'84 K10 Engine Build Questions

[Marshy]

Update time.

My truck is going to the muffler shop tomorow to get some exhaust work!

I registered it today, got my 10 day temp inspection and my plates. I was going to take it down to the shop today but ran out of time.

I've been driving it around on my property a bit moving some firewood bothering the neighbors up and down the road to get things borken in. I decided to changed my oil last night for the first time, decided to put in Mobile Super Synthetic (5w30). THEN, I went and bought a MSD Street Fire HEI and read the instructions and found out that the distributor gear has a break-in period and it says not to use synthetic!
So I drained the synthetic today and put some conventional 10W30 in it like the instructions call for. Tomorrow the distrubutor is going in and Im taking it down to the shop for the exhaust to go on.

I just read this thread about another memeber having issues with their Street Fire HEI. Hopefully I do not have similar issues. I wish I had a nice timing light to check the timing curve... Anyways, I'll post pics of the exhaust and maybe a video clip when I get a chance to tune it some. Right now with open headers it brakes up hard mid range RPM. I need to get the exhaust on so I can make this a drivable truck again.

http://67-72chevytrucks.com/vboard/s...=496678&page=3

[Marshy]

HEI was installed today. I set initial timing at 8* BTDC and used the C setting on the limiter plate for the vacuum advance. This restricts vaccum advance to 8-11 degrees. The mechanical advance has 22 degrees and the instructions say its all in at 4000 RPM. The engine felt noticeably better with everything set up like this but I didn't waste any time trying to tune an engine with open headers. The shop I took it to is going to check the timing curve and make an adjustment (if needed) after the exhaust goes on. The guy was nice and super excited to see my truck. Idk if its because he was seeing dollar signes or because he liked my truck... I told him I wanted shash cut tips and to exit them behind the tires at an angle. I can't wait to hear those 40 series delta flow mufflers!

[storm9c1]

Ha, that was my old thread from years ago. I don't know what was wrong with me back then but I had a heck of a time getting the timing figured out on that engine. I wanted to do it old school with no digital timing light but then gave up and bought a digital one. Glad I did. I've used it a million times since then to map out timing curves. That whole project was just a run of bad luck. The good news is that once I got the weights, springs, and canister changed, everything fell into place and the truck still runs good today with that setup, several years later. So I must have done something right. I wouldn't worry too much about your Street Fire. Mine is still working. It was just a bear to tune in stock form. Who knows if they have changed the design since then. But I bet it's still made in China. Either way, your shop should be able to work out the tuning if necessary. My tuning was quite different than most who throw those in lighter cars.

[Marshy]

Originally Posted by storm9c1

Ha, that was my old thread from years ago. I don't know what was wrong with me back then but I had a heck of a time getting the timing figured out on that engine. I wanted to do it old school with no digital timing light but then gave up and bought a digital one. Glad I did. I've used it a million times since then to map out timing curves. That whole project was just a run of bad luck. The good news is that once I got the weights, springs, and canister changed, everything fell into place and the truck still runs good today with that setup, several years later. So I must have done something right. I wouldn't worry too much about your Street Fire. Mine is still working. It was just a bear to tune in stock form. Who knows if they have changed the design since then. But I bet it's still made in China. Either way, your shop should be able to work out the tuning if necessary. My tuning was quite different than most who throw those in lighter cars.

Well I found it helpful, thanks. At first I wasnt sure if I should even install the limiter plate ( I didnt know anything about them a few days ago). I decided to set it at C for 8-11 degrees. That should be good for total timing. I feel like the mechanical is set high at 4000 RPM per the instructions but hopefully the shop can confirm that RPM without any vac assist before/as they map the curve. I did end up using ported vac but might switch it to manifold to help bring in the vac advance sooner since that would help this heavy truck. I would really like to buy a nice light but I would only use it once on this truck so its not a good investment at this point. Not when Im looking at about $4-500 for the exhaust and probably nearly a grand for new tires.

[fleetsidelarry]

Originally Posted by Marshy

... I did end up using ported vac but might switch it to manifold to help bring in the vac advance sooner since that would help this heavy truck. ...

