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SBC lacking power

2488 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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Thanks for all the replies fellas.

  • Poncho it’s 0-100km so 0-60 miles sorry.
  • 75gmck25 that was my estimate based the cam and parts. I think I need to recheck the damper to ensure it hasn’t spun at all. Also have to get an AF gauge to check things. Although I wouldn’t think carb tune would be around 200hp. Especially when it runs smoothly with no smoke.
  • curtis73 it is possible. Looking JE pistons site even that low of compression or 1 point is 4-6% still doesn’t account for the massive power such. I am sure the secondaries are opening, I can hear them sucking, although I might have to stick a paper clip on the secondary pump to check by how much.
-Bogie you raise some points that are valid and I know they are not ideal but low RPM should be better. I never realized a tranny could be that big of a parasitic drag. There are definitely some things to try but want to try to cross off everything I can before dumping money or pulling heads off.
-johnsongrass1 the rear gear is 3.73.
-Mousecountry I am not sure what you mean by post your tune up specs. The initial timing is currently set at 14 and 34 total by 2800. I haven’t touched the carb yet as the plugs are telling me it in the ballpark and it starts, idles and drives perfectly. Just a slug.
Rustbucket- I know, the tires are only 6 inch wide and I couldn’t get them to spin at all. As stated previously, I think I need to check the damper hasn’t spun and that TDC is indeed TDC.

I don’t get to work on it except on weekends so will let you know my findings.

Thanks again.
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Yeah, I need to triple check the timing Rustbucket. Will put the piston stop in and go right round, back the other way then split the middle. That should tell me if I am setting it to the right mark.
Thanks again gents. Gives me some easy things to check first. Before I throw money at it.
Thanks for the reply gents.

I will get the block number, I have looked it up before and it’s out either a 62 truck or 80 truck. Both were turds looking at the power numbers. However, the pistons are not the 4 valve relief dish ones. They have a slight dish with no valve relief like the magnum 360 ones. Heads are 64cc and head gasket is 0.38 compressed thickness. NOT great compression but still shouldn’t kill it that bad.

I have ordered an air/fuel ratio gauge to check the carb and tuning. But I think Curtis may have nailed it. That is the sound I can hear at WOT! It’s a pretty distinctive sound that I have never heard. I bit like a turbo blow off valve. I will see if I can get a video. I guess I would drive, go wide open and then check the plugs and they would darken in the time that I went WOT the back to the garage so was thinking all was in the ball park. That’s why you need an Air/fuel gauge.
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