Shoud I relieve my block

Dale
While its true I do spend most of my energy running a supercharger which would for the most part not be effected greatly by lower compression created by the relief.

BUT here's some testing results from two test runs that took place in July with our car taken without running the supercharger. Here's the details with the supercharger removed I replaced it with a hand made intake I'm experimenting with that has two Holley two barrel carbs set on top. The engine is the same 292 cubes we run burning VP 116 octane racing gas the car as I wrote earlier is over 3000 pounds. The first test run I held the RPM to 5000.
From a standing start at the measured timed 1 mile the speed was over 130 MPH at the 1.5 timed mile mark the speed was over 140 MPH.

Upon checking date I decided to add two more degrees of timing now 23 all in and actually go bigger on the jetting. For this second run the RPM was increased to 6000. The speed attained at the 1 mile mark was now 143 MPH and at the 1.5 mile mark 153 MPH. The second run speed is more than 10 MPH faster than the current record at Bonneville set by an engine that measured well over 300 cubes. There's a lot more left in our new normally aspirated gas combination I'm certainly looking forward to more testing on our stock block Ford flathead.
Ronnieroadster
 
Jack E/NJ said:
Thanks! What are those speckles that seem to be on the seats? Pits?


531747
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The ports were touched up before the valve job was applied - this was pre-valve seat work.
 
Ronnieroadster said:
Dale
While its true I do spend most of my energy running a supercharger which would for the most part not be effected greatly by lower compression created by the relief.

Ronnieroadster
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I agree with you Ronnie - I would ALWAYS be running a 3/16" deep or so relief on a racing style engine or really any decently performance modified engine (like everything you and I build). What is important for folks to understand is that in our applications the HP we pick up by increased flow more than offsets any compression ratio losses. Flow is everything for all racing engines - flatheads included.

It is the same reason one can buy a set of out-of-the-box AFR 195 heads for a SBC, stroke it a bit and make over 500 HP with a hydraulic street cam and a single 4 barrel. It is the top-end technology (and cams) that have made the biggest differences in horsepower gains for our classic OHV engines.

On the other hand, having high compression but lack of flow might work at low RPMs on the street, but it will never make HP at higher RPMs and one might not even get to higher RPMs. :eek:

We're on the same page . . . as usual! ;)
 
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At the other end of the spectrum I'm confident not relieving the block on a "stock" rebuild. For my use I'm looking to maximize low end torque not horsepower. With overdrive I don't need or want higher rpm capability, I want maximum torque below 3000 rpm. I use stock intakes, distributors, and camshafts. I was very impressed with the drive-ability of the motor I helped my friend build for his family's 1950 Mercury: .060 over 8BA block (we would have bored smaller but it took that to clean up), 4 inch crank, EAB cam, stock heads shaved to get .040 above the pistons (EAB heads probably would have been more torque, but we stuck with the Mercury marked heads), stock carburetor and distributor, no port work. The car owns overdrive at 80 mph with the engine spinning less than 2900 rpm.
 
38 coupe said:
At the other end of the spectrum I'm confident not relieving the block on a "stock" rebuild. For my use I'm looking to maximize low end torque not horsepower. With overdrive I don't need or want higher rpm capability, I want maximum torque below 3000 rpm. I use stock intakes, distributors, and camshafts. I was very impressed with the drive-ability of the motor I helped my friend build for his family's 1950 Mercury: .060 over 8BA block (we would have bored smaller but it took that to clean up), 4 inch crank, EAB cam, stock heads shaved to get .040 above the pistons (EAB heads probably would have been more torque, but we stuck with the Mercury marked heads), stock carburetor and distributor, no port work. The car owns overdrive at 80 mph with the engine spinning less than 2900 rpm.
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Very close to what I'm running in the '41 Merc. 8CM cam and EAB heads, but 2G Rochester and Chev distributor. Great power low and mid range, perfect for the application.

Agree with the serious performance guys here though...it's all about air flow when things get serious. Cool stuff!
 
