Thread: vavle size for 283

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I have tried to find the answer to this by searching the forums but I didnt find a clear cut answer.

I have 67 chevelle with the original 283 in it. I would like to put new heads on it as
1. Dont want to have to add lead
and
2. Would like more power.

My question is, will the 283 accept 2.02 valves without any machining, or does it have to be bored out to handle valves that size?

if i remember correctly the 283 in my nova was 1.72/1.50..... so yeah you would have to machine the heads to accept larger valves, and really no matter how much bigger, the heads would have to be machined for proper valve sealing..... or else your valves are going to be sticking open when they're supposed to be closed

Hmmm, I thought you could put 2.02 fuely heads on a 283...

I remember hunting them down for my 283 but ultimately couldn't afford them. (high school)

Originally posted by kcress
Hmmm, I thought you could put 2.02 fuely heads on a 283...

I remember hunting them down for my 283 but ultimately couldn't afford them. (high school)

You can, but the cylinder wall of the smaller bore will shroud the intake valve and disrupt the mixture kernel as it tries to maneuver around the valve/cylinder wall and the mixture velocity will decrease going from the relatively small 283 intake port passages into the larger head ports, so cylinder filling may fall short of your expectations. Changing to an aftemarket intake may make matters worse. Now, you've increased the head port volume AND the intake runner volume, so you'll have to buzz the little motor tighter to generate a good negative pressure in the heads and manifold to facilitate cylinder filling. To make any horsepower out of it, you're going to need to change the cam and carb to ones that makes power at higher rpm's, so now you've given up bottom end power and vacuum in favor of mid-range and top end and it's no longer any fun to drive on the street. Of course, you'll need headers to complement all the rest of these changes and that dictates a new exhaust system.

If all this sounds like a nightmare, that was my intention. I've been there and done that one too many times over my 45 years of hot rodding. Rather than spending in excess of $2,000 and still having a P.O.S., I'll offer two alternatives.

1. If you can live without the additional power, take your heads to a good head shop and have hard seats installed along with a good 3-angle valve job.

2. If you want hard seats AND more power, yank the little 283, wrap it in plastic and store it in the corner of the garage so that whoever buys the car from you down the road can return it to original if they want to. Spend $500 for a used, good running stock 350 and bolt it in. I'd be looking for a late 70's, early 80's unit. Do a compression test on it before handing over the green. A motor with 130-140 psi on all cylinders will make as much or more power than the modified 283 and it will do it down low in the rpm range where the car will still be a pleasure to drive. If you want a little more poop, add a mild cam and headers.

Like I said, been there, done that many times.

Note to another board member:
O.K. Scooter, your turn to bust my chops

Nice reply tech. Great points.

Nick were you actually asking about putting bigger valves into the heads you already have??

I wouldv'e never imagined trying that. Isn't there water very nearby?

B/S you can spend 2 grand if you want to but it aint needed. pop it .30 or.60 drop in a comp cams 280-h for.60 or a 270 h for .30 a set of headers a good set of 194.1/6 heads will do you just fine and an edelbrock performer rpm manifold with a 600 holley and bang you've got a nice little 13 second ride it'll run damn good.............or for more power ask me and i shall tell.

NOTE to board member techinspector1: QUIET YOU

Originally posted by techinspector1
You can, but the cylinder wall of the smaller bore will shroud the intake valve and disrupt the mixture kernel as it tries to maneuver around the valve/cylinder wall and the mixture velocity will decrease going from the relatively small 283 intake port passages into the larger head ports, so cylinder filling may fall short of your expectations. Changing to an aftemarket intake may make matters worse. Now, you've increased the head port volume AND the intake runner volume, so you'll have to buzz the little motor tighter to generate a good negative pressure in the heads and manifold to facilitate cylinder filling. To make any horsepower out of it, you're going to need to change the cam and carb to ones that makes power at higher rpm's, so now you've given up bottom end power and vacuum in favor of mid-range and top end and it's no longer any fun to drive on the street. Of course, you'll need headers to complement all the rest of these changes and that dictates a new exhaust system.

If all this sounds like a nightmare, that was my intention. I've been there and done that one too many times over my 45 years of hot rodding. Rather than


spending in excess of $2,000 and still having a P.O.S., I'll offer two alternatives.

1. If you can live without the additional power, take your heads to a good head shop and have hard seats installed along with a good 3-angle valve job.

2. If you want hard seats AND more power, yank the little 283, wrap it in plastic and store it in the corner of the garage so that whoever buys the car from you down the road can return it to original if they want to. Spend $500 for a used, good running stock 350 and bolt it in. I'd be looking for a late 70's, early 80's unit. Do a compression test on it before handing over the green. A motor with 130-140 psi on all cylinders will make as much or more power than the modified 283 and it will do it down low in the rpm range where the car will still be a pleasure to drive. If you want a little more poop, add a mild cam and headers.

Like I said, been there, done that many times.

Note to another board member:
O.K. Scooter, your turn to bust my chops