1995 K1500 header install

[Fast355]

I was running 0-70 in 8 seconds in nearly 100*F weather in a 5800# truck with a 5.6L engine and 1 3/4" primary headers. It got out of its own way pretty quickly.

http://www.youtube.com/watch?v=lELdtvmah2A






I also towed with it, plenty of low-midrange grunt over stock.


The Express has Thorley Tri-ys and gained noticeably as well even shifting at only 4,900-5,000 rpm in Tow/Haul mode.




Doug Thorley even used dual 3" pipes to mate the headers to the factory Express van exhausts. I reduced from 3" to 2.75" to 2.5" at the cats and used a dual in/single out muffler.



The van has a huge gearing disadvantage compared to the 5spd in the Titan yet it still pulled down a respectable ~8.xs 0-60 and 11 sec 0-70. For a 6,200 lbs beast with only a 3.73 gear and a 4L80E it is not short on torque by any means. The 4L80Es tall 2.48 1st and 1.48 2nd gear ratios are like having a 3.00 rear gear with a 4L60E in first and a 3.23 in 2nd and the 60 lbs stock 13" torque converter also doesn't help the off the line jump very well either, despite having a dual stator and 2,200 rpm stall speed. When you go WOT from idle it kinda lags, hesitates for a second, then takes off like a proded bull!

http://www.youtube.com/watch?v=-6DZhPN7VHQ

Finally the 99 Burb....0-80 mph in 13 seconds on an uphill onramp in 90*F weather.

http://www.youtube.com/watch?v=LYdyu501Z4Y

Like I said I think I have a little first hand experience at making these engines run pretty strongly.

I also had both 1 1/2" long tubes and 1 5/8" tri-ys on the same engine in my G20, the larger tri-ys blew the smaller headers away from off-idle through redline.



When I put the healthy TPI enging into the G20 I was glad I had the extra headroom to make more power.

[old truck guy]

Im no expert but I've done a ridiculous amount of research in choosing headers for my build. The general consensus on primary size is where you want your power, smaller = low and mid range while larger = more top end. Port alignment and collector size/design are every bit as important as primary size. Just because you saw gains with larger primaries doesn't mean it is because they were larger, its the complete package that makes a difference.

Superchevy has an article on a header test using a smeding 383 and 4 different size headers. The 1 1/2" primary, while intended to just establish a base line for the test, supported well over 400 hp and ended providing the best overall power curve below 5000 rpm. The larger sizes didn't pull ahead until 4500+ and at the sacrifice of low end. Headers by Ed states that there is no point in having a primary size larger than your exhaust valve so if you have a typical svc with 1.5" valves, no need. Unless you're building a high rpm motor, bigger is not better.

If your talking vortec heads, the biggest problem is port alignment. Unlike standard sbc heads, vortec's have a raised port (approx 60% of the port is above the bolt centerline) so smaller primary headers tend to cover the top of the port. Bigger primaries while uncovering the whole port present sealing problems at the bottom of the flange.

I myself went with a set of flowtec 11508 flt headers (less than $150). Basically the same headers in superchevy's test, 1 1/2 primary and 2 1/2 collector. Replaced the wimpy 1/4" flanges with a set of 3/8" cnc cut flanges that I bought on ebay from Hells Gate Hotrods. He sells a set of sbc for $45 and made me a custom set for the vortec port alighnment for less than $100. I went a step further and bought a set of Meg's weld on merge collectors from cone engineering for $125. After finish assembly I sent them to a place called pro kote Indy in Indianapolis and had them professionally cleaned and ceramic coated for $220. Just got them back and they look awesome. For less than $600 I got ceramic coated, perfect fit headers with perfect port alignment and plenty of sealing surface.

Assembling motor now. Let you know how the do when I get it running.

[BLG355]

Assembling motor now. Let you know how the do when I get it running.

The cam in your signature is one of the ones I considered using. It actually came down to the that one and the one I am using now which has much less lift. I'd like to hear how it works for you.

BLG

[old truck guy]

The cam in your signature is one of the ones I considered using. It actually came down to the that one and the one I am using now witch has much less lift. I'd like to hear how it works for you.

BLG

Yeah I was concerned about lift too. Spring upgrade in my vortec's is good to about .550 which is right where the advertised lift for my cam is but it's spec'd with 1.6 rockers. I went with 1.52 which brings my total lift down to about .522. Your, s sounds like a nice build. A bit more than mine. Is that isky enough cam?

