363 windsor road race results & a couple of questions

[KnightEngines]

Had this one on the dyno yesterday, results were as expected, but the tune was quite different!

The basics of the motor are:

Dart block, 4.125" bore, 3.4" stroke, 5.4" rod
Scat steel crank
Scat pro sport H beams
Racetec custom pistons

Early trickflow twisted wedge heads, 2.055/1.6" valves, port work & reshaped chambers
Super vic intake
256/262 on 108 solid roller, around .680" lift
Crane valve train (1.7 rockers), isky springs

11:1 comp, pump fuel
850 quickfuel carb
MSD ignition
1 3/4" 4-1 pipes

Moroso road race pan, mellings pump etc.

Built as a hillclimb/circuit race & street engine - an all rounder that'll live on he street & make enough to be competitive on the track while running on street friendly pump fuel.

Dyno sheet:

Ryan 363 dyno by tony knight, on Flickr

Now the tune & the questions!

2 wierd things with the tune - total timing it wanted was 24 degrees, we started at 28, went up 2 deg & it dropped power, went back 2 deg & it picked up, went back another 2 & it picked up again, moved around a little either side & settled on 24 deg total, never showed a hint of det.
Never had a windsor require that little timing, I did reshape the chambers for burn & the TW chambers are quite nice, but 24 deg is really not much!

Next wierd thing was jetting, it was hot on the front 4 & cold on the back 4 in EGT's, we ended up with a 81 jets in the front with power valve & 76's in the rear with no power valve, if you include the fuel from the power valve it functionally ended up with 89 front & 76 rear - with that jetting EGT's were within 100 deg F from highest to lowest.

Any input anyone can offer here?

Motor is happy, everything looks great, but scratching my head a little over jetting & timing!

[427dart]

You mentioned street use also so how did run below 4500 RPM ?
Looks like a nice build and yes that is strange with just 24 degree timing. Was this 93 octane E10 pump gas?

I run the TFS High Port heads with 10.3 compression and run timing at 32-34 degrees on my Dart type 4.125 bore x 4.00 stroke 427.

[Walter R. Malik]

Looks like a good package.

I have seen a little better peak power and band with a Professional Products intake for that RPM level; with P-38 Kaase heads though.

It almost seems as if the secondary blades of the carb are not opening to a full 90 degrees.

[KnightEngines]

Runs nice below 4500, we pulled it from 3500 earlier in the day, but no need to punish the poor thing while we're dialling in the tune!
Fuel was our 98, equivalent to US 93 pump swill.

Walter- definitely had WOT, checked it myself.

Dunno, one of those things I guess - no point arguing with a motor, just gotta give it what it wants!

[MELWAY]

I probably wouldn’t stagger jet carb based on egt alone.

How did plugs read for mixture on base ring. Did they confirm your large jet spread

[SupStk]

I've experienced fuel distribution issues with a SBF Super Victor which stagger jetting seems to cover. One case had equal primary jets and a left to right stagger of 4 jet sizes in the secondary. In that instance it brought the EGTs closer pulled BSFC in line.

[pamotorman]

I would recheck the TDC marks on the damper

[tuffxf]

G,day Tony,
Like you say give it what it wants!
Mine with a flat top 24 max as well, fuel side is probably all tied up with the manifold.
Well done!
Cheers

[KnightEngines]

James - getting the egt's even was worth almost 10hp, all plugs read good after last couple of pulls, it's good where it is, just wierd what it wanted to get it there!

Timing Mark's are good, I made the pointer for it while I was building it so I know its bang on.

[russxr67]

Any idea what the heads and intake flowed to see if it was a restriction?

I've seen motors that wanted an inordinately high jet number when that scenario presented itself.
After porting the heads and intake the jet sizes went down and power went up.

I'd have thought that combo would have been more suited with a 750 carb.

[Geoff2]

EGT variations sound like F/A distribution in the manifold. Probably stating the obvious. Chrysler used to use dams & ribs mounted on the floor of the rich runners as a way of evening out the flow. Dams were about 1/8"high & mounted across the floor at the entrance to the runner from the plenum.

[KnightEngines]

Russ - heads & intake flowed plenty! Heads were just short of 300cfm at .650" lift with a good velocity profile.
The reason it hangs on so high in the rpm is the heads & intake, It's out of cam by 7000, the heads carry it up higher.
The jetting overall is smaller than the carb came with out the box, it's just ass about with more jet in the front & a lot less in the rear.
Above 7000rpm it's pulling a bit over 1.3" of vac on the carb, I reckon the carb sizing is pretty good, it's sharp & responsive down low & accepts WOT at 3500rpm or a bit under on the dyno - it'll take WOT even lower in the car.

I'm 95% sure it's not a manifold issue - there wasn't hot & cold cylinders on their own, just the whole front 4 were hot & the back 4 were all cold, I ported the manifold, it doesn't have any plenum issues.

I reckon it's a carb issue, when I get the motor back to the shop next week I'm gonna pull the carb apart & have a squiz at it.

[Newold1]

Don't know much about TFS Twisted wedge heads but in looking at the those early chambers and especially the location and angle of the spark plug entry over almost the center of the exhaust valve and the radical change in the line of the chamber wall on the plug side it very much reminds me of the chevy Fast Burn aluminum heads chambers. I know in a few of the SBC's I have done with the Fastburn heads that were reworked some for better cfm's and using compressions of about 11.5 to 12.0 to 1 on 93 pump gas they also did not like a lot of timing usually made best power around 29-30 deg. and power would fall off if we tried squezzing them up around 32-34 deg. Seems as though the creation of the fast burn by chamber shape and those spark plugs way over on the exhaust was a timing determiner. Maybe that's part of what's happening in your little jewel. It's just a theory but might be a similar situation.

[MELWAY]

James - getting the egt's even was worth almost 10hp, all plugs read good after last couple of pulls, it's good where it is, just wierd what it wanted to get it there!

Timing Mark's are good, I made the pointer for it while I was building it so I know its bang on.

That’s some good gains with tuning. Did plugs show the rich and lean spread before you stagger jetted?

[MELWAY]

James - getting the egt's even was worth almost 10hp, all plugs read good after last couple of pulls, it's good where it is, just wierd what it wanted to get it there!

Timing Mark's are good, I made the pointer for it while I was building it so I know its bang on.

That’s some good gains with tuning. Did plugs show the rich and lean spread before you stagger jetted?

Did you have any fuel flow data for front and rear of carb?