Hello all, I have read the fantastic 2011 "Flathead Block Relieving for High Performance Flow - How To" post from Bored&Stroked, and I'd suggest it to anyone about to tackle the job of relieving their Flathead Ford for the first time. I didn't want to hijack that thread but... I am about to jump in on mine using the router and die grinder method. I'm looking for a little advice on how deep I can safely go with my 4.25 stroker build. I've read everything from 0.085 to 0.1875, and I can't exactly put it all together and measure it because the final machine work hasn't been completed, and the rotating ***embly is off being balanced. From what I can figure, a .125 relief cut will leave me with a decent compression ratio, but I don't know if that's safe with the 4.25 stroke. Disclaimer: I can turn a wrench, have a tool & die background, and have tinkered with flatheads for a few years, but I am not a professional, just a guy trying to learn as much as I can as I go. My engine specs are: 59A block, bored 3.312, intake and exhaust ported, (also manga fluxed, thoroughly cleaned and de-rusted, sonic checked cylinder walls, new valve seats) 4.250 stroke Eagle Crank 7" **** Rods 3.312 Ross Pistons (80576) Offenhauser 425 heads 1.6" oversized Manley ProFlo intake valves 1.5" Manley ProFlo exhaust valves 3x2 intake with Stromberg 97 Primary and dual Stromberg 88 secondaries New adjustable lifters, springs, oil, and water pumps, etc TBD Schneider cam regrind with all specs and use case in mind Just for added info, I had major cylinder wall damage from a loose wrist pin, and then a rear main bearing failure, which kicked off this rebuild for my full fendered steel 1933 Tudor. The intent of this build is to be able to run the car in New England vintage drags, and hit the road even if the tune isn't ideal for the street. I'm hoping the significantly increased displacement will make up for some of the low-end torque that may be lost. I am currently running the OEM 3-speed and banjo rear, but I have a T-5 for it and will upgrade the rear end eventually. Any advice on my depth of cut before I start irreparably altering this 80-year-old hunk of cast iron would be greatly appreciated! Respectfully, Cody EDIT: On further reading, Joe Abbin of Roadrunner Engineering, who has flow bench data in his book, recommends 0.100 to 0.125 max
I had a 60 year love affair with Henry’s finest—-flathead ford v8 ——-owned,bought,traded over 50 engine over a half century/ after fully relieving every block I built for myself(probably 15 engines) I decided to relieve ONLY THE INTAKE side which operates on vacuum or suction and would leave the exhaust side alone because it was expelled under pressure and kept a little bit more metal to aid in the compression. One of the last engines I built had these exact features and pulled 150 h p at the flywheel with only a .080 overbore and a stock stroke(3 3/4)using a mild cam and Edelbrock slingshot with 2—97 carbs. My 32 Henry cabriolet ran 80 mph in the 1/8 mile with the appropriate gear(3:91 locker) and 3:00 on the street/70 mph was 1900. FLATHEADS FOREVER.
Just remember that any relief work you do will result in a lower CR as you are increasing the combustion chamber size. Joe Abbin does recommend relieving the block, but he also recommends bolting a blower on top. I did a lot of relief work and porting on mine but included that in the calculations before buying pistons for the merc crank. Do the relief work but add the supercharger!
aussie mike davidson advocated the intake-only relief for better compression, and i think that was tried way back when as well!
Thank you to those of you who responded above. For the sake of anyone who has the same question, I'll post my conversation thread with Dale below (with his permission). I had also reached out to Ronnie Roadster about the issue, and he got back to me with a recommendation of going .080 to .085 deep, saying that any more won't help much. (Ron has a mountain of flathead experience between a lifetime of hot rodding and racing at Bonneville, and has built one of the fastest flatheads on earth, which holds several records.) While I was waiting to hear back from Ron or Dale, I remembered that I had Joe Abbin's book, and spent some time going throught it. Joe's book recommends .100 to .125 based on flow bench tests (along with a wealth of other information about the % of flow gained in intake and exhaust by t******* and porting specific clearance areas in the intake and exhaust ports, and HP gains he has seen with specific modifications. Out of respect for the author, I won't repost his material here. Buy the book, it's worth it.) Dale (Bored&Stroked) recommended .125 to .150, which after some discussion was .125 All three have slightly different recommendations, all valid based on their personal experience building and racing. I have the utmost respect for these guys, their commitment to hot rodding, their willingness to help out fellow enthusiasts and p*** on their hard-earned knowledge.
