased flow (depending on head & chamber design) - granted, nearly all of this increase occurs above 3000rpm where most of our street driven engines see little time, so it's usefulness from an expense vs results standpoint on a street engine is marginal, at best. But the flow is there.

 

I spend something like 30 hours on porting, gasket matching on my french block .
and it works well!

to get a good rev up you must do a good port job, that's what I think!

 

If I put capsons I would have to kill you all.This should help feed the fire though.

 

I know this is basic Flathead porting, but many theories are being batted about. I have some thoughts on the subject as well.

1.) If true efficieny is the goal I think that most if not vitually all Flathead ext manifolds and headers are built wrong. Granted where that header bolts on is nearly 10 inches from the valve seat but vitually everything I see "forces" the end port exhaust flow to make a hard turn just after leaving the block. I have run powder through the Flatty's ports with compressed to see where the flow wants to go. (crude I know but it works) Those end ports should have their exit straightened by radiusing and removing the right angles directly in the path of flow. (whish I knew how to illustrate this on the computer). Then this should be complimented with a header design that comes off the block at a similar angle that the exhaust flow "wants" to go (which is aimed at the center of the block). Essentially a tight "W" style header would do the trick.

2.) The above wont amount to a hill of beans if the end exhaust port pockets and port entry windows are not opened up and smoothed out. A whole bunch of improvement can be made here very easily with just some careful reshaping. I will do this to all Flatty's even stockers. I feel that a bunch of heat gets concentrated around these restrictions.

It's important to note that the futher advanced French Flatheads have curved end port exhaust boxes in an effort to remove some of these right angles and give a better approach to the exhaust port outlet. In this military engine I'm pretty sure this was done to reduce the heat concentrations more so than high speed performance gains. I know some racers have acually moved the exhaust port exit over to completely eliminate this problem, which is cool but not very practical on a street engine.




Now as far as the intake side goes the greatest thing Ford could have done would have been to raise the cam or used some sort of a cam follower that would have inclined the valves at more of an angle to the cylinder. The best representation of this that I know of can be found in the incredible Pierce- Arrow V12. Those valves are at about 30 degrees to the cylinders. When the valve moves, it opens right over the cylinder. The corresponding straighter port has a better chance of "emptying" right into the cylinder. Albeit all the flow occurs on one side of the port in this situation. If Ford would have done this and maybe gone to a bigger bore when they redesigned for the 8BA they might still be running the Flatheads. In fact the Pierce- Arrow V12 was very viable well up into the `70's in Seagrave firetrucks and such. Of course this is'nt a practicle solution for any engine that was'nt designed this way from the very begining. BUT! there was one very brilliant dude that got the same effect in a very clever way. None other than Barney Navarro himself. He raised the roof of the cylinder head and effectively changed the intake valve's angle of attack at the cylinder. He then restored compression by using a "pop- up" piston which fits right up into the cylinder head cavity. The intake flow goes up in there. This is a much better situation than trying to get the charge to flow another 90 degree turn over the edge of the cylinder.








I'm sorry I know this post is way off track. I'm stuck inside waiting for a phone call and I've had a ton of caffiene.

 

Ok, never thought I'd say this...those pictures need captions!
At least for us dummies.

 

Amazing what info you find when using the "search" function!

 

has anyone found a reliable filler that holds water and pressure when doing MAJOR block port surgery ?

 

Devcon steel has worked in the past.