73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: msc5195 on December 28, 2009, 06:07:16 pm
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OK here it is I bought this 1984 GMC SIERRA CLASSIC with a fresh 383 stroker build. The seller told me that the engine had 750 miles on it when I bought it. The specs on the engine were advertised as follows:
350 Small Block
2 Bolt Main
400 Crank turned 10 thousandths on Main and Rods
5.7 Rods
3.75 Stroke
Keith Black Hyper Tech Pistons
Speed Pro Rings
Lunati Cam 515 Intake 515 Exhaust
112° Lobe Separation
300 Duration at 50 thousandths
Pete Jackson Timing Gears
Stock Heads with Stronger Springs
Ersen Roller Rockers
415-425 Estimated Horsepower
480-495 Estimated Ft Lbs Torque
The engine seemed to run fine. Although I was being very gentle on it it still seemed to have lots of power. I started hearing a slight tick in under the valve cover on the driver side so a mechanic friend pulled the cover to find a very loose rocker arm on the #5 exhaust valve. We attempted to tighten but it just wouldn't tighten all the way. While turning the engine over we noticed that the valve was only opening about 40% of the others. This is when I was told that I either had a collapsed lifter or either I lost a cam Lobe. HOW SICKENING!! Well after consulting another mechanic I started tearing the engine apart. The cam was removed and not only was it found to be different then what was said at time of sale it was also missing two lobes! Yes, two lobes. As far as we can see everything else listed appears to be as described. The cam that was in the engine was the following Lunati Bracket Master II:
advertised Duration (Int/Exh): 300/300
•Duration @ .050 (Int/Exh): 246/246
•Gross Valve Lift (Int/Exh): .515/.515
•LSA/ICL: 108/104
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 2500-6500
•Includes: Cam Only
Part Number: 00012
This was a very Lopey cam which gave me problems with vacuum at lower RPMs.
Now with all of that said lets say a stock cam is a 1 and the above radical cam is a 10 then I want something around the 5 range. Something that will be user friendly in a everyday driver and get at least 10-12mpgs or better. Something that has a fairly smooth idle with a little lope. I am looking at two different Howards Cams the two that I have looked at are
OPTION #1
Chev SB 262-400
Application: Max Marine
RPM Range: 1800-6000
Lift w/1.5 Rockers: .465/.488
Adv. Duration: 294/302
Duration @ .050": 224/234
Lobe Sep. Angle: 112
OPTION # 2
Application: Max Oval
RPM Range: 1600-6200
Lift w/1.5 Rockers: .450/.450
Adv. Duration: 290/300
Duration @ .050": 224/232
Lobe Sep. Angle: 112
Any and all input and/or reccommendations will be GREATLY APPRECIATED!!!!!!
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I'd pick option 1 if you are nailing it down to two. Now why did it wipe out 2 lobes? Did you do a failure analysis?
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Not narrowing it down to just these two so please do make recommendations
Not sure why but tend to think it had alot to do with improper break in procedure. Mechanic friend said he too lost a lobe on a Lunati cam in a drag motor with less than 1000 miles and the local Machine shop mentioned that they have seen a couple of Lunati failures. I have absolutely no idea why it happened. Thought about contacting Lunati to see if they were interested in the cam and the two lifters for investigation. All other lobes and lifters look fine.
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For my 383 for MY 1984 Sierra Classic, I got this one: http://www.summitracing.com/parts/ISK-CL201264/ on the shelf. More accurately, on the window sill.
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I picked out a Summit K1103 for my 383. It's got a little bit of lope, bu the vacuum's fine and it performs very well.
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I've had nothing but good luck with the cheaper summit cams and have quite a few motors out there living on over 100k since I built em.
http://www.summitracing.com/parts/SUM-K1105/
Nice idle sound, strong vacuum still, works well with good heads.
http://www.summitracing.com/parts/SUM-K1107/
noticeable idle, ok vacuum at idle (rec. reserve can), must modify heads to perform well
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I have the Comp Cams XE268H cam and I like it. It could work well in your application too but that's just my .02.
I see you have stock heads. Do you know what kind of stock heads? Are they 'double hump' or Vortecs at least?
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With those kinds of lift you should make sure that 1) Your springs can handle it and 2) Your retainer is not bottoming out on the valve guide.
