355 SBC 640hp with iron heads on avgas

[KnightEngines]

The vane can affect pressure recovery, if you get it right it can help the flow distribution around the circumference of the valve, without the vane to guide things a little you have less control over where/how the air passes through the curtain.
On some engines it makes no difference, on others it does - typically something like a well designed raised runner head will see little to no gain from a vane, wheras something like a 23 deg SBC head that tends to load up the long turn more than the short turn can see good gains from directing the flow towards the centre of the cylinder.

Don't take this as gospel, it's just my opinion!

[zums]

Nice work, are your bottom cuts radiused/blended to the seat 360* on the intake, what size valve and throat, ss width, looks good
Tom

[KnightEngines]

Valves are 2.08 & 1.6"
Throats are about 90% intake & 88% exhaust - varies a little, throat is cut closer on bore wall side & short turn than on bore centre & long turn.
Bottom cuts are blended into the throat except the 65 deg, which just has the edge broken with the sanding roll, it's fully blended right to the seat on the short turn tho.
Exhaust bottom cuts are fully blended.
I can't remember the SS width, but it was pretty wide, just short of valve dia.

[mdabbott2009]

Nice work

[rewguy]

Looks awesome.....I really dig it. Nice work!

[rewguy]

wen you measure the area at the PR, what was your height and width, and what do you take out for corner radius? Just curious, and thanks!!

[KnightEngines]

To be honest I don't recall, I just looked up my calc sheet for the heads to get the MCSA at the pinch.

& I just realised I read the wrong sheet, these were nowhere near 2.1" LOL, they were 2.4".

Roof was raised a lot, I had to run a bead of weld along the top of the runners on the intake to get some gasket sealing area back.

[Tuner]

How do you account for the engine running above 2800 RPM on that airplane gas? Did you have to take the whole engine and the dyno too up to 10,000 feet to start it, or just the engine, and once you got it started on that high altitude gas how did you get it hooked back up to the dyno?

Nice job of blending above and below the seats to the chamber and port.

[KnightEngines]

1st race last weekend, set a new lap record for the class - carb spacer was left off for that race meet as they ran out of time to drop the engine down on the mounts a little to get it under the hood (not allowed to cut, but can shift the motor a bit).
Without the carb spacer it drops 30hp, so as soon as they can get it all to fit she'll be 30hp up on what it was to take the lap record.

[redliner]

Waaaay Cool! Keep us posted and lettuce kno how much ya carve offn the record with the spacer on...

[KnightEngines]

A tad more off the record a couple of weeks ago, spacer is still not fitted - they reckon it has a bit much power as it sits, having a hard time hooking it up out the corners so she's inconsistent in lap times.
We may look at camming it up a bit more when the spacer goes on - make some more top end HP where it can be used & soften up the midrange so it can hook a bit better out of the corners.
Also looking at fitting a vac pump - it's currently just wet sump with breathers on the covers & has developed a couple of leaks, hinting than crankcase pressure is a bit high, vac pump should add a few HP & help the seals.

Basically just need the power delivery tuned a little to make it more drivable.

[BrazilianZ28Camaro]

How do you account for the engine running above 2800 RPM on that airplane gas? Did you have to take the whole engine and the dyno too up to 10,000 feet to start it, or just the engine, and once you got it started on that high altitude gas how did you get it hooked back up to the dyno?

I noted a little sarcasm on your reply, so I suppose you endorse the use of AV gas on high performance engines?

[Chipped tooth]

I use AV gas allot......

I use an extremely tall velocity stack!

[Tokyo Torquer]

Congrats on the ice breathing engine!

mike

[Tuner]

To make it easier for the driver to control the power coming off the corner, slow down the throttle linkage by arranging the lever ratios to give less carb travel vs. pedal travel in the early part of the throttle opening. If your driver thinks the fastest way off the corner is to flatfoot it at the apex you might look for another driver.

Add a bellcrank if you need to, but usually mimicking the lever angles and ratios of early (' 55 up until cable) Chevy pedal and carb levers will do the trick. In nearly all old Chevy cars and PUs the angle of the lever from the firewall pivot to the carb pull-rod connection is closer to 45 degrees than vertical.

When the lever on the engine side of the firewall pivot is horizontal, motion of the pull rod is 100% vertical. When the lever is vertical, pull rod motion is 100% horizontal. Lever at 45 degrees, pull rod motion is 50% each. For translation of driver's foot motion to throttle shaft rotation, the levers on the carb and driver's foot are opposite in effect to the lever on the engine side of the firewall pivot. .

Most constructed race cars have the lever nearly vertical on the engine side of the firewall pivot and angled rearward toward the driver's foot below the pivot, and that arrangement is exactly backwards if you want to have more control of the mid-range of the throttle opening to give the driver better control of the power application.

You can also retard the timing some. If you are crafty you can arrange the distributor advance curve to soften the RPM range coming off the corner and advance to best power at higher RPM. If you are using an HEI it is fairly easy with the right parts. (375 cam, 41 weights and the big .048" wire diameter springs that come in the MSD billet distributors new out of the box with the eyes shortened a bit and preloaded .010" to 015")

I would do both the linkage and the advance curve. When you seek advantage it only makes sense to use them all.