Best compression for Crower 60919 cam help
 

Looking to build a .040 over 428 motor. Going into a 1967 Firebird, TKO 600 with .64 OD, 3.73 gears on 26.3 inch tires. Decided on the 60919 cam, as I already have one. It will have forged pistons, rods and crankshaft (3" main, 4" stroke). Heads are SD Performance prepped #62's that flow 250 @ .550 lift, 1.7 installed hight with Crower 68405 springs. Intake is an early 1971 HO, and I will be running a Q-jet and long branch manifolds. I will be running 93 octane, but it needs to work on 91 octane (just in case). I still need to pick my pistons. What compression should I be building this motor to. This is a street car. I should add that it will be zero deck, .039 head gasket, Rhoads V max lifters and Crower 1.65 roller rockers.
Thanks in advance.
Peter

I have almost your exact setup except with Edelbrock round ports. I have the TKO600 with 3.70 gears and a 26 inch tire. My compression is 10.25:1 and it runs on 93 GREAT. It’s a wonderful combo and makes much more power than I need. It even runs AC.

Oh yeah I used Crower Cam Saver lifters and 1.7 BBC rockers

In the above reply have you noticed that he's not running Aluminum heads?

With those lifters, iron heads and the fact that gas will never get any better from here on I would build for 9.5 to 1.

I did not factor in the iron heads, good catch!

Do you happen to know what you cranking compress is? Also what is your cams ICL?

Stan

Do your homework regarding the 68405 spring installed at 1.700" and the low spring pressure !

In addition note the amount of distance from coil bind at your max lift ! It is excessive !

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I will look at it. I picked up these heads off the internet. They were run long enough for a cam to go south during initial start up. Previous owner sold them and went to aluminum. That is the way they were set up. any recommendations. I do have another set of heads prepped by SD Performance. They are a set of 670's that flow better, other then the .100 intake flow, where they are less (79.7 vs. 90.0). I was saving them for a 455 build. They are converted to 45 degree intake seat angle, and have 995 springs also installed at 1.7. Is that any better ?

The 68405 is rated at only 110 lbs at 1.700", unless the specs have been changed. That said, never trust what a catalog states. I would recommend that you test any spring with their retainer in place at the actual 'verified' installed height.

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I would try for around 9.5:1 also. However, I have been running the TRW factory 428 replacement style forged pistons with the 13cc dish with 614 heads, Crower 68405 springs, 236/244 hydraulic cam, 1.65 rockers and factory RAIV style intake with a Quadrajet since 2016. I would say my compression is around 10:1. I have always ran it on 91 octane without any signs of detonation. It is a very fun and reliable combination.

Anyone have the cam specs on the 60919 cam? Aren't they simuilar to a RA1V
Thank You.

GT

Yes it’s similar to the RA4 cam other then the lobe sep.

Note that with the RA4 cam in a 1970 400 the seat pressure was 124 and the open pressure with the 1.65 rockers was well over 330 if I recall right,!which was and still is the highest in the industry used on a hydro
cam.
Once the springs broke in there was 110 on the seat and 320 open.

If your starting off with fresh springs giving 100 on the seat and around 270 open then don’t expect the motor to want to rev over 5600 too well, at least in terms of the intake valve.

If your up around 5600 and you hear backfires thru the carb you know why.

I have found they are are not all that similar. I don’t think a 60919 can run as much compression as a RA4, those 9.5 estimates are pretty close, and with aluminum heads 10:1 is about it. The 60919 is quite a bit more aggressive than the RA4. The 60919’s I have checked had has less seat timing than RA4, the 60919 in a higher compression 455 will barely lope and has good vacuum, very noticeable compared to an actual RA4 cam.

60919 approximately duration average 286*/295*@.006”

RA4 grinds (SPC-8 Melling all ground by CMC)

292*/303*@.006”.


The LSA is moved in to 112 instead of RA4’s 113.5, also has more built in advance. It comes on stronger in the mid range than a RA4 grind. The 60919 is ground on a different cam core with narrower lobes, very noticeable when you have them side by side.

We mostly quit using the 60919 because they seem like they vary a lot in how they are ground, I don’t think they are ground on a CNC machine. I have seen the seat timing vary 18* @.006” tappet lift from one cam to the other between 60919s. That way is too much, it is best to check your cam.

If you have an old 60919 from 15 years ago that has a 113* LSA, I think it is closer to a RA4, and has quite a bit more seat timing.

Sounds like the RAIV Crower isn't as good as it once was.
I always leaned towards the melling versions. Similar to what Jay is mentioning when I was talking to a bunch of guys in the PS series they all pretty much agreed at the time that they liked the melling Pontiac cams as they always checked about spot on.

Jay would also set the 60919 up with 120 lb seat pressure, lower 300s spring rate. With a note that at a very high peak rpm level there could be the potential of some valve float. I highly suspect at a rpm higher than anticipated here, that and it would depend on the valvetrain mass involved.

And as noted a valve spring will lose pressure with run in and use.


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Not necessarily stuck on the 60919. It came with a parts package I bought. It's just that I read that the 428's 4 inch stroke is a little more efficient then the 455's and respond better to 112 LSA. But I am not sure which version I have as there in no cam card, and I do not know how old the cam is. I do have a Melling SPC-8 as well as the Edelbrock RPM performer plus #7157 which I think is identical to the Melling cam. If they are a better pick, I have no problem using either one of those. I was thinking about the DSS forged piston with the 14cc dish, which would bring to about 10:0 compression.

I have often wondered about the Pontiac cam cores that I have seen with narrower lobes then the factory cams in terms of longevity!

Gach steered me to the 60919 and I have been thrilled. I cannot compete with this guys on cam "knowledge" but I will say that in my particular engine it is great. I still lopes in a 468 and has good vacuum.

There are applications where the 60919 is better, and in other places the RA4 CMC grind’s do better. Crane had a RA 4 grind is another version different than these others also that is ground noticeable different too.

If the compression is on the higher side, about 10:1 or just under, then use the SPC-8 or the Eddy cam. If the compression is a bit lower in the mid 9s the 60919 does not need Rhoads lifters and performs better.

Jay, I have one of those Crane cams, for use in a 455. How does it differ?
Jeff