Interesting comments. I think flatties will wind up level, set your level on your intake you want to use and set it level, left-right; front to back. Nail the engine down right there. For all the guys wailing about driveshaft angles and universal joint angles etcetcetc think about every race car built has the engine setting deadnuts level and if a bonneville land speed car, a nascar, a prostocker etal don't have a universal joint problem then you won't either. I think the original reason for the engine to set at a 3deg angle is so the return oil will run to the pickup at the rearward bottom of the sump - it has nothing to do with the life of a $30 universal joint. Some intake manifolds are designed to bring the carb back to level when the engine is set at 3degrees, as far as i know all flatties are flat. Its your car, build it however you feel.
oj, I haven't played pro stock for about 35 or so years. Our engines set @ 3 degrees. We tried flat as that was what was comming down the pike at the time, we found that we made better ETs with the crank angle @ 3 degrees. I cannot give you a reasonable reason why. In drag racing you see all sorts of strange configurations, I remember an altered for instance that was set at a real extreme angle toward the rear, I believe it had to do with crank height and getting the transmission under the floor. The difference here is that the car probably only ran 20 miles a season? and it got freshened more often than my old beat up parts hauler.
Yes and No. True that flatties were originally set up level/level. Level at the intake and level with the frame. That seemed to work with a torque tube. But, as several dozen articles on this site will mention, with an open drive line you want your engine angle and pinion angle at 3 degrees down and 3 degrees up respectfully AND it has everything to do with the life of a $30 universal joint as well as driveline vibration. As an aside, the only deviation I have heard from this is with a carb powered gasser. Because of the extreme front end lift off the line, the engine was actually set 3 degrees down in front. Doubt that's the issues here.
the only things i have encountered over the years if the angle between trans and rear end is to severe is shitload of vibration causing u-joint failure and tailshaft bushing wearing out. with the carb level at ride height match the output shaft of the transmission within 1 degree of pinion angle and your good.
There are two different angles on flatheads...early to 1948 manifolds are level as in parallel to the crank, late 1949-up are tilted several degrees. Both were of course meant to be parallel to the ground in their different vehicle mountings. I let my torque tube do its own math on pinion angle
Carb mounting boss set to level, then make sure the pinion angle on the rear is the same as the trans so the universal joints are 'in phase'. Cheers.
And as a minor datum point, I once long ago ran a stock '52 engine in my '48 for a while because that was what I had. I was far too inexperienced to notice or worry about the manifold angle, and never had any problems that could have been attributed to that.
Bruce Sometimes we over think things way too much. That life were as simple as when we were first starting out. I remember once I had an old Y block with a 4 bbl. I wanted to run a later holley so I just made an adapter out of plywood. I know today that it will not work but it worked just fine back then.
On the simple...there are all sorts of minor problems in putting a '52 in a '48. I had no money, a tool collection I could carry easily with one hand, no access to electricty and no drill, welder, or anything else higher tech than a ratchet, and nearly no idea what I was doing. No problem...all that needed to happen happened, and I don't even remember how!
To be perfectly honest, top et drag cars - doorslammers, altereds, dragsters - the crankbolts is 11ish inches off the ground an the pinion is 15-16ish inches off the ground so that the engine runs uphill into the rear. Look at a pro fed, the engine runs uphill. Doorcars etc are the same way, just kinda hard to see it all.
The thing with any type of drag vehicle especially a pro type of a drag vehicle is that the engine does not have to live a very long time as compaired to a street vehicle. Technology and theory has changed a ton in thwe last 35 years as well. Now this is a little off topic for the thread and something I have never paid any attention to for whatever reason, what is the crank angle on a Ford with a front sump? Maybe one of us (meaning you OJ ) should start a thread with crank angles of different engines, it would be good information to have access to on a site where everyone is a buildier to some extent.
I am honored that you should consider me for such a noble and worthy cause but it is well documented that i am way too stupid to make a study of anything more complicated than a door hasp. But a collaboration of you and Bruce could result in the definitive crank/pinion angle thread to end all threads - i bet you could get Inland Driveline to sponsor it! What'day say?
