Good afternoon, I posted a message about a month ago that my rebuilt long block Flathead Ford V8 would not rotate past the 2 o'clock position and opposite direction not past the 7 o'clock position. I thought I would give an update and share some of my learnings with the rest of the Flathead nuts. The root cause of the problem was the pistons hitting the heads! I have a NOS 1951 block, Merc crank, Isky Max-1 Cam, 1952-53 Ford EAB Cast Iron heads, and Egge L-991 Merc Standard bore pistons. So I could talk intelligently about my problem I took some measurements with a 1" dial indicator. - The peak of the Domed Pistons is .235-.240" above the deck of the block, the edge of the pistons are below the deck. - The EAB heads measured .165-.175" in the piston area (no wonder they hit!). The cir***ference of the domed area in head was less than 3". The valve clearance in these heads was .395-.400" (good clearance for my Max-1 cam). - I have some 8BA heads that are original but in bad shape in a couple of the piston areas (severe pitting). The first thing that I immediately noticed is the cir***ference of the domed area was visually larger than the EAB heads. I heasured 3.5" with a set of calipers. The heads measured .250" in the piston dome area. However, the valve clearance measured only .340" (not sufficient cleance for my Max-1 with .350" lift with .014 valve lash). After calling Egge, H&H, Edelbrock, and Offy this is what I found. Egge Merc pistons and Egge Ford pistons have a compression height difference of only .042"! There should be .125" difference in pin height between Merc & Ford pistons (Ross pistons have .125" difference between Merc & Ford pistons)! Egge's first question when I called them was, "Are you using stock or aftermarket heads?" Egge said that there pistons may hit aftermarket heads but should not hit stock heads. I think Egge needs to add stock 52-53 EAB Ford or EAC Merc heads to the list of heads that will hit! When I called H&H they said, "Egge Pistons will hit almost everything"! Edelbrock pulled a set of heads off there ***embly line and measured .195" max dome height. Offy measured a set of 425 heads for me at .220" max dome height. H&H will re-dome a set of heads for $150 but without them physically having the engine block to take multiple measurements on the dome I am sceptical of the "redoming" being very precise! So I have come to the conclusion that I need to find a set of NOS 8BA heads and fly cut the valve area to clear my Isky Max-1 came. Road Runner Engineering in New Mexico (the blower people), can do this machining for me but they currently do not have any 8BA heads. If anyone has a set of prestine 8BA heads please let me know. The moral of the story, if you are going to use Egge Merc Pistons (part # L-991) then you most likely have piston to head clearance problems on everything but a stock set of 8BA heads!!!! Thanks, Josh
Which pistons did H&H recommend to use? Can't you machine the pistons if they are thick enough? Michael
that involves a major tear down, I guess he could get a sawz-all with a long blade and just cut the top of the pistons off at block level.(j/k of course)......buuut, at this point, I would do what he is doing w/ another set of heads and a bit of machining time and he's driving.
I would look at 1CM or 8CM? OCM? mercury heads also. I have some 8BA heads that look good but I haven't had any of them checked out. Should be easy to find though, if you don't find what you want PM me and I will check it out.
In the dome area, I think all stock Ford and Merc heads are going to be pretty similar as I believe the piston dome is the same throughout. I think your EABs must be milled. Volume differences are going to be in the transition area and where it intrudes into dome mostly. Are the Egges the ones with a dome shape that is like a cone almost?? I have seen pistons like that, but do not know what brand they were. If so, I would call them S****. You can cut down the very top* til it clears, but there would be no possible way to get the dome area to follow the shape of the head dome closely and that is the whole point. Gasket thickness is circa 050, I think...you really need to find a flatheadiste in your area who can lend you some stock heads (few are milled, in my experience, look at circle size) and aftermarket heads known to be unmilled so you can test. Tests...first, lay on heads with no gasket and rotate. If heads don't move, you have enough clearance...but probably too much. Next, heads and gaskets (preferably used) lightly bolted, rotate slowly to see if clear, then put in multiple aluminum foil balls and check thickness remaining after rotating. If thing look good, check all across pistons with more balls, hoping for reasonably even clearance. Check valves at TOP and BOTTOM...they are canted, reliefs in heads probably aren't. *field expedient if desperate...grinder, cut all till flat circle you have ground is same size on all 8! This can be quite accurate! You will of course be done out of any real quench if you are stuck with conical piston, and will be limited in compression and timing...poor fit here is very bad for all aspects of performance
Make a mold of the pistons and block deck.I've done this on OHV head combustion chambers to get custom domed pistons made.Then you can use resin or wax to get a reverse mold .If will be a bit difficult if you can't get the block deck level so you can pour Plaster of Paris,but some sort of clay will work.Just remember to carefully seal around the pistons so no mold **** gets into the rings.I use a very thin layer of Vasoline on the metal parts as a mold release.
Yes , I had exactly the same thing with my blown motor. Egge Merc 4" 100 over pistons , Isky max 1 cam . New Edelbrock heads. .060 head gasket. hey whats goin on here ,pitons hit the head. Called H&H they werent to sure then but Mike H said they really only use ross pistons. We didnt want the compresssion to high so laid some kids silly putty on top of the pistons and turned motor over to gauge clearance issues. We ended up turning about .025 out of the heads and a similar amount off the pistons . Strange thing was after we had done this and CCd the combutioon chamber twice and re re checked calculations we ended up with the CR being 7.3 to 1. Dont know it should have been at least 8.7 being a big motor. But better low as its a blown street motor. Maybe these arent ford pistons just something else the happens to nearly fit.
