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| 4bbl 225 question https://slantsix.org/forum/viewtopic.php?t=54087 |
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| Author: | moparfreak [ Tue Dec 17, 2013 9:34 pm ] |
| Post subject: | 4bbl 225 question |
I have picked up a offy 4bbl for my 85 ram got headers as well to go with my cam .436 lift 244 duration had 60 thousand taken off the head and gasket matched the ports. I have been thinking am I going to need to change the fuel pump from stock? I am not sure if I had mentioned it before but when I got the truck the truck the engine was seized and the truck had been parked outside with no hood or head there are some pretty nasty spots in the cylinders so I am also playing with the thought of punching it out 30 thousand after which I am thinking larger valves are probably in order |
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| Author: | ceej [ Tue Dec 17, 2013 10:55 pm ] |
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I noted a couple things in your post that I'll address. First, you have an '85. Does it have hydraulic lifters and rockers? The 244 Mopar cam I'm familiar with is a mechanical cam. Are you converting over to a mechanical valve train or is it already? What do you have for a distributor/Ignition system? Second, the stock fuel pump system is capable of delivering enough fuel for even most racing applications. Based on the build you are suggesting, it is more than adequate. Third, if there is obvious damage to the bores, you should at least get it cleaned up at a machine shop, and plan to re-ring. Since it was stuck and water damaged, I'd lay odds that it needs to be over-bored. The machine shop should be able to tell you how much. You should look at all bearing surfaces as well. And Fourth; oversized valves are not necessarily going to give you much return with the cam and compression levels you are indicating. Cutting the head .060" is putting you in the bare minimum range for a 4bbl carb of any sort, unless the head has already been cut. The important number is the chamber size. To determine where your static compression is, you need to take some measurements. Those measurements need to be based on the short block once all machine work is done. Also, if you choose to change over to larger valves, you will have to re-measure the chamber once the new valves have been installed. verify that the combustion chambers are properly aligned to the bores, and clearance for them. Do not put a bump in compression onto old rings. They will break. When you bump it up, plan to replace them. If it cleans up with a hone, taper is within limits, and bore is within spec, install new rings. Stick with the smallest over bore you can get away with. Oversized pistons don't amount to much change in displacement with the small bore size of a slant six. Save the meat in the cylinders for later use. The small increase in displacement will be virtually un-measurable in the seat of the pants, or at the timing booth. With a 4bbl and headers, it will make more pleasing noises, but those should not be construed as an increase in horsepower. Coupled with other modifications, horsepower gains can be realized. Timing curve and dynamic compression will play into the equation tremendously. The Offy is a great four barrel intake for street/strip use. What carburetor were you planning to use? Know that there aren't any ready options that allow for bolting it on and driving it. CJ |
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| Author: | moparfreak [ Wed Dec 18, 2013 12:58 pm ] |
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The 225 was not hydraulic when I got the truck I have replaced all the rings and bearings and have a complete gasket set. The rings might be for not now but what do you do. I really don't want to over bore it but might not have any choice. I picked up a 4bbl from a 340 at a swap meet no idea on the size but was hoping it would work after a gasket kit |
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| Author: | ceej [ Wed Dec 18, 2013 1:49 pm ] |
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OK, now I have a better picture!  You'll have to decide if you need to over bore the engine. If you have bore damage, and want to start pulling more power out, I would recommend going to the next over bore size available, typically 0.030" over. We need to ID the carburetor. A 340 can use a bunch more carburetor than most slant sixes, so it may be more useful as trading stock at a swap meet. What manufacturer is the carburetor, and what are the model numbers stamped into it? CJ |
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| Author: | moparfreak [ Thu Dec 19, 2013 10:36 pm ] |
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I have had the truck for years. Been slowly collecting parts with my slant six build evolving over the years. To think at one time this was going to be a super six bolted to a automatic now I have a manual with headers and a 4bbl |
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| Author: | Rug_Trucker [ Sun Dec 22, 2013 7:03 pm ] |
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A 340 carb? Stock came with big honkin 800cfm Thermoquads, unless it was a '70 or earlier. Depending on how deep the pitting is in the cylinders is how big you'll need to punch out the bore. |
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| Author: | moparfreak [ Sun Dec 22, 2013 8:08 pm ] |
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I have no idea of the size but am pretty sure it is a afb I do have a 400 Coronet with a thermoquad it is huge and half plastic. I know I need to be under about 500 cfm. I am storing some parts for my dad one of which is a 273 4bbl intake with the carb have thought of doing a carb swap |
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| Author: | Rug_Trucker [ Sun Dec 22, 2013 9:35 pm ] |
| Post subject: | |
AFB's and AVS's have the model number stamped on the front throttle plate on the left facing the carb. We can find it by that. If it is a real340 carb it will be an AVS. |
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| Author: | RyGuyTooDry [ Mon Dec 23, 2013 5:09 am ] |
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I know it's off topic but I'm from Ontario as well! if the cylinder walls have damage just send it to a shop to get bored out. Last thing you want is to get it together and have to take it apart again. I know some good shops in the niagara and Hamilton areas. |
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| Author: | moparfreak [ Sun Jan 05, 2014 10:26 am ] |
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Well I went out to the shop and grabbed the carb it is a avs and has H7 4401S |
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| Author: | Rug_Trucker [ Sun Jan 05, 2014 2:02 pm ] |
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68-69 383HP AVS. Probably 425-500cfm. The 70 383HP Holley was 480cfm. |
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| Author: | moparfreak [ Sun Jan 05, 2014 3:36 pm ] |
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ok but where can i find this info for future reference |
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| Author: | Rug_Trucker [ Sun Jan 05, 2014 6:11 pm ] |
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Quote: ok but where can i find this info for future reference
I typed in the number plus Carter carb into Google. I don't know of any sites that list the AVS's. There is a Mopar website called Moparfins and they have a bunch of carb info. http://moparfins.com/Repairs/Carb/Carb_List.htm They don't designate the HP (Magnum) status for these carbs. So your carb may be a good one to sell to a restorer. I have 3-4 4131 AFB's. I have one off a 429 Cadillac, and one from a 340 Buick motor. I love my Carters! |
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