Looking to make some more power, welcoming ideas/advice

[mt-engines]

If you find a better head in an oval port under 300 in size for a bbc anyone could afford let me and others know about it. I did not say you absolutely must change the heads just suggesting for the size engine he already has. You have a hard on against afr heads talk to them about it. Anything I have seen in a fully CNC brodix head sbc or bbc is half again the cost of the AFR heads.

The trickflow oval ports are very nice castings, big seat ring and have lots of material. I think they were 280cc. Made just under 700hp on a 496 with them with a basic bowl blend and VJ.

Edelbrock has a few different lines of heads that are great... His heads arent a problem.. Im not suggesting him change his heads, because he won't gain anything by switching.

The BB2 heads are only 300cc 30cc smaller than a 990 casting. And flow 60 CFM more. The air speed is a lot better than the old rectangle ports.

His intake and cam are the restriction. He has addressed that. I would suggest a victor o if he wants to keep the velocity for street driving over a victor r.


I dont have a hard on against AFR.. They are just the most overrated cylinder head known to man. I love them, because I pick up huge power after I port them.

You'd run an oval port intake on rectangular port heads? Interesting. Tell me more. Do you blend the oval ports in the intake to match the rectangular port gaskets, or just bolt it up and let it eat?

I normally just Bolt them right up.

[tjs44]

I have found with stick shift cars and driving around at low(under 2000)RPMs that my engines did not like single plane intakes or tight LS cams.They would hit a spot and would start bucking and would have to pull it back a gear.FWIW,Tom

[mt-engines]

I have found with stick shift cars and driving around at low(under 2000)RPMs that my engines did not like single plane intakes or tight LS cams.They would hit a spot and would start bucking and would have to pull it back a gear.FWIW,Tom

A lot of that is your tune.

[BILL-C]

I replaced the Brodix supplied springs and retainers on a set of rec port race rites with a set of Comp cams conical springs and retainers and picked up another 300 rpm before we lost controll of the valvetrain on a similar hydraulic roller application. The Brodix dual springs and steel retainers are very heavy and end the party way too soon.

What kind of RPM limit were you finding with the brodix springs and retainers?

At 5800 rpm the brodix supplied springs started to act up.

[GRTfast]

I replaced the Brodix supplied springs and retainers on a set of rec port race rites with a set of Comp cams conical springs and retainers and picked up another 300 rpm before we lost controll of the valvetrain on a similar hydraulic roller application. The Brodix dual springs and steel retainers are very heavy and end the party way too soon.

What kind of RPM limit were you finding with the brodix springs and retainers?

At 5800 rpm the brodix supplied springs started to act up.

Hmm. Well I’ve had my current configuration. To 6500. It’s way done marking good power by then, but I’ve turned it that hard a few times without any weird sounds or anything to suggest something weird is happening. Maybe that’s because my current cam isn’t very radical?

Will be interesting to see how these springs work with this new cam. What is the symptom(s) when you start to lose control of the valves? I’m very tuned in to what the engine is doing (we did a lot of engine development in my former life as a pro kart racer). What would be I listening/feeling for?

[mt-engines]

What kind of RPM limit were you finding with the brodix springs and retainers?

At 5800 rpm the brodix supplied springs started to act up.

Hmm. Well I’ve had my current configuration. To 6500. It’s way done marking good power by then, but I’ve turned it that hard a few times without any weird sounds or anything to suggest something weird is happening. Maybe that’s because my current cam isn’t very radical?

Will be interesting to see how these springs work with this new cam. What is the symptom(s) when you start to lose control of the valves? I’m very tuned in to what the engine is doing (we did a lot of engine development in my former life as a pro kart racer). What would be I listening/feeling for?

You would be listening for valves hitting pistons and what have you.
you can feel i a huge loss of power and almost like a mechanical rev limiter.

[swampbuggy]

Years ago, about 30, a close friend of mine worked on a set of GM oval port heads. He blended the oval intake ports to a rectangular port intake manifold. He said it ran very good. Anybody else tried this ? Mark H.

