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SBC lacking power

2486 Views 37 Replies 18 Participants Last post by  Moosecountry

I am hoping someone can help shed some light on my current set-up. I know this has been raised a lot on here before but I couldn’t find anything that really gave me an answer.

I have only just got my 66 C10 with a 350 on the road and it feels like a bit of a slug/like it is still a stock motor (before all the upgrades happended). I have measured the 0-100 and its around 10 seconds (shifting manually on the TH350) which is slower than my 1.2 litre Volkswagen Polo and from a rough calculation would equal around 150 hp at best. The engine is as follows:
  • Stock bottom end – standard bore and compression test is all within 4% of each other
  • New alloy heads with 195cc runners, 64cc chambers 2.02 intake and 1.60 exhaust which are a little big but looking to go a 383 in the future. Flow numbers are:
  • Lift Intake Exhaust
    200 145 106
    300 192 135
    400 232 160
    450 242 168
    500 242 178
  • XE262h cam – Was a comp cams kit with timing chain, lifters and springs
  • Edelbrockperformer RPM intake
  • Brawler 650 carb (brand new) vac secondaries
  • Flowtechheaders – 1 ½ primary, 3 in collector but runs a duel 2 ¼ in exhaust to Flowmasterstraight through mufflers
  • MSD StreetfireHEI distributer – new MSD leads and spark plugs
  • Initial timing is set at 14 degrees and total 34 degrees (all in by 2800 rpm)
  • Stock TH350
  • Stock Converter
  • Rear gear ratio 3.73
  • Rear tire height is 28 inches

The car starts, idles and cruises perfectly and sounds strong but just doesn’t seem to have much go at all. The plugs are not fouling or over rich or lean. My question is whether I am just expecting tomuch out of the engine (although looking at the dyno sheets from comp cams for the cam I am not) or whether it sounds like something is a misssomewhere? While I feel like it would benefit from a looser converter I don’t feel like this would change the accelationthat much.

I have ordered a cam degree kit to check whether it has been installed retarded and is the correct cam. No loose lifter and pushrods spin when cranking so don’t think I have wiped a lobe.

Hopefully I have provided enough info for someone who knows more then me.


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I would start with the carb. No carb (despite how they advertise it) works great out of the box. Did you adjust anything or change jets?

Try this: During one of your 0-100 tests, lift up on the throttle to close the secondaries. Does it slow down a lot? Holley carbs tend to focus a lot on the primaries and then the secondaries are just "here's some more petrol and air, we're not sure how much of either." I've had some that would accelerate harder on just the primaries, but when I opened up the secondaries it actually made less because it was going crazy lean.

I would also like to know what the stock bottom end is. There are a gazillion 350s out there from the early 70s through early 90s that have dished pistons. It's possible you have 8:1 compression when you really need 9.5:1
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Do you have the ability to post a video of a WOT acceleration? If the secondaries are going lean it has a very distinctive "waaaahhh" sound.
1 - 2 of 38 Posts