The Ford Barn

fredeuce · 03-22-2021, 04:51 AM

I am starting a rebuild on an 8BA motor on my brother in-laws 54 Customline. (Here in Australia , the '54 models still had a flathead). This engine was pulled down and put into storage years ago following a valve seat insert dislodging .

I am now assessing this block to determine what we need to do to rebuild it.
Generally it appears to be a good candidate as it has a standard diameter bore and standard diameter crank.

There is about a 0.004" ridge in the bore so I am thinking of a .020" overbore and new pistons. This is a stock rebuild . No hot rod stuff here except perhaps a set of headers.

I am curious about the dislodged valve seat insert. I have cleaned out the block to examine for cracking in the block that may have caused it to release. I can't see any cracks at this time . So far so good.

Can anyone offer any other reasons why these valve seat inserts might dislodge?

I did notice that the valve was burnt in two locations 180 degrees apart. Its not clear to me if the burnt valve may have caused the seat to dislodge or resulted after the valve seat became loose.

I look forward to any comments or advice.

chuck stevens · 03-22-2021, 07:59 AM

I have a 8RT (52 TRUCK) that dislodged the exhaust seat two different times, on the center cylinders, there were no cracks in the block.. I have had it repaired, in the car, and the repaired seats have been aright, but I'm worried about the other ones. Speedway makes a over sized harden seat, then have the block bored to fit the seat. It made it home both times!! I would put the new seat in the freezer over night, for a good tight fit.

Bored&Stroked · 03-22-2021, 07:03 PM

There is no reason that I can see for the block not to be usable. What is normally done is that the seat pockets are machined for over-sized seats and then the new ones are pressed in. Make sure you have a machine shop that knows flatheads! You cannot cut the pocket deeper - there is "water down below". The new seat will be too tall, so they'll use carbide seat cutters to cut the seat down to the correct height.

Given the size of the block, normally these types of operations are done in a special machine that can be correctly setup for the correct valve angles. The valve/seat angles on each side of the block are different - so they need to know what they're doing when they setup the block to re-bore the seat pockets.

At my machine shop, all this work is done in a vertical milling machine that has a special "crankshaft saddle" fixture to mount the block in (it indexes off the crankshaft main bearing bores). The saddle guarantees that the block is correctly aligned. If your machine shop isn't setup for this specific work - find another one . . .

Pete · 03-22-2021, 07:45 PM

Valve seat rings usually come loose for 2 reasons.
1- The valve stops sealing for various reasons and the seat overheats, cracks and comes
loose.
2- The ring was not installed with enough press. Should be .005 in cast iron.

It is a bad idea to put a new ring in an old hole without skinning the OD and squaring the bottom.

mercman from oz · 03-22-2021, 08:22 PM

Here are larger pictures showing the Valve Seats. Very interesting.

GB SISSON · 03-22-2021, 10:45 PM

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For me and my eyesight, I can see this valve seat image much more clearly on my laptop screen than I could if I was staring at it from a foot away in person with my reading glasses on...... I have noticed the same thing with such things as frame stamping of serial numbers. This is amazing technology. Was this taken with a cellphone or a digital camera? I have a similar valve seat situation on an otherwise excellent looking 8ba block, but has some differences so will start my own thread later.

fredeuce · 03-23-2021, 07:43 PM

Thanks to all who responded. Good information and tips.

Time for a chat with my machinist to get the ball rolling.

vincent · 03-24-2021, 02:44 AM

I once made an expandable insert in the valve guide location with a hardened, steel pin. When this was locked into the valve guide hole I was able to put my homemade little adjustable cutter onto the pin and drive it with a handheld drill. The cutter cleaned the recess of the valve seat perfectly on the circumference and the bottom of the pocket. Thus the pocket was ready for a new seat without pulling everything apart. I think it should be possible to heat the casting enough and cool the ring to get the desired overlap. Would save you pulling the engine. To cut the seats I use the PEG10. https://theultimatetooling.com/en/pr...-seat-grinder/

Bored&Stroked · 03-24-2021, 05:56 AM

Also, if it was mine, I'd probably take a close look at all the seats and ask myself should I be replacing others as well. Usually I have all the seats done at the same time on the mill - such that they're all cut to the same heights/depths and I know the press fits are correct. You can tell from the photos that some of the other seats are pitted/worn - so consider doing them all.

As Pete noted, you'll need to go to an oversize seat and redo the seat pocket - for the correct fit on the new seat - at the very least for the problem one. Make sure they just skim the bottom and don't try to cut it deeper for the too-tall seat they will undoubtedly purchase - the new one needs to be cut down to size.

