improving flow for the 3FE’s top end (8 Viewers)

[mmw68]

We did a Port and Polish on my 3FE FJ40 project. It runs great. Was it worth it? Who knows. On my FJ62, stock engine, with the H55 - it runs great, but I think that is due to the H55.

Keep up the good work!!!

 

[RockDoc]

S**^%^%& It just occurred to me that the new exhaust valves are shorter than the ones that came out of the head. I should have ordered the ones that are 4.98" tall, not the 4.88" tall ones

So I guess I'll have to see if I can get me 6 or the 4.98" ones. Even if there is enough adjustment in the rocker to account for the different length, the springs are going to bind and the angle between the rocker and the tip of the stem isn't going to be ideal. Why didn't it occur to me to measure before I ordered

On the plus side, I think I just found a source for these valves that will ship to Canada And slightly cheaper on the exhaust valves too. http://www.rpmmachine.com/si-valves-chevrolet-claimerv8.shtml

 

[Yspen]

my 2F with 3F head rebuild

Thanks Rockdoc , you inspire me .

I decided as part of my rebuild to remove the obstructions on the flow behind the valves - exhaust ports mostly .

The casting ridges in the outlet port can clearly be seen

Cutting them down carefully

Halfway there - better airflow out of the combustion chamber

It is clear that on the areas where there were ridges behind the valve were traps for carbon buildup . That in itself is good enough
reason to do this .

 

[RockDoc]

Nice

Take your time, remove a little at a time and keep your eyes protected. Cleaning things up isn't that difficult to do, is it?

 

[RockDoc]

A few before and after comparisons so I can see better what I've done:


Head in general

Intake ports

Exhaust ports

Chamber

 

[Yspen]

Nice

Take your time, remove a little at a time and keep your eyes protected. Cleaning things up isn't that difficult to do, is it?

Good advice

Fortunately I'm a dentist ( endodontist ) and used to drilling / polishing in confined spaces .

 

[PabloCruise]

Great pics Doc and Yspen!

 

[dwrtoy]

turd polishing at its finest!

 

[RockDoc]

turd polishing at its finest!

I'm planning a TRD spoof logo..... vinyl sticker, maybe something etched into the valve cover

 

[RockDoc]

S**^%^%& It just occurred to me that the new exhaust valves are shorter than the ones that came out of the head. I should have ordered the ones that are 4.98" tall, not the 4.88" tall ones

So I guess I'll have to see if I can get me 6 or the 4.98" ones. Even if there is enough adjustment in the rocker to account for the different length, the springs are going to bind and the angle between the rocker and the tip of the stem isn't going to be ideal. Why didn't it occur to me to measure before I ordered

On the plus side, I think I just found a source for these valves that will ship to Canada And slightly cheaper on the exhaust valves too. SI Claimer Valves from RPM Machine

So, after trading an e-mail with Jim and digging out a '83 2F head for comparison I think I know a bit more now. It seems that there was a change in valve length and rocker arm shape for the exhaust valves between the 2F and the 3FE. Here is what I found:

Both the 2F and 3FE have even positioning of the valve seat between the intake and exhaust valves.

Both the 2F and 3FE have even positioning of the spring seat between the intake and exhaust valves.

On the 3FE the exhaust valve is longer than intake valve, on the 2F the lengths are even.

On the 3FE, the rocker arms for the exhaust and intake valves are slightly different to account for this difference in length, on the 2F the intake and exhaust rocker arms have the same geometry from tip to tip.



So, I think I can use the valves I have, as long as I use the 2F rocker assembly to work with the even lengthed valves. but I better take a closer look at the two rocker assemblies to make sure this is the only change in geometry between them.

 

[stereophile33]

have you considered unshrouding the valves a bit? Not too much to loose that great squish band, but enough to aide flow and flame propagation.

Also have you considered raising the floor of the ports? The short turn on these things is fairly minimal, lots of slow moving air on the floor of the intake and plenty of back flow on the floor of the exhaust.

Also does anyone know what the most we can safely take off the deck of one of these heads? I've heard 100 thou bantered about but I wonder if more is a possibility.

 

[RockDoc]

have you considered unshrouding the valves a bit? Not too much to loose that great squish band, but enough to aide flow and flame propagation.

I gave it some thought early on, but in the name of not screwing up what I've already done and keeping from unbalancing the volumes between cylinders, I drifted away from the idea. The new valves are only marginally larger than the stock ones (1.84" vs. ~1.82"), so there shouldn't be much added shrouding. Plus I'm getting to the point where I want to get the thing together more than I want to monkey around with it anymore..... might take another look though, the pics in post 101 do suggest shrouding on the short side, and they are taken at stock lift, rather than what the hotter cam will give...

Also have you considered raising the floor of the ports? The short turn on these things is fairly minimal, lots of slow moving air on the floor of the intake and plenty of back flow on the floor of the exhaust.

At the velocities I could get with the vacuum set-up the flow seemed to be heavily biased towards the short side of the intake valve, both before and after modification. I don't have any previous experience, but from what I've seen in books, the short side radius already seems pretty generous in these heads without raising the floor. There are pics of silicone moulds taken from the ports on the 3rd page that give a good illustration of the shape.

Also does anyone know what the most we can safely take off the deck of one of these heads? I've heard 100 thou bantered about but I wonder if more is a possibility.

I've heard a 0.100" thrown around too. I doubt I'll have anywhere near that cut off this one. I'll give the machinist a volume I want and let him figure it out, assuming no change from stock volume (ignoring the change in valves and volume added by smoothing the chamber surface) I figure about .030" to give me a safe boost in compression with the longer duration cam and the longer stroke of a 2F under it.

 

[RockDoc]

Been waffling back and forth on engine coatings for quite a while, and finally pulled the trigger on some from Techline.

Ordered some bake on metallic-ceramic thermal barrier (CBC-1), bake on dry film lubricant (DFL-1) and rub in lubricant (PKSX). Also ordered some CSB exhaust coating.

The stuff looks simple enough as far as application.. time will tell, time will tell. I'm not planning to put much $$ into the bottom end, so if it turns out to be a learning experience, I won't be out much more than time.

 

[lehiguy]

I had .070" shaved from my old 2F's head. Ran strong for what it was. Rocker adjustment was sufficient to get it where it should be without changing push rods. Needed premium though, the low-grade wouldn't cut it after that.

 

[Mikesta]

That video information is impressive... as is your step-by-step process!!

 

[RockDoc]

Coatings showed up today. Packaging was really well done, so looks like a decently caring company. Picked up a kitchen scale for balancing the piston/rod assemblies too.

 

[OregonCruzer]

awesome thread Rock!

 

[cruiserpants]

Great thread - I'm impressed - thanks for taking the time to post this.

You deserve a doughnut !

 

[RockDoc]

Thanks guys. Working on putting together an elocked front axle right now, then back to the engine stuff.

 

[stereophile33]

Rockdoc.

It's looking good. I'm wondering what peak RPM you are shooting for in your porting and the reason for the move to larger valves.

what cam are you running?

any other engine mods or is it an all stock 3F?