Well engine is about done
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Topic: Well engine is about done
Posted By: mufflerboltz
Subject: Well engine is about done
Date Posted: 08 Apr 2014 at 7:41pm
| Engine is dang near done. Came up with 316 ci all said done, not to bad since it started out as a 201. Running buick valves, nice port job and all that needs to be done is a cam grind or find a good ground cam for 1800-2000 rpm range. The big question is that I can run a custom intake/header, would this be any benefit over reworking the stock manifold? I was going to run 1.625 id tubing for the intake side and smooth the transition from the carburetor to the intake. What are your opinions on a custom header/manifold? Thanks guys! |
Replies:
Posted By: mgburchard
Date Posted: 08 Apr 2014 at 7:50pm
| Nice little engine tell us how it unfolds |
Posted By: wi50
Date Posted: 08 Apr 2014 at 10:42pm
|
Down in that low of an RPM range the exhaust header really won't be much of an advantage....but you're going to build one anyway because the original type intake manifolds really suck and it happens to be easy to do. The neck is to short, the air has to turn a sharp 90 degrees and the air coming out of the carb is still not really attached to anything after going around the throttle shaft and plate. Then the manifold pulls the air completely opposite directions on the overlap of half of the intake cycles..... left- right -right -left -left- right-right- if you were standing looking at the manifold. Yeah, with work the manifold can flow some decent air. With work the carb can. Bolt them together and see what you get, you'll be disappointed. So fabricate a small plenum and intake manifold. Put some thought into it to get the flow pattern right. You won't be able to build the runners long enough on the exhaust to give much of a "tuned exhaust length" benefit though as the RPM is so low it will resemble a cell phone tower. The good news is with a decent intake the engine will be able to tolerate a little more duration on the intake lobe of the camshaft than it could with the factory type cast manifold. The bad news is that it doesn't much matter what valves are in the head or how smooth or shiney the ports are. There's still only so much air that is going to get yanked and pushed around that 90 degree corner in the head and there's very little radius to that corner. Down at the 2000 RPM range the engine has a lot of time to breathe. The mistake you will likely make is to use to big of tubing for the exhaust. Use 1.625" or 1.5" OD on the intake but the exhaust can likely benefit from 1.375" to scavange better. The other thing is a small collector diameter, there's 4 even pulses with time to evacuate, a large diameter collector and pipe is going to kill speed, and loss of this airspeed will kill scavanging. Smaller is better. Don't think that the engine is 1/2 of a 632 cid big block V8, it's no where close and it fires evenly where the V8 does not and needs a larger collector. Something to think about is that I only ever had a 1.875" outlet on the collector on the header I built for mine......when I ran an updraft carb. I ran the exhaust tubes in a rotational firing order, meaning that the tubes went around in order rather than firing across from one another. ------------- "see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet" |
Posted By: wi50
Date Posted: 08 Apr 2014 at 11:04pm
|
Here's an old picture of my updraft intake. The tubes stuck into the plenum about 3/4" and were belled pm the end. If you follow the exhaust tubes in the rotational order they are 1-3-4-2 and were all equill length. What a @#$!% figuring it out. I had made the intake plenum fairley large but on a low speed engine I would make it much smaller. A 1.625" diameter intake tube will be about 1.5" or so ID, this gives an internal cross section area of 1.76" which is about right for the size and velocity you are going to want. 1.5" tubes would give you a 1.5" area, this may even be better for low RPM. When I do the math on what a 316 cid engine should use for air at 1800 RPM, I think 1.5" tubes will be better, but that's just my idea. I think either size is fine. I ran 2" tubes, but I also ran a 2 1/8" bore Zenith carb off a 670 cid Cont. engine with a lot of mods to the carb, and I had 1.8" and 1.9" diameter venturis for it. I also ran a Stromberg NAR6B carb that used a 2.4" throttle bore. I had tuned the exhaust for peak torque at 4500 RPM and the engine would usually go in the 5800 range and sometimes over 6000 rpm...I needed around 400-440 cfm I figured to feed the engine, where a 316 cid at 1800 RPM is going to need only 150-170 or so. I don't figure a very high volumetric efficiency rate on these tractor engines.....You need a carb with a 1.1" venturi (just guessing as a place to start) or so and intake runners with a 1.4"-1.5" inside diameter.  A picture of the downdraft setup,  ------------- "see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet" |
Posted By: CAL(KS)
Date Posted: 11 Apr 2014 at 4:09pm
|
Boltz- cant offer any help with the intake but was curious what you went with for rods, bore, stroke etc.? if my brother ever gets some money we can finish his build. so far we are going to be 4.155x5.4. did you convert to full flow oil are are you keeping bypass system? ------------- Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20 Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
Posted By: mufflerboltz
Date Posted: 11 Apr 2014 at 9:09pm
| 4.28 bore with JD 404 sleeves and Chevy bb pistons, farmall h rods, 5.5 stroke. Keeping original bypass. Hopefully it all works out. I got all the ideas from talking to a very nice friendly gentleman on this forum. Just want to say thanks to him for taking all my phone calls even though most of the time I called him at the wrong timing. Lol I'm suppose to go down to the shop Monday night and check some things over hopefully there is no bad news. |
Posted By: CAL(KS)
Date Posted: 12 Apr 2014 at 8:07am
thanks, good luck. my help most likely came from the same individual  we are using H rods also. wish i was close enough to drop by the shop, we would probably have more done lol.
------------- Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20 Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
Posted By: mufflerboltz
Date Posted: 12 Apr 2014 at 8:55am
| Yeah, my first hook is in about 3 weeks and I'm thinking we are now t going to make it |