I really don’t anything about the subject, but I’m curious as to how cam selection might affect any endeavours in terms of relieving the block as it relates to both naturally aspirated and forced induction. I have two C69A block, and one is relieved (I ***ume by factory), and the other isn’t. I find that kind of weird.
(Convo with Dale/Bored&Stroked as mentioned above for those who may be looking for similar information) Hey Cody - here are some thoughts: 1) Given that you already have your pistons, you can't move the ring pack down a bit, so I'd probably be a bit more conservative on the relief depth and keep it at .125 to .150. 2) Use blue die-chem and an old gasket to sketch the profile - scribing the gasket shape into the blue die-chem. 3) I don't use a router, I use 1/4" shank carbide bits for most of the work. I use a tree-tip type of cutter shape with a high speed 1/4" air grinder All of the cutting is done with the air grinder on its side, using the sides of the carbide cutter. I will use a double-cut bit for the initial heavy material removal, then a single cut to smooth things out - before sand paper rolls They make cutters with extra long 1/4" shanks - I buy them on Amazon for reaching down the ports. I use the same tree/flame type shaper. 4) Use two hands on the grinder - so that you can control it and not let it jump the bit out of the area you're working on. Just keep shaving a bit at a time - you'll get the hang of it. 5) If you don't have any, buy a 1/4" sand-paper roll mandrel from McMaster Carr for sand paper rolls. If you're going to be doing porting, get some longer arbors to reach down into the ports. I buy bags of the sand paper rolls in grits ranging from heavy - like 50, up to a few at 320 for final polishing. I buy them with an 1/8" hole and in lengths about 1 1/2 inches. If you're going porting, you don't want the intake ports all super polished. Guys do this because they think it looks "cool" - but it causes fuel to pool. I'd go to 80 or 120 grit max on the intakes. On the relief and in the exhaust ports you can use a high polish finish - so you finish with 240 or 320. Cylinder Bore Edge: You can gently take the really sharp edge off where the relief meets the bore, but don't round it. Studies have shown that a sharp edge performs the best. All of the above needs to be done before your machine work is done (especially the valve job!). I've done a ton of porting and relief work, so I'm very good at controlling the cutters and sand-paper rolls. If you're new, take an old valve and guide and put it into the valve areas where you're doing the relief. This will help prevent you from screwing up the seat material. This is important when you're using the carbide cutters as they can remove a lot of material - even on hard seats. Best of luck - if you have any more questions, let me know! Sometimes I'm a bit later answering as I'm super busy putting up a new shop building. Take care, Dale As my old buddy used to say . . . "Gas, Gr*** or ***" - nobody rides for free ! Seemed he was always alone . . . Bored&Stroked, Yesterday at 9:48 AM Report Reply Cody_Kobra Dale, I appreciate all the information! I read through your 2011 post on the subject a few times, it was a great resource. I have already ported the block using exactly the method you've described. I started on the outside of the block, cleaning up flashing, etc., just to get a feel for how the cast iron cut with the carbide burrs, then I moved onto the exhaust exit ports. Once those were looking good, I moved on to the intake and exhaust bowls and intake ports. For a first-timer, I think I did a pretty good job. A few nicks on the surfaces, etc., but nothing that won't clean up when the block is lightly decked, and my valve seats are replaced. I went easy on the undersides of the valve seats and will clean those up a bit more after the new seats go in. I have 1/4 shank carbide endmills (square and round nosed) being delivered today. I'm going to give it a go with those in my router for roughing to get a uniform depth, and then round out the necessary areas with the flame/tree-shaped carbide burrs in my die grinder, and finish with the stones and paper rolls, etc., as I did on the port job. I appreciate guys like you who are willing to p*** the information on to the next generation of hot rodders. You're truly helping to keep the interest alive. I live close by Ronnie Roadster, so I also reached out to him as well. He just got back to me this morning and suggested going 0.085 deep max, as in his experience, he hasn't gained much by going deeper. I also dug out Joe Abbin's book and found his flow tests, where