I had the same problem. 8BA with EAB heads, L-100 cam. 4" crank. Egge Merc pistons. I had to cut .030 from the tops of the piston, machining from the center out to zero. Clayed the clearance and still lacked .020. I didn't want to take any more off the piston so I machined the heads taking another .020 and wound up with .055 running clearance. A lot of factors here to consider but the fact is that Egge pistons will need some machining somewhere. Some blocks have been decked and some heads have been milled. Always clay every combustion chamber to know exactly what you've got .
Egge must have a changed something since I put this engine together a couple of years ago. Egge .040 pistons and running Offy 400 heads and Merc 4" crank, didn't hit without a head gasket while turning it over. Vergil
I'll probably get beat up for suggesting it but ... Old time drag racers in So Cal have been known to double up copper head gaskets on over-decked flathead blocks and still win. revrev
Naw, thats cool. All that stuff has been tried. I saw recently a ridiculously thick copper head gasket to try to find some clearance. I like to put them together so that if I need to repair the thing on a trip I can do it without custom parts.
Contact H&H @ 818-248-2371 about using Navarro High Dome heads - these are for the 59A block but will bolt to the 8BA block after blocking a couple water jacket holes. They should accomodate a .250 dome and your high-lift cam.
I've got a virgin pair of EABs for my 8RT in the '36 p/u. They are also smaller in the combustion area - look like they've been milled, but haven't. I think the EABs are smaller here too. Can provide pics when I get home if needed. To the original topic - Personally, I'd toss the Egge pistons and run Ross, but probably a bit much at this point in your build and easier/cheaper to machine some heads to suit.
I would have clearanced the heads . It probably would take almost a whole afternoon. Next time I would use other pistons but in the meantime I would be mobile and enjoying the ride. A piece of modeling clay in each whole coated with ink or paint would find you the spots on the heads which equals the centre of the piston domes. Using the stop on your drill press you could drill each chamber the required amount to clear That would give you a small register point and you could blend outward from there. Pistons are probably really ford tractor pistons as they share similar dimensions. Anyway you would be done and driving it without trouble. It is amazing what can be done with a bit of care and a good reference point. The small drill will set the depth and give you the central position. If you dont trust the postive stop on your drill presss then set the depth for full travel just touchng the spot whare you need clearance and then shim the head up the amount of extra depth you need. That way there is NO WAY of going too deep since the quill on the drill is at full extension. A paper pattern with a centre hole will give you a way to lay it out so all will be as close as possible. I think a careful person could come with in 1 cc which would be far better than most stock heads anyway.
Hi Josh, the highlighted section of your post answers the question!! There should be a minimum of .100" difference between the Ford and Merc slugs. If Egge doesn't acknowledge this difference then you need to change vendors. The difference you state is the same as the difference between the Ford and Merc strokes with the pistions at TDC! You cannot blame the heads with only a .042" C.H. variance? You MAY run into a ring location problem if you try to "fit" the incorrect slugs in there! Thanks, Gary in N.Y. P.S. I have about 3 "Flatties", all 4.000" Merc's, in here now for builds, and all with Ross slugs. Ross uses a 1.436" C.H. PLUS the .187" D.H. for the 4.000" Merc strokes!
On clearance...there are lots of ways to get badly shaped/wrong height pistons to not hit the heads, BUT most are poor paths to follow. You need a fairly close fit to the dome area, circa 040 AND you want that fit to be consistent over the whole quench area. If all clearance is large OR if you are fitting a cone to a dome and have correct clearance at only one point, you are losing power, gaining excess sensitivity to knock and unwillingness to tolerate high compression, etc. Chevy let its customers study this intensively in the early 1970's when they almose eliminated quench...remember all those 1973 350's chugging and knocking up hills as tiny Japanese cars whizzed by? If your pistons are totally wrong, accomodating them is a very bad idea...engine costs money, wrong piston/combustion area kills it all. Swallowing the loss and getting proper pistons would be wise.
I was planning on using Speedy Bill's 3-ring pistons with EAB heads on my next '51 Merc flattie build. Does anyone have good or bad feedback on THEM? C'ya - RAY
I've used the pistons Patrick's sells with good luck when I need cast. Never used Speedway's stuff, so can't comment. Patrick's was cheap...
Capitan Insano 03-18-2009, 11:52 AM "I had egge change their dome on the pistons because it hit every head. It was a continual problem. Now they finally have the same dome as Ross Pistons which never hit. Since the change I have not had to dome heads as much". Mike H&H Flatheads This was copied from the archives. I believe the change was early 2008.
Very true. Most people, even some who claim knowledge of performance engine-building, don't realize how important a tight quench is.....whether it's an ohv or a side-valve motor! On a flattie, that will arguably never see 5K rpm, you could probably run the PTH clearance as tight as .025-030" without smacking the head. And, as Bruce pointed out, you wanna have that clearance consistant over the entire surface of the piston dome. Please excuse my ignorance, Ernie - but I'm not familiar with "Patrick's". I Googled it and searched the HAMB, but came up with zilch. Do you have a link or the full name of the company? THANX. C'ya - RAY
They're not on the web (in this day and age!) and now I got a PM from someone saying Patrick uses Egge pistons, so my original suggestion is moot anyway. Speedway? Who do they use?
I haven't a clue who supplies Speedway's pistons...........it's a cinch THEY'LL never tell, lol! THANX, anyway. C'ya - RAY
i purchased a set of flathead pistons from speedway a couple of years ago and there was a sticker on the box that indicated that the pistons came from Mississippi. the machine work looked so bad [compared to ross pistons] i just sent them back to speedway and ordered a set from ross.
I used .100 egge pistons in my merc rebuild last winter. Also used the higher compression edelbrock re-pop heads. When I put the heads on with or without the gaskets they hit. The problem was the bottom of the chambers was not big enough due to the over bore. All I did was blend the bottoms in and then solder squish to check the clearance.
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