This one isn't for everyone with a Ford/Merc flatmotor, but the folks wanting to go quick and fast will understand and appreciate it. EXHAUST BAFFLES The siamesed inboard exhaust runners on Ford and Mercury flatheads are problematic in that one exhaust valve will begin to open before the other with which it shares a runner is completely closed, resulting in exhaust gas exiting the one cylinder entering the other, diluting the intake charge thats being drawn in. This isnt a significant problem in stock motors. In a modified flathead, with a performance camshaft, however, it is significant, particularly with lots of overlap and at higher speeds. From back in the day, flathead builders have mitigated the problem by installing a baffle at the top of each siamesed runner, between the exhaust ports. A common, commercially available baffle is held in place with a longer-than-stock stud. This baffle is effective, but it's also rather bulky, adding some restriction which is not particularly a good thing. Experienced racemotor builders usually made their own baffles from 1/8-inch steel plate, shaped to fit the runner and welded in place. This type of baffle was effective and added only minimal restriction to the runner. The downside was that its installation could result in cracking of the block caused by the heat of welding. Veteran flathead racemotor builder Ed Bing Binggeli demonstrated his favorite method yesterday, a method of securing a 1/8-inch baffle with minimal welding and thus little or no danger of cracking. The pattern for the baffle is 3-5/8 inches long. You can scale it using a photo manipulation program such as Adobe PhotoDeluxe. Send the image file to your own disc, open it in the photo program, crop it to the dimension lines, size it to 3-5/8 inches horizontal, save it, and print it out. It should be the correct, full size. In any event, it will be close enough to begin. Grind a slight counterbore in the top edge of the baffle, about 2-1/2 inches from the upper end. (It's best to fit the baffle into the runner, after the "trench" described in the next step is cut, and centerpunch the actual location of the counterbore through the bolt hole.) Grind a point on the end of a headbolt. The bolt, engaged in the counterbore in the baffle, will hold the baffle in place during welding. With a small-diameter stone or burr, carefully grind a trench in the center of the bottom of the runner. It need be no deeper than 1/16 inch. The trench will hold the lower edge of the baffle in place. Now you can fit the baffle to the runner, removing just enough material from the baffle to get it to fit snugly. Install the baffle in the runner, taking care to line it up in the exact center, seated in the trench, with the counterbore on top of the baffle lined up with the bolt hole. Screw in and tighten the bolt just snug enough to prevent the baffle from moving. Weld the top end of the baffle to the block at the heat riser passage. Its not necessary to weld the passage closed. In fact, doing so increases the potential for weld-heat cracking. If you want to block the heat risers, do so in the manifold. That's it, simple, inexpensive and flatmotor high-tech.
that's really cool...but i spent a long time finding this good block and i don't know how to weld so i'll save this for a future motor
Gooood Tech ! The Baffle is only welded to the block in one area? What did you use for welding? TIG or MIG ?? Michael
Yes, it's welded in place through the heat-riser port. The trench in the runner keeps it from moving around. Either welding medium will work.
Mike,Thanks,will save this info and try on next project.Really good thinking on Bings part .Thank him also please.Keeping hatchets in a flat motor has all been a challen,mine seems to take off for parts unknown about once a season.More? Pleeeeze.
Mike, you seem to come up with "flathead tech" at just the right time! Was trying to "fit" a set of the cast iron baffles on Wed and gave up because who ever made (cast) them wasn't even close! Now I have another way!! Next, you will have to post a pictorial on "mounds bar" crank shafts! (you have to see what Mike does to a MERC crank!! )
Yes, Dave, I get the hint! I finished Rick Guasco's block (he said, name dropping), and will finish the racemotor block for Speed Week '04 Wednesday. Your crank, with the rough carving already done, is right next to my bench, the first in line of three cranks I'll be doing, although the other two won't be receiving the same level of finish that yours will. Is this what you had in mind?
OH YEAH! Every time I see that picture, I have a strange "stirring" in my loins! Next, you should post the pics of WHY doing that (polishing) to a Merc crank pays off!
Crankshaft carving for a flathead racemotor that will probably spin not much tighter than 5500 rpm isn't going to provide a big slippery-crank gain like you would find in a 7000-10,000 SBC racemotor. The gain is not inconsequential, however, but the big positive that I see is that carved and polished flathead race cranks are super tough and capable of withstanding and surviving some serious failure mischief.
Has anyone ever seen some hard data on how effective baffles are for siamesed exhausts? I certainly don't mean to question av8's knowledge, and I definitely appreciate his great post and clear pictures. I've just heard a number of conflicting opinions about whether or not the baffles work effectively, or if the effect of resticting the exhaust flow with them is more detrimental than seperating the flow. But, in the end, all I've ever heard is opinions. Has anyone seen any actual numbers, like on a flow bench, that shows how effective baffles are? --Matt
[ QUOTE ] Has anyone ever seen some hard data on how effective baffles are for siamesed exhausts? I've just heard a number of conflicting opinions about whether or not the baffles work effectively, or if the effect of resticting the exhaust flow with them is more detrimental than seperating the flow. But, in the end, all I've ever heard is opinions. Has anyone seen any actual numbers, like on a flow bench, that shows how effective baffles are? --Matt [/ QUOTE ] Matt, you raise a good point. Almost all the reasoning for using exhaust baffles that I have been able to find is based on the "dilution of gasses" therory. As a "died in the wool" flathead fan, I have done "exhaustive!" research on the subject. I have found lots of "flow specs" on heads, intakes and exhaust manifolds, but have never come accross specs regarding exhaust baffles. Many of the "flathead gurus" all state the reasons why they use them, but never show any "hard" evidence to what "gains" were achieved. The reasons make sense, and I guess I'll "follow the crowd" and use them in my engine. The "ultra thin" ones that Mike show above; in my mind, can't cause too much restriction. The cast iron ones seem to fill the port which might cause restriction.
Great post. Real live hot rodding for the flathead that doesn't look as imtimidating as porting and relieving the block. This goes to Tech-o-matic unless anyone has more good stuff to add.
Coupla thoughts: Great ideas for retention--how about a slotted plug for the crossover hole for a no welding retainer? I don't think actual flow testing would work on this--we are talking pused flow here, and different pulsed flows interfering with each other, and a relationship with intake flow thrown in... I think only dyno testing would work, and I think results would be dofferent at different RPM and probably also with different headers.
[ QUOTE ] Coupla thoughts: Great ideas for retention--how about a slotted plug for the crossover hole for a no welding retainer? [/ QUOTE ] Bruce the only reason I can see that the sloted plug would be objectional would be the fact that the intake manifold heat risers would be non-operational. When you live in a cold climate like I do; those heat risers help get the temp up at the base of the carb(s) so you can get underway quicker. But, your idea does make sense.
The Jalopy Journal
