71 c10 just feels slow. Ideas?

[Slammed71C10]

I have a 71 c10 long bed. 355, flat top pistons, 9.5:1 compression, ported/polished/3 angle valve job 882 heads, large cam(can’t find my spec sheet for some reason), air gap intake, Edelbrock 600 mechanical carb, and a ford 8.8 with 4.11 gears. I’m really poor with timing so I had my neighbor do it with his timing light. Truck idles and runs excellent.

The problem. It has a th350 transmission 3000 stall with the 4.11 rear gears. I take it out and it just feels so slow. Takes off great, has good power through 1st, but as soon as I slap it onto 2nd it just doesn’t seem to have as much get up as it should. I have a 94 integra show car that feels faster with a pretty stock 4 cylinder. Am I missing something? Are 355s just slow or am I doing something wrong?
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[Mike C]

My 355 in my Camaro runs 12.6's at 110 mph. 3500# with me in it on street tires and has done that since 1994. So no. With trough flat tops and 64cc heads it's 9.8:1 or just a bit more.

No way you have 9.5 compression with flat tops and 882 heads. You'd be lucky to have 8.8 if your block was decked so that's part of the problem, but most likely you need to optimize ignition curve. That's at least where I would start.

How much cam is in the motor?

[Slammed71C10]

The shop that built the motor told me I should be right at 9.5:1 compression. Is there an easy way to check that?

I can’t find the cam card and haven’t been able to for about a year. The cam is suppose to be over 500/500 with 1.6 roller tip rockers. I know the rockers are for sure 1.6 roller tips as I picked them up from the store. The cam they had to order after I had a lunati lifted explode and destroy my last cam.

[68Stepbed]

Sounds like mismatched engine parts. In other words, the heads, cam, carburetor, compression ratio, stall converter, and rear gears are all out of whack and not working well together.

[Slammed71C10]

I guess I don’t really understand. Everything on paper should be in the same rpm range. We had a 2000 stall and swapped to a 3000 which woke the truck up off the line for sure. The truck originally had 3.08 rear gears and was so slow I get like a lawn mower could outrun it. What should I be looking at? A top end kit maybe?

[68Stepbed]

I know you said you can't find the cam card, but knowing the cam specs would be the most helpful.

The most devastating new to hear after building a new engine is to find out all your parts aren't matching up for the right combination, and now you have to spend more money.

Before investing in a whole top end kit, talk to some experienced engine builders, and ask about custom cams. The local machine shop here will custom order a cam for every build he does according the vehicle weight, gears, stall used, and intended purpose of the vehicle. He never buys part numbered cams.

[Slammed71C10]

This was definitely a part numbered cam. It’s from comp cams. It’s between 500 and 550 lift. Not over 550 tho. I haven’t seen the cam card for over a year so I’d just be guessing without pulling the cam.

The engine was built at a local engine shop who is also the only Imca crate engine shop in the area. So they have a ton of experience. It wasn’t originally intended for the 71 c10, but I hadn’t purchased a vehicle at the time of build. The rear gears, trans, and stall all came later with the switching out of stalls being the first change.

[geezer#99]

Doesn’t make a lot of sense swapping out the top end just to end up right back where you are now.
You need to learn about timing your motor.
You need a dial back or digital timing light.
Here’s a link on how to time your motor.

https://www.badasscars.com/index.cfm...&product_id=76

[Slammed71C10]

I have no issue asking my neighbor for help on timing and I have no doubt that the timing is correct. Like I said the truck runs great. It just doesn’t have the power I feel like it should with how it’s built.

[Slammed71C10]

Timing is set at 11 initial and 36 full advance at 3000rpm. We are out in the garage watching tv, so we decided to check it out just to make sure. It’s been checked with a Bosch digital timing light with the truck at 160 temp.

[geezer#99]

That’s not even enough initial for a stock smooth idle small block.
With your cam, compression, intake etc you should be closer to 20 initial (all in by 3200) with 12 in mechanical and 10 from vac advance.

[Slammed71C10]

20 initial and 42 total???? The link you sent me reads otherwise. It’s at 11 degrees with the vacuum advance plugged and 36 full advance at 3000rpm.

[geezer#99]

You should read it again.
I ran a sb like yours years ago.
22 initial, 12 mechanical and 10 vac advance. Never pinged, started hot or cold instantly, idled at 750 rpm.
I’ve run other motors with 30 degrees locked out without a problem.
The link shows you how, not exactly the numbers you need.
You need to adjust and test.

