Your thoughts on chamber sizes...
04-17-2007, 11:14 PM
#1
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Your thoughts on chamber sizes... I'm sorting together the top end on my motor now and I need to make a decision on chamber size for my heads. Here's the rundown...
The heads are a used set of TEA stage II 5.3 castings that currently have 60cc chambers (not sure of the amount milled to arrive at that volume), the pistons have 4cc valve reliefs and sit .010" out of the hole, the gaskets are .045" cometics, and the cam is an MS3 on a 113 lsa.
Now, with everything as is, the compression would be around 11.0:1 with DCR comming in at a weak 7.98:1.
I had originally planned on milling the heads .015" to bring the chambers down to around 57cc (assuming .005" = 1cc...someone correct me on this if I'm wrong) which would bring static up to 11.47:1 and help the DCR out a little with 8.28:1. I was toying with the idea of advancing the cam 4 degrees in addition to the milling to bring the DCR up to 8.6:1
Now, fast forward to last night when I checked PTV clearances. Using the checker spring/dial indicator method I got .140" intake and .145" exhaust with the cam installed straight up. This got me thinking...perhaps I could mill the heads .030" instead and bring static up to 11.95:1. With the cam installed straight up DCR would still be a respectable 8.62:1. (Again, this is assuming that .005" = 1cc)
Thoughts, opinions? Let's here 'em...
The heads are a used set of TEA stage II 5.3 castings that currently have 60cc chambers (not sure of the amount milled to arrive at that volume), the pistons have 4cc valve reliefs and sit .010" out of the hole, the gaskets are .045" cometics, and the cam is an MS3 on a 113 lsa.
Now, with everything as is, the compression would be around 11.0:1 with DCR comming in at a weak 7.98:1.
I had originally planned on milling the heads .015" to bring the chambers down to around 57cc (assuming .005" = 1cc...someone correct me on this if I'm wrong) which would bring static up to 11.47:1 and help the DCR out a little with 8.28:1. I was toying with the idea of advancing the cam 4 degrees in addition to the milling to bring the DCR up to 8.6:1
Now, fast forward to last night when I checked PTV clearances. Using the checker spring/dial indicator method I got .140" intake and .145" exhaust with the cam installed straight up. This got me thinking...perhaps I could mill the heads .030" instead and bring static up to 11.95:1. With the cam installed straight up DCR would still be a respectable 8.62:1. (Again, this is assuming that .005" = 1cc)
Thoughts, opinions? Let's here 'em...
04-17-2007, 11:30 PM
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Im no engine builder but sounds like it would work. Just dont mill em to much to the point where ur manifold wont bolt up because ur holes moved. What calculator/formulas did u use to come to the dynamic compression ratios, I need to figure this out on my engine as well. good luck on ur build
04-18-2007, 01:04 AM
#3
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you do not want to mill the heads too much because you'll affect intake seating and flow.
60cc on 5.3s look like already a .015 mill (ported 5.3s are usualy 63cc, you could verify that with TEA).
Your original thought of another .015 for 57cc is a good choice. That is a total of .030 mill which has no effect on intake fitment and raises your DCR. Add 2* advance and that should be killer.
60cc on 5.3s look like already a .015 mill (ported 5.3s are usualy 63cc, you could verify that with TEA).
Your original thought of another .015 for 57cc is a good choice. That is a total of .030 mill which has no effect on intake fitment and raises your DCR. Add 2* advance and that should be killer.
