Ported Chevy 083 heads, the tpi project

[Carnut1]

Kenny, I did a Saturday Lt1 thread a while back and did up a 48mm throttle body with before and after flows. In fact my sf600 could not pull 28 inches on it. Hit that and see how much it helps, Thanks, Charlie

[Carnut1]

Since you will be flowing on your sf300 you will need to use lower depressions and convert. I didn't think about it at the time but after porting the bench pulled less inches of water so I know the flow improved. Thanks, Charlie

[Kenny M]

My bench is a 600. I'm not really trying to get much out of this. I was just playing and testing the difference.
Trickflow 175 out of the box @.500 235CFM
083 stock 185
With the 083 Edelbrock lower. TPS runners and stock T Body. 155CFM
175 Head 189 CFM
Any small mods I have tried have really added nothing.

Have have done a great job !. I have a ton of data on this setup back in my showroom stock, Prototype Automotive days.
Never could find much power. The carbed L69 engine was Much easier to add power.

I am going to flow the 083 head with the complete Stock setup just to see the difference.

[Carnut1]

My bench is a 600. I'm not really trying to get much out of this. I was just playing and testing the difference.
Trickflow 175 out of the box @.500 235CFM
083 stock 185
With the 083 Edelbrock lower. TPS runners and stock T Body. 155CFM
175 Head 189 CFM
Any small mods I have tried have really added nothing.

Have have done a great job !. I have a ton of data on this setup back in my showroom stock, Prototype Automotive days.
Never could find much power. The carbed L69 engine was Much easier to add power.

I am going to flow the 083 head with the complete Stock setup just to see the difference.

My bench is an sf300 that has been upgraded to sf600 specs. Mine too has only one manometer. Thanks, Charlie

[LoganD]

A note on surface finish:

Surface finish makes nearly zero difference for the flow of AIR by itself in a running engine. You might actually measure a flow difference with difference finishes on the bench, but flow benches are a static condition with low reynolds numbers (laminar flow). In a running engine, with the valve opening and closing, the air starting and stopping, compressing and expanding.....your reynolds numbers go up. You are generally dealing with turbulent flow, particularly with long runner lengths. This means that worrying about a boundary layer is a waste of time.

With OHC engines, we actually spin the cam at varying RPMs on the flow bench to look at this.

[Carnut1]

My bench is a 600. I'm not really trying to get much out of this. I was just playing and testing the difference.
Trickflow 175 out of the box @.500 235CFM
083 stock 185
With the 083 Edelbrock lower. TPS runners and stock T Body. 155CFM
175 Head 189 CFM
Any small mods I have tried have really added nothing.

Have have done a great job !. I have a ton of data on this setup back in my showroom stock, Prototype Automotive days.
Never could find much power. The carbed L69 engine was Much easier to add power.

I am going to flow the 083 head with the complete Stock setup just to see the difference.

Kenny if it is not too much trouble could you pour that stock 083 head. I should have and didn't. Thanks, Charlie

[Carnut1]

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Tough to see but the Pitot said airspeed in this corner is 100 ft/sec faster than any other spot on the radius from plenum to runner. You don't know until you test for it. Thanks, Charlie

[Kenny M]

I will pour the head soon.

[Carnut1]

I will pour the head soon.

Thanks!

[Carnut1]

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Question for non pro airflow guys, Why the large cut on the inside radius of a turn?
Question for pros, will this change the tuning frequency of the runner? Thanks, Charlie

[NewbVetteGuy]

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Question for non pro airflow guys, Why the large cut on the inside radius of a turn?
Question for pros, will this change the tuning frequency of the runner? Thanks, Charlie

I have no idea for that weird cut on the inside radius of the turn... sitting on the edge of my seat now.

Guess on 2nd ?: Only as much as the average inside diameter changes because of the cut out section and even then very little change. (Length contributes MUUUCH more to tuned frequency than ID. Note: I learned that from BadSS who is an EA Pro Wizard with these intakes. (Good to see you chiming in on this thread, by-the-way!))


Adam

[NewbVetteGuy]

So what makes a GREAT TPI roller cam?