he recommends 0.100 to 0.125. Now I've got your 0.125 to 0.150 recommendation too. Three highly respected experts in the field, with 3 different experience-based opinions, but hey, that's Flatheads for ya! lol I had originally posted effectively the same question I had for you as a forum post (linked here). Would you mind if I posted your response with credit for the benefit of others in the same boat? Thanks again, Cody Cody_Kobra, Yesterday at 11:32 AM Edit Report Reply Bored&Stroked Member from Midwest is the Best! Hey Cody, some things to think about are related to your expectations for the engine and how you plan to use it. I heavy relief doesn't really provide much value unless you're planning on spinning the thing over about 4000 rpm and have enough port volume to feed it and enough cam duration to use it. Truth is, very few street flatheads are used in this manner, though some of us (like me) like to build very high-end racing style flatheads and I do wind mine up quite a bit. So, if you're primarily street driving, then consider a partial relief that doesn't lower your compression much, but aids flow out of the valves into the transfer area. Compression is your friend (especially at low speed). Also, if you have steeper gears in the rear-end (like 3.25 or 3.54), then compression really helps in getting away from stop-signs. A relief lowers compression - so it takes HP away from the lower RPM ranges. Here is a picture of what I'd call a street relief . . . maybe you do a "tweener" where you minimize the depth, but really blend into the lower valve eyebrow area? As my old buddy used to say . . . "Gas, Gr*** or ***" - nobody rides for free ! Seemed he was always alone . . . Bored&Stroked, Yesterday at 11:52 AM Report Reply Bored&Stroked Member from Midwest is the Best! Also, you can post anything that I mention . . . there are really no "secrets" involved! LOL As my old buddy used to say . . . "Gas, Gr*** or ***" - nobody rides for free ! Seemed he was always alone . . . Bored&Stroked, Yesterday at 11:53 AM Report Reply Cody_Kobra My intent for the car is to be able to compete in some of the Vintage Drags that have been popping up around New England, while still being able to street the car, even if the tune isn't really ideal. I currently have a stock 3 speed and OEM banjo, but I have a T-5 waiting. With my 3x2 intake, and heavy port job, I think she'll be breathing much better. Schneider will be grinding me a cam based on the aforementioned use case and with the other engine specs in mind. Based on my rudimentary calculations, even with a .125 relief, I should still end up with a 9:1 or higher compression ratio because of the 4.25 stroke and 63cc Offenhauser 425 heads. Joe Abbin's (Roadrunner Engineering) book with the flow bench results concurs with what you are saying with regard to the relief not doing much below 4k. In fact, it shows that its actually (slightly) detrimental below a certain amount of valve lift, but picks up a lot at the higher lifts. I don't think I should post his charts on the forum, but if you haven't seen them, they are definitely worth a look. With all that in mind, I should be flowing much better than stock, and the mild relief sounds about right. Views: 2 Cody_Kobra, Yesterday at 1:27 PM Edit Report Reply Bored&Stroked Member from Midwest is the Best! I'd probably go with a .125 relief and blend it is really well around the valve areas (the angled pockets below the valves). If you block already has good seats in it, there is no benefit to replacing them - just have a good 3 angle valve job done on them. The only time I automatically replace seats (unless they're damaged or worn out) is when I go to 1.72" intake valves. Then you have to actually machine out the seat area and not many machine shops have the right equipment to do it on a flathead block. As my old buddy used to say . . . "Gas, Gr*** or ***" - nobody rides for free ! Seemed he was always alone . . . Bored&Stroked, Yesterday at 2:58 PM Report Reply Cody_Kobra Seats were all a bit ate up before I went to town on the valve bowls, and with the 1.6 intake valves they have to be reworked anyway. Shop is already planning on it. Cody_Kobra, Yesterday at 6:39 PM Edit Report Reply Bored&Stroked Member from Midwest is the Best! New FYI - going to 1.6 valves doesn't really require different seats. But, having new ones put in isn't a bad idea. Make sure they don't cut the seat depts any deeper than they are now. As my old buddy used to say . . . "Gas, Gr*** or ***" - nobody rides for free ! Seemed he was always alone . . . Bored&Stroked, Yesterday at 7:37 PM Report Reply Write your reply...
