Inliners International Forums General Discussion Hi Performance 1.6 + exhaust valve for 230-292

After seeing all the great information about the 1.94 intake valve. I thought it would be good to start the same thing for the exhaust. Lumps are out as only PES makes them and they are not a bolt in. I take it the same general rules apply. Unshrouding to a scribed line at the cylinder wall. Porting down into the bowl area. This is a start but where do we go to really make them flow without welding?

Bowl areas & the short turn radius.

And of course,,,the valve job angles,& throat are very,very important.



MBHD

I agree with Hank.
Now on all my heads, new hardened seats are used along with the 1.6 valves. Not as much metal needs to be removed as with the intakes. I like to put a downward ramp after the guide.

A cutter is used to make the nice seat for the new valve. it cuts way down into the seat and into part of the bowl. Then it all gets blended out.

Use a felpro race gasket to give the exh flange to cut out to.

Porting takes lots of time and patience. tom

Armond, if you compare the cubic inch per cylinder vs. the valve area, most six cylinders are undervalved in stock form.....an interesting side effect of larger valves on the exhaust side is that they usually increase fuel mileage by a small percentage. A 250 with a 1.625 and a free flowing exhaust system might be a good place to start.....as Hank and Tom have: said the area around the bowl and the quide will give the most benefit....the law of diminishing returns apply after that; I usually raise the roof to match the gasket and just clean up the rest for the street....the floor is already too low so don't spend a lot of time here.....fats

I'm installing an Eaton M-90 on my 230. This should, roughly under boost, be the same volume per cylinder, as a 460 V8. I need all the exhaust I can get. A nice side effect with the freer flowing exhaust is better gas mileage. Lord knows, if I want to drive this thing down to San Antonio for the Inliner convention next year, I need it! What's the number on that Felpro gasket?

Armond,the performance gasket for the exhaust is a 1448; port size is 1.38 x 1.72 (Fel Pro #)....I wasn't aware of the supercharging in my earlier post....in that case go for the 1.625 and take the sides of the port and the roof out to the gasket; you'll need the flow volume....fats

Armond, for forced induction its usually good to try to make the exhaust flow at least 80% of what the intake flows. This isn't an absolute, just rule of thumb give or take a little bit. On some engines this just isn't possible, but it is a goal to try and reach none the less.

I think the best you can do is about right. 1.625 and a good porting out to the felpro gasket. I'll build the freest flowing exhaust I can and call it good. Thanks gents

I'll go against the grain on this one for the sake of argument - bigger exhaust valves are over-rated.

From a mass-flow standpoint, most of the spent charge exits the cylinder early in the exhaust cycle before the exhaust valve even approaches max lift because it is under pressure still. Only a small portion remains to be exhausted during the rest of the (blow-down) cycle. So what IS IMPORTANT is making sure you have great flow numbers at LOW LIFT, when the valve first opens and when the valve finally closes. To do this consider the valve seat angle and placement (stock is not necessarily optimum), valve edge profile, and of course, the bowl contour carefully. I think that is of greater importance than the ratio of max flow numbers of intake/exhaust. Given that, a bigger valve will likely have better low-lift flow than a smaller one, but not always.

My altered uses 1.5" exhaust valves.

Well, apparently Mr. Lee Lasley (Leelites) is still trolling around the site and took exception to my statement "Lumps are out as only PES makes them and they are not a bolt in". It was my understanding that these lumps take considerable work to install. Entailing much work on the head itself. To me, this takes them out of the "bolt in" category, even if a bolt does hold them in place. I in no way meant it to be a put down of PES or Clyde. If I have mislead anyone, I apologize. Mr. Lasley also thinks he was banned from posting on this site because he "put down" Mike Kirby. All this time I thought it was because he was engaging in belligerent and rude behavior, but I could be wrong about that. Nuff Said!

If you use the PES lumps and raise the manifold floor to match them what gasket is used?

You can use the stock gasket,,,it will not hurt the airflow.


MBHD

I guess a PES flow test is inevitable at some point then....

Yes, a flow test and what is involved in the installation would take some of the "Black art" out of it. I've always thought Clyde was on to it but the casting quality and additional work made them difficult for the average hot rodder. I had no idea you could use the stock gasket! I guess you fill in the bottom with the lump and cut away the top to raise the port?