[MadBill]

There have been several ST threads about this. AIR, they all expressed amazement in finding that a rectangular port manifold on oval ports ran great as-is but lost power when the latter was blended to it.

[BILL-C]

What kind of RPM limit were you finding with the brodix springs and retainers?

At 5800 rpm the brodix supplied springs started to act up.

Hmm. Well I’ve had my current configuration. To 6500. It’s way done marking good power by then, but I’ve turned it that hard a few times without any weird sounds or anything to suggest something weird is happening. Maybe that’s because my current cam isn’t very radical?

Will be interesting to see how these springs work with this new cam. What is the symptom(s) when you start to lose control of the valves? I’m very tuned in to what the engine is doing (we did a lot of engine development in my former life as a pro kart racer). What would be I listening/feeling for?

On engine dyno the engine power would drop off very suddenly. Changing springs let power curve continue a few hundred rpm more before falling off abruptly.

[GRTfast]

There have been several ST threads about this. AIR, they all expressed amazement in finding that a rectangular port manifold on oval ports ran great as-is but lost power when the latter was blended to it.

Yeah that’s weird. You’d think a big perimeter step in the port would be a big flow killer. Maybe the turbulence atomizes the fuel better?

[BILL-C]

Oval port heads have a proper cross sectional area for your typical street car. The rectangular port heads suffer from low velocity at that monster intake flange opening, so opening up the correct oval port size to the wrong rectangular port size is a step in the wrong direction. Filling the rectangular port intake a few inches in and blending to the oval port head would probably work alot better. If you put any value on your time, then it's cheaper to just buy the right intake.

[GRTfast]

Oval port heads have a proper cross sectional area for your typical street car. The rectangular port heads suffer from low velocity at that monster intake flange opening, so opening up the correct oval port size to the wrong rectangular port size is a step in the wrong direction. Filling the rectangular port intake a few inches in and blending to the oval port head would probably work alot better. If you put any value on your time, then it's cheaper to just buy the right intake.

I get it, I'm was just commenting on MadBill's post that putting a rectangular port manifold on oval heads works well sometimes, because you'd think a big flow trip around the perimeter of the port would be a bad thing.

That said, it is often the case that what seems intuitive isn't what works. Back on our 125 two strokes, they had reed valves in the intake track. A company came out with a different style reed valve assembly that looked super restrictive. Had a big cross bar in the middle of the flow path, and less overall cross sectional flow area. Basically looked like a massive choke point. We put one in and without making any other changed the engine started pulling from 500rpm lower, and held peak HP for almost 1000 rpm longer. Within a few months of that assembly being released, everyone had it on their engine.

[GRTfast]

question... I've been thinking about going to the thinnest MLS head gasket when I am putting my new cam in, in order to get the compression up some. I calculate that I can go from the current ratio of 9.6:1 to almost 9.9:1 by doing this.

The question is, is it worth the effort? I would have to check the piston/valve clearance to make sure it is ok as the mls gasket is about 0.013" thinner.

would the power gain from a 0.3:1 increase and tighter squish be noticeable? How much power would one expect to gain from a change like this?

[dannobee]

Good rule of thumb is 2% per point. Given that, 0.3% increase in compression would be worth 0.6% power increase. Do with that info what you wish and see if it's worth it in your case. If it's already apart, maybe. If you'd have to pull it apart to make the change, there would be better ways to make a bigger difference.

[GRTfast]

Good rule of thumb is 2% per point. Given that, 0.3% increase in compression would be worth 0.6% power increase. Do with that info what you wish and see if it's worth it in your case. If it's already apart, maybe. If you'd have to pull it apart to make the change, there would be better ways to make a bigger difference.

Thanks for the info, that is not worth the effort. The new cam and my new ignition system will have to be good enough, which I am sure they will be. The new ignition has already made a nice noticeable difference down low/part throttle. My current cam is "way wrong", so I am excited to see what this new one does.