Guessing game - Milling's effect on head CFMs?
Guessing game - Milling's effect on head CFMs? Just an attempt to liven up the LTX section a bit.
When a set of heads gets milled down, there is a negative effect on the CFMs that the head flows. Tony from AFR assured me that the CFM hit is well worth the gain in compression on an NA build, and of course I completely trust his experienced opinion.
That didn't stop me from being very curious anyway, so when I dropped my heads off at my shop for a milling and benching to send the results to Llyod, I asked them for an extra baseline flow benching to compare
.
The heads are 67ccs, and I am having them milled down to a much more friendly chamber size of between 60 and 62ccs - wherever the machinist feels comfortable taking them to. In general you can't mill more then ~6ccs (around .030 mill on most SBC heads?) before you start effecting the intake seal, and the last thing I want to do is have to get the intake worked to seal properly...so in short I am limited to around 60ccs minimum, which is fine for my zero decked block and -5cc flattops to get decent compression and an ideal quench height.
I've never seen any hard data on this before, so any guesses on the CFM loss from a 5-7cc mill?
I'm sure most of the audience here won't care about such small details(its not a lid conversion or cc306 thread
), but it is interesting to me nonetheless so I'm going to share the info in case anyone else is curious.
Of course there is much more to a heads performance then its raw peak CFMs - that is why an LSX with heads that flow 280 will still outperform an LTX with heads that flow exactly the same on a bench. This thread is basically just for the sake of discussion and entertainment.
When a set of heads gets milled down, there is a negative effect on the CFMs that the head flows. Tony from AFR assured me that the CFM hit is well worth the gain in compression on an NA build, and of course I completely trust his experienced opinion.
That didn't stop me from being very curious anyway, so when I dropped my heads off at my shop for a milling and benching to send the results to Llyod, I asked them for an extra baseline flow benching to compare
.The heads are 67ccs, and I am having them milled down to a much more friendly chamber size of between 60 and 62ccs - wherever the machinist feels comfortable taking them to. In general you can't mill more then ~6ccs (around .030 mill on most SBC heads?) before you start effecting the intake seal, and the last thing I want to do is have to get the intake worked to seal properly...so in short I am limited to around 60ccs minimum, which is fine for my zero decked block and -5cc flattops to get decent compression and an ideal quench height.
I've never seen any hard data on this before, so any guesses on the CFM loss from a 5-7cc mill?
I'm sure most of the audience here won't care about such small details(its not a lid conversion or cc306 thread
), but it is interesting to me nonetheless so I'm going to share the info in case anyone else is curious.Of course there is much more to a heads performance then its raw peak CFMs - that is why an LSX with heads that flow 280 will still outperform an LTX with heads that flow exactly the same on a bench. This thread is basically just for the sake of discussion and entertainment.