Somewhere in my past I missed this improved relief In the 60's and earler I relieved all my engines, but I wasn't in organized track racing, just street drags and a trip to Oarange to dragrace among the sky divers. Early track engines were relieved, but after a few years I discovered most builders stopped that. MY first trip to Bville was also interesting, Most of the blocks I saw there didn't have reliefs either NOT havinf FACTFUL information. I stopped relieving bocks and suggested to others that it didn't improve power and economy. I feel better now, however I've also made some port improvements that I don't think many people have done and have tried to post them on the barn these past few day with no luck. Very high STUPID factor here. I have some help coming over tomorrow and that might solve the problem
I have literly hundreds of pics of my experimenting back when I had my dyno, Most of the engines I built for coustomers were run on it for grakin and to prove the output. Non of them mad much HP but allot of torqur,
Gramps
 
Ron,
I would be very interested in what modifications you found to improve low end torque. Your book and JWL's book go into low end torque, but none of the other flathead books really cover the subject. Flathead engine books almost always are about making top end horsepower numbers and/or looking modified with lots of polished aluminum parts.
At this point my limited understanding is maximizing low end torque is all about more displacement (longer stroke since I want to keep the cylinder walls thick), higher compression, and a stock camshaft. With a stock intake and carburetor do you think there is any benefit to any port modifications?
 
B&S>>>Now Pete . . . show us the "AFTER" view of the chambers!>>>


38C>>>You know serious performance work is happening when someone welds up the chambers on brand new heads.>>>


Aye!!! :eek: Even I couldn't bring myself to do this. I however might be tempted to attach a plate and use a form-working hammer to do something similar ---- but reversible.


531789
 
JWL covered this in his book however he said that on A full rave block relieving did help tom Beaty, The Beean bandits, John Bradly, art Christian etc. all ran fast FH.s they all relieved their blocks. They couldn't all have been wrong...
 
Bored&Stroked said:
Now Pete . . . show us the "AFTER" view of the chambers! :D
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I don't have any pics of that but just imagine a completely flat surface for flat top pistons.
The slight kickout in the chamber on one side is straightened to get maximum area available. Edelbrock heads do not have this kickout so they are a bit easier to do.
Sometimes the transfer area is welded back to the edge of the valve. This is the area that is machined to adjust the compression.
 
Hey Pete, have you ever tried any type of flat-top popup piston? Would seem that you'll still get the compression, but open up the roof of the chamber? Obviously, this is what Harley did with the KR - about a 3/16" pop-up. This is what I did with the FlatCad - to mimic the Harley. BUT, I've never had the luxury of time, money and a dyno to try different combinations.

I'd love to have a 1-cylinder engine with a flathead port, head, chamber setup - to test all sorts of things on a motorcycle dyno! LOL

Or maybe cutup a block and make a V-Twin flathead for testing. :D
 
Bored&Stroked said:
Hey Pete, have you ever tried any type of flat-top popup piston? Would seem that you'll still get the compression, but open up the roof of the chamber? Obviously, this is what Harley did with the KR - about a 3/16" pop-up. This is what I did with the FlatCad - to mimic the Harley. BUT, I've never had the luxury of time, money and a dyno to try different combinations.

I'd love to have a 1-cylinder engine with a flathead port, head, chamber setup - to test all sorts of things on a motorcycle dyno! LOL

Or maybe cutup a block and make a V-Twin flathead for testing. :D
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Dale,

I often think about doing this with a single cylinder Briggs & Stratton motors that can be had pretty cheaply. I've also thought about bench grinding the cam as well just to fool around with some ideas.

Any know how closely related a B&S flathead is to a Ford?

Tim
 
When I was an engineer at IH in the 60's and 70's, we had a single cylinder engine built for combustion chamber studies. As I remember, it had about a 250 lb flywheel. Once a rocker stud broke during a test and it took about 5 minutes before the engine stopped.
 
Bored&Stroked said:
Hey Pete, have you ever tried any type of flat-top popup piston? :D
Click to expand...



No. When you are trying to get maximum compression, why do something that
decreases compression.Two flat mating surfaces are the minimum area attainable.
Also, the flame front travels faster over a flat surface rather than one with
humps, valleys and corners..
 
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