I'm not sure what you're expecting here, but I don't see how the weight of the vehicle matters regarding manifold vrs ported.

by switching to manifold you will have vacuum advance at idle as opposed to ported where you won't have any (or not much). small blocks like more advance at idle so this makes for a better idle by adding the vacuum advance to the initial. but once you come off idle the two sources work the same. under load, both will reduce the amount of vacuum advance because the amount of vacuum drops under load.

if the HEI has 22 in it, remember that Vortecs are supposed to like 32 total, then you're pretty close already at 8 initial (the vacuum advance doesn't factor into this)

everybody NEEDS a timing light

[storm9c1]

Originally Posted by fleetsidelarry

if the HEI has 22 in it, remember that Vortecs are supposed to like 32 total, then you're pretty close already at 8 initial (the vacuum advance doesn't factor into this)

everybody NEEDS a timing light

I definitely agree. But 32 total is only a target. Depending on many other factors (compression, cam, vehicle weight), you may be able to run more or less. I could only run max 28 degrees on my heavy truck and stay out of the ping zone on 87 gas. I could push it to 30 with 92 octane, but that makes for an expensive fillup. And with the kind of traveling I was doing, who knows what quality gas I was getting on the road. So I compromised.

I also agree that SBCs like using manifold vacuum. And I recommend using that port. But it's OK to experiment and learn the difference.

No matter which port you use, the vacuum advance does factor into cruising, since it comes in under higher vacuum. I was getting some pinging at cruising and small grades, so I had to use both the limit plate and an adjustable can to keep the vacuum advance happy. This stuff can be fun!

[fleetsidelarry]

Originally Posted by storm9c1

.....No matter which port you use, the vacuum advance does factor into cruising, since it comes in under higher vacuum.

absolutely

Originally Posted by storm9c1

This stuff can be fun!

I agree! often frustrating, but when you do your own tuning it's more rewarding (well, 99.9% of the time ) and you know what you have AND (most importantly, for me) why you have it

[Marshy]

OK fellas, got my truck back with the exhaust on and can hear the valve train chattering. Looks like I'll need to set the valve lash.

[Marshy]

Larry and Tom, you were both right about the timing. I've got it at 8* initial and the vac assist is hooked to manifold. I'm looking at buying a tuning kit for this 1405 carb and getting the truck on a chassis dyno. I mapped my ignition curve in 500rpm increments and have another post going about timing. One thing to note was that when I had the vac hooked to the carb port the engine would diesel when I shut it off. That's because the throttle plate had to be open a little to idle and it was on the power circuit and didn't want to shut off. Once I got the vac on the manifold I was able to close down the throttle adjustment and now when I shut if off it acts right. Thanks for the words of wisdom.

[Marshy]

[fleetsidelarry]

that is real nice, Marshy, good job!

[Marshy]

Thank you. The only thing I have left is to put the wheel centers on and the tailgate handle. I need hardware in both cases.

[Captainfab]

I agree....very nice

[Marshy]

Little update...

I just ordered some new roller lifters. Using the old lifters was a gamble and I lost. I have 2 or 3 that wont pump up and when I set the lash they are 3 or 4 turns in farther than the others. I can constantly hear one or two lifters making noise. If things work the way I want it I will have them done by Monday (3 day weekend!).

Right now I'm contemplating removing the head gaskets and putting in a thinner one while I'm at it. If I'm ever going to do it now is the time. I just feel like the engine could benefit from the little extra compression.

[Marshy]

Got things tore down last night and found 4 lifter that failed. All part pieces accounted for but one shim under the lifter top was chewed up a little. I'll fish a magnet around the galley for any particles and give it a wipe down. I picked up a set of FEL Pro 1094 head gaskets with 0.015" compression thickness. They are ready to go on, all ready to unbolt the heada and swap them in.

[Marshy]

Finished a couple of small things yesterday evening and fired the truck up. Man it runs so much smoother now, wow! No lifter noise at all, the way it should be. While I had the headers off I noticed a pin hole in my passenger header at the collector and one in the #5 down tube. I'll have to take care of those soon. I also took the time to wire wheel and paint my headers.


