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What OEM Heads Does a Stock 2012 103" Twin Cam Use?

Rod Stewart

Rod Stewart

Active Member
Just wondering if the heads used are the 17728/29-08 castings with 1.850/1.575" valves, or something else? I believe they are 85 cc chambers and are drilled for ACR's, but not sure.
Thanks for any info.
Rod
 
In checking looks like your P/N is for most models except for Dynas. Some Dyna models have that # some have a different P/N. They should have the ACR drilled because the 103 came with them. Valve diameter should also be correct. On SE heads they are 1.875 int.(oversized)/1.575 exh.(standard) per a spec. sheet on SE heads from HD.
tourbox
 
Thanks tourbox; good info.
I see that the Pro CNC ported heads pn 16500013A with the same 1.875/1.575" valves (are these the SE heads?) are rated at 254 cfm; whereas the stock 17728/29-08 heads are rated at 199 cfm; all at 0.550" lift. That's 27% more flow, whereas the intake valve size difference is only 25 thou! So the porting seems like it makes a huge difference.
Speaking of flows, does anyone know what the rated flow of the original '99-'06 heads pn 16723/25-99 is supposed to be? They have smaller 1.750/1.450" valves, so it must be considerably less than the 199 cfm of the '06 heads.

Thanks,
Rod
 
Rod Stewart said:
Just wondering if the heads used are the 17728/29-08 castings with 1.850/1.575" valves, or something else? I believe they are 85 cc chambers and are drilled for ACR's, but not sure.
Thanks for any info.Rod
Click to expand...

Pretty sure you are mistaken on the intake valve size cited in the above post. The intake valve for the 96"/103" motors has been 1.805" since '06. IIRC,twin cam exhaust valves have always been 1.575"; however the intake valve has changed from time to time. '99-'00 intake valves were 1.845" (same as Evo). '00-'05 intake valves were 1.800" and '06 up intakes increased to 1.805". I don't recall any TC heads with 1.750"/1.40" valves. The

I don't know what HD says the flow rate of the early OEM heads is but did see the results of a test by John Sachs when the '06 heads came out. He flow tested three sets of heads, '06, '05 and '02. At .560" lift the '06 heads flowed 126.5; '05 flowed 115.5 and '02 flowed 117.6 at 10" which would be 211.25 at 28" for the '06; 192.8 for the '05 at 28" and 196.4 for the '02 heads.
 
dolt; thanks for the extensive clarifications.
Not sure where I got the 1.750/1.450 valve sizes; I assume from this forum but I did not document that. Anyway, I stand corrected.
Same with the 96"/103" valve sizes. I think I must have transposed a couple of digits to get 1.850 instead of 1.805; not sure.
The flow data you quoted is quite interesting. The HD values are quoted all at 0.550" lift, but I don't think they specify the inches WC that the flows are based on. Hopefully whatever they used; it is consistent. Interesting that in John Sachs tests the '02 heads flowed more than the '05 heads. Do you recall if his tests were based on one head of each year, or a pair, or more?
Rod
 
John's flow data showed the same flow at .500" lift for the '05 and '06 heads as the flow at .560" lift; there was no increase in flow from .500" to .560" lift. The '02 head flow increased from .500" lift to .560" lift but the increase was not much, about 5cfm IIRC.

The difference in flows between the '02 and '05 heads at .560" lift is marginal and could be attributed to the setup, instrumentation, etc. and for all practical purposes should probably be considered equal. However, the '05 heads flowed slightly better at .500" lift than the '02 heads.

I don't recall if John used one head from each year for the test or a pair but suspect that the test was done on one head from each year. I would also suspect that if he had tested a pair, you could have seen marginal differences in flow between the pair; wouldn't surprise me.;)
 
So as I interpret this data dolt, it seems that for standard (non-ported) heads, either '05 (and prior) or '06 (and later); there is not much if anything to be gained installing cams with a valve lift more than .500", all other things being equal.
For sure if you are custom porting the heads, or going with the CNC ported heads, there is a considerable flow increase possible with higher lift cams in the .550" range and more. (This is just in respect of the heads alone for purposes of this discussion, realizing that many other factors play into getting the best total inflow and outflow of the entire engine.)
Would you agree?
 
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Rod Stewart said:
So as I interpret this data dolt, it seems that for standard (non-ported) heads, either '05 (and prior) or '06 (and later); there is not much if anything to be gained installing cams with a valve lift more than .500", all other things being equal.
Click to expand...

Not quite. We have been discussing flow at .500' and .560" lift but the '06 heads flow better at lower lifts than the '05 and earlier heads. I will dig out Sach's test data and post the difference. So to be precise, the '06 heads offer a advantage over the earlier heads up to .500" lift.

Rod Stewart said:
For sure if you are custom porting the heads, or going with the CNC ported heads, there is a considerable flow increase possible with higher lift cams in the .550" range and more. (This is just in respect of the heads alone for purposes of this discussion, realizing that many other factors play into getting the best total inflow and outflow of the entire engine.)
Would you agree?
Click to expand...

Agreed; however, ported heads also provide better flow at the lower lifts as well.
 
Understood dolt, and I see the variables.
That would be great if you could post Sach's data. My interest in these head variables is really peaked!
Rod
 
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