Charlie if this is way too far off-topic from where you want this thread to go, let me know and I'll just in and delete it and create a new thread.


I'd love a discussion on this subject, though.

My understanding is that you want a duration that puts your torque peak at the RPM that the combination of your intake runner length and ID are "tuned for" (then you can adjust upward or downward from there depending upon your torque / hp goals). -My guess continued: This is why you see some of the old-school TPI recommendations for really pretty small durations with the stock TPI intakes but on combos where you have porting and aftermarket runners and bigger heads, you see the intake duration #'s go up from folks like Mike Jones (I have a mini DB of these long runner builds from a few of the people participating on this thread currently. -When your duration starts to move up beyond that you're not GAINING anything and you're losing torque down low.

Beyond that there's the typical recommendations for wide LSAs, but I think that's more because most TPI people are using the stock GM ECUs that came on TPI motors and they can't deal with the low vaccuum. (There's a couple aftermarket TPI magazine article builds using aftermarket ECUs and the LSAs get tigher.) Mike Jones recommended a 110 LSA on my cam for my FIRST intake but was sure to validate that I filled out the form correctly and was using a Holley EFI; my assumption is if I would've said I didn't need power vacuum brakes the LSA would've gone tighter still. (I don't see why a wide LSA is strictly REQUIRED with a long-runner TPI-style intake.)

Lift: As much as you can get/afford to do with some reliability. My understanding is that since you're "Duration Limited" with long-runner intakes, to make more power you need more flow for more of the time. With the larger heads that end up in the larger power long-runner builds, getting the valve into the "good air" longer pays dividends. As you are really kinda "stuck" with intake open and intake close events to hit your wave tuning, more aggressive ramp cams and rocker ratios are your friend. (For my Profiler 195cc, FIRST combo MikeJones speced out a cam with 0.600" intake lift exactly with my 1.6 rockers)

Firing Order: Because of the air contention on adjacent cylinders is even more intense with these intakes an LS-style firing order swap cam would be better, too. (Wish I would've known this before I ordered my cam.)

I don't want the thread to devolve into bickering, but I have to think that a max effort TPI-style long-runner build would do well with large ID runners, large heads (one size too big for the RPM: (210cc)) because it means a slightly higher tuned RPM (ID increase moves the tuned RPM up a LITTLE) and LOADS of flow, and then a 50 degree valve seat angle-based valve job -to get the port speed up AND because MAYBE, JUST MAYBE having a 50 degree valve seat-based valve job slightly increases the strength of the reflected wave (if air gets "pulled on harder" via a steeper valve seat angle, as He-who-shall-not-be-named always says, then wouldn't the strength of the wave created by the air slamming into the shutting valve be stronger and with a 2nd reflected wave, long-runner intake like a TPI that seems like a useful thing?).



My random thoughts from trying to glean as much information from long-runner builds as I can and read between the lines (no actual expertise...)



Adam

[Jim2527]

Question for non pro airflow guys, Why the large cut on the inside radius of a turn?

Changes pressure. Pressure changes = flow/velocity change. That cut will allow you to control location of the flow downstream.

[Orr89rocz]

When your duration starts to move up beyond that you're not GAINING anything and you're losing torque down low.

Beyond that there's the typical recommendations for wide LSAs, but I think that's more because most TPI people are using the stock GM ECUs that came on TPI motors and they can't deal with the low vaccuum.

More duration will force air flow in up high. The power curve will tend to hang on after peak. The long runner tunes for lower rpm peak for hp but cam duration will help some in keeping power from falling off to much

Torque loss down low isnt really hurt that much imo. Long runner still tunes for trq at 2800-3400 rpm where most guys will have converter stall near that so off idle to 2400 rpm isnt needed. And more cylinder pressure there could make it sensitive to fuel and timing if you try to put any compression in it

Cams can be tighter lsa on stock tpi comp just fine if you know how to tune. Maf or speed density. Question is does the long runner intake change lsa required? Most sbc seem to run good in the 107-110 lsa range. Vizards formulas have shown some dyno correlation there. But those are shorter runner carb dual and single planes. How does 17-22” of runner change things?

[Carnut1]

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After blending cuts.