[HO455]

I recommend getting some sort of way of measuring the performance of your truck. It can be as simple as this application for your phone.

https://www.popularmechanics.com/cars/a3661/4288189/

Or buy and install an actual accelerometer or find a friend with a stopwatch and an empty stretch of blacktop. Or even better a dragstrip. Or spend a day on a chassis dyno tuning the combination. Be prepared to put in some hours. Only change ONE thing at a time and then test. Keep a record of results and the changes.
Any method of measuring the performance in a repeatable way will allow you to get positive results. It's my experience your internal butt measurement device will lie to you every time.
I've driven mid 11 second cars with high stall converters and low gears that I would have bet money were slower than my high 12 second GTO with a 1800 stall and 3:55 gears.
What diameter is your convertor? Not all convertors are created equal.
What diameter are your rear tires?
What RPM are you shifting at? What is RPM after shifting into 2nd gear?
Have you had your distributor curved to match your drive train? Like Mike C said your ignition needs to be optimized to the rest of the engine.

You are at the fun part now! The search for all the horsepower you can squeeze out of your combination.
Good hunting!

[Slammed71C10]

Originally Posted by HO455

I recommend getting some sort of way of measuring the performance of your truck. It can be as simple as this application for your phone.

https://www.popularmechanics.com/cars/a3661/4288189/

Or buy and install an actual accelerometer or find a friend with a stopwatch and an empty stretch of blacktop. Or even better a dragstrip. Or spend a day on a chassis dyno tuning the combination. Be prepared to put in some hours. Only change ONE thing at a time and then test. Keep a record of results and the changes.
Any method of measuring the performance in a repeatable way will allow you to get positive results. It's my experience your internal butt measurement device will lie to you every time.
I've driven mid 11 second cars with high stall converters and low gears that I would have bet money were slower than my high 12 second GTO with a 1800 stall and 3:55 gears.
What diameter is your convertor? Not all convertors are created equal.
What diameter are your rear tires?
What RPM are you shifting at? What is RPM after shifting into 2nd gear?
Have you had your distributor curved to match your drive train? Like Mike C said your ignition needs to be optimized to the rest of the engine.

You are at the fun part now! The search for all the horsepower you can squeeze out of your combination.
Good hunting!

It’s a 10 inch 3000 stall converter(no idea on brand). Tires are 28.5 by 10 3/4 wide drag radials. Shifting at 6000rpm. I wouldn’t even know where to have a distributor curve matched. The local track is closed for the year, so what would you recommend using to do the research? I have raced a friend who runs a consistent 13.00 in his mustang(bracket car), and he completely smokes me every time we race. I take him off the line on the street and then it’s just over from there. Usually 3-4 car lengths roughly between us. I live out in the country so we have plenty of room to mess around halfway safely.

[Slammed71C10]

I do know one of my first steps I would like to know what the truck actually weighs with me in it. I have stripped a decent amount of unneeded stuff out of it. Replaced the fuel tank, which leaked, with a fuel cell in the bed. Removed the hvac box and accessories, since when I got the truck I went to turn on the heat and had to grab a extinguisher and put out a fire under the dash. No ac/no power steering. Battery has been relocated to the bed. I’d like to think I dropped a little weight. Which I know doesn’t mean much, but it’s a start. Next step will be to fix my solid front suspension and get something that lifts a little bit so I can transfer weight better. Then I’ll get it to a shop maybe that has a dyno to see what I can get out of it that way.

[HO455]

Originally Posted by Slammed71C10

It’s a 10 inch 3000 stall converter(no idea on brand). Tires are 28.5 by 10 3/4 wide drag radials. Shifting at 6000rpm. I wouldn’t even know where to have a distributor curve matched. The local track is closed for the year, so what would you recommend using to do the research? I have raced a friend who runs a consistent 13.00 in his mustang(bracket car), and he completely smokes me every time we race. I take him off the line on the street and then it’s just over from there. Usually 3-4 car lengths roughly between us. I live out in the country so we have plenty of room to mess around halfway safely.

10" convertors in my experience are tighter when they lock up and are more efficient driving around town as result. Good choice.
I can't recommend a device to measure your elapsed time as the one I habe is no longer made. But this link should be able to start you looking in the right direction. You also might post a question about accelerometers in the racing and high performance section.
As far as the curving the distributor you can do a fair job of it with a good adjustable timing light and a timing tape installed correctly on your harmonic balancer. It involves changing the weights and springs on the advance mechanism (under the rotor inside the distributor. Forgive me but I don't want to assume what you know ) in order to get the timing to advance at the rate the engine needs it to.
Are you running a HEI distributor, factory points style or an aftermarket distributor?
Do you know if the engine builder degreed the camshaft when it was installed? Is it a solid lifter cam or a roller cam?
Another simple thing to check is to see if the throttle plates on both primary and secondary bores are fully open when you step on the throttle and floor it. A friend or a brick can hold the pedal down while you check to see if the throttle is fully open.

I have to go for now good luck.

