Reverse split cam

[daves8]

Had the 3.45 LSD fitted and gearbox shift points and speedo recalibrated today.
Haven’t given it hell as the recommendation was to drive sensibly and run in néw diff before doing so.

with Very modest throttle I can see it has more responsiveness down low.

hopefully it keeps me satisfied enough to not cam!

 

[RevNev]

So that is all talk with no data. I gave a comparison and you wrote a feel good story.
Your race team must suck because you refuse to take in new info.
I've been learning from the number one porter in the USA.

Here's some data for you, 3 national circuit racing championships with production based cars and currently hold the category lap records at Mallala, The Bend, Eastern Creek, Bathurst, Symmons Plains and Wanneroo. It did suck when someone got our lap record at Winton and Wakefield Park but nevertheless when you can match this with some practical experience, come back and have a chat!

These achievements didn't happen because I'm better than someone else, they happen from passion, persistence and experience slowing cars down with modifications you think should work theoretically and you discover in practice, they don't work and you start again. I got the racing bug in 1980 making a junior speedway Mini run on methanol with a side draft Weber and it went on to win the state title back to back in '81 and '82. With 41 years practice, it'd suck like crazy if I'd leaned nothing in a near lifetime of modifying road and race cars.

 

[shane_3800]

Here's some data for you, 3 national circuit racing championships with production based cars and currently hold the category lap records at Mallala, The Bend, Eastern Creek, Bathurst, Symmons Plains and Wanneroo. It did suck when someone got our lap record at Winton and Wakefield Park but nevertheless when you can match this with some practical experience, come back and have a chat!

These achievements didn't happen because I'm better than someone else, they happen from passion, persistence and experience slowing cars down with modifications you think should work theoretically and you discover in practice, they don't work and you start again. I got the racing bug in 1980 making a junior speedway Mini run on methanol with a side draft Weber and it went on to win the state title back to back in '81 and '82. With 41 years practice, it'd suck like crazy if I'd leaned nothing in a near lifetime of modifying road and race cars.

Sorry I was drunk when I posted that other post.
But just because you have fast track cars prooves nothing about head porting.
If you were given a drag engine to build from scratch you would be at the bottom of the field because there is very little in common between the heads.
Track racing is usually chassis and areo dependant and engines are quite restricted. Are you even allowed to port heads in your class?

Just because you have experience in X dont come at me talking like an expert about Z.

I my self have been playing with cars since I was a kid hell I tried to rebuild my dads Holden Shuttle engine when I was 12 with basic hand tools needless to say it didn't work out but I learnt.

I don't really care if anyone here listens to me talking about cam choice and head porting. I'm learning how to do it properly and my goal is to be able to select cams for heads and select the right heads to have engines prodyce 1.4ftlbs per cubic inch and above.
Go look at engine dyno figures.and you'll soon learn how rare 1.4ftlbs is.

 

[moveage]

I have near stock heads and make 616 ft lbf out of 370 ci. Sure is rare (250 psi BMEP) for NA as in turbo territory, but work was mainly with pistons and deck to reach DCR of 10.22, runs high ethanol fuel, and valve timing rather than FI or tailored heads.
CVVT, medium lift high pressure valve curtain in high squish smallest chamber and indexed plugs.

 

[shane_3800]

I have near stock heads and make 616 ft lbf out of 370 ci. Sure is rare (250 psi BMEP) for NA as in turbo territory, but work was mainly with pistons and deck to reach DCR of 10.22, runs high ethanol fuel, and valve timing rather than FI or tailored heads.
CVVT, medium lift high pressure valve curtain in high squish smallest chamber and indexed plugs.

I would check the correction values on the dyno. I saw a sprint car engine making 1.8ftlbs. Darrin Morgan who worked for Reher Morrison racing, MAST, BES ect said that 1.73 is the max you can make N/A and thats a 124% VE.
Using the SAE corrections your figures might lower from 1.7 to 1.6.
But that is top end power so good effort.

 

[RevNev]

But just because you have fast track cars prooves nothing about head porting.
If you were given a drag engine to build from scratch you would be at the bottom of the field because there is very little in common between the heads.
Track racing is usually chassis and areo dependant and engines are quite restricted. Are you even allowed to port heads in your class?

Circuit cars engine wise are reliant on torque and the ability rev fast and they also resemble a road car more closely than any other type of racing. Drag cars are useless on the street and the worst and most dangerous setup imaginable for a road car particularly when they're fast, don't turn and don't stop. Having said that, I haven't been drag racing since 2002 but the last time we won modified street with 400 Chev HQ Holden with a 10:96 pass and road registered with a VP Commodore 355 mechanical roller (circuit) engine with an 11:28 pass.

In the same year (2002) we spent about 40k on CNC development with Yella Terra Dash 9 alloy Holden V8 heads and ended up with 644 horsepower on an engine dyno with a 358ci Holden V8, mechanical roller and Perkins slide manifold in a VR Improved Production Commodore with a Hollinger gearbox. However in the process of that, 2 sets of heads didn't work along with 6 camshafts thrown under the bench that in theory, should have worked but didn't. The exhaust that worked best was an 1 7/8 primary Tri-y, 2.5" secondaries into a twin 3" X-pipe system.

