8BA Edelbrock head clearance

[61Klassic]

Hi all.
The good folks over on the HAMB suggested I ask this on here.

Does anyone know the max valve lift on an Edelbrock 1115 (flat)head.
I've contacted Edelbrock but still awaiting a reply 4 days later.
Also has anyone flycut these heads for extra valve clearance and know how much material there is to play with?
Thanks
Kev

[Ol' Ron]

The Edelberock heads have a CNC machined combustion chamber that provides aprox .450" over the valves.

[GOSFAST]

Originally Posted by 61Klassic

Hi all.
The good folks over on the HAMB suggested I ask this on here.

Does anyone know the max valve lift on an Edelbrock 1115 (flat)head.
I've contacted Edelbrock but still awaiting a reply 4 days later.
Also has anyone flycut these heads for extra valve clearance and know how much material there is to play with?
Thanks
Kev

Hi Kev, you should have no head-to-valve issues with the any of Edelbrock's Flathead castings.

Having said that we do machine the valve pockets in their smaller chamber castings occasionally, not in the 1116's however, see the photos below. The shot with the ruler is an 1116 piece and is over .500" deep as CNC machined from the mfr. The second photo is a pair of Offenhauser, these had smaller chambers going in! The earlier heads also show the "fire-slots".

We also tend to "fire-slot" most builds we do, and we always check for proper spark plug thread depths before the heads get bolted on!

Thanks, Gary in N.Y.

P.S. Hi Ron, hope all is well by you guy's up that way!

[61Klassic]

Thanks Ron and Gary, much appreciated.
I have these heads on a stock 239 at the moment but will be transferring them onto a heavily ported and relieved block and wanted to get as much flow as possible so was hoping to flycut over the valves, blend and unshroud the valves as you show Gary with a possible radius behind the valves. Possibly getting the chamber nearer to 70cc.

[supereal]

When in doubt regarding valve to head clearance, you can use the "clay" method that was common years ago. You place common modeling clay in the valve areas of the head, then install the head using the gasket. Don't tighten the head nuts beyond finger tight, then turn the crankshaft at least one full revolution. When you remove the heads you will get an impression showing any interference between the valve and the combustion chamber. That is an old "shade tree mechanic trick.

[Ol' Ron]

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When considering air flow in the combustion chamber, a flow bench is a handy tool. Back in the late 80's I did some extensive test to determine the best combustion chamber design, along with port flow. THis was with a homemade flow bench. Later in the 90's I had a professional flow bench, and this backed up most of my results. THe method I used to check airflow over the valve was quite simple. I ran a flow rest with the valve at say .350" lift and .150" clearance over the valve. Measured flow. THen I placed a layer of clay over the valve and measured the flow again.No noticeable gain in flow. I can't say this for certain in a running engine. and the RPM you're running at. However in a "street engine", compression is more important.

[GOSFAST]

I brought this back up, Kev is looking for some "real" numbers on the 1115 Edelbrock casting!

We rarely have that part number heads around here, we generally use the 1116's, but I can put some numbers here! I'll also place a photo below of an 1116 we have here now!

All the numbers I'll put here are (nominal), meaning very close!

The thickness above the valve pockets is .780"+.

The thickness directly above the piston dome area is .250"+.

The valve pocket depths as machined by Edelbrock measure .500"+ down from the head surface. You could "flycut" these .100"+ if necessary and still be very safe! I would say the 1115 heads could be cut even further and be safe also?

These 1116's come with the machined 74cc chambers where the 1115's come in at 61cc's. Generally speaking, most times there's no add'l machining required on the 1116 heads. The larger chambers lend themselves very well to "strokers" or "blown" units.

Thanks, Gary in N.Y.

P.S. I will add here, all the later model (8BA) Edelbrock heads (1115's/1116's) start with the same casting and are machined accordingly. The thickness above the pistons is the same on either the 1115's or the 1116's, but most likely would have a "larger" thickness number above the valve pockets on the 1115's due to less material being removed and a lower number than the .500"+ depth from the head surface for the same reason?? Here's a shot may help further, keep in mind these are on the 1116's? On a side note you can see the head in the photo is already set up for our "pinned" decks!

[61Klassic]

Thanks for the response Gary, a lot quicker than Edelbrock.
Good to know they use the same castings.

[61Klassic]

OK, so with the material in the head over the piston, has anyone tried using 4" pistons on a 4.125" crank and machining the head .125" and blending into the valve relief.
In theory this would allow compression to be kept high while allowing good flow up high in the chamber as opposed to relieving?

