Downsizing valves
Downsizing valves I have cnc ported 862 heads with REV 2.055//1.57 valves. I plan to install these heads on stock cube 346 LS1 with TR224/227 camshaft. From my research, it looks like the intake valves are too large and will cause shrouding. I also noticed that intake valve seats were not replaced, so I have to install new seats anyway.
Is it possible to go smaller, replace intake valve seats and use 2.00 valves where 2.055 once were?
I suppose the bowls are usually blended to the valve size? So how will smaller valve affect port flow if the bowl is blended for bigger valve size behind seat?
Is it possible to go smaller, replace intake valve seats and use 2.00 valves where 2.055 once were?
I suppose the bowls are usually blended to the valve size? So how will smaller valve affect port flow if the bowl is blended for bigger valve size behind seat?
Last edited by cino; Feb 10, 2019 at 12:31 PM. Reason: Typo
I have cnc ported 862 heads with REV 2.055//1.57 valves. I plan to install these heads on stock cube 346 LS1 with TR224/227 camshaft. From my research, it looks like the intake valves are too large and will cause shrouding. I also noticed that intake valve seats were not replaced, so I have to install new seats anyway.
Is it possible to go smaller, replace intake valve seats and use 2.00 valves where 2.055 once were?
I suppose the bowls are usually blended to the valve size? So how will smaller valve affect port flow if the bowl is blended for bigger valve size behind seat?
Is it possible to go smaller, replace intake valve seats and use 2.00 valves where 2.055 once were?
I suppose the bowls are usually blended to the valve size? So how will smaller valve affect port flow if the bowl is blended for bigger valve size behind seat?
I can take pictures of ports and chambers. I have no idea who did the work. I bought them from someone on this forum years ago and they were on the shelf ever since.
Last edited by cino; Feb 10, 2019 at 06:28 PM. Reason: Typo
A 2.055” valve in a 3.898” bore is less than 53%.
A 2.00” valve in a 3.78” bore is 53% and thats a stock 5.3L
A 2.165” valve in a 4.065” bore is more than 53% and thats a stock LS3.
I think you should just run it.
Chamber
Chamber
Intake
Intake port
Exhaust
Exhaust
Thank you KCS for your expert opinion, it means a lot. To not affect port flow I guess it’s better to stay with big valves.
Lately I did a lot of reading about valves, shrouding and velocity to come to conclusion that 2.055 valves are too big and too heavy for nothing on a stock bore LS1. In my case, I have to replace intake valve seats, because outer edge of 2.055 valves seat on aluminum, so I thought of installing stock 2.00 valves. I just don’t know if the rest of the bowl is opened too big for smaller valve and how this will impact the port flow.
Any opinions about port work? Good or bad?
Well from the pics those heads have a top shelf program on them . As for the valve size , for argument sake let's say 2.04 is a ideal size for a 3.9 bore your not that much bigger. What makes you think the valve job was not cut for those valves.I would dyecum the seats and lap them, have you measured the throat diameter ? The REV valves are good , I'd run the 2.05 you have .
Last edited by omc8; Feb 10, 2019 at 08:56 PM.
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Thank you for your opinion. I am convinced to stay with 2.055 intake valves. I didn’t measure anything. Just visually I see the seat cut in aluminium where the valve makes contact. At this point I will bring it to a machine shop to check them out, take all measurements and let them do what’s needed.
Thank you for your opinion. I am convinced to stay with 2.055 intake valves. I didn’t measure anything. Just visually I see the seat cut in aluminium where the valve makes contact. At this point I will bring it to a machine shop to check them out, take all measurements and let them do what’s needed.
It makes sense. I don't know much how to check it, Just noticed the outer edge of intake valve seems to be sitting on aluminium or maybe the heads are just machined that way to make room for valves. I will bring them to a good engine shop for evaluation. Decided to keep 2.055s.
The flow numbers provided from seller with heads are rather impressive, but it could be just the "forged" numbers, who knows. This is why I asked what knowledgeable guys here think about port and chamber work.
Here is the flow data:
100: 66/54
150:105/83
200:143/108
250:169/132
300:199/147
350:229/165
400:254/181
450:277/192
500:295/200
550:310/206
600:316/212
The flow numbers provided from seller with heads are rather impressive, but it could be just the "forged" numbers, who knows. This is why I asked what knowledgeable guys here think about port and chamber work.
Here is the flow data:
100: 66/54
150:105/83
200:143/108
250:169/132
300:199/147
350:229/165
400:254/181
450:277/192
500:295/200
550:310/206
600:316/212
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I don't think smaller valves will work; doesn't look like there's enough seat. They would just suck up into the ports.
If you have em and you're gonna run em anyway, just run em as-is. Maybe take some of those Scotchbrite looking things from Standard Abrasives and clean up any sharp edges left over from the CNC, without altering the shape of anything in any way. Don't try to get fancy somehow. They are what they are at this point.
Might want to lay the gasket you're going to use on em though, make sure the fire rings are clear of the chambers.
If you have em and you're gonna run em anyway, just run em as-is. Maybe take some of those Scotchbrite looking things from Standard Abrasives and clean up any sharp edges left over from the CNC, without altering the shape of anything in any way. Don't try to get fancy somehow. They are what they are at this point.
Might want to lay the gasket you're going to use on em though, make sure the fire rings are clear of the chambers.