[BLG355]

I thought about going with a larger cam, but I do planning on doing some towing and I wanted a big increase over stock without any drivability issues. To keep things simple to pass the PA emissions test, I decided to go with the Edelbrock TBI intake so the EGR was physically bolted in the proper place. So that lead me to look at the Dart S/S heads, which stop increasing flow rate at .500" lift. And the dart heads have a very nice combustion chamber, plus it is 72cc. I wanted to keep a good quench distance of .039 and with flat tops with only 2 valve reliefs, I am right at 8.0 dynamic compression with this cam. So, for this motor, this cam has incredible torque, plus just enough to pull 5500rpm shift points. I upgraded to the 454 throttle body because I was down to 88kpa at 5200rpm, now the motor is over 95kpa at 5500+ rpm(not that I need it there). If I was going with different heads I probably would have went for the comp cam, but I do love Isky grinds. I use them in race motors with excellent results.

BLG

[Roadknee]

The cam in your signature is one of the ones I considered using. It actually came down to the that one and the one I am using now witch has much less lift. I'd like to hear how it works for you.

The Isky with 1.6 rockers and the comp with 1.52 rockers will have pretty similar valve lift curves. The Isky comes off the seat a little quicker, but the Comp will have a few more degrees duration above 0.200" tappet lift. The Comp with a slightly wider LSA and more exhaust duration might pull slightly harder above 5,000 rpm. I think their characteristics will be so close, it would not be worth the effort or expense to change from one to the other.

If a person were to spend about an hour swapping relevant parameters from BLG's bin to Old Truck Guy's, I think it would run and drive pretty good on the first try.

[Fast355]

I worked on a 97 C1500 5.7 truck Thursday evening. Installed BBK shorty headers into 2.5" Jegs offroad head pipes and matching catback exhaust. Then swapped on a set of Jegs 1.6:1 full roller rockers. A Volant cold air intake and March underdrive pulleys. The truck already had a built 4L60E and 3.90 gears with a Grizzly locker. Runs around on heavy 20" wheels. Truck also already has a larger 454 radiator and 34" Tahoe Efans. I had previously swapped an 0411 into this truck and HP Tuned it. Was seeing about 200 gms/sec airflow. Now seeing 260 gms/sec and the truck is a completely different truck power wise. Next up is a hotter cam.

[old truck guy]

If a person were to spend about an hour swapping relevant parameters from BLG's bin to Old Truck Guy's, I think it would run and drive pretty good on the first try.

Putting the heads on as we speak. Hopefully have the motor back in by the end of the weekend. Dave W has created my start up bin already and is sending it to me. Hopefully its close on start-up :-). Be interesting to compare it to BLG's.

[old truck guy]

Im no expert but I've done a ridiculous amount of research in choosing headers for my build. The general consensus on primary size is where you want your power, smaller = low and mid range while larger = more top end. Port alignment and collector size/design are every bit as important as primary size. Just because you saw gains with larger primaries doesn't mean it is because they were larger, its the complete package that makes a difference.

Superchevy has an article on a header test using a smeding 383 and 4 different size headers. The 1 1/2" primary, while intended to just establish a base line for the test, supported well over 400 hp and ended providing the best overall power curve below 5000 rpm. The larger sizes didn't pull ahead until 4500+ and at the sacrifice of low end. Headers by Ed states that there is no point in having a primary size larger than your exhaust valve so if you have a typical svc with 1.5" valves, no need. Unless you're building a high rpm motor, bigger is not better.

If your talking vortec heads, the biggest problem is port alignment. Unlike standard sbc heads, vortec's have a raised port (approx 60% of the port is above the bolt centerline) so smaller primary headers tend to cover the top of the port. Bigger primaries while uncovering the whole port present sealing problems at the bottom of the flange.

I myself went with a set of flowtec 11508 flt headers (less than $150). Basically the same headers in superchevy's test, 1 1/2 primary and 2 1/2 collector. Replaced the wimpy 1/4" flanges with a set of 3/8" cnc cut flanges that I bought on ebay from Hells Gate Hotrods. He sells a set of sbc for $45 and made me a custom set for the vortec port alighnment for less than $100. I went a step further and bought a set of Meg's weld on merge collectors from cone engineering for $125. After finish assembly I sent them to a place called pro kote Indy in Indianapolis and had them professionally cleaned and ceramic coated for $220. Just got them back and they look awesome. For less than $600 I got ceramic coated, perfect fit headers with perfect port alignment and plenty of sealing surface.