On drag cars also, probably the G forces moving the gas in the bowls has more effect than minor angle problems...it's hard to believe carbs can function as well as they do in some of the faster accelerating cars! On a street car, park your coffee cup on top of the carb while you work. If it falls off, you may need to study angle issues.
Well bruce stays pretty busy and I am a no account. What do ya say bruce? ya wanna start a crank angle thread with me? I'll help honest I will. We have done some pretty extreme mods to carbs over the years to overcome the problems with Gs. Now you can actually buy carbs already set up with all the mods already done.
If you are running a hood, leveling the carb surface on the manifold is the easy way to go. If you are not running a hood, and you've built some rake into the car, then an engine at any angle other than parallel with the frame looks dorky. Set the engine where you want it; adjust the transmission mount so the engine is parallel to the frame, and adjust the pinion angle so it's parallel with the transmission. Clearly, this does not apply if you are using a torque tube. A non-dorky rake is less than 5 degrees. Another HAMBer might know differently, but I'm thinking that 5 degrees has little impact on the movement of the carb float's needle valve. The change in the volume of gas in the float bowl is not relevant, as the bowl volume is sized for a wide variety of gas flow rates.
My Buick 215 appears to have a six degree offset between the carb plate and the tranny ouput. I'm thinking of splitting the difference, about two degrees down (forward tilt) on the carb plate and about four degrees down out the back. Thoughts?
Different carbs are designed differentlyd . Goes along with float levels - Going up hill you will have the carb tipped back and your foot in it to climb what ever it is. 30% grade, up a trailer ramp , parking garage, wheels up launch or whatever... Going down hill , your carb will be tipped forward & you'll be on the brakes more than a need for fuel. There is also increased or decreased leverage imposed on the needle thru the float due to buoyancy and location of the fuel. Modification to the floats can correct for that. Hard cornering also has an effect on that.
Yes, if the the stock intake manifold is any indication, the 215 has as least a six degree difference between the carb plate and tranny output. In my case I am also going to go with the nominal 2/3 degree down angle on the output shaft for two reasons. First if I keep the carb plate level, the engine "looks" wrong. the valve covers and exhaust manifolds dip down in the rear and it looks like I made a mistake on the install. Second the output shaft angle would be too sever. I'm using a Jag rearend which, due to the solid differential mount, calls for a zero degree pinion angle. If I match that up with a 6 degree output angle, i will have trouble down the road. As far as leveling the carb, I plan to fab a 3 degree spacer wedge to make up the difference.
Level the carb flange, unless you are doing hill climbs, then make a adapter to set the carb at the angle of the hill.
"It isn't the volume of the float bowl that matters, it's the height of the fuel in the bowl ... When you change the height of the fuel level without a corresponding change in jets and/air bleeds, you change the amount of fuel delivered for that amount of manifold vacuum and are changing the fuel/air mixture ratio. That's why setting a float level is a basic adjustment to check when overhauling a carb." Agreed. But my point is that most mechanical systems have built-in accommodation for small changes in operating variables, and the change in fuel height caused by a 5-degree rake is negligible. Otherwise, you'd have to set your float with much higher accuracy than is normally required. Of course, if your fuel pump is failing, float is set wrong, needle valve is rusty, carb is undersized, and there's a hole in a vacuum line, you're not helping things by adding another variable - such as carb rake - to the system. Also, forgot to mention that a nearly-invisible shim can re-level a carb on a raked engine, as can machining an angle into the carb-mounting surface of the intake manifold. It takes a better eye to spot a shimmed carb than it does an engine that sits "crooked" in the chassis rails.
"Accelerating" being the key word, here. We do not feel speed, we feel acceleration. This is because the fluid in our inner ear is not moving when we are set at a constant speed. The fluid in a float bowl works the same way. On carb equipped drag car, jet extenders are used in the secondary bowl to prevent starvation on launch as the fuel sloshes toward the rear. A float with cutouts is used to clear the extended jets. It seems as if the OP is building a street vehicle. No need to over think it. He should set it level, and then get the pinion angle set after the vehicle is complete with weight on wheels. Anyone worrying about hills, should go watch "Bullitt" again.
