427 coming along

[tpepmeie]

Originally Posted by Pete

Man did we ever screw Todd,sorry Todd
Maybe start a new thread.

If we can get a couple of sponsers for gaskets,car,dyno time/expense we can do the testing that Paul mentioned.

I'm also interested to see what the magic porting # would be.

Pete

Man you guys can screw up a good thread! Appreciate all the comments, although I didn't mean to start a "mine is bigger than yours" argument. I think a lot of the trend toward big holes is to get the flow #'s up. As long as the required airflow can be achieved, smaller is thought to be better. If anybody is really interested, search SpeedTalk for "discharge coefficient".

Ryan is right...SpeedTalk forums rock. I've learned a ton from those guys.

I am making a polyurethane port mold of my heads & housings today, just to get a better idea of the shape and area throughout. The inside mic shows a min cross sectional area not much bigger than the stock casting.

This A-B test you guys are talking about would have to include swapping both heads and housings and plenum. It all needs to work together. Huge port heads on small port housings would not be a fair comparison, and vice versa. I would offer my stuff for such a test, but it would be tough to just bolt on to someone else's motor. Valve stem heights are different, lifters are different, cams, and so on. Can't discount the need to tailor the cam profile to the port velocity either. That was a primary input into the lobe profile (ie, flow at different lifts, and port velocity).

Good stuff guys.

Todd

[Demps]

Man, you guys are awesome! I would be dangerous with time and money.

One thing I desired (when I wussed out and paid someone else for the mod) was area under the [power] curve. My 415 made more power down low (with LPE B cams-->smaller exhaust) than dyno's I've seen with Stg III cams. My car is not the most powerful and I have not had a chance to track it yet but it pulls very well. I did not go with bigger valves for $ vs gained when it came down to that vs eating.


Scales are different on the two graphs but...
My car:




Cam'd 415 Marc did (from his site):



I'm not a dyno bench racer by any means...just proud to have what I have and learn more from the smart folks.

[flyin ryan]

Originally Posted by tpepmeie

Can't discount the need to tailor the cam profile to the port velocity either.

Absolutly Todd, that is key.

[scholtmj]

I think those two dyno charts makes a good point about what you want the motor for. As Demps said, he wanted more power under the curve or what I assume is a very streetable power band. The second motor made much less hp at 3500rpm and didn't make the big number till much higher in the rpm range; maybe it's used as a race motor and sees high rpms quite often.

I asked Marc H about a 385 with stage 3 cams and this was his response:
"I dyno'ed a 385 with SGC Stage III cams that a customer brought in. I was able to tune it to 503 whp. That's 593 crankshaft hp. Torque at 3500 rpm was 325 at the wheels. The engine was way over cammed. The idle was very rough. 3500 rpm is an important speed if the car is driven on the street. Compared to my 385 package with stock cams the engine had -65 torque at the crankshaft. I don't think that the torque loss is worth getting the additional 28 chp.
The most cam that I would recommend is Stage II intakes and stock exhaust cams."

Back to topic.....tpepmeie, are you going to reveal your cam specs?

[flyin ryan]

Originally Posted by tpepmeie

This A-B test you guys are talking about would have to include swapping both heads and housings and plenum. It all needs to work together. Huge port heads on small port housings would not be a fair comparison, and vice versa.

My exact feelings as well, only way to do it. Everything 'Starts' at the valve seat.

[flyin ryan]

Originally Posted by scholtmj

I think those two dyno charts makes a good point about what you want the motor for. As Demps said, he wanted more power under the curve or what I assume is a very streetable power band. The second motor made much less hp at 3500rpm and didn't make the big number till much higher in the rpm range; maybe it's used as a race motor and sees high rpms quite often.

I asked Marc H about a 385 with stage 3 cams and this was his response:
"I dyno'ed a 385 with SGC Stage III cams that a customer brought in. I was able to tune it to 503 whp. That's 593 crankshaft hp. Torque at 3500 rpm was 325 at the wheels. The engine was way over cammed. The idle was very rough. 3500 rpm is an important speed if the car is driven on the street. Compared to my 385 package with stock cams the engine had -65 torque at the crankshaft. I don't think that the torque loss is worth getting the additional 28 chp.
The most cam that I would recommend is Stage II intakes and stock exhaust cams."

Excellent post

[jonszr1]

i understand the need for a complete setup ie heads inj housings and plenum. i was just offering to see what different porting on inj housings and plenum on a basicly stk motor . what i have decided inon doing is 2 different tests. 1 testing the stainless works headers and corsa exhaust that is currently on the 92 .then changing it out for the jeal headers and dr gas spin tech set up that is on the 90. then changing out the ported stuff off my 90 onto my 92 . famoso has 2 ,2 day sessions consecutive . weekends . wekend one will be the exhaust and weekend 2 will be the injector housings and plenum . am going to bill bs. next week to have a new clutch setup put in as i hope to make 10-15 runs each weekend .so for the hijack . i really like the thought of the smaller contured ports to make power .

[XfireZ51]

Originally Posted by tpepmeie

...Can't discount the need to tailor the cam profile to the port velocity either. That was a primary input into the lobe profile (ie, flow at different lifts, and port velocity).

Good stuff guys.

Todd

My turn to screw up Todd's thread. Very true tho Todd. At the time I was deciding on a cam profile for my 84 after installing TFS 23D heads, I read several articles by David Vizard. He very much is of the opinion that optimizing cam timing events and profile are a function of the port flow. More specifically, he focuses on port flow at low lift (< .200") which is where overlap takes place. By deciding where you want power peak, itself a function of runner length and induction system flow capacity(ie I shot for about 5000rpm on a ported/modded Xfire manifold), this defines the optimum LSA for the desired rpm range.
He also recommends that minimum valve lift be 25% of valve diameter. This produces an unobstructed "window" for the airflow past the valve head. His article(s) that I read were directed to 2 valve Chevy heads.

[Pete]

Oh boy now we went to cams.
Did some testing there also.


Well here are some findings on 421ci with SGC Stage II's these are Intakes .237 .440 Exhaust .237 .440.

We changed the exhaust cam with a .224 .425 car picked up 10-20+ thru the curve with gains at peak.

I never said bigger is better.
I never tested a 34mm or 35mm ports maybe they will make same HP as 36mm somebody do it and let me know.
I have tried bigger 38mm fully siemesed plenum/IH's with no gains this was on my 350.
I really think big inch motors would benefit from big siemesed & dropped plenum /IH's

On the above Dyno sheets it's not like the 415 making 350rwtq at low rpm is going to drive like a slug down the street.

Pete

[XfireZ51]

Originally Posted by Pete

Oh boy now we went to cams.
Did some testing there also.


Well here are some findings on 421ci with SGC Stage II's these are Intakes .237 .440 Exhaust .237 .440.

We changed the exhaust cam with a .224 .425 car picked up 10-20+ thru the curve with gains at peak.

I never said bigger is better.
I never tested a 34mm or 35mm ports maybe they will make same HP as 36mm somebody do it and let me know.
I have tried bigger 38mm fully siemesed plenum/IH's with no gains this was on my 350.
I really think big inch motors would benefit from big siemesed & dropped plenum /IH's

On the above Dyno sheets it's not like the 415 making 350rwtq at low rpm is going to drive like a slug down the street.

Pete

Pete,

I think my point and I believe Todd's point is how interrelated port flow and cam timing events are. In the effort to optimize/maximize the results,
(and this isn't new stuff) the cam needs to take maximum advantage of the airflow made available through the induction system and the heads.
Too many times people choose the cam first without much regard to the cylinder head design and flow characteristics.