Tractorsport Flowbench Forum Archive

Posted: **Mon Feb 02, 2004 6:26 pm**

Been thinking this through my brain for a while now and I am wondering how other people adapt heads to their bench? Do you have different adaptors for each head? Do you have one adaptor for different heads? How do make sure the head is centered over the hole? Do you make sure the dia of the adaptor matches the cylinder bore exactly ie .010 .020 etc over? U using the head bolt holes or clamping it fast with something else? Is there a bolt hole list somewhere for different heads? Could we make a list of bolt hole patterns for various heads. Just thinking out loud here trying to spark some discussion. I'm not testing much more than my flathead engines so I don't have alot of ideas to share . . .

Posted: **Mon Feb 02, 2004 7:10 pm**

My bench is built around 90mm outside diameter stormwater plastic pipe. It is very convenient for me because it is a tight interference fit into a 3.5 inch hole (88.9mm). Also the cylinder bore of my engine is 86mm which also corresponds closely with the ID (85.7mm) of the same plastic pipe.

So the test hole in the top of my bench is 88.9mm, and I bolt a long piece of one inch MDF under the cylinder head located by four recessed bolts around the cylinder being tested. An 88.9mm hole in this MDF at the precise bore centre locates the head exactly over the test hole.

An eight inch length of press fitted plastic pipe then dowels these two holes in exact alignment without leaks. The head and its piece of MDF sits flush on top of the flowbench, and the plastic pipe extends underneath projecting mostly inside the bench entry plenum.

I have two test holes in the top of my bench. One hole sucks, and the other hole blows. For exhaust side testing I just move the head across to the blow hole. The blow hole is fed directly from the output of my centrifugal blower, the last section of 90mm pipe being a straight vertical run about two feet long, containing a static pitot tube a few inches below the head to measure blow test pressure.

Posted: **Mon Feb 02, 2004 10:39 pm**

Your best friend is a machinist, make a table(four legged fixture) and adapters for each head you flow(old head gasket as a template) and tap all four holes to bolt head tight for no leakage. Bore should be within 1mm of actual bore size( start with a pipe size your going to use the most) and either sleeve or go bigger smaller with the fixture. Valve openers are another one to leave to a machinist as these guys are very inventive(spend your time doing the other work). Just my two cents worth,

Posted: **Tue Feb 03, 2004 12:54 pm**

My setup is like Tony's. Only difference is that I'm using steel instead of plastic and wood. I turned the cylinder to size on the lathe and I think that the 1mm recomendation is pretty good.

SWB

Posted: **Mon Feb 09, 2004 4:03 pm**

I plan on using 4.5"OD, 4.25ID clear pexi tubing for my cylinder moch up.
I have 4.03" bores. I will have to cut out another section of this same pipe, cut it down the side and insert it inside the 4.25" ID to get 4" ID.
Anyone every heard of some type of clear flexible films that are 1/16 or 1/8" thick that would work also?
I haven't seem any yet but it would be easier than inserting a pipe inside a pipe.

I plan to insert this Clear pexi over 4" white PVC concentrically. and hold it perpendicular to the bench using 2 MDF snections 6" by 20" on top and bottom similar to the comercial pexi units sold by flow bench makers.

Posted: **Sat Feb 14, 2004 3:22 pm**

My plenum entry is a 5" toilet flange. I use threaded inserts in holes in the bench top. Then I can buy flanges of different sizes as necessary, flip them over and bolt them down to the bench to make different size adapters. Each adapter gets its own gasket so I dont continually wear out the same one. To attach the adapters to the bench I use 4 1/4-20 thumbscrews that go into the threaded inserts and hold the flanges tight together. HTH

Posted: **Tue Feb 17, 2004 6:38 am**

It is better to replicate what the flow will see on the given engine, fit appropriate size sleeves into the bench top simulating the actual bore size of the engine the head is for.

Make the sleeve length a minimum of 1.5 times stroke length of the engine.

Position of head on bench:

Fit the head to the stripped block with about 2 bolts & flip it upside down. Scribe the bore dia onto the head deck.
Remove head & you will see the scribed circles you made, this is where the head should be positioned on the appropriate sized sleeve, replicating the the flow the engine will see when running.
If your flow is turbulent or other wise not good, this is what your engine is getting---fix it.
Hope this helps.

Posted: **Thu Mar 04, 2004 11:36 pm**

I was stumbling around my local scrapyard today and found a bunch of PVC sheet in various thicknesses and diameters. I plan on making the top and bottom of my fixture like the professional ones you see on the net and make removeable sleeves from round PVC to slip inside for various bore sizes. My question is; does anyone happen to have dimensions from one of these fixtures or a good idea of what size I should make it for various heads? I have only worked on small engines so I've not messed with bigger heads yet. I want to get setup if and when I do any testing on them. What would be standard size cylinders? I want to make the outside dia of the adaptors a tad bigger than the biggest cylinder I might see.

Posted: **Fri Mar 05, 2004 12:47 am**

Bruce,

For small block Fords, the nominal bore is 4.000" and overbore is 4.030

For small block Chevy:

3.671" x 3.100" = 262
3.750" x 3.000" = 265
3.500" x 3.480" = 267
3.875" x 3.000" = 283
4.000" x 3.000" = 302
3.736" x 3.480" = 305
3.876" x 3.250" = 307
4.000" x 3.250" = 327
4.000" x 3.480" = 350
4.125" x 3.750" = 400

Popular crank swap engines
4.125" x 3.480" = 372 (400 block with 350 crank)
4.000" x 3.750" = 377 (350 block with 400 crank)
4.030" x 3.750" = 383 (350 30 over with 400 crank)

John

Posted: **Fri Mar 05, 2004 8:48 am**

Bruce,
Here is the dimensions of a superflow V8 adapter.

The 4 small holes that you cant read the dimensions on are 5/16"

Posted: **Fri Mar 05, 2004 7:51 pm**

Thanks for the replys!

I plan on making the cylinder adaptor a removable cylinder and have a different one for each test I perform. Well thats my plan anyways for right now. I'm sure one adaptor will not cover all things one can test on the flowbench . . .

Posted: **Tue Mar 09, 2004 4:06 pm**

How are heads secured to a typical fixture? I find that a Chevy SB head bolt pattern too close to the bore to use bolts.

John

Posted: **Sat Feb 28, 2009 2:35 pm**

Posted: **Sun Mar 01, 2009 5:31 pm**

[color=#000000]When you flow in the exhaust mode and going from 4.25" to 4" doesn

Posted: **Sun Mar 01, 2009 8:15 pm**

Don't ask me why, but I have seen similar Superflow Headadaptors on the web. I tought I would remove the step with a biased cut.

Daniel

Tractorsport Flowbench Forum Archive

Cylinder head adaptor?