03-22-2021, 07:59 AM	#2
chuck stevens Senior Member Join Date: May 2010 Location: upstate new york Posts: 758	Re: 8BA Valve Seat Insert I have a 8RT (52 TRUCK) that dislodged the exhaust seat two different times, on the center cylinders, there were no cracks in the block.. I have had it repaired, in the car, and the repaired seats have been aright, but I'm worried about the other ones. Speedway makes a over sized harden seat, then have the block bored to fit the seat. It made it home both times!! I would put the new seat in the freezer over night, for a good tight fit.

03-22-2021, 07:03 PM	#3
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,062	Re: 8BA Valve Seat Insert There is no reason that I can see for the block not to be usable. What is normally done is that the seat pockets are machined for over-sized seats and then the new ones are pressed in. Make sure you have a machine shop that knows flatheads! You cannot cut the pocket deeper - there is "water down below". The new seat will be too tall, so they'll use carbide seat cutters to cut the seat down to the correct height. Given the size of the block, normally these types of operations are done in a special machine that can be correctly setup for the correct valve angles. The valve/seat angles on each side of the block are different - so they need to know what they're doing when they setup the block to re-bore the seat pockets. At my machine shop, all this work is done in a vertical milling machine that has a special "crankshaft saddle" fixture to mount the block in (it indexes off the crankshaft main bearing bores). The saddle guarantees that the block is correctly aligned. If your machine shop isn't setup for this specific work - find another one . . .

03-22-2021, 07:45 PM	#4
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,407	Re: 8BA Valve Seat Insert Valve seat rings usually come loose for 2 reasons. 1- The valve stops sealing for various reasons and the seat overheats, cracks and comes loose. 2- The ring was not installed with enough press. Should be .005 in cast iron. It is a bad idea to put a new ring in an old hole without skinning the OD and squaring the bottom.

03-22-2021, 08:22 PM	#5
mercman from oz Senior Member Join Date: May 2012 Location: Queensland, Australia Posts: 10,361	Re: 8BA Valve Seat Insert Here are larger pictures showing the Valve Seats. Very interesting.

03-22-2021, 10:45 PM	#6
GB SISSON Senior Member Join Date: Jan 2014 Location: Orcas Island Washington Posts: 4,916	Re: 8BA Valve Seat Insert Sponsored Links (Register now to hide all advertisements) For me and my eyesight, I can see this valve seat image much more clearly on my laptop screen than I could if I was staring at it from a foot away in person with my reading glasses on...... I have noticed the same thing with such things as frame stamping of serial numbers. This is amazing technology. Was this taken with a cellphone or a digital camera? I have a similar valve seat situation on an otherwise excellent looking 8ba block, but has some differences so will start my own thread later. __________________ Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)

03-23-2021, 07:43 PM	#7
fredeuce Member Join Date: May 2010 Location: South Australia Posts: 50	Re: 8BA Valve Seat Insert Thanks to all who responded. Good information and tips. Time for a chat with my machinist to get the ball rolling.

03-24-2021, 02:44 AM	#8
vincent Senior Member Join Date: Jun 2020 Location: Germany Posts: 204	Re: 8BA Valve Seat Insert I once made an expandable insert in the valve guide location with a hardened, steel pin. When this was locked into the valve guide hole I was able to put my homemade little adjustable cutter onto the pin and drive it with a handheld drill. The cutter cleaned the recess of the valve seat perfectly on the circumference and the bottom of the pocket. Thus the pocket was ready for a new seat without pulling everything apart. I think it should be possible to heat the casting enough and cool the ring to get the desired overlap. Would save you pulling the engine. To cut the seats I use the PEG10. https://theultimatetooling.com/en/pr...-seat-grinder/

03-24-2021, 05:56 AM	#9
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,062	Re: 8BA Valve Seat Insert Also, if it was mine, I'd probably take a close look at all the seats and ask myself should I be replacing others as well. Usually I have all the seats done at the same time on the mill - such that they're all cut to the same heights/depths and I know the press fits are correct. You can tell from the photos that some of the other seats are pitted/worn - so consider doing them all. As Pete noted, you'll need to go to an oversize seat and redo the seat pocket - for the correct fit on the new seat - at the very least for the problem one. Make sure they just skim the bottom and don't try to cut it deeper for the too-tall seat they will undoubtedly purchase - the new one needs to be cut down to size.