Theory is fine, but it doesn't beat physical testing and never will is what I've learned over the years. The other "golden rule" I've learned is use the smallest of everything that doesn't rob an engine of top end horsepower. If bigger heads make no difference, put the smaller one's back on!

 

[Immortality]

Someone should just pull their head in and go back to watching youtube....

 

[shane_3800]

Circuit cars engine wise are reliant on torque and the ability rev fast and they also resemble a road car more closely than any other type of racing. Drag cars are useless on the street and the worst and most dangerous setup imaginable for a road car particularly when they're fast, don't turn and don't stop. Having said that, I haven't been drag racing since 2002 but the last time we won modified street with 400 Chev HQ Holden with a 10:96 pass and road registered with a VP Commodore 355 mechanical roller (circuit) engine with an 11:28 pass.

In the same year (2002) we spent about 40k on CNC development with Yella Terra Dash 9 alloy Holden V8 heads and ended up with 644 horsepower on an engine dyno with a 358ci Holden V8, mechanical roller and Perkins slide manifold in a VR Improved Production Commodore with a Hollinger gearbox. However in the process of that, 2 sets of heads didn't work along with 6 camshafts thrown under the bench that in theory, should have worked but didn't. The exhaust that worked best was an 1 7/8 primary Tri-y, 2.5" secondaries into a twin 3" X-pipe system.

Theory is fine, but it doesn't beat physical testing and never will is what I've leaned over the years. The other "golden rule" I've learned is use the smallest of everything that doesn't rob an engine of top end horsepower. If bigger heads make no difference, put the smaller one's back on!

Yes I agree. A head porter I've been paying attention to always has said you wont pick the right cam first go and you need to dyno test.

But with heads just as Matt at MBE sates first is cross sectional area then come coefficient of discharge.
So smaller is better does not apply to drag cars this is because just as Matt states they can't fit enough cross sectional area into the head.
However MBE's circuit ports are substantially smaller for the same RPM and cubic inch.

Another head porter explained it this way. Take your torque peak and your HP peak and the rpm spread between the two is where you want your shift points. On a drag car you want a very narrow window on a circuit car you want it 2000rpm plus. This is what determines roughly cam specs and port cross sectional area and is why drag heads need massive cross sections.

 

[moveage]

@shane_3800 I get what you are saying, if there is no limit to the level of stress and endurance of the block and rotating mass, then for the given 6 litre capacity as OP you could also create

“A”: An entirely new induction path, customise a significantly upgraded fuel system, fabricate custom drag race headers to suit custom made cylinder heads that have a revised CSA.

Supposing further that money were no object (NB OP not overly keen on cost of lifting the lids etc) the brick wall is not any of the above. It is GM’s accepted engineering that limits the factory block and rotating assembly according to proven stress and endurance. Bearing in mind OP definitely doesn’t want to rebuild every few drag runs, quite the opposite.

GM warrants (NA 6.0 and 6.2) alloy short block to 480 and 319 T7 FI 6.2 block to 620 ft lbf but internally for the LS9 daily at just over 600 GM specifies incredibly exotic parts including forged metals and alloys in the rotating assembly.

All that’s to say I agree when the sky is no limit with all the money and specialty / custom engineering maybe also consider modified heads. But given limited resources and clearly defined parameters of stress and endurance limits, an overhauled crack-tested block TPP honed with forged rods and pistons (possibly crank) defines the next practical level for a performance build.

Apart from purely academic reasons, why would you anyone want, never mind pay for all the paraphernalia at “A” above to suit larger CSA / head design if just hand tidied stock heads and a well planned build will outperform the bottom end?

Above point builds on my tuning pressure video posted here earlier - that also reflects the prevailing engineering trend in all ICE - VVT (and lift) wins convincingly over variable length and cross section runners not just for performance but for a road car most importantly efficiency through the RPM. BMW, Porsche, MB, Fiat (Ferrari) proved that over the past 20 years.

Apart from obvious mild hand porting and valve job (you get included else for quids with exchange o/haul heads) CNC / race heads are, for all reasons above, a huge waste of time effort and money and should be relegated to one of the overpriced last items to consider for a streetable sub $20k LS build in 2021.

 

[RevNev]

Yes I agree. A head porter I've been paying attention to always has said you wont pick the right cam first go and you need to dyno test.

But with heads just as Matt at MBE sates first is cross sectional area then come coefficient of discharge.
So smaller is better does not apply to drag cars this is because just as Matt states they can't fit enough cross sectional area into the head.
However MBE's circuit ports are substantially smaller for the same RPM and cubic inch.

Another head porter explained it this way. Take your torque peak and your HP peak and the rpm spread between the two is where you want your shift points. On a drag car you want a very narrow window on a circuit car you want it 2000rpm plus. This is what determines roughly cam specs and port cross sectional area and is why drag heads need massive cross sections.

An engine is an air pump and the amount of air an engine can consume naturally aspirated, is determined by the cubic capacity and RPM. A great example of a head too big, is the old 4V 351 Ford heads they discovered on a 351, work best with port restrictors reducing the intake flow capacity to increase air speed. Using a bigger (better flowing) head than an engine can consume "WILL" lose torque and slow the car down.

The only time bigger works on a V8, if you're injecting methanol into the ram tube of an independent runner (8 throttle body) manifold because the methanol content in the runner robs the engine of air. With this application, a head flowing more than the engine can consume will work, but it wont work with an open plenum (LS type) intake manifold.