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| A100 engine build https://www.slantsix.org/forum/viewtopic.php?t=64950 |
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| Author: | a100gary [ Fri May 29, 2020 4:47 pm ] |
| Post subject: | A100 engine build |
I got a line on a slant 225 on craigs list locally ($75) and started building a backup engine for my A100 pickup. We put an Oregon 819 cam in it, cleaned up the block, and now I am starting on the head. My machinist likes the high volume oil pump, but I told him I wanted to keep the oil pump that matched the cam. My goal is to put this in my Dodge A100 to add a little attitude but stay reliable. On the head I want to enlarge the exhaust valves to 1.44, 318 valve springs and keep the compression around 8.5. I already have the BBD super six package and enlarged single exhaust. Am I missing anything? What about Magnecore ignition wires? I am set up to use late model electronic ignition. Gary |
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| Author: | Joshie225 [ Fri May 29, 2020 5:04 pm ] |
| Post subject: | Re: A100 engine build |
Measure and calculate the compression ratio. You're likely to be shocked at how low it is and how much needs to be milled off the head for an adequate compression ratio with that cam. 8.5:1 would be fine, but I'll bet you it's below 8:1. Also, please degree the cam so the intake centerline is 102-104° ATDC. The intake side of the head needs more help than the exhaust. So do a bigger intake valve if you're only going to do half the head. Good call on the oil pump. You'll probably want more initial ignition advance and less total timing than the distributor now has. This means shortening the advance slots. |
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| Author: | a100gary [ Fri May 29, 2020 10:27 pm ] |
| Post subject: | Re: A100 engine build |
Joshua, I have the timing my current engine set at 10 BTC, and it is running strong. What are you thinking? I was recently talking to a friend who said he used vacuum to find the "sweet spot" when setting the timing. I am not sure if I even have a vacuum gauge! Since my purchase of this new engine, I have been able to refine and improve the performance of the engine that is in the truck. A bigger intake over exhaust was my first inclination, but my machinist said exhaust. Looking at some of the posts here. I've heard that improving exhaust flow will give you more pop at lower rpm's. This is where I live. I am not street racing, winding it out. I am just using this vehicle as daily transportation and light hauling (three months out of paint). Looking cool and getting thumbs up from people who have never seen a flat nosed pickup. Thanks for your response! Gary |
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| Author: | drgonzo [ Sat May 30, 2020 7:35 am ] |
| Post subject: | Re: A100 engine build |
Your machinist is wrong and seems to be basing his opinion on his experience with other engines, mostly V8s. The intake flow needs help on the slant six. If he won't do the head right, I'd find another machinist. |
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| Author: | Joshie225 [ Sat May 30, 2020 8:40 am ] |
| Post subject: | Re: A100 engine build |
10° initial timing usually leads to excessive timing once the mechanical advance is all in. You don't want more than about 30-32° total timing with the initial and mechanical together. You need a dial-back timing light or a distributor machine to check it. Seeing as you already have larger exhaust you're doing fine exhaling so long as the muffler is free flowing. The larger intake valve may cost you a tiny bit of torque right off idle, but the power increase everywhere else is worth it to me. Installing the cam with the proper phasing and increasing the compression ratio are 2 big factors in torque production. If you don't increase the compression ratio you'll lose out on torque and economy. An increased compression ratio will make the engine more octane sensitive and heat is a aggravating factor. I would get an air cleaner with a snorkel if you don't already have one and duct cool air to the carburetor. This is good for power and knock resistance. Wideband O2 sensors are a great tuning aid. The Super Six BBD is calibrated for emissions and is right on the edge of being too lean on a completely stock engine. With the cam change it is likely to be far too lean which will cost you power and make the engine more octane sensitive and may even lean misfire. Be prepared to tune the carburetor. Something else sometimes overlooked is that trucks and vans have more road load and need more throttle to run a given speed. This means more heat in the combustion chamber. Trucks and vans are specified to run a colder spark plug than passenger cars. So the NGK plug we love is a little too hot for a truck. |
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| Author: | a100gary [ Sat May 30, 2020 4:16 pm ] |
| Post subject: | Re: A100 engine build |
Joshua, I checked the intake center line on the cam specs and it is 106. Exhaust is 114. About the road load in my truck it is usually carrying my 182 lb load only. Cold air induction is a hot topic for me. I have a doghouse and not your normal under the hood space. I just bought an old super six air cleaner with a 273 base. What is the best way to get cold air into the carb? Thanks guys!! Gary |
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