604 crate lsa question.

[blackflag]

Got a question about the lobe separation angle on a 604 crate engine. If most circle track engines run best with a tighter LSA such as a 106 for example. Why do you think GM put it at 112?

[F-BIRD'88]

Cause the GM cam was not designed for circle track.
Or for a typical single plane intake.
"Drivability" idle quality is a issue .

[pdq67]

What cam is it?? The GM last three digits..

Is it the old -962 cam because if it is, it really needs like 11 to 1 CR to run like it was designed to run.

The old .450"/.460" hy-cam??

And to this day, I never could figure out why GM never made a high performance 10 to 1 CR hy-cam!! My new '67 Camaro's 350SS engine had the old -929 hy-cam in it so go figure!! ---- Shades of the 283" engine stock cam!!

I say this because back then dammed near all their engines were either like the lo-po- 8.5 to 1 CR engines OR regular grocery-getter 10.25 to 1 CR!!

The great old -151, the -962, the -178, and the old -346 cams all ran best at 11 to 1 CR!!

Only the way old, little-bitty, -097 Duntov cam was used in like 10 to 1 engines at one time or so and even then, I think the early Big Dog 327 engines were 11.25 to 1 CR or there about's AND they ran the -097 cam... As well as the 270, 290 and 315 hp, 283"s....

pdq67

[blackflag]

I thought that GM 602 and 604 engines were designed for circle track,why wouldn’t they put a cam that would work? It seems to work very well on dirt and pavement just about every race track in the country runs them, and comes with a hi rise single plane intake. Just curious why lobe separation is so wide on the cam.

[pdq67]

Again, what cam is it and please post back it's spec's!

Thank you,

pdq67

[In-Tech]

Stock 604 cam is:
.474" .510"
208/221 @.050"
112 LC
$264.00 at summit

https://www.summitracing.com/parts/nal-10185071

[Keith Morganstein]

Look at the cam in the 604 crate engine..........

Camshaft Type (P/N 10185071): Steel hydraulic roller
Camshaft Lift (in.): .474 intake / .510 exhaust
Camshaft Duration (@.050 in.): 208° intake / 221° exhaust

This hydraulic roller tappet cam is used on the 350 ZZ3 & ZZ4 engines.
The duration at lash point in degrees (intake/exhaust) is 275/280
Duration at .050" tappet lift (intake/exhaust) is 208/221
Maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 474/510.
Valve lash is zero/zero and lobe centerline is 112 degrees.

[F-BIRD'88]

This cam works fine for the purpose. Most "604” crate motor class engine do not allow a cam swap. But if they do a custom cam with more duration and say a 108 LSA will make some more power and torque with headers ( and the single plane intake too.)
Eg hyd roller 232-236 108/104 needs correct springs.
A bit more mid to top end. Every thing you do to the heads is a bonus.

[ProPower engines]

I thought that GM 602 and 604 engines were designed for circle track,why wouldn’t they put a cam that would work? It seems to work very well on dirt and pavement just about every race track in the country runs them, and comes with a hi rise single plane intake. Just curious why lobe separation is so wide on the cam.

The reason for building them that way is so the driver has to rely on torque to pull the car off the corners.
Most groups that run them have an RPM chip rule so they can't rev too high. Its a good deal for a guy that is starting out with nothing but there is some HP to be gained with a custom build where rules allow. As a builder I hate them but as a racer they can be the difference between running 2-3 seasons on a single engine with maintenance like replace the V/springs etc or spend a ton on customs.
I wish IMCA allow that program back in the late 80's and through the 90's rather then the $325 claim deal

[blackflag]

Thanks guys for the help. I know some times I’ve seen the crate late models out qualify the super late models. In some cases that’s a few hundred horsepower. It must be a very thought out engine combination.112 might be a decent lobe separation for circle track in some cases.

[looper]

Hi,
The crates are under 10-1 compression and limited to 6500 RPM. Wider lobe centers will hold cylinder pressures better. The cylinder heads flow adequately for the horsepower and RPM. Crates are not a perfect combination of parts, but it works.

[CamKing]

When we "Fix" the 604 crate cams, we tighten up the LSA to 110, and they make more power, everywhere.

[pdq67]

Dam, am I getting old!

Sorry because I was talking about flat-tappet cams here instead of rollers because of not knowing any better!

My bad, I got to get with the program and catch up on what cams are being used now.

But all this said, I will run a solid lifter flat-tappet cam instead of a roller IF it is, "SPEC'ED", the SAME!!! Only because I worry about roller lifters coming apart is all.

pdq67

[ProPower engines]

The 602 crates are FT cams as well.
Just saying but most have a 5800 max chip they must run.

[blackflag]

Yes it’s strange how well those motors really work. For a few dirt examples. Ive see them run well on little small slick bull ring type tracks and the next night be at a half mile hauling it almost flat out. On a hooked up momentum type track they were turning faster time in the feature than the supers run. Of coarse track conditions probably were a lot different. But still impressive. Also they run the for 100 laps or so at a couple of half mile pavement tracks and run really good. Not as fast as super lates on pavement though. Also seen a couple of those engines in sprint cars run really well with local 360s when track was slicker. Not really sure if they are going into those engines and and fixing them like Mike said. I know someone who bought a new one with a good driver and had trouble running top 5, then they sent it some where to get freshened wink and it becomes a winner.