Hot Rods 8ba Flathead with 4 inch crank pistons slap heads

Fellas, I have a good friend that has taken his 8ba to a local shop. He took with a good block a Mercury 4 inch crank and Offenhouser heads. The shop ordered rebuild parts from Egge machined and ***embled the motor. At start up it was ovious the pistons were hitting the heads. The shop told my buddy that it was those cheap chinese heads so my buddy bought a set of Navarro heads from H and H. They were installed and still pistons hitting heads. This includes thicker gaskets that were suggested by the shop. Now the shop says they spoke with H and H and they say there heads wont work with there pistons and the shop says send the heads to H and H to be reworked. We need help. What is the correct and best solution? Plese respond

 

Willing to bet the pistons were bought with a pin height for 3.750" stroke.
Dave

 

I feel sure thats the case. What do you think of the shops solution?

 

Does Egge sell a stroker piston?

 

If the engine is bored the "dome" in the head has to be enlarged to match..

 

It was bored to 3 5/16 but the Offey heads are machined for that modification

 

I feel for you. Take a minute and read the thread below:

http://www.jalopyjournal.com/forum/showthread.php?t=556178

 

I ran into the same thing. i clearanced the cylinder head combustion chamber to clear the pistons without a gasket so the gasket gave me a margin of safety. Seems to have worked out well.

John L

 

Why would they machine the heads for clearance when the proper way is to buy pistons with the correct pin height? The stories don't jive here.

The enlarged dome needing extra machine work doesn't sound right either.

 

Just went through the above post again. What's important is that a lot of people had problems with Egge 4" pistons and not having enough piston clearance. I had contacted Egge about the problem but they just blew me off.
I ended up measuring the actual piston clearance and had the pistons recrowned to get to the desired clearance.

 

Just went through the above post again. What's important is that a lot of people had problems with Egge 4" pistons and not having enough piston clearance. I had contacted Egge about the problem but they just blew me off.
I ended up measuring the actual piston clearance and had the pistons recrowned to get to the desired clearance.

 

They bought Ford pistons because it was a Ford motor and did not know enough to realize the implications of the Merc crank.
The pistons at least have presumably been pounded to death, and everything else needs careful checking.
The machinest...I don't know what to say!
A machinest under 70 years old probably would not know what "Merc crank" implies, but even if your friend failed to explain that he should have noticed some unusual protrusions and worried about head fit. Heads were obviously aftermarket...and anyone with real world experience should also know that nothing aftermarket should be ***embled without checking fit and clearances.
And re***embling with different heads while NOT wondering if pounding might have been a bad thing for pistons and NOT wondering about clearance after experiencing negative clearance...holy ****. Lack of knowledge about parts the age of his grandfather was not surprising, but carelessness followed by re***embling and repeating the same damn thing without any though process at all about a catastrophe is astounding. This is a K-Mart reject operating complicated stuff...
This is at best utterly thoughtless work, and I betcha the guy is going to blame the parts and blame your friend and so on.
You do NOT want him doing the repairs, so losses are inevitable. Take the shambles somewhere else for autopsy and rebuild.

What to do?? Yeah, great idea, alter expensive parts to fit a serious mistake, then re***emble using the pistons that now have no ring clearance and probable cracks!

What to do...buy proper pistons and rings of same type and start measuring, hoping they will be right for the bores as done. Have rods checked for distortions (by someone else, obviously), look over bearings for clearance AND PROPER CURVATURE AND FIT as a good pounding will alter everything.
Buy a manual and re***emble yourself.
The machinest should be snipped up into gaskets so the world gets some use out of him.

Only other worry here...there were once some egge pistons made with CONICAL head rather than an arc. I think those are extinct, but look at the shape and also see if they pounded exclusively at the center. If so maybe the pistons were junk, but the guy should still heave checked clearance and it is absolutely incomprehensible that he didn't check on he SECOND ***embly.
The pistons needed are of course simply Merc pistons with pin height placed to account for the 4" stroke.

 

I had the correct pistons. The Offy heads were machined in such a way the combustion chamber dome was incorrect. I only had to remove approximately .030 of material in an area about 1 1/2 inches in diameter. The top of the dome was flat. I ran into issues with the Offy heads, intake manifold, and trans adapter as discussed in another thread. The pistons would have protruded out of the cylinders if they had been the wrong ones.