Interesting - thanks for the input. Agreed, even with a two or three degree down angle off the front of the carb plate that engine looks severely dipped to the rear. I'll add "carb spacer wedge" to the bottom of my massive list of things to do on this car. Thanks!
Shot in the dark answer is 2-degrees uphill for the intake manifold mounting flange. Need to know the type of rear suspension you will be using to be accurate. It helps to know the front too but I'm guessing transverse spring and beam axle. Why? b/c this is a matter of the relationship ship between the front universal joint, rear joint and the driveshaft angle which are dictated by the suspension, to a large degree. Because pinion angle and rear suspension determine how the pinion gear will be "climbing" the ring gear in relation to the Instant Center (IC), this gets very complicated. I'd expand on it but there are numerous variables and it would get lost in this thread. The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion it ideally be 0 degrees. Also the angle of the joints, which is dependent on the type of driving affects u-joint wear. BTW a torque tube changes everything. Carb angle comes secondary to this and can be adjusted by milling the carb mounting flanges if necessary (probably not) ie. think Edelbrock Victor Junior, it like most modern aftermarket manifolds angles the carb forward (uphill). Why because fuel has weight and the distribution of that fuel weight in a float bowl affects the fuel curve ratio. Modern aftermarket manifolds have angled carb flanges so the carb is level under power therefore maintaing a proper fuel curve for the engine. I read this info decades ago in a Holley carb and manifold tuning book real harcore info for people not afraid to cut their carbs into pieces to make them better. Book is still available. Believe it or not even the shape of the float bowl vent affect the fuel curve. Check out a Victor manifold modified for a Stock Car. The flange is perpendicular to the engine why? That makes more power but most people can't tune well enough to accomplish this so Edelbrock, and the other manifold manufacturers make the over the counter version with the flange angled. I told you it can get complicated! We could go on but why? PM me if you need it more specific.
Actually it is the volume because the volume has mass and mass has weight. Even though the fuel is being drawn through the jets it is also being pushed harder by atmosperic pressure and then we can take into account the area on top of the fuel. the larger the area the bigger the push, given there is equal applied pressure. Also consider bowl vents as I mentioned in my other post. I have literally leaned the entire fuel curve a couple jets sizes by changing vent angles on Holleys. It is a very useful tuning aid for those who really tinker with carbs. Believe me not trying to come down on you. I admire your thinking. But if it helps you to think in these terms you might even go faster since I'm guessing you turn the screws on your engines a little more then most guys.
P/S 35 years ago, that must have been a ladder car or early 18 hole, 4 link, tube car. I'm guessing you mean pinion angle and not crank angle. The angle of the crankshaft would have had little affect on the vehicles performance, other then a horrible vibration if the two u-joints were at differing angles. It is pinion angle and the rear suspension angles that dictate the Instant Center (IC) and that is determined by the type of rear suspension. Although I suppose if the weight bias over the front axle center line changed due to the engines attitude it may have had some affect on the launch. IC and its relation to driveshaft and pinion angles are some of the lesser understood chassis dimensions and we could write forever on it and likely never come to agreement but if someone out there is really interested I suggest the Jerry Bickel and/or Chris Alston books that cover rear suspensions for drag racing. There are many others but they are just rewriting what these two men have been doing and improving for decades. A word of caution before you buy, these books are not beginners reading. I'd hate to see someone spend the money with good intent and not get anything from them because they were over their head. I also learned one very important thing while racing professionally, never under any circumstance do you take a performance tip from a fellow competitor at the track. He is there to beat you, not help you beat him to the finish line. Take it or leave it, but at the professional level people are being paid to beat eachother and I know very few people who work there butt off to give away hard earned knowledge without something in return.
Contrary to popular belief, pinion angle should not be measured relative to the ground. It is the difference in angle between the pinion shaft and the driveshaft that is important. Excess angle here and at the transmission shaft end of the driveshaft causes a mechanical reduction in the amount of power that reaches the rear wheels. Useful info I sourced from the web that I thought would fit here well. Can't remember from whom but Thanks to someone!
the angle of the engine is also to prevent air pockets in the cooling system from being trapped at the back of the block.
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