455 Intake manifold ideas
 

Looking for real‑world feedback on Tomahawk vs ’72 H/O aluminum for my street 455

Here’s the combo:

ENGINE

• 455, .030 over

• SD‑ported 6X‑8 heads (264 cfm)

• Cam H1750

• Advertised duration: 280° / 288°

• Duration @ .050: 223° / 231°

• Lift (1.5 rockers): .463” / .485”

• LSA: 110°

• Q‑Jet (800 cfm)

• Doug’s 1‑7/8” headers

DRIVETRAIN

• 200‑4R

• 2400 stall (flashes ~2600–2800)

• 3.23 gear

• 225/60R15 tires

CAR

• 1965 GTO convertible

• Street use: roll‑ons, cruising, some track

QUESTION

Which intake works better with this setup? I plan on staying in low 5000s rpm, so Performer RPM probably not ideal?

If those -8 heads have only had a clean up mill then I would mill those heads .050” to .060” before doing an intake swap.

Dual-Plane.some good choices. Probably in this order:

Factory iron (port matched, means get the grinder out).
Speedmaster ( mild port matching, means get the grinder but not much to do).
Performer RPM. ( probably need grinder to port match ).
72 HO manifold: ( port match, means get the grinder out)

Seems you got to grind for intake runner CSA match.

The HO will be faster at the track with a good pass

Not nearly enough camshaft for a single plane... The Tomahawk excels at a higher RPM than that camshaft will go and the camshaft excels where the single plane intake is lazy... In use you would end up with a truncated power band = narrower than usual

FWIW, my ported #488945 picked up 56HP over a stocker.

The OP is not going to pick up 56 hp with only 260 cfm heads under either intake manifold!

Truman Fields told me with stock intake try a thicker carb gasket and tune it. I cant remember if open or closed though.

Assure Full advance gets to 34* at ~2400 rpm ( no vacuum adv ).

Assure Secondaries open fully with gas pedal. Tune the Q-JET for crisp Accel Pump response, and Sec Air damper action. Then try thinner=richer Sec Rods.

Hmmm, the cam seems 10*-15* shy on the Intake side. Compare to my signature cam sizes ( i can't see em until this posts) for what is too much duration ).

So maybe 1.65:1 on the intakes only? Not a daily driver so Lobe Life not too big a worry.

Some really great comments. Thanks guys. AI brought me down a bad g rabbit hole. I have a torker 1 and Holley 750 double pumper on it now. I do want to put a rebuilt quadrajet 800 cfm quadrajet on it. I’m thinking I may want to experiment with the qjet, adapter, and keep the Torker 1 on it and see how that goes for street driving.

I've not seen where anyone has indicated he would. Good job of reading comprehension.

So you’re saying there’s a chance a grinder may be in my future lol. I’ve done some on my last Buick GS so that’ll be alright. New to pontiacs so not familiar with speed master… is that a modern RPM? Also, in your order are you saying the iron intake is the best fit? Even with my 2400 stall? Thanks!

If that 455HO intake is a new reproduction, keep in mind that the port alignment is probably WAY off. May require extensive grinding to get them anywhere near close.

And your reply in post number 6 wasn’t put up with the intention of alluding to that?

Give me and others on this string a break.

Regarding your SD‑ported 6X‑8 heads (264 cfm).
Depending the a amount of port work done to them some grinding may be necessary on a "Tomahawk" intake as well.

See posts 18 & 19 here:

https://forums.maxperformanceinc.com...omahawk+intake

Other comments within that thread might be of interest as well.



.

You already made an assumption and you were incorrect.

I didn’t imply or allude anything, other than I run a ‘72 HO intake, and they have a decent potential.

If you inferred anything else than that, it’s on you.

I’m out.