[AG]

Originally Posted by 73ta

600hp 494" RA manifolds won't flow enough for that engine IMHO.

I agree, 600 hp with headers and I know I'll be killing hp with the RA manifolds. That's why I am struggling with the decision. I'll either use a TII or an RPM intake and dyno the motor with headers first and then with manifolds and then make my decision.

[scott70]

Back in the 80s I had a local exhaust shop make some exhaust for my 70 gto. I put on some ram air manifolds and I had a set of log manifolds. I think the outlet on the logs were smaller than the ram airs. He looked it up in his book for all the factory bend angles and stuff. I remember him telling me his book said to use 2" pipe and expand the end to fit the 2.25' outlets. He said it would be better just to use 2.25" pipe ..it would give me more power and I agreed.
Fast forward 40 years....The 3" pipes must be a improvement even though its necked down on the end. Im trying to keep a stockish look under the hood thats why I still have iron heads, intake and exhaust.

[65 Lamnas]

I didn’t spend the money to port my heads to 322cfm, and upgrade the intake valves to 2.19”, to wonder how many ft/lbs of TQ I’m losing by running manifolds. No one makes them to fit my ‘65 Lamnas anyway….so it’s a moot point for me.

The 1-7/8 Dougs fit great and tuck up nicely, so there’s really no downside.

When my engine was dynoed, I was more interested in how much I was leaving on the table due to intake choice….hood clearance, single vs dual plane, etc.

So we dynoed 4 intakes and found out. This summer, I hope to correlate the engine dyno results to the 1320 dyno….gonna have an intake shootout day.

[Dragncar]

So.................... what did the dyno say ?

[73ta]

Originally Posted by AG

I agree, 600 hp with headers and I know I'll be killing hp with the RA manifolds. That's why I am struggling with the decision. I'll either use a TII or an RPM intake and dyno the motor with headers first and then with manifolds and then make my decision.

30-50 hp drop was noticeable in my 462" 570 HP engine. Headers are a pain in the ass, but worth it IMHO. Spent money cnc porting heads & intake to gain HP, not going to leave that much on the table. Stocker or under 500 HP manifolds make sense.

[Lee]

Originally Posted by Skip Fix

I'm sorry a set of ported heads, Northwind ported intake Holley and we barely drop HP and TQ with manifolds?? Heck Lee on his chassis dyno and a stock 455 lost more. Look at my recent dyno testing 2" vs Tri Ys and what we lost!

455, 66 casting heads (stock, other than valvesprings), non-adjustable valvetrain, 7.8:1 compression ratio, Performer, Qjet, HEI, cam mentioned in signature below, 87 octane. Used a wideband, AFR corrected to ~12.8:1 for both run.

Stock log manifolds vs. Tribal Tubes Tri-Y headers.

Same exhaust/mufflers, other than what had to be cut out to fit the headers.

[grandam1979]

Originally Posted by Lee

455, 66 casting heads (stock, other than valvesprings), non-adjustable valvetrain, 7.8:1 compression ratio, Performer, Qjet, HEI, cam mentioned in signature below, 87 octane. Used a wideband, AFR corrected to ~12.8:1 for both run.

Stock log manifolds vs. Tribal Tubes Tri-Y headers.

Same exhaust/mufflers, other than what had to be cut out to fit the headers.

Had that same 455 in my G/A years age with a comp 280 cam not my favorite but was in it when I got it. HSD and a 800 Holley speadbore it went 12.88@107 I have no idea of HP but it ran ok and it would run on anything you put in the tank.

[AG]

Originally Posted by 73ta

30-50 hp drop was noticeable in my 462" 570 HP engine. Headers are a pain in the ass, but worth it IMHO. Spent money cnc porting heads & intake to gain HP, not going to leave that much on the table. Stocker or under 500 HP manifolds make sense.

I can't argue with that.

[Jay S]

Anyone seen a PUMP GAS naturally aspirated engine that was dynoed with EXHAUST manifold's that did better on peak power than this Pontiac engine MRE did in the video? Round port? Even from a different engine platform like a modern LS, BBC, Ford 385 series or a Hemi? Not counting header combos or race gas, just something using exhaust manifold’s on pump gas. I am not coming up with anything on pump gas beyond 600? This was 623HP@5700.

Friendly dyno?

[Skip Fix]

Jay I have not but I have seen some "generous" dynos that the motor never "ran the number" by the wt/mph on the car. The "stingy' Stuska we used on my 455 pump gas in my TA was below what the calculators say. 525 on the dyno 124 MPH weighing 3750. 587 on Wallace calculator. Pump gas and a Torker II not a Northwind!

[Region Warrior]

After watching vid pretty impressive.
Questions.
Hand ported heads. Intake and exhaust. No flow #s.
His pontiac guy Steve gave no basic cam specs.
Understand but really l I me lsa.
40 yrs after trying 108-110-113 looking try 116-118.