[steverino]

Lots of great info , I'm following closely and learning quite a bit.

I'm curious ponyakr and AG, what rockers do you use with your RA4 style cams and rhoads lifters ?

Also lots of good info in the Jeff Smith sbc article, although they did use alum heads, maybe it had an effect on the detonation (or lack there of) ?

My builder's experience was similar in dyno testing of circle track racing engines as well as (mostly bbc) customer's street engines, insofar as the compression ratio net gain (for a street car certainly with unknown quality variances in pump fuel) was no worth even approaching 10 to 1, I had to plead with them to plain the heads to raise me to 9.4 (could even be 9.25-9.3)

In any case, many folks shared their insights with me before I selected cam for my 455 with tripower and stock 6X (milled for 99cc chambers), and I appreciate it, one o fthe things that this forum is great for !

I deliberated between; 1) RA4, but wasn't certain if it would perform as expected with 1.5 rockers . 2) crower 90243, and finally the choice I made, 3) the xe274

The scary thing is that some reputable builders as well as cam manufacturers were highly recommending the 268, I am glad I read Jim Hand's book, and decided to go "one size up", due to the larger displacement, I don't think I would've been happy with the 268

I am probly lucky that after almost 3k miles, the lobes and lifters seem to be ok thus far .

Now I am more "in tune" with the "sewing machine sound" , the engine can be a bit "ticky even with great oil pressure at steady rpm's
It does like a bit extra timing 16 initial (36 total), and 91 octane, but as long as gas is reasonable, I'm ok with that

The performance is great in fairly heavy 66 gto conv with 4 sp and 3.23

I know the power band is shortened, done by 4900 rpm, but that again is ok for my use, actually favorable to me, I do love the torque, which the 455 excels at anyway

I have had a few issues with the combo, we had to change valve seals to positive style, again , help from here on the forum helped me to pinpoint the issue (the builder had miscalculated the valve lift/seal clearance)
but with a stock cooling system, we've been running great and never too hot

So I'm sure my bottom end is good
I'm pretty certain that my heads are going to be a limitation to the total power I can make, but that is fine, I really want to keep the stock look under the 66 tripower

My question is, If I do decide to make a cam change at some point down the road ( I have considered it, but it's on the back burner for sure), what hydraulic flat tappet would I go to ? My heads are no clearanced for the 1.65 rockers, so I'm thinking maybe the crower 90243 still ?
I do see that respected builder Len Williams advertises a good power number from the RA4 style cam (which I believe is what he uses), and with 1.5 rockers and rhoads lifters, so maybe that would be a better route ?
I know that a roller and aluminum heads are where "all the power" is at nowadays, but
As I said, just thinking about it for now
Thanks for the info and all the great input !