Th 283 has another opening at the back of the block, next to the distributor, where there was either a road draft tube (early engines) or a PCV valve (starting around 1962). The block is different at both ends also, there are additional passages that a 305 doesn't have.
You will want a pcv. If you want a pvc 305 I'm pretty sure it'll just melt at idle. You CAN take a later block and make it look more vintage. I drilled the back of my intake for a pcv valve. Been covered here a few times, try searching. Good way to inspire you.
Sure if you want oil to leak out all over from the pressure that builds up in the crank case. I'm assuming what you are really asking is can you put an early intake with the oil fill tube on it along with early valve covers with no breathers or fittings for a pcv valve. That answer is yes but you will have to figure out how to fit a pcv valve somewhere. Guys usually find a spot in the manifold at the back of the engine where they can drill a hole for a pcv valve to fit and vent the crankcase there. Just like David posted while I was typing.
I have seen an article where if you wanted to use two of the old Offy style breathers on your valve covers. Mount them just like you normally would towards the intake side of your valve covers and drill the holes in the valve covers. One you assemble just like normal with the bolt on top,use that for the drivers side,the other you take a piece of brass shim stock and block it off so it can't breath. Then drill and tap the sealed off one on the end towards the back of the engine for a brass 90 degree fitting with a 3/8 nipple,then run your hose to the back of the carburetor where you could install your PCV. You will have to run an oil fill tube that has a cap with no holes,in other words sealed off. If you do it in this manner your PCV will pull from the opposite side of the engine where the breather is open and operate like it's suppose to. I hope my description is good enough to follow. Message me know if you have any questions.
You need one of the following, a 283 block and road draft tube. A pcv valve . I'm sure you understand how the volume changes in the cylinders as the pistons go up and down. Well the volume in the crank case ( under the pistons) changes too plus there is dome additional pressure from blow by. The Road draft tube provided a draft or vacuum on the crank case. Your pcv valve will provide a more effective vacuum to the crankcase . If you were to run only a fill tube to provide intake and exhale of crankcase, you would be blowing significant amounts of crankcase vapors out of the fill tube and have a grimy oily mess under your hood. You could try it and see.
I did what Davidbistolas did. works nice, people ask me about my 283. They wonder why I did all the work on it to make it look like that. If you have to ask....
Thanks guys I now have a plan to run Corvette valve covers and old 4bbl intake on my 305. Hope it don't push oil all over ........... I think a pvc drilled in will be the plan .
I like to run the P-C-V valve in a hole drilled in the back of the manifold, like David did. In that hole, I install a baffled grommet, which takes care of any oil that might come up. With a late-model 90º PCV valve, it is a straight shot to the back of the carburetor base.
i tried what davidb did but did not work for me, i went from vented cal custom valve covers with no pcv to sealed chrome stock 283 covers and drilled the back of my intake and installed a baffled grommet and recommended pcv valve to carb base, this turned out real nice and seemed to be working at lower rpm's but...when i jumped on the freeway for a road trip this weekend after about 30 miles at 70-75 mph it started missing real bad. after pulling over to check it out found my plugs were full of crap and i was about 3 quarts low on oil..WTF ? i got oil coming out dip stick, filler tube, higher rpm's is where im having more problems with this, its always run ok but not a lot of power, compression averages about 130,seems to me im getting just too much blowby and its just pushing oil out, any thoughts on this ?
This subject seems to get beat like a dead horse .... but what the heck ... Eckler sells a oil fill tube off a 71 Nova etc with a bung hole it for a PVC to run to the carb, and you can get a dome cap that is airtight also has the tab for the carb return spring.... it looks pretty clean
Use the oil fill tube for the breather (make sure the cap is setup to be a breather, not a sealed cap), and drill the back of the intake for the PCV. You won't have any problems if you do that.
Jim, Do you or anyone have a pic of this earily style pcv valve system?. To get my car and running I just put a frost plug in that hole and am currently running just regular late model pcv system. that I personally don't like the the look of really. But I would love to look at option of switching it back! J
I do but have driven both and if I had a choice between the two it would be a 283,I worked at a Chevy dealer in the early 80s when GM was stingy with the larger V8s and the 305 was a joke.
thats exactly how i had it setup, thats why im thinking maybe i have a excessive blowby problem if this setup is working for other engines
I want to see pictures of this baffled grommet you used . It should allow 100% fee air movement and block the oil. Its also design for a valve cover environment not the center of the crankcase. As a rule, most engines should have 140 to 160 lbs. Of cranking compression with no more than 10% difference between any of the cylinders. OK their are an infinite number of variables that will move those numbers around quite a bit. Like from 90-190 or more on a healthy engine . But the important part is that they are the same across all the cylinders. If it ran perfectly fine with your old valve covers there's no need to rebuild or go on a blow by chase because your workaround isn't working.
You definitely need a baffle to protect the PCV from splashed oil. I got a perfect low-milage 400 sbc for $100 because it was sucking up oil splash.
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