If you're running something like 882 heads these are WAAAYYY to much cam for them. You might wanna check out some better flowing heads. If a head swap is out of the question you might want to stick to something 218 @ .050 or smaller.
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UPDATE:
Keep in mind that The very first time I took this truck to my local mechanic friend for some carb work he said that the engine had the wrong harmonic balancer and flex plate installed unless it was internally balanced. I called the engine builder and he tells me that "Yes it is internally balanced as I paid 300.00 to have it done", he even give me the name of the machine shop that done the machine/balance work.
I went ahead and purchased
OPTION #1
Chev SB 262-400
Application: Max Marine
RPM Range: 1800-6000
Lift w/1.5 Rockers: .465/.488
Adv. Duration: 294/302
Duration @ .050": 224/234
Lobe Sep. Angle: 112
After installing the cam I filled the motor with Brad Penn Break in Oil and started the engine. Truck sat there and idled at 2200 RPMS for 20 mins to mate lifters to the cam. After this time we adjusted the timing and the carburetor. The truck seemed to run fine but had a slight rattle. Sounded like a diesel engine. Had a very well experienced mechanic/hot rod engine builder tell me that the rattle was due to too much clearance between the pistons and cylinder walls. I drove truck for about 100 miles and noticed that I had an oil leak at the rear of my oil pan. We put truck on the rack and this is where we discovered that it wasn't the oil pan but appeared to be the rear main seal. We pulled the pan and it all went down hill from here. Once the pan was pulled we removed the rear crank bearing to see that it was literally ate up! Remember from above it was internally balanced. Well, HE LIED!!!! Once the crank was visible I called the machine shop and gave them the engraved job number and they told that this was never balanced or paid to be balanced.
This was where I made the decision to pull her out and tear her down. All main bearings, rod bearings and cam bearings are bad. I am going tomorrow to pick up a 350 short block to get me back on the road while I rebuild the stroker to a 400hp aluminum head pump gas friendly motor.
Not only were the bearings bad but there was literally .006" clearance between the pistons and the cylinder walls, almost all of the ring gaps were aligned wrong and some of them had .008" -.010" gap in the rings. There were many more problems found but I will stop here.
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I have the Comp Cams XE268H cam and I like it. It could work well in your application too but that's just my .02.
I see you have stock heads. Do you know what kind of stock heads? Are they 'double hump' or Vortecs at least?
Heads are worked over 882's I just picked them up from the machine shop today and they have new valves and springs installed. Springs were matched to the cam that I will be running. As stated in previous post I purchased a stock 350 shortblock and will install a small cam along with these heads. This will hold me over untill I get my aluminum head 383 rebuilt.
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You used a primer to prime the engine before you started it right?
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You used a primer to prime the engine before you started it right?
Yes I used a primer with my cordless drill and pressure got up to 30psi.
It was very un believable how sorry this engine was assembled. Just for reference here are some of the things we found wrong.
2 of the transmission bell housing bolts were missing, 1 was 1/2 way out and the others were loose.
1 flex plate bolt was missing
2 header bolts, 1 from each side of the engine was missing
The first two head bolts were some what loose so we checked the rest with a torque wrench and they were only torqued to 40ft lbs
Wrong Harmonic Balancer installed
Wrong Flex Plate installed
Holley 600 Carb was missing the vacuum diaphragm for the secondaries. This was completely removed from the carb therefore the secondaries we not even opening up.
The guy I got this truck from just had the engine installed and had put 700 miles on it prior to me therefore I do not know what break in oil or procedure was used if any at all was used. It has become a game of he said she said and the engine builder claims he was never paid for the engine which he says that he is owed 4000.00.
Thats all right my daddy always told me that you live to learn and I have learned a lesson here. With this I am fully involved with the removal of this engine and installation of the temporary engine. I will be fully involved shadowing a very well experienced engine builder thru the complete 383 rebuild. I will be asking questions and taking notes. I am eager to learn and I want to know exactly what I have first hand.
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Def put that engine aside for either parts or a rainy day rebuild. So many people think they can build an engine and can't even put their shoes on correctly.
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Wow, that's terrible :( I know that whenever I see any car that's being sold with a brand new engine with 0 miles or very little miles on it I'm suspect of the engine build. If it's got 0 miles on it, how does one even know if it will run well, besides initial start-up?? I looked at a truck that supposedly had a brand new 383 (about 350 miles on it). But the guy who was selling the truck just bought it a few months prior from the guy who built the engine and the truck but he's selling it already? The motor itself was quite dirty and it almost overheated when I test drove it due to the rad being empty. Strange.......
