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Perhaps off topic but we keep hearing about unshrouded valves flowing more. Well, open chamber heads on a smog era SBC had better air flow characteristics than the 60's. However, the 1960's era heads made more power and it wasn't just because of higher compression. It was due to the better burn characteristics of the heads or better quench. According to Terry the duratec already has great burn characteristics due to its pent roof design. So my point is this: What's the story with the 3.0 heads? Flow ain't the whole story. Which heads really make more power?
stock 1998 silver frost SVT E0 #1545 out of 6535
* K&N drop-in air filter
* DMD
* Koni's w/ stock springs
* Autolite double platinum
* Tranny cocktail
* Mobil 1 Snyth Oil @ 60K miles
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Is this power calculations based on the old hp system? In the 70's the system was revised somehow though I don't know all the details, anyway it was revised and the engines that were rated on the newer system were rated lower.
Anyone else know anything about this?
warmonger
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
See My Mods
'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black
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IIRC the old system was rated WITHOUT any accessories and at the crank. The new system is with accessories and at the crank. Originally posted by warmonger:
Is this power calculations based on the old hp system? In the 70's the system was revised somehow though I don't know all the details, anyway it was revised and the engines that were rated on the newer system were rated lower.
Anyone else know anything about this?
warmonger
Ryan
Trollin!
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Originally posted by Swazo:
I've heard that some scca racers have bumped up their red line on stock internal 2.5L SVT's to 8K with no issues!
But that's what I hear, so I'll take that with a grain of salt. But if it is true, then surely the 3L can reproduce same 8K redline with more durability.
Well, my car's 2.5 rev'ed to 7700 (new fuel cutoff) with no problems. I haven't broken in my 3.0 yet, but it sure feels like it'll rev that high also.
dion
98 SVT, 200 whp/190 lb. ft tq (tuned by ADC), 3.0, P&P heads w/2.5L valves, optimized TB, MSDS, SCA 2.5" catback, SHOshop UIM/LIM, underdrive pulley set, TD's, Koni/H&R, BAER/TCE, Progress, CF1 products
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I have a book on porting SBC cylinder heads. Gross/Net HP ratings not a factor with up to date modern real world dyno and flow testing.
Also, the NASCAR heads tend to be extreme improved versions of the old 60's style head chambers. Flow/distirbution is addressed with runner, manifold, mirrored port and head angle design.
stock 1998 silver frost SVT E0 #1545 out of 6535
* K&N drop-in air filter
* DMD
* Koni's w/ stock springs
* Autolite double platinum
* Tranny cocktail
* Mobil 1 Snyth Oil @ 60K miles
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Originally posted by dion:
Originally posted by Swazo:
I've heard that some scca racers have bumped up their red line on stock internal 2.5L SVT's to 8K with no issues!
But that's what I hear, so I'll take that with a grain of salt. But if it is true, then surely the 3L can reproduce same 8K redline with more durability.
Well, my car's 2.5 rev'ed to 7700 (new fuel cutoff) with no problems. I haven't broken in my 3.0 yet, but it sure feels like it'll rev that high also.
Hmmm...that is about where I want my redline to be when I'm done with my 3L swap. Which way did you go about bumping the fuel cutoff point?
2005 Ford F150 SuperCab FX4
1964 Chevrolet Impala SS
1998 CSVT: 354HP/328TQ @ 10 psi, now gone 
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Originally posted by holycowSVTpaul:
1. Also, the NASCAR heads tend to be extreme improved versions of the old 60's style head chambers. Flow/distirbution is addressed with runner, manifold, mirrored port and head angle design.
2. Well, open chamber heads on a smog era SBC had better air flow characteristics than the 60's. However, the 1960's era heads made more power and it wasn't just because of higher compression. It was due to the better burn characteristics of the heads or better quench.
1. ...and comparing oversized 2-valve extreme lift race heads to a 4 valve hemispherical shaped head run via roller followers and dual low lift camshafts is a great comparison...
2. Unshrouding the valves is a good thing. It promotes better air flow and chamber swirl. You are not changing the overall shape of the chamber.
Also then try and explain the fast burn heads and their unshrouded valves. They make better power right out of the box then most professionally ported heads do.
Another thing to remember is that when going 3L you also want to install the larger valves. You'll be changing the area around the valves anyway (not too mention porting the intake passage before them) so not finishing to unshroud them at the same time would be foolish. It does not take a significant amount a material removing to do such.
2000 SVT #674
13.47 @ 102 - All Motor!
It was not broke; Yet I fixed it anyway.
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Originally posted by Swazo:
Originally posted by dion:
Originally posted by Swazo:
I've heard that some scca racers have bumped up their red line on stock internal 2.5L SVT's to 8K with no issues!
But that's what I hear, so I'll take that with a grain of salt. But if it is true, then surely the 3L can reproduce same 8K redline with more durability.
Well, my car's 2.5 rev'ed to 7700 (new fuel cutoff) with no problems. I haven't broken in my 3.0 yet, but it sure feels like it'll rev that high also.
Hmmm...that is about where I want my redline to be when I'm done with my 3L swap. Which way did you go about bumping the fuel cutoff point?
It's a Superchip. The now defunct SCA had a chipped burned, and asked that the soft limit be set to 7600 with a fuel cutoff at 7700. I plan on having a local Diablosport dealer burn a chip on the dyno once my car is broken in. It'll baseline at SHOshop on the stock computer settings, and then I'll take it to Diablosport afterwards and see if they can do anything with the car.
dion
98 SVT, 200 whp/190 lb. ft tq (tuned by ADC), 3.0, P&P heads w/2.5L valves, optimized TB, MSDS, SCA 2.5" catback, SHOshop UIM/LIM, underdrive pulley set, TD's, Koni/H&R, BAER/TCE, Progress, CF1 products
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Ok, I'm aware and I admit comparing 2 valve wedge heads to 4 valve hemi heads is not a fair comparision but I only used it as an example suggesting that unshrouded vales ain't the whole picture in the quest for more HP. I only asked a question if you remember correctly.. Which heads are better? Terry emailed me and responed jag/ls heads are! Didn't say why though (aside from direct acting cams).. Sure would like to hear!
stock 1998 silver frost SVT E0 #1545 out of 6535
* K&N drop-in air filter
* DMD
* Koni's w/ stock springs
* Autolite double platinum
* Tranny cocktail
* Mobil 1 Snyth Oil @ 60K miles
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Joined: Aug 2000
Posts: 4,713
Hard-core CEG'er
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Originally posted by dion:
Originally posted by Swazo:
Originally posted by dion:
Originally posted by Swazo:
I've heard that some scca racers have bumped up their red line on stock internal 2.5L SVT's to 8K with no issues!
But that's what I hear, so I'll take that with a grain of salt. But if it is true, then surely the 3L can reproduce same 8K redline with more durability.
Well, my car's 2.5 rev'ed to 7700 (new fuel cutoff) with no problems. I haven't broken in my 3.0 yet, but it sure feels like it'll rev that high also.
Hmmm...that is about where I want my redline to be when I'm done with my 3L swap. Which way did you go about bumping the fuel cutoff point?
It's a Superchip. The now defunct SCA had a chipped burned, and asked that the soft limit be set to 7600 with a fuel cutoff at 7700. I plan on having a local Diablosport dealer burn a chip on the dyno once my car is broken in. It'll baseline at SHOshop on the stock computer settings, and then I'll take it to Diablosport afterwards and see if they can do anything with the car.
Do our engines make power that high? 7700 RPM is really high!
Derek
Scion xB 5-spd
Previous: 2000 Silver Frost SVT
Please share the road with cyclists.
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