procomp junk vs 604 crate in dirt modified

[CamKing]

Those rules aren’t bad.

Rules here are modified 604 4bbl, that will make 490 HP, or open 2bbl that can make around that at much higher RPM. Or a spec 4bbl that has to have a cast crank (fuse). The modified 604 wins most of the time.

Where is the extra 90 go coming from in these engines?

Since there's so much cheating going on with the 604's, many tracks are letting you change a lot of the parts. Many tracks allow you to change the cams, to any hydr roller, change springs, change rockers, etc.....

[phantomfab]

Those rules aren’t bad.

Rules here are modified 604 4bbl, that will make 490 HP, or open 2bbl that can make around that at much higher RPM. Or a spec 4bbl that has to have a cast crank (fuse). The modified 604 wins most of the time.

Where is the extra 90 go coming from in these engines?

Since there's so much cheating going on with the 604's, many tracks are letting you change a lot of the parts. Many tracks allow you to change the cams, to any hydr roller, change springs, change rockers, etc.....

I just now noticed the word "modified" in that statement. I believe the extra 90 go is easily attainable in that case.

[phantomfab]

You can easily make more power then the 604, without having to increase the RPM. The problem, normally, is that the 604's get a weight break, and/or a taller rear spoiler. The problem most guys get into, is they focus on making much top-end power, then the 604's, and get beat off the corner, and on re-starts. We actually went back to a hydraulic cam in the 228-236 range @.050". This gives you about 20 more HP then the 604's, but makes a lot more power on the bottom end.

What heads were you using on that combo? And do you mean a hydraulic flat tappet or roller? Because isnt the 604 already a hydraulic roller?

Most were with GM heads, but some were with aftermarket replacement heads. We went from mechanical flat tappet cams, to hydraulic flat tappet cams, because the rules for the "open" motors, didn't allow rollers. With our 237/237 hydr F.T. cam, and our limited travel lifters, we could keep the max RPM at 6,800, and make 420hp, and 440lbs.

I'm a little confused here. Why go from solid to hydraulic because the rule stated not roller cams? Wouldnt a solid flat tappet perform better than the hydraulic flat rapper? And which GM heads? And heads as cast or ported? I have seen some ported smog heads in that range but didnt have the flat torque curve. I was wondering if the large 210 intake runner in the procomp with a smaller cam would give me a faltter torque curve but still keep it above 400...or am I looking at this all wrong? That and the procomps are aluminum head I have that is cheap enough laying around to dictate the idea of a cheap combo.

[CamKing]

The mechanical flat tappet cams made a ton more HP, but would get beat at low RPM's. Since the 604's get the weight advantage, and extra spoiler, I figured we needed to focus more on low-end power. With our hydraulic flat tappet cams, and our limited travel lifters, we can make the cam act real short, at lower RPM's, so it'll run with the 604's on restarts. Off the corner, we have a ton more torque, so as long as you can hook it up, you've got the 604's beat. The hydraulic cam gives up 30hp on the top-end, but it still has more top-end, then the 604's.

[CamKing]

If the RPM's are dropping down on restarts, below 3,000rpm, the 210's are going to hurt you. You would be better off with a set of Vortec heads.

[phantomfab]

If the RPM's are dropping down on restarts, below 3,000rpm, the 210's are going to hurt you. You would be better off with a set of Vortec heads.

We don't usually drop rpm on restarts at any track I travel to. I usually keep RPM in the 55-7500 range currently. That's including restarts. On long runs I hold 6500 at mid corner out to 7500 at end of straight. With this procomp my goal is to turn 5-6500 or maybe 5500-7000 range around the track. I will most likely chip this engine at 7400 because of the stock rod bolts.

[phantomfab]

If the RPM's are dropping down on restarts, below 3,000rpm, the 210's are going to hurt you. You would be better off with a set of Vortec heads.

I actually have never been in a class that would drop as low as 3000 or under on a restart.

[barnym17]

we won a few races by being in front on restart we were using a direct drive glide paced using low gear took off at the stripe shifted to high . the burts and brinns were all lugged down at low rpm didn't have a low gear to use. lol

[CamKing]

If the RPM's are dropping down on restarts, below 3,000rpm, the 210's are going to hurt you. You would be better off with a set of Vortec heads.

We don't usually drop rpm on restarts at any track I travel to. I usually keep RPM in the 55-7500 range currently. That's including restarts. On long runs I hold 6500 at mid corner out to 7500 at end of straight. With this procomp my goal is to turn 5-6500 or maybe 5500-7000 range around the track. I will most likely chip this engine at 7400 because of the stock rod bolts.

In your case, you should be fine.
There are many classes that don't allow shifting on restarts.
In those classes, if someone with a 604 is in the lead, they slow the field way down on the restart, to get an advantage over the open motors.
The average RPM range we see, across the country, for these types of classes is 4,500-7,200rpm for the open motors. Some tracks have much slower corners, some have much faster. If you're not dropping below 5,500rpm, you're running much faster tracks, then most guys running against 604's. For you the bigger heads shouldn't be a problem. You should also be fine running a solid flat tappet in the range of 248/252@.050"

[Jim2527]

In regards to 604's... What are they running for springs/retainers/rockers etc. up to 7,000 rpm-ish?

[phantomfab]

If the RPM's are dropping down on restarts, below 3,000rpm, the 210's are going to hurt you. You would be better off with a set of Vortec heads.

We don't usually drop rpm on restarts at any track I travel to. I usually keep RPM in the 55-7500 range currently. That's including restarts. On long runs I hold 6500 at mid corner out to 7500 at end of straight. With this procomp my goal is to turn 5-6500 or maybe 5500-7000 range around the track. I will most likely chip this engine at 7400 because of the stock rod bolts.

In your case, you should be fine.
There are many classes that don't allow shifting on restarts.
In those classes, if someone with a 604 is in the lead, they slow the field way down on the restart, to get an advantage over the open motors.
The average RPM range we see, across the country, for these types of classes is 4,500-7,200rpm for the open motors. Some tracks have much slower corners, some have much faster. If you're not dropping below 5,500rpm, you're running much faster tracks, then most guys running against 604's. For you the bigger heads shouldn't be a problem. You should also be fine running a solid flat tappet in the range of 248/252@.050"

Perfect! Cause a cam I have already is in that range. What rpm range will this combination work the best in? Just being an educated guess on this but I am curious.

[phantomfab]

Also, what type of intake would be best? I have a victor jr, torker, and performer rpm that is available on the shelf. lol Really dont think the RPM would be that great of a fit for the rpm range but I was just curious if it was even an option.

[CamKing]

Run the Victor Jr, and gear it for 7,200rpm.