Figured I'd share with you guys. Earlier this year, I sold my 850 Holley carbs to a guy. We talked about his setup a bit, gave him some thoughts, and figured that would have been the last I heard from him. Today, I get home from work, and check the mail. There was an envelope from him. Opened it up, and inside was his dyno results, and some general info on the tune/combo, and a thank you. Thought that was cool of him. Anyhow, here's what he had

454 bored .030 over, 460ci .

GM IRON 049 Oval Port heads

8:1 compression

B&M 420 Blower with twin 850 carbs

240/248 112 LSA FLAT TAPPET hyd cam

Engine made 694HP at 6,000 RPM, and 675FT lbs, at 4500RPM.

6lbs of boost, 32* of timing.

Not a bad little combo imo, with such low static, flat tappet, stock iron oval heads, etc.

That's some nice power from some simple parts. I can't believe how much more power the bigger blowers make than my 177.

Alot freak out about a larger blower, thinking they take so much more power to turn. The cooler air charge, outweighs that by far. 6 psi of cool boost, is much better than 6 psi of hot boost.

If I had to choose, good blower, crappier heads, or good heads, crappy blower, I'd go with the better blower. Of course, good heads good blower is the ticket, but not always in the budget. I learned the benefits of swapping out a 177 blower for a larger blower, years back.

Flat tappet with iron gm ovals, nearly 700hp with 6psi on a 460ci, not bad at all. Still made 522ft lbs at 2000rpm.

That made 140hp more than my 468 with rectangle port heads and more compression. Makes me wish I wen bigger than 177. He does have more cam than me. My hp peaked at 5600 rpm. I wonder how much better rectangle heads vs ovals are under boost?

prob not a huge difference between a set of 049's, and gm rectangles flow wise. I do think he had a few things done to the 049's, I can find out. A sure way to limit power, is with a short duration cam, and small blower making lots of heat.

My 468's made 800hp on two different dyno's with 420 blowers, they have good flowing heads, decent hyd roller cams, etc. I think the 420 Megablower is a good fit for a hot 454 build, or 502 build. Its between a 6-71 and 8-71 size wize. I tried the 250 blowers as well, the 420's still much better.

Thats a great boat engine, with some simple parts.

Thumbs up

Had all three on relatively identacle builds. Big difference. Not really even a comparison other than to see big gains each time you go bigger. Some/many cases that lead to more than just power though. 177's still seem to have a sound of their own though. Btw I've got two sets of low hour 049's if you ever had interest. One nice advantage of SC's though. Unless going for 100 % max potential power the heads never really seem to care a ton WITHIN reason.

many trash the thought of ovals, but just not the case as there are a couple that make really good power

Curious -

what exhaust?
any reversion risk?
longevity?
Octane requirement?

Wish I had more room under the cockpit floor to accommodate a small blower x 2. Could leave my 8:1 454s as is, replace peanuts with reasonably priced ovals, add some oil coolers, and keep rpms below 5,000. Having 600FT/lbs torque from lower rpms would be ideal on my pig of a vessel - the arnesons like torque to get on plane .... then you back it off.

From what i have seen, the shape of the port on the average roots blower build, isnt a game changer. On NA engines, ovals work really well, if you are looking for low speed torque numbers. However, with a whipple, or roots, and rectangle ports, theres gobs of torque avaliable at low rpm.

Last year, there were two very similar engines built by oso members. Both 454 based with 177 blowers. One had afr 265 ovals , other had 305 afr rectangles. There was minimal difference in torque output, as well as minimal difference in hp output. Both made in the 675-700hp range, afr heads, custom hyd roller cams.... at that hp level, the induction combo was the limiting factor. Even if you had super awesome full hand ported custom heads, end of the day, the small 177 and single carb, can only do so much, only move so much air.