John L

 

You can buy pistons for the 3.75" or 4" stroke. You would notice very quickly if your pistons stuck out .250" (actually .125" ;-)! We are talking about maybe .030" in my case.

I don't understand the enlarged dome theory either...

 

Ok I understand now. I had the exact same problem with brand new Edelbrock heads, then checked and found the same happened with the Offy heads as well. I am sure the problem is with the Egge pistons, which have too much curvature, which gives them enough clearance on the perimeter, but not enough in the center. Check my old thread above, I think on last page where I plotted the two curvatures in relation to each other.

 

Bruce may be a little harsh but what he says is true. Any time you are using after market parts it is imperative that you check the fit. The old saying about what happens when you ***ume is true. ***-u-me.

John L

 

The truly astonishing parts are these: Not checking with the SECOND ***embly, and ***uming both for the second ***embly and for the suggested repairs for third ***embly that pistons (and everything below them) were good to go without even a glance!

 

I feel bad because I recommended the guy to my buddy. He had built to flatheads for me but I had bought the rotating ***embly from Speedway including heads and had no problems. Now Im not sure which way to steer my buddy. This stuff is expensive enough to do once but twice and extra heads ****

 

and he still has junk

 

Thanks everybody. It been a big help

 

I have to come down with Bruce. There's no excuse for not verifying clearances on
ANY build.
I agree that the rods and pistons were likely seriously damaged, even if not visible
to the naked eye.
Collect what's left of your stuff and take it to a qualified shop for careful inspection.

 

I did battle with EGGE pistons on an 8BA for a 4" crank. They were made wrong. Probably those mentioned by Bruce. EGGE says they since corrected the problem but that didn't help me when I was building the engine. Apparently a batch of pistons went out with high domes. I build a few flatheads and will never use them again.
The engine had not had the deck cut. The heads had never been cut. Initial ***embly had .015 Piston to head clearance with gasket installed. I machined .030 from the top of the piston going down to zero at the edge not to reduce the ring land thickness. .030 is all that I dared, could have probably taken more. Now I have .045. Tried another set of heads and got the same clearance. I was shooting for .055 so I took another .010 from the combustion chamber. I measured the pistons against another set and they were indeed too high. Caused me a lot of grief. However the engine came out OK and runs fine.

 

It's a big enough h***le if you catch the problem. What really pissed me off was that Egge knows about this and acted totally clueless and gave me a big FU! I used the search function and came up with multiple threads on the same subject. How is it that this only happens with the Egge pistons. The solution should not be to have $600 heads to be modified and made unsuitable for use with anything else than the miserable lumps from Egge.
Sorry for the rant, but this particular subjects gets me every time....

 

I have to side with Bruce....I mean there's this thing called stroke,rod length, and compression height. If you need a special shape dome to fit a chamber ( cylinder head) we would use a s**** flat top piston with proper valve reliefs ( if needed) and modeling clay. Made many a custom piston...good luck!

 

Well Mike I'm sorry that the problem was not seen, but as I'm sure Bruce and anyone else out there who puts these together will say Clay, Clay, Clay, thats just part of doing it right............

 

A couple of things that will determine how much the piston protrudes or sits low is
deck height (has the block been surfaced) and crank stroke (was it reground with a specific stroke or just to clean up). Merc cranks very often end up a little short on stroke when they are stroked to 4 1/8.
In the old days we always ordered 4 inch stroke pistons for a 4 1/8 stroke crank and they came flush to the deck.
Nowdays after measuring the stroke and the deck height you can either figure it out yourself or tell the piston manufacturer the numbers and they will make the pistons to come flush.
There are way too many variables to just buy parts and ***ume they will fit.

 

Carl, it wasn't my motor that grenaded, I caught it when I clayed the heads;-)
I just jumped in. The thread ***le was like a red flag waving in front of my face...

 

sorry Mike sometimes old age creeps in......

 

For sale flathead with two sets of heads. Cheap.

 

Just Kidding. After all of the trouble we have had with parts from China, it is disappointing to hear you can't even depend on Egge.