Yes,,,according to leelites,it's the best lumps out there. I also think leelites is a salesman for PES. LOL

That would be interesting to see also,,,,anyone have an intake & PES lumps out here?

;-)

MBHD

I'll be glad to contribute flowbench time and machine work, if others would like to help with product contributions....

I have a set of PES lumps and an Offy manifold that I will adapt to fit them, I cut the center out of it to fit it to a GM TBI. It's for that old 4 pile project I started. I also have stainless valves( 1.94 & 1.60 ) Crane springs, roller rockers and a few heads. I just need knowledge, skills and a few "get off your butt" pills!

We will find out about the intakes soon enough.
I'd like to know more about what is involved to mount lumps in the exhaust.
Armond, can you elaborate? Tom

I wish I could Tom, getting solid information out of Lee is like pulling hen's teeth. They must bolt in but how? He did say the best head to use was the one with the smog ports as they have more meat at the top of the port. Lee's or Clyde is your best bet. My head came back from the shop, hot tanked and clean, magged and ready to start removing the bosses and port. I'll be taking pictures for the 12 Port News, should be fun.

Well, I striped an old 250 and bolted the freshly cleaned head to it. The idea of scribing the cylinder wall onto the head with the hopes of unshrouding the valve was complicated. The combustion chamber is already over the cylinder wall by close to 1/8th inch. There is a little to be gained on the side opposite the sparkplug and next to the sparkplug but man, it's tight in there! So, just for giggles, I cut a 3 7/8th circle in construction paper and sat it over the scribe line. With a 2.02 valve, there was less than 1/16th inch between them! I can now see why so many people use the 1.84 or 1.90 valves. The 2.02 still had more curtain area available despite the shrouding. I'm not sure how this would effect flow but it seem a good (flow tested) unshrouding would net an overall gain. It also shows that flow testing on these heads must be done with a cylinder attached to be valid. The quest continues!

You can notch/bevel/chamfer the top of the bores a bit for better flow also,,BBC's do that from the factory IIRC?

I plan on knotching the bores on my 250 block.


MBHD

Armond/Hank,
I have an old 250 (junk) block. The big valves do get shrouded by the cylinder for sure. I'll take my sawzall ( same one from vids) and chop a piece from it to reveil the safe thickness that can be removed. Really going to use a portable bandsaw. Tom

Can anyone confirm this? How much more metal is there in the port roof and how can it be measured?

Not sure about the thickness,,but Ive seen Mike kirby dyno w/the smog heads & uses the air injection ports to install EGT sensors.Qty 6

MBHD

As long as you have at least 1/8" of clearance around the OD of either the intake or exhaust valves and the combustion chamber, this is more than adequate to unshroud the valves. I'll see if I can post some pics of a cylinder that has been relieved to show how much you can go. Keep in mind not to open the chamber up beyond the gasket outline, or you risk exposing the gasket to the extreme combustion temps directly. It needs to stay protected and concealed between the block and head deck surfaces.

Literature I have read (I think it was a British research paper) said you need at approximately .25 x the valve head diameter to be free of cylinder wall shrouding; e.g., a 2" valve will be shrouded if closer to the cylinder than 1/2".

I think your engine can bust that research paper wide open Greg, im sure the valves in your 300 are closer than that to the cylinders,im sure Ambrose's are too, as are probably any other engine ever made. Thats probably why the Brits never had much in the way of notable performance engines if they based their development off of that type of thinking.

Steve and Bob use a canted valve arrangement. One of the advantages of this type of head is that, like the hemi, the valve moves AWAY from the cylinder wall as it opens. I moved my valve guide closer to the center of the cylinder to more closely approximate the optimum - not exactly an easy machining task.

From the Vincent Black Shadow motorcycle to the Rolls Royce Merlin, the Brits made some pretty darn good performance engines. I'm not too proud to steal speed secrets from anybody - even the Lymies.

We stuffed a 2.150" intake valve and a 1.610" exhaust valve into a 3.937" cylinder bore. Doing the math that only leaves .177 for clearance between the two valves and on each side of them for bore clearance. Probably not the optimum set-up, but it still ran good considering.