Assembling motor now. Let you know how the do when I get it running.

[Roadknee]

Like I said I think I have a little first hand experience at making these engines run pretty strongly.

I don't think you'll find anyone who will disagree with that. I've personally been very impressed with your results for about a decade now. I simply don't agree with your opinion that 1-1/2" headers are holding back my stock LO5. FWIW, I don't think it would gain or lose anything measurable with a decent set of 1-5/8" headers either.

[Fast355]

I don't think you'll find anyone who will disagree with that. I've personally been very impressed with your results for about a decade now. I simply don't agree with your opinion that 1-1/2" headers are holding back my stock LO5. FWIW, I don't think it would gain or lose anything measurable with a decent set of 1-5/8" headers either.

Its possible your stock cam has a choke hold on the engine and it just can't move any more air through the valves but honestly I have never not seen gains with headers.

[Roadknee]

Its possible your stock cam has a choke hold on the engine and it just can't move any more air through the valves but honestly I have never not seen gains with headers.

I might have found an explanation. Since I began tuning this engine a year and a half ago I've fought knock retard. Looking back at my latest log it was pulling timing at WOT and the max the engine ever saw was about 13 degrees. This is with 92 octane fuel. I decided to take a risk and disable knock retard. I kept the spark table pretty conservative with about 5 degrees at 400 rpm and 20 degrees at 4,000 rpm WOT. Went for another run and my 0-60 times increased... due to violent wheelspin off the line. So I compared 40-60 mph times and the increased timing dropped a full 0.5 second. Yes, knock counts were climbing the whole time but at this point I don't care. If it blows up I'll need to get off my behind and put the new engine together.

Earlier in the week I took a trip to the west side of the state over two mountain passes and honestly the truck has never run this good since I bought it in 1999. More power everywhere and ultra smooth. I had the laptop connected for the trip over and even driving conservatively it picked up 11,000 knock counts in the first 150 miles. They really start to climb at about 2/3 to 3/4 throttle and 2,500 rpm, but the engine is only seeing 20-22 degrees of timing. As I stated earlier, at this point I'm done worrying about it.

[ony]

roadknee, I got a 4.3 v6 that is worn out and it developes a lot of knock counts and I hate it.i put a set of fine wire bosch plugs in it and it help the knock counts.stock engine almost stock timming table the ac delco plugs would look blue as if thay were glowing at 70mph cruise on the ground side of the plug. the old 288 don't retard timming with the bin I have. it might be the bosch plugs are a little shorter than the ac plugs, it didn't cure my knocks but it helped using them fine wired plugs.

[tayto]

I might have found an explanation. Since I began tuning this engine a year and a half ago I've fought knock retard. Looking back at my latest log it was pulling timing at WOT and the max the engine ever saw was about 13 degrees. This is with 92 octane fuel. I decided to take a risk and disable knock retard. I kept the spark table pretty conservative with about 5 degrees at 400 rpm and 20 degrees at 4,000 rpm WOT. Went for another run and my 0-60 times increased... due to violent wheelspin off the line. So I compared 40-60 mph times and the increased timing dropped a full 0.5 second. Yes, knock counts were climbing the whole time but at this point I don't care. If it blows up I'll need to get off my behind and put the new engine together.

Earlier in the week I took a trip to the west side of the state over two mountain passes and honestly the truck has never run this good since I bought it in 1999. More power everywhere and ultra smooth. I had the laptop connected for the trip over and even driving conservatively it picked up 11,000 knock counts in the first 150 miles. They really start to climb at about 2/3 to 3/4 throttle and 2,500 rpm, but the engine is only seeing 20-22 degrees of timing. As I stated earlier, at this point I'm done worrying about it.

go with a hotter plug. i had a similar problem my knock counts would be maxed out within a 30 minute drive. went from a r44lts to a r42lts plug (ac delco) and knock counts dropped to the teens. i like ac delco plugs only. apparently proper torque on the knock sensor is crucial as well. I think it's 13 ft.lbs. you can also add a brass elbow (90 or 45 degree) to "lessen" or TUNE the knock signal.