[Slammed71C10]

Originally Posted by HO455

10" convertors in my experience are tighter when they lock up and are more efficient driving around town as result. Good choice.
I can't recommend a device to measure your elapsed time as the one I habe is no longer made. But this link should be able to start you looking in the right direction. You also might post a question about accelerometers in the racing and high performance section.
As far as the curving the distributor you can do a fair job of it with a good adjustable timing light and a timing tape installed correctly on your harmonic balancer. It involves changing the weights and springs on the advance mechanism (under the rotor inside the distributor. Forgive me but I don't want to assume what you know ) in order to get the timing to advance at the rate the engine needs it to.
Are you running a HEI distributor, factory points style or an aftermarket distributor?
Do you know if the engine builder degreed the camshaft when it was installed? Is it a solid lifter cam or a roller cam?
Another simple thing to check is to see if the throttle plates on both primary and secondary bores are fully open when you step on the throttle and floor it. A friend or a brick can hold the pedal down while you check to see if the throttle is fully open.

I have to go for now good luck.

HEI distributor from skipwhiteperformance. Idk about the cam degree, but it is a solid lifter cam for sure. We did have the issue months ago of the carb not using the secondary’s when I floored it, but that issue has been since fixed.

For adjusting sprints and weights is there a good starting point or is it just kinda a guess and check job?

[Ironangel]

Give it more timing...At least find out where it starts detonating and then back it off a bit see where your at...I never run less than 15 degrees initial in anything performance oriented...Put the whip to them pony's!

[HO455]

Originally Posted by Slammed71C10

HEI distributor from skipwhiteperformance. Idk about the cam degree, but it is a solid lifter cam for sure. We did have the issue months ago of the carb not using the secondary’s when I floored it, but that issue has been since fixed.

For adjusting sprints and weights is there a good starting point or is it just kinda a guess and check job?

To start the distributor was assembled and installed. Hopefully it was at least spun to see that the mechanical advance worked, but Check the timing at idle and at every 200 RPM until it stops advancing. That will give you the baseline curve, i.e. the starting point. Every engine is different and will need a different advance to optimize it's performance.
Here are a couple of links to give you a good overview of what curving the distributor involves. If you have any questions just ask.

http://www.superchevy.com/how-to/dis...curving-power/

http://www.gofastforless.com/ignition/advance.htm

You say the cam is a solid lifter cam. Have you checked the valve lash? If so what is it?

[weim55]

I’m going on about 35 years of performance engine building and tunes, Here are the most common issues of poor performance on a small block Chevy.

Timing tab does not reflect true TDC. There many different factory timing pointer positions and various balancers with the timing mark also in different positions. Now add all the aftermarket variations........ A must to check if this is correct before any timing adjustments.

The cam is too big for the application or wasn’t phased correctly from the factory. Yes aftermarket cams can be ground incorrectly. Need ALL the specs on the cam card.

Incorrect valve adjustment, valves adjusted too tight bleeding off compression.

Cam is going flat from excessive wear.

The above said, I could quickly list at least 50 things that could be causing the issue that you’re dealing with. It might not have any engine issues at all and be problems on the drivetrain and vehicle side. Lack of power will usually encompass a combination of issues that need to be assessed and corrected. If I were you I would look into it and find someone who is very experienced with tuning issues On performance oldschool V8s. Someone sharp could go through that in an hour and conclusively find your issues. Pay the $$ and just do it......

Steve weim55 Colorado

[Killer Bee]

buy a corvette, may be less painful than another sbc internet diag




just kidding.. sometimes ya gotta dig deep and keep fighting until you figure it out.. good luck!

[Oydllay]

Second all of that! Always make sure the pointer is actually @TDC. I've seen this screwed up alot.Wrong balancer/pointer combo. Also seen those multi keyway double roller timing chain sets installed wrong more often than not. Its easier to do than you would think! Truck will launch great with the 3000 stall converter and low rear gears with the cam timing off but fall on its face in the higher gears. Does the idle seem rougher than it should?

[Slammed71C10]

I swapped out last night to a Holley 650 double pumper carb and before it started snowing out took the truck for its final drive of the year. Completely different truck. I am assuming that something may have been wrong with the carb and it wasn’t supplying the correct amount of fuel. It definitely accelerated faster, feels like it pulls harder, and smokes the tires off from a 30mph roll(never did that before). I obviously have some other issues that may need to be addressed, but I think a fuel issue was part of my problem to begin with. Like I said the truck ran and idled amazing, but just didn’t feel like it had the power it should have. Now it feels considerably better.

[68 P.O.S.]

Originally Posted by Slammed71C10

HEI distributor from skipwhiteperformance.

Ewww, this could be your problem right there. Myself and many others here have had nothing but problems with Skip White. At the same token, there's several folks who have had no issues. Regardless, they are lucky considering what a POS Skip White is. There's a thread somewhere here outlining all of the shortcomings of these distributors. I recommend getting ahold of a real distributor and testing it out.

I'm glad the carb change helped, but I'd still look at changing dizzys.