[SWV]

Hi,

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.

Thanks,

Jamie

 

[poncho62]

When you are saying 0-100, are you talking miles/hr or kilometers/hr? If it's miles, you are flying.

 

[75gmck25]

A stock converter will hurt your low end with that cam in a heavy vehicle, but mid range and up should be fine. I would expect overall horsepower to be in the 325-350 HP range, depending on how high the compression is with those heads on a stock 350 block.

You should try adding a little more base timing, since the aluminum heads should tolerate it without pinging. If you are willing to add a wideband AFR gauge that would help with tuning. It’s possible that you are too lean overall, or even have malfunctioning secondaries. It’s much easier to see what’s happening when you can view AFR.

 

[ExcellenceAuto]

3:73 with a 28 inch tire will be ok for highway cruising, but lack a little from a dead stop.
Remember, that truck is very heavy and probably not easy to push by yourself.
How does it do from a 30 mph roll, and punch it?

In order to have stout acceleration, you will need more gear. But then your hiway cruising will suffer because of a lack of overdrive.

 

[lmsport]

put a fuel pressure gauge on it, even temporarily, and verify that you have sufficient fuel to make power

 

[2old2fast]

Your c-10 weighs approximately 21/2 ton with the aerodynamics of a concrete block , that's 2 strikes to start with . you say " stock bottom end " what year , what vehicle did this " stock " motor" come from ? ' 66 would be a 283 or 327 IIRC .?

 

[curtis73]

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

 

[BogiesAnnex1]

Cam is too mild the XE262 is basically an RV cam, you need at least the XE268 which doesn’t seem like much but is a day to night difference. The 650 carb ain’t nothin to write home about either, nor is your 2.25 exhaust system.

Aluminum heads typically use very thick head gaskets, if you follow the manufacturer’s selection of .049/.053 thick gasket along with the standard SBC piston being .025 in the bore at TDC you end up with with inadequate compression and no effective squish quench this exacerbated by a stock bottom end that might have worn out rings and bore walls plus that deep round dish piston better suited to making Chicago deep dish pizza than contributing to compression and squish/quench. To get power out of aluminum heads you have to make them work harder which Vis-a-Vis cast iron which is easy to do without getting into detonation. otherwise they run the cylinder cooler than iron and that costs buckets of power. So just bolting them on a stock bottom end doesn’t do much more than empty your wallet, you gotta build into their strengths and likes most of which comes in getting the compression way up along with the squish/quench function. Guys pay far too much attention to port flow, not that it isn’t important but it’s only one player and it alone cannot overcome other technical deficiencies. To a big extent compression and squish/quench can be improved with a .023 thick thick Cometic C5245-023 or C5269-023 MLS head gasket, these are the high price spread. A bit easier on the budget is the GMPP composition gaskets at .028 inch thick part 10105117 or 14096405.

In the real world your truck is heavy and final rear gearing is subject to tire size, big tires take away from the 3.73 axle ratio so if this is like a working farm truck with tall tires the 3.73 is not near as effective as if it was in a Z28 Camaro.

My experience with pickups is my old 34 got a 256 out of a 53 Merc. The 62 with a 292 got a 430 out of a 60 Lincoln. The 69 with a 352 got a 428, my 78 Chevy with a 350 got a 454. My 89 S15 with an Iron Duke 4 got a 350. You can see the current running through this.

Then comes the tranny where old automatics strapped to frisky young engines don’t do a good job of transferring that power as they prepare to die.

Bogie

 

[johnsongrass1]

What rear gear?
4:11's were common on those 12 bolts with a manual and tall tires.

 

[Moosecountry]

post all your tune up specs?

 

[Rustbucket366]

Weird. My 78 C20 350 with a Crane version of the l82 cam (difference is its a 106 lsa), 882 heads, and the most basic Chinese dual plane will ignite the tires until I have no tires left if I want. You definitely should be making more power.

Are you 100 percent positive your ignition timing is correct?

 

[SWV]

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.

 

[Rustbucket366]

I'd check for a semi accurate timing reading. Most issues are caused by timing. However, it seems like you know how to check that and adjust it. The reason I asked if you were positive on the timing isn't because I was doubting you as much as we all often overlook things regarding the ignition. Perfect example of my own. Could not figure out why a 383 wouldn't run right and the balancer mark was jumping around. It was dumping fuel through the secondaries at idle and fouling plugs. Same exact thing happened to me when I magically had a rock (or something) holding the secondary needle open and fouling plugs not even a month later. Weird.

 

[SWV]

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.

 

[Rustbucket366]

That will work although not totally necessary. What is important is a steady mark through the rpm range of the mechanical advance. As in it should increase with engine rpm up to the point the mechanical advance is at its peak, and then decrease. The mark should not wave or flicker around under throttle at the rpm where the mechanical advance is at its highest.

Once you have determined the ignition system to be operational, then you can move to carb tuning and hopefully not a rebuild due to flat lobes or whatever the current thing is.

 

[Moosecountry]

what you can do is advance timing until you get ping at higher rpm under power. Then back off timing slightly until it no longer pings at higher rpm. This is not accurate but close enough to see if you find power. If you find a bunch of power then go to the trouble to verify timing marks. If no substantial increase in power we have other issues to chase. If A/f is way off then dial that in next. 12.5-13:1 at wfo is a good place to start. I run my engine at 12.2:1 at WFO for the type of power I want with my parts. Also check carb linkage that gas peddle to the floor is actual w/o at the carb. Then we tune secondary opening rate (make sure it is opening)

 

[Moosecountry]

after all this is confirmed do a roll on hard acceleration in second gear from 2500 rpm to redline. Note at what rpm the power rolls off? Should pull clean past 5500 rpm but sometimes if fuel delivery is weak then power drops off at higher rpms. Same can happen with a stock GM HEI coil. A separate coil is needed after 4500 rpm.

 

[Rustbucket366]

what you can do is advance timing until you get ping at higher rpm under power. Then back off timing slightly until it no longer pings at higher rpm. This is not accurate but close enough to see if you find power. If you find a bunch of power then go to the trouble to verify timing marks. If no substantial increase in power we have other issues to chase. If A/f is way off then dial that in next. 12.5-13:1 at wfo is a good place to start. I run my engine at 12.2:1 at WFO for the type of power I want with my parts. Also check carb linkage that gas peddle to the floor is actual w/o at the carb. Then we tune secondary opening rate (make sure it is opening)

I do actually agree. It makes no difference if the timing marks are accurate as far as reading them. Adjusting it to what it likes best has always worked for me. Can I say for a fact my GMC C25 likes 38 degrees? No. I don't bother with piston stops or any of the over analytical stuff. I'll just say that I do know what timing it likes based on tuning and it runs very strong.

 

[Rustbucket366]

Good point about the secondary opening rate (if it's a vacuum secondary). Either way, if it has secondaries it may not be opening them properly. Personally, I haven't experienced this but it is something to take into consideration. Only issue I've had with secondaries was WAY too much fuel. This goes for all 4 barrels, holley (4150 and 4160), edelbrock, quadrajet. Hell I even rebuilt an autolite 2 barrel and it sucked. Seriously. It sucked a lot more fuel than a 2 barrel should. I should say the autolite suckage was pre rebuild. It was fine after.

 

[SWV]

Thanks again gents. Gives me some easy things to check first. Before I throw money at it.