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New Motor Still Having Problems...
I bought a 350 short block from a very reliable and reputable engine builder and machine shop. The block is a 1979 350 block bored 60over. I had my 882 heads reworked at the machine shop. Now with the engine together and running good with 1200 miles on it I broke a rocker stud on the passenger side. We were able to replace the stud without removing the head. After stud replacement I attempted to drive and it was spitting and sputtering bad. We then found out that the coil was very week/bad. I replaced Coil, Distributer Cab and Rotor. Now the #1 cylinder is running cold. If you spray the pipes with water the #1 pipe does not flash. All of the following items have been tried.
• The #1 cylinder holds 130# compression with NO leak down.
• Filled with air and the valves are sealing as there is no leak by
• Sprayed carb cleaner around intake and carb while running looking for leaks but none found
• All Lifters have been adjusted with engine running. Adjusted with ½ turn of preload.
• Replaced intake with a n Edelbrock Performer RPM Intake with Fel Pro 1205 high performance gaskets
• Valve springs checked and they are NOT broke
• Erson Roller Rockers appear to be moving the same at all of the other cylinders
• Tried running with a standard rocker arm
• Verified that push rods are NOT bent
• We removed the Holley 650 carb and swapped it with 2 separate Holley 650’s from two different trucks which made no difference at all. My 650 worked well on both of those trucks.
• Listened to the engine with a stethoscope to verify no vacuum leaks small leak was discovered and repaired at brake booster fitting.
I have two very seasoned Mechanics working on this with me. They are both very puzzled and dumb founded as to what the problem is. I guess the next step is to pull the head and investigate from there.
ANY AND ALL HELP WILL BE GREATLY APPRECIATED!!!
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I know you said you replaced most of the ignition components but you verified you have spark? Swapped plugs and wires? Before you pull the heads you can remove the springs and stroke the valves in the guides to see how they feel. You could also see if they were bent. Have you done a basic compression test? Did you inspect the rockers very closely to see that they were going down at the same rate? Is your truck cursed? LOL
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I do not like the idea of adjusting the valves with it running. I would re-adjust the valves with the engine off. If it still runs poor double check your plugs and firing order. If they look ok, do a compression test on all cylinders.
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I know you said you replaced most of the ignition components but you verified you have spark? Swapped plugs and wires? Before you pull the heads you can remove the springs and stroke the valves in the guides to see how they feel. You could also see if they were bent. Have you done a basic compression test? Did you inspect the rockers very closely to see that they were going down at the same rate? Is your truck cursed? LOL
Yes We did a compression check on this cylinder and while you are turning the motor over the gauge peakes out at about 155 to 160 psi. Stopped turning motor and gauge stopped at 130psi. Gauge held at 130psi for over 5 mins with no leakdown.
I did not replace the wires but we did swap them around to verify that the wire was not bad. Also my mechanic friend did check the Ohms on the wires.
We did not check the rockers with a dial indicator but too the naked eye they appear to be moving all the same amount.
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I do not like the idea of adjusting the valves with it running. I would re-adjust the valves with the engine off. If it still runs poor double check your plugs and firing order. If they look ok, do a compression test on all cylinders.
Valves were originally set with engine off. They were checked and readjusted with it running to verify there adjustment. I was running a set of Bosch platinum II plugs but my mechanic friend told me to replace them with a set of autolite 25's.
Yes the firing order has been checked, rechecked and verified to be correct. I will be doing a compression check on ALL cylinders tomorrow when I get off work
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Ok.....More info available. My mechanic friend hooked a vacuum gauge up to the front port of the carb port where the distributer vac advance connects. When the gauge is connected at idle it continuously flucuates from 10" down to 2" of vac. With the donor carb from a second truck the vacumm is still flucuates 10-2" In Hg thus indicating an engine problem and not a carb problem. With my current carb placed on a second test truck the vacumm holds a steady 15-16".
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Ok that is not an actual leakdown test. The Schrader valve in the compression gauge will hold the pressure. Perform an actual leakdown test. A good engine will be less than about 12%.