I picked up a couple 1/4" shank carbide end mills, 1 regular, 1 round end. I inserted one at about 0.050 depth in my router for a test cut on the first cylinder. So far, so good! I plan to cut all 8 to this depth, then go back and bring it down to my max depth, then go back and bring it to the edge with the round end mill, then get to blending with cartridge rolls.
Nice! I like it when people are determined to get something done! It looks like it worked like a champ! I ***ume you knocked out all 8 by now?! 3blap.
Looking good and the plan sounds good. I may be repeating information stated above but take a peek at the Tex Smith The Complete Ford Flathead Engine Manual by Ron Ceridono and Mike Bishop's porting guide. I'm really interested in the Barney Navarro "eye brow" relief which basically rolls the edges to improve flow while keeping compression up. With all your parts & plans, I would also consider using, at least, a support strap on the center main. They are seemingly simple, but work very well. Ultimate would be steel caps, but that means they'll need to be line bored. Good luck with this and keep us posted.
A support strap isn't a bad addition - you can buy them for a fair price at Speedway. I also recommend ARP main studs. It is important to have the line-bore checked (especially if you replace the stock studs and add a center cap support). Usually you'll be just fine - but sometimes things aren't what you hope for.
I'll also add installing a welded in a windage tray in the pan. You can get universal fit units and cut to fit. This will help with parasitic loss.
Thanks to all for the comments and support. I'm getting after it a couple of hours here and there when I have time between work, kids, etc. I got all the routing done and used a shaped stone to clean up the edges with an old head gasket in place to protect the surface in case of slips. Next up, smoothing out the transitions and breaking the edge at the cylinder. A little feedback on the router method. It worked great for getting a perfectly flat and measured depth of cut with a very smooth finish; however, when it came to using the round endmill on the edges, it got harder to control as there was less and less deck surface to rest on, and I found that I had to take very light cuts, maybe .010 to .015 at a time in order for the end mill not to want to bite and pull in. This lead to my first couple of cuts getting a little squiggly on the edges. This was easily smoothed out with the shaped stone, but I can see it becoming a problem if you accidentally go past your gasket edge line by more than a hair. BanjoRear, thank you for the suggestions. I have a few books that I'm working from, including "How to Rebuild & Modify Ford Flathead V-8 Engines by Mike Bishop and Vern Tardel" and Joe Abbin's Roadrunner Engineering "The Key - Best of Flathead Ford Tech" (in addition to the great posts I've found on HAMB, FordBarn, and from those previously mentioned), but I don't have either of the Tex Smith book. I'll keep an eye out for that one if you think its worth having in addition to the others. Joe Abbin seems to have flow-bench tested each area of porting and smoothing for intake and exhaust areas, as he provides a % of flow increase for each area, though I don't recall seeing this data specifically for smoothing the "brow" area. I'll take a look. He does, however, do***ent that block relief results in intake flow improvement of 5-15% ( high compression head with 63cc chamber benefited the most at 15%), while exhaust ports flowed 1-13% better (center ports gained the most). BanjoRear & Dale, the support strap is a good idea. Ronnie Roadster suggested the same. I actually have the big steel center main and front caps produced by H&H, but my machine shop is very hesitant to line hone m with block because of an offset issue they had with one previously, which is why Ron suggested the straps instead. I'm shooting for a high-performance (as flatheads go) street/strip build; however, I have no plans on adding a blower to this one, so I'm hoping the straps will suffice. Ron made sure I'd be using ARP studs as well. BanjoRear, I was just reading about the advantages of a windage tray and oil s****ers yesterday. I have to look into that a little deeper. I've never fabricated either, but I may have to take a crack at it. I know some Merc pans had a windage tray, so I may try to find one of those. I'll post some shots after I clean it all up with the cartridge rolls. -Cody
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