Got me one today neat motor no cracks has factory hollow lifters. It was a truck motor it has double groove bottom pulley. Any history on these on the reilving process. Im puting it in my roaster till i get my other block done. I blew a head gasket on my old motor and the rings were bad. Billy
I've got a couple of factory relieved Mercury 99's & they look almost as if they are done in a single swipe with some type of milling apparatus ( not as fancy as you would of got from a performance engine place but still effective ) one's goin in my Roadster... I have been told that the military used them over here... Bren Gun carriers maybe.. Spence.
You are right. If you clean the relief up really good you can see the machine marks left by the mill when it made a p***. If you want to finish a traditional relief job you have a good start as the depth is already established in a consistant manner. I'm sure you could take it deeper but I don't see the need for a strictly street application. I would take a head gasket, scribe out the ends of the relief and go for it. Frank
That relief was a quick and dirty fix for truck engines, not so much for any increase in power, but as a way to reduce cracking. Ford realized the block was too thick there and caused stresses that weren't so bad with the relief. It also lowered the CR which is good on a truck engine that is lugged down a lot. If you clean up the corners and match the reliefs to the head gasket, the engine will perform well, especially if you add some high compression heads to get back some CR. And it probably won't crack!
When I got my '46 in '66 it had 60K original miles (My English teacher drove it to work & to the grocery store for 20 years) and the engine didn't look like it had been touched. Unfortunately when I got it, I started to drive it like I stole it. The old oil had waxed up the pick up screen on the oil pump, so things started to F up pretty fast. When we cracked the engine open to start the rebuild I was surprised to see that it was already relieved, see'in as how I expected to have to do it myself, I was relieved. I've been curious about that to this day, I thought at the time that only the flattie builders were doing that for better breathing on the modified engines.
The ONLY factory do***entation I have ever seen on relieving is on a different flathead, the big truck 337 type. A service bulletin says they were starting to relieve those in production as a cure for cracking, and gave dimensions for dealers to relieve earlier blocks. I believe the relieving began on wartime 29A type engines, and the postwar valve angle change was stated to be to improve valve area water jacketing...some rumors are that late 29's got that valve angle change during the war. Ford chambers were made to follow the flow coming off the valve seats, so if they were after more transfer area flow I think they would have relieved head some more...I strongly suspect this was a factory attack on cracking, and after the war was done mostly on trucks, probably because those are the only engines that can get run at full throttle for long periods under normal cir***stances. By the way, back when I was a kid and could find old-timey flathead mechanics to talk with I was ***ured by different highly experience mechanics that relieving was a sure cure for cracking and that relieving was a sure way to get your engine cracked!
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