[Ol' Ron]

Agan, relieving a block offeres little in the way of improving airflow in the cylinder, unless the head has been cast in a way to improve compression. AS in early Hi Compression heads
Yes, installing a 3 3/4 stroke piston on a 4" cramk, then boring the head for .050" piston clearance will give a 276 engine 9:1 CRn

[GOSFAST]

Originally Posted by 61Klassic

OK, so with the material in the head over the piston, has anyone tried using 4" pistons on a 4.125" crank and machining the head .125" and blending into the valve relief.
In theory this would allow compression to be kept high while allowing good flow up high in the chamber as opposed to relieving?

Hi Kev, I see two very real issues with what you're asking, first, it'll be a real headache to machine the dome sections on the heads and keep them accurate (as in the correct radius, etc.). If I recall they are machined using a 14" radius cutter. Second, I would suspect the top ring wouldn't really like where it's now located?? More so if you have a relieved block??

Not too long ago I was actually speaking with a tool mfr about having a blade made to do exactly what you're asking, machine the dome area in one shot on the CNC. When I learned about the thickness number already in play I backed off that idea pretty quick.

Thanks, Gary in N.Y.

P.S. One more issue I would have, even with the Edelbrocks, I'm already not really that comfortable with their .250" dimension as it is now, unfortunately "it is what it is" so to speak. If I'm reading you correctly you want to make area that thinner yet??? I have repaired a couple cracked Edelbrocks in the past directly in that dome area, both were from (B&M) "blown" units.

[61Klassic]

Hi Gary.
Thanks for the input. I have a buddy who’s an engineer and willing to make a radius cutter.
But from what your saying, only leaving .125 material in the head above the piston would be too thin and liable to crack.
So what heads would people have used to try a 1/8 pop up piston? I believe Ron said he had tried this in another thread?
Thanks for all your input guys

[Pete]

Originally Posted by 61Klassic

Hi Gary.
Thanks for the input. I have a buddy who’s an engineer and willing to make a radius cutter.
But from what your saying, only leaving .125 material in the head above the piston would be too thin and liable to crack.
So what heads would people have used to try a 1/8 pop up piston? I believe Ron said he had tried this in another thread?
Thanks for all your input guys

If you want to go fast, go to a flat top gas ported piston. You will need to fill the heads for this.

[Lawrie]

I,m going to use some edelbrock 1125 heads on my 99a engine that had the cracked cast iron heads, I could not find another set of cast iron heads with the 75 cc chamber.
So hope these 1125 heads will help the fuel economy with their 65 cc chambers.
And they are on special at summit.
Is there any need or advantage in putting in the fire slot, these are for our 33.
Lawrie

[Ol' Ron]

I think that if you want to CNC your own combustion chamber, you should start with an Iffy head, as they were thicker back a few years ago. Not sure about noe. as for boring a head for the piston clearance I made a cutter from a file and ground it in a lathe with a fixture set at the radius I wanted and hand sharpened it by hand. I poste some pics of that about 10 years ago.

[Ol' Ron]

The heads I used were Grancor and had previously been bored for a pop up piston. The engine and all associated parts was last seen in a junk yard in Yuba city CA. back in 07. Be nice to know who ended up with it.

[Brian]

OK, so with the material in the head over the piston, has anyone tried using 4" pistons on a 4.125" crank and machining the head .125" and blending into the valve relief.
In theory this would allow compression to be kept high while allowing good flow up high in the chamber as opposed to relieving?





61, Actually, what you're proposing, the pistons would only pop up 1/16", not 1/8", so very doable....
The extra 1/8" stroke is made up 1/16 at top and 1/16" at bottom of stroke.

[Pete]

In the old days, "off the shelf" racing pistons did not come to the top of the block by varying amounts, depending on mfg., so it was standard practice to order an 1/8 in. less stroke pistons for a given stroke.

[Ol' Ron]

Unfortunately, Unless you have allot of cubs and a low lift cam. It's hard to get hi compression in a flathead. You have ti get air into the engine to make any power. OR Nitro. Blowers are nice.

[61Klassic]

Just bringing up an old thread of mine. Ended up borrowing a few heads. None of the off the shelf heads fitted with my .430” lift cam and 1.72” valves. Ended up getting a pair of MCF heads from Gollers Hot Rods.
Still had to work the chambers a bit which are now at 82cc. Spark plugs are in a good location on these heads.
With my custom made valves (Farrea, non dished) I have 9.26cr which sounds ideal, especial with how much I should be able to flow in the higher rpm