[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 !

[AG]

Originally Posted by 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 !

I use 1.5 ratio roller rockers with the regular Rhoads lifters and it is tickey when warmed but it doesn't bother me, some people can't stand it. To me, the 455/RAIV cam is a tough low budget combo to beat with or without Rhoads lifters, mine is in my "family" car and I love it and don't need anymore power than it has. The motor I am building for my '68 Bird will have the Old Faithful on a 114 LSA, Edl CNC chamber CNC ported heads on a 461 but won't be a daily driver like my '72 vert family wagon.

[ponyakr]

I used the reg Rhoads and stock 1.5 rockers. I realize that Cliff and Jim Hand say the 1.65's will make more power. But in my situation, I was bracket racing. I was not trying to make max power, or lowest ET. What I needed was a smooth idle at 800rpm, in gear, and lots of bottom end, off the line torque, so I could run a stock 13" converter.

Another reason I didn't run 1.65 rockers was that I'da had to hog out the pushrod holes. And it would'a just put more strain on the valve springs. Hey, I even ran stock bottleneck studs and 3/8 polylocks. Running 1.65 rockers was just not worth doing, for my purposes. If you haven't bought a cam yet, and you want more than a RA4 with 1.5 rockers can give, you can just use the extra money the rockers would cost and have a cam ground like you want it.

You could hear the tick. Some people just can't stand it. Even some guys that love a lopey idle, and loud exhaust, seem to hate Rhoads lifters. I really can only see a lot of advantages to using Rhoads lifters. Hey, they will extend the power range of most any cam. (Yeah, I realize they are not good for small cams and the steep ramp cams.) You can get by with more of a top end cam, but still have a decent idle, good vac, and more low end than possible without the Rhoads. It's a win--win. So what's not to like. Plus they have real snap ring retainers, instead of the flimsy paperclip style which some lifters have. I've read that Rhoads begin life as Johnson Hy-Lift lifters, and are then modified by Rhoads.


Hey, I was aksed to leave a Pontiac forum for recommending the RA4 / Rhoads combo. They said that was old, out of date technology, that nobody had used in 30 years. Most of them thought the CC XE cams were best for almost every app, regardless of cube. And a respected Pontiac engine builder, was leading the charge. He even said he recommends rollers, unless the customer absolutely insists on a flat tappet. That's all I'll say about that.

[OCMDGTO]

Don't mean to get off track, but Ponyakr I can't believe someone almost kicked you off a forum for giving your 2 cents-isn't that what a forum is all about? Weather or not it is old tech who cares as long as it works & you are sharing your experience. Not everyone wants to spend $ on a roller, and you can't deny a proven combo. For the record I am a roller fan, and having Cliff Ruggles & Dave Bischop share info on here is like Xmas for any Pontiaddict.