If you don't have or want to buy the tool you can make your own out of an old spark plug and an air compressor hose fitting. It's not very accurate but if you don have a valve that's not sealing you can air the air escape out the intake or exhaust.
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Ok that is not an actual leakdown test. The Schrader valve in the compression gauge will hold the pressure. Perform an actual leakdown test. A good engine will be less than about 12%.
If you don't have or want to buy the tool you can make your own out of an old spark plug and an air compressor hose fitting. It's not very accurate but if you don have a valve that's not sealing you can air the air escape out the intake or exhaust.
We pumped the #1 cylinder full of air with the air compressor and listened for air escaping but did not hear any. None at intake or at exhaust pipes.
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The next step I would perform is a running compression test. Using your compression gauge, take the Schrader valve out of the gauge. With the engine running, you should probably see around 75 psi or so. I would compare it to a known good cylinder. The needle will bounce around but you should be able to see an average value.
If it's low, you are not building compresion. If it's high, air is not getting out of the cylinder. Gives you a good idea how effectively the cylinder is breathing.
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Josh is correct the compression gauge will not show you leak down except for what's in the gauge. What does the vacuum gauge read when you 're driving it?
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Josh is correct the compression gauge will not show you leak down except for what's in the gauge. What does the vacuum gauge read when you 're driving it?
I am on night shift so we didnt work on it today. I did call the engine shop that built the bottom end and they are saying that it ia a geometry problem within the valve train. I am getting mixed info as to pushrod length and other concerns. I am running Erson Roller Rockers. They are true rollers. I have the std press in rocker studs. My cam is a Howards .465/488 lift cam and on their web site they reccommend two seperate pushrods. 7609 and 7940. the 7609 rods are 7.3000" and the 7940 rods are 7.2000" but I am running standard 7.8000" rods. This may be a type error on their site. Also, I have been told that it isnt good run press in studs with true roller rockers.
Anybody want to buy a good looking 1984 GMC with fresh engine? Needs slight tune up! LOL!! Seriously I am at the point of selling this demon possesed truck!
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Don't give up yet! Hang in there you'll stumble across it sooner or later.
I'm a little skeptical on the valvetrain geometry theory. I would think that it would affect all cylinders and tyically too long or short of pushrods will increase valvetip wear and side load the valve guides.
The only problem with press in studs is that they can pull out with higher lifts and spring pressures. Have you checked to see if that's the case?
On the other hand that's a pretty sharp truck...would you deliver to Michigan? :)
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Don't give up yet! Hang in there you'll stumble across it sooner or later.
I'm a little skeptical on the valvetrain geometry theory. I would think that it would affect all cylinders and tyically too long or short of pushrods will increase valvetip wear and side load the valve guides.
The only problem with press in studs is that they can pull out with higher lifts and spring pressures. Have you checked to see if that's the case?
On the other hand that's a pretty sharp truck...would you deliver to Michigan? :)
Yes we did check to verify that studs are all the same. I too agree that if it was a valvetrain issue then why is it only the #1 cylinder that is cold? Then again what caused the stud on the #4 cylinder's exhaust valve to break. And as far as delivery to Michigan.... I could always use a little road trip. LOL!
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I personally run screw in studs and guide plates on any engine I put rollers on. I never adjust them with the engine running either. Start over at zero lash on the base circle of the cam and see what it does.
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We pulled the head today and there was water in the #7 cylinder and all of teh valves especially #1 and #7 cylinders looked like CRAP! We poured mineral spirits in the head and they were all leaking around the valve seats. These heads ONLY have 1200 miles on them since they were reworked. Makes me wonder if they even done anything to the valves like they said they did. Oh well back to the machine shop they go! Gonna request that they make it right AND refund me my 265.00 to cover my labor and down time!
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Hope you finally get it straightend out!
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Took head back to machine shop and explained problem. Left it there for them to check. They called next morning to say that all is well and they couldnt find anything at all wrong. When we picked it up the owner said "You will probably put this back on and have no problems at all. you want ever know what the problem was" when he said this it lead me to believe that he did find and fix something but just isnt saying what. Well we reinstalled the head and the truck now runs perfect. Fired right up and runs very smooth. Now with that fixed I can move on to the digital dash, lowering kit, stereo system and finish the interior.
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Glad you got it fixed! Too bad that if there was a fault, no one admitted it.