I used VHT FLAME PROOF header paint. I thought they looked great and then when I started the truck this happened (WTF?).


Any guesses what happened? It burnt off like it was a layer of plastic. I believe I screwed it up by using the wrong primer... see anything wrong in this pic?

[Marshy]

Okay, one issue I was having yesterday evening was getting this engine to idle properly. I'm going to check for air leaks today but for a moment assume there arnt any. I can't get it to idle under 1200 RPM with the vacuum advance hooked up to manifold vac. I had the idle set screw backed way off so that was not a factor. The only way I could get the idle down was to lean out the idle screws. Maybe my approach is wrong, should the vacuum advance be hooked up while I set the idle mix screws? I don't understand why it wasn't to idle to high. I ended up putting the vac advance on ported vacuum last night on my shake down drive to get it home.

[Marshy]

So I took the truck on a 200+ mile round trip with a full size car trailer in tow. The engine ran great! Those smooth lifters and added compression made a big difference. It pulled a 3100 lb car and trailer (duel axle) with ease. I bumped the initial timing to 12* and left the vac advance on ported vacuum. Only had some spark knock once when I was reaching a steep hill and had my foot deep into the pedal. I'm going to get a vac gauge to properly set the idle mix then see about getting a calibration kit for the carb because its on the rich side mid throttle. The engine runs a little warmer than before but was rock stable the whole time, even pulling fully loaded. The best part is the exhaust sound IMO, I'm just in love with the way it sounds. To me, it's exactly what that truck should sound like and having tall gears (essentially a 3 speed) means I get to stretch in second some.

[storm9c1]

Maybe my approach is wrong, should the vacuum advance be hooked up while I set the idle mix screws?

Timing is the only thing that should be set with the vac advanced unhooked. Carb tuning should be done with it hooked up.

You should be fine with manifold vacuum. I'd give it another shot. If you can't get it to idle down, I would suspect a vacuum leak. If you are sure you don't have a leak, then you can set your initial timing back down to 8 or 10 degrees and see if that lowers your idle enough. Also check idle in gear and tell us what it is. Also are you sure that the engine was fully warmed up and off the choke fast-idle cam? I didn't go back and check what kind of choke you have, but make sure it's fully disengaged.

Glad to hear it's running good. Looks good too. Keep up the good work. There's always a few tweaks that are needed along the way...

[tjsblazer]

Just curious, what are you using for exhaust?

[Marshy]

Originally Posted by tjsblazer

Just curious, what are you using for exhaust?

1-5/8" long tube headers with 3" collectors, then reduced to 2-1/2" pipe straight into flow master super 40's which turnout in from of the rear wheel with 3" slash cut tips, no cross over pipe.

http://s600.photobucket.com/user/WMa...22740.mp4.html

The truck actually sounds smoother than it did in this video. Putting in the new roller lifters made a big difference in performance and idle quality. To the average person it likely sounds unchanged though.

[Marshy]

Originally Posted by storm9c1

Timing is the only thing that should be set with the vac advanced unhooked. Carb tuning should be done with it hooked up.

You should be fine with manifold vacuum. I'd give it another shot. If you can't get it to idle down, I would suspect a vacuum leak. If you are sure you don't have a leak, then you can set your initial timing back down to 8 or 10 degrees and see if that lowers your idle enough. Also check idle in gear and tell us what it is. Also are you sure that the engine was fully warmed up and off the choke fast-idle cam? I didn't go back and check what kind of choke you have, but make sure it's fully disengaged.

Glad to hear it's running good. Looks good too. Keep up the good work. There's always a few tweaks that are needed along the way...

Yes, engine was fully warmed up and I have a manual choke (it was off) and it's a standard trans so can't check in gear. :-)
I sprayed some MAF cleaner around the base and it seems there's a small air leak at the throttle shaft, otherwise no leaks aside from that. I'm still planning to take a dive in the carb and verify float height and check the throttle plate distances. I ran out of time last week and just put it back on after the lifters and head gasket change. The piston rings must be seating in because the motor feels a little stronger every time I drive it.