Q&A

Mailbag: Improving ET and 60-ft. Times in a 455-Powered 1967 Pontiac GTO

 
1967 pontiac gto - mecum

(Image/Mecum Auctions)

Q: My 1967 GTO has a 455 Pontiac powerplant with Edelbrock 87cc heads, .030 over Ross pistons, Total Seal rings, Eagle rods, a Crower cam (int./exh. duration 248°/252° @ .050″, lift .512″/.524″, lobe separation 112°), 1.5 ratio rocker arms, and Clevite bearings.

The engine was shop built and balanced, and is also equipped with an Edelbrock 850 cfm carburetor, Torker II intake manifold, MSD 6AL-2 ignition, and a Mallory Unilite distributor. My drivetrain includes a Centerforce clutch, Richmond Gear 5-speed (3.25:1 first gear), and a Moser 9″ Ford rear end with a 3.25 ring-and-pinion. I’m also running Hoosier 26″ x 9″ x 15″ slicks.

My car weighs about 3,650 lbs. (with me and a half tank of gas) and launches at around 3,600 rpm. My 60-foot times are from 2.0 to 2.2 seconds, and my ¼-mile time is in the 12.70s. I’ve seen GTOs in magazines running in the 11-second range (with less cam and inferior heads).

What’s wrong with my setup? I need some help!

A: It sounds like you’ve built an awesome hot rod, so let’s see what we can do to lower those ETs!

Your 60-ft. times should be closer to 1.5 or 1.6 seconds to get the results you’re looking for. If you’re using traction bars, tuning them might help you get off the line quicker, plus your 3.25 ring-and-pinion is not the best choice for drag racing.

We suggest that you move up to at least a 3.70 rear gear—Richmond Gear’s 3.70 set is a great choice for high performance street and strip duty. With the proper ring-and-pinion ratio, your Goat should be turning between 5,600 and 6,000 rpm when you cross the line.

Finally, you should check your fuel pressure at full speed and in high gear to make sure your engine is being fed properly!

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all.

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3 Comments

  1. John Maloy says:

    Change to a 3:90 or 4:33 Ring and Pinion / your 60 footer should improve and your E.T.

  2. Get rid of the edelbrock carb. Try demon or good ole holley, you’ll find it’ll wake it up.

  3. ballard david says:

    my 71 lemans has a 550h.p. butler build all pontiac 462 stroker, our weight is similuar.(heavy vehicles) u gotta change the gear ratio, i do the 60 ft in 1.5 seconds & finish the 1/8 in 7.5 seconds, Also, either get rid of the edelbrock carb & go with a performance machanical secondary or go fuel injection. I got rid of a demon 750 mechanical & went fuel injection,will never go back to a carb again!!! 390 is a great choice for this size of vehicle & do not be ashamed of the times, this is a heavy vehicle & every thing you read in a magazine is not correct, a lot of inflating goes on to sell magazines,parts etc… I & u both know it’s horsepower -vs. weight rating. so lighten the car or add more power, or just be satisfied with some small(but expensive) changes & enjoy your gto

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