Hey folks, I recently scored a NOS 4-71 still in its shipping wrap. So, supporting the HAMB i purchased the intake and 3x2 top from Elco Heads (Terry) . What is everyone using for internals and what advise can you share with me on building a nice blown mercury for the street. Leon
Factory rear end plate is just as good as an aftermarket plate. Install zerks on the end plate so you can grease the bearings. Leave internal clearances stock. The case becomes hot & raises . This tightens the gilmore drive belt more than you would imagine, leave belt loose, check tension when blower is hot. I would start with a 1 to 1 pulley ratio. I would run about 7 to 1 comp ratio. I would start with total timing of only 20 degrees. These are only suggestions. Greg
Flathead Merc? If so, I suggest some work downstairs on the mains and a bunch of porting and relieving. If you don't own Joe Abbins book on building a blown flathead, start there. It is the best advice I can offer.
My 8BA is running a 471, 8 pounds of boost on 8:1 compression My main caps came from HandH flatheads. Always build on a good foundation. A lot of guys don't want to blow $1000 on mains but I wanted my motor to hold together. I think the mains were $500 and another $500 to cnc them to fit and line. My merc crank. These motors are still fragile down below so watch the boost. bored, Ported and relieved, all per the book. Bolting on the blower is the easy part. If you have any questions I'm happy to share.
This is good advice, especially building your bottom end with boost in mind. Too many just screw the bottom end together and expect it to hold up. Sometimes you get lucky and most of the time you just think that denial is a river in Egypt when you don't take your time with your foundation.
Uncommon Engineering do a kit to suit, use multiple V-belts rather than gilmer style as it's more period correct IMHO. Or this style crank girdle bearing in mind that a FH is ONLY a 3 bolt main block and NOT a 5 bolt block as in later V8s. H&H, Flathead Jack or Baron Racing would be good starting points. Block with caps will require line boring. I'm no expert however you need to factor in HP as to how much $$ you spend on the bottom end as that is the key to longevity. Build it right and strong, build it only once.
That is the plan! Being in Canada on a island in the Atlantic Ocean, the parts quest will take a little more time than if in the USA. This is why i am asking for everyone to share their knowledge so i can build it once, build it right. Thanks! Leon
Cripes Leon, good for you, no seriously, in the middle of the Atlantic Ocean. The only thing better than finding an NOS 4-71 blower is finding an NOS 6-71 blower! How does one find themself in this position?
mgtstumpy, Is that a Doug King girdle? It looks like one I bought from him several years ago. I wish I could buy another, I have a project that could use one..
There was a equipment dealer who went broke many years ago! All the old parts were bought up cheap..the blower never found a new engine.. So, $100 later it found its way home with me!!! I also scored a new 6v71 some years ago.. same type of situation.
Make sure you “pin” the rotors to the shaft.If this really was a n.o.s. Blower,it was meant to turn less rpm’s(diesel use) than the 4-5k you will encounter with the Merc motor. My diesel mechanic(50 years experience) was happy with the .010 clearances we achieved with my 3-71. He stated that tightening up the clearances to less than .010 would not be beneficial enough to make a great difference. Flatheads Forever!
Gladly, it is a 49 8BA that I found on CL in Tacoma 5 years ago. No cracks, beautiful empty block with a minimal machine work done. Also scored a merc crank that was 10/10, 2 sets of shot peened 8BA rods (one set NOS...not any more), that merc timing cover and misc pieces. Basically, the guy was getting out of rodding and sold me his stash. Bored .125 over with 3 ring Ross pistons, stainless chevy valves, Navarro blower heads (decked to dial in compression), Navarro intake and blower all courtesy of HandH. CNC steel main caps, ported, relieved, high volume pump, adj lifters, ARP hardware, etc. Basic flathead.
I don't know why you would port and relieve or install large valves. The blower will make it breathe. If this engine is for street use there is such a thing as too much HP (see advice above about reinforcing the bottom end). Suggest you build it on the mild side. When you get it running good, and broken in, you can change the pulley ratio for more boost.
For one thing those that you have listed are restrictions. Restriction adds to a higher boost reading which is also higher heat. Heat causes detonation. This is especially a problem in flat heads. Putting more boost to a motor can be one of the easiest horsepower adders yes. There is no 100 percent solid horsepower gain per pound of boost that I know of(yes there are equations boost gain). It seems that history has proven that each pound of boost applied to a more officiant base combination will often net a more effective end result. Many have increased airflow and lost boost while still gaining horsepower. Sent from my iPhone using The H.A.M.B. mobile app
I do not claim to have any "original" flathead knowledge. All I know and all I have built is solely based on the success of others. And I am not ashamed to admit it
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