Q&A / Tech

Mailbag: Budget Tips for Lowering 60-Foot Times (and ETs, Too)!

 

Q: I need some help getting my 1969 Camaro in the 12s at the track. The car has a 350 small block (bored .010-inch over) with 10:1 compression, .488/.510-inch lift hydraulic cam, ported Chevy “turbo” iron heads, Holley 750 cfm double pumper carburetor on an Edelbrock Performer RPM intake, Mallory Unilite distributor and coil (38 degrees total advance), and Hedman 1 5/8-inch primary headers dumping into 2 1/2-inch Flowmaster dual exhaust. The engine is hooked to a Turbo 350 transmission with a 3,500 rpm stall converter. The rear axle has 3.73 gears and a posi unit.

The suspension has been updated (traction bars, adjustable shocks, new rear leaf springs and shackles) so I don’t think the problem is there. I am using a set of street-type slicks.

My best quarter-mile run to date is 13.142 at 101 miles-per-hour with open headers and 104 octane fuel. My 60-foot time was a 1.907, and I shifted at 6,500 rpm. The car runs and drives great, and I’ve been told it should be running in the high 12s.

I’ve also been told to switch to 1.6-ratio rocker arms (I have 1.5-ratio rockers now), install a bigger cam, and use a 4.10 or 4.56 ratio rear axle gear. Any suggestions would be appreciated.

A: Your problem lies in your 60-foot times.

A 1.907 is closer to the time we’d expect from a car with radial tires, not with slicks. You say the suspension is OK, but we’d suggest giving it another look. For example, check your pinion angle—you want it to be around four degrees. To insure good weight transfer, set the front shocks to a 60/40 or 90/10 setting, and the rear shocks to 40/60. Also, check to see if your rear springs are stiff. To do this, push down on the car’s trunk lid. You should be able to push it down a couple of inches before the suspension starts to stiffen up. If the car doesn’t budge, you might want to consider a softer set of springs to help the car launch better off the line.

There are a couple other things you can do at the track that will help get where you want to go. Before you make a pass, do a really good burnout to get your tires nice and sticky. After each pass, pull a spark plug and take a reading (try to avoid idling the engine too much). We think you’ll find the carburetor is running too rich and needs to be rejetted. This will improve 60-foot times and throttle response, too.

We’d focus on these areas first before swapping out a bunch of parts.

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

Tags: , , , , ,

9 Comments

  1. 104 Octane is way too high for that combo. Start at 93 and work your way down. You might find it can run on 91. That change would put you in the 12’s.

  2. I agree, with an automatic trans,he should be using a vacume secondary carb, 750-780cfm. I think that would improve the launch.

  3. Dennis Bowman says:

    I have a 68 Camaro, ZZ4, TH350, 4.10 gear, 275/60 M/T ET Street. 12.80’s to 12.90’s no problem depending on the weather. I would def agree about the carb, the 750 vacuum secondary would be the way to go on this combo. I run 90/10 calvert front with 50/50 competition engineering in the back, sub frame connectors and Cal-Tracs. My car will 60ft in the low to very low 1.70’s. If that car is tuned properly I would expect it to like 91 pump gas just fine. I also use a stock HEI with less timing than that. You don’t need more anything unless its gear. You would be surprised how mild my combo is.

  4. Yeah my motor is a blueprint and balanced 306 from blueprint engines. It dyno’d 390 horse and 375 ft/lbs and they recommend a 600 vac. Secondary which is what I run and they used on the dyno. I also have an auto trans and 4.11 rearend. Often times people do use too much carb and it just kills your bottom end. I also agree 104 is too much for a 10:1 compression. Hope this helps.

  5. I was also thinking, for that engine 6500 seems really high to be shifting at. My old 289 had iron heads and the cam had .472/.496 lift with an edelbrock rpm and 600 carb, I was shifting around 6200, I actually lowered my shift point to 5800 and picked up over a tenth and gained a lot of consistency.

  6. Disconnect front sway bar , possibly taller front tyres ,or springs.battery in boot.3 degree down pinion,use wedges from local speed shop or summit as above softish to push down .the big one come down 100 rpm at a time on shift point till you go slower! Read plugs go and ask an old guy how at the track what to look for timing and fuel on the plug be aware of tyre pressure for your type ,brand ask! the above will make a difference and get you there and there’s more in it .☺ Talk to people at the track with similar combo good luck go hard enjoy

  7. Zeppo Jaworski says:

    R.C you built this all by yourself and it shows. Almost all the suggestions so far should get you pointed n the right direction. I especially laughed at using such high octane fuel. That is like using a blow torch to light a cigarette. A bunch of overkill. All these guys gave a whole lot of good pointers, follow their lead and you will be just fine.

Leave a Reply

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.