New engine....spark knock, heat, and heads...... - Off-Road Forums & Discussion Groups
GM Standard IFS Trucks & SUV's All discussion of full sized IFS Trucks, SUV's to include Suburban

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 06-20-2001, 07:29 AM
**DONOTDELETE**
Guest
 
Posts: n/a
New engine....spark knock, heat, and heads......

I finally got my rebuilt 350 in my truck, after over a year of piecing together the engine. It is a '76 .060 over 4-bolt main w/ federal mogul 17cc dish hypertectic pistons (HP423 I think), reconditioned rods, .010 under crank (ballanced), 252 High Energy bumpstick from comp cams, double roller timing set, stock oil pump, Brand new Vortec heads, performer intake, Edelbrock 1406 performer carb (600 cfm), stock non-computer controled HEI distribuitor, 8.8mm plug wires, manifolds w/2" duels, and bosh platnium plugs (suposed to fit a '98 1500 350).
My first problem was heat, the temp gauge would keep rising and falling like the thermostat was bad. I replaced the thermostat but no change. Finially it would take off heating up real fast so i would shut it off. After a few seconds or a minuite or so I could run it again for a while. It runs a constant 160 without a thermostat at all. A mechanic friend said it sounded like the lower radiator hose is collapsing to him. I havent checked it yet.
I also have a bad spark knock problem. I have the timing advanced so much it is real slow cranking over, im running 93 octane and i still hear knocking and pinging under a load. The carb seems to be running a little rich ( can smell strong exhaust if behind the truck and if you step on the gas at idle black puffs out). I havent ever messed with the carb out of the box.
And finially, just for discussion, how do you all think vortecs stack up against 882 heads, The ports on the 882's on the old 350 looked a good bit bigger then the vortecs, i have heard a lot of noise made about the vortecs though. Thanks for any help.
Mike


Good Guys Wear Bow-Ties
[img]/wwwthreads_images/icons/wink.gif[/img]
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 06-20-2001, 06:28 PM
Veteran
 
Join Date: Jan 2000
Location: Sweden
Posts: 930
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: New engine....spark knock, heat, and heads......

Canīt help you with the pinging but if I were you Iīd back off the timing a little bit. Ping kills engines ! A rebuilt engine is gonna run hotter while itīs breaking in. It should however not be as unstable as youīre describing it, so Iīm clueless (whatīs the odds on that?[img]/wwwthreads_images/icons/laugh.gif[/img])

As for the 882 heads port size, while certainly important, isnīt gonna outflow Vortecs without an extremly good port job. The shape is whatīs most important, especially the shape directly under the valve, if you know what I mean? [img]/wwwthreads_images/icons/crazy.gif[/img]. Many ppl, including myself[img]/wwwthreads_images/icons/crazy.gif[/img], who tries to port their own heads concentrate on areas easy to reach and polish them to mirror-like fininsh. This might increase exhaustflow with 1% at itīs very best. Wasted hours[img]/wwwthreads_images/icons/laugh.gif[/img]

Andreas

<font color=blue>Member of the secret sbc400 club</font color=blue>
Andreas is offline  
post #3 of (permalink) Old 06-20-2001, 10:08 PM
Keyboard Implanted
 
dave's Avatar
 
Join Date: Sep 1999
Location: Vancouver, Washingon
Posts: 2,346
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: New engine....spark knock, heat, and heads......

I'm wondering if you set the timing with the vacuum hose connected to the distributor vacuum advance canister. A 76 pickup would need the distributor vacuum advance hose removed from the vacuum advance canister when setting the timing. I'm wondering if you have the vacuum hose for the distributor vacuum advance canister connected to "ported" vacuum. Ported vacuum will be about 2 - 3 Hg when an engine is at idle. A ported vacuum source will quickly rise to about 14 Hg when an engine at idle has the throttle opened very quickly.

I'm wondering if you have a vacuum leak around the intake manifold. If the engine gets an extra source of air, the fuel air mixture will be lean. A lean fuel air mixture will cause an engine to overheat and have a knock.

I've used Vortec heads on a SBC 400 last summer. The engine did not have a problem with using 89 octane unleaded gas. It's been using 87 octane unleaded gas most of the time. I think the compression ratio of your engine is about 9.1:1. I would think you could use 89 octane gas, and maybe 87 octane gas depending on the emission blend used your area.

I've learned that the Vortec intake manifold is real tricky to seal, compared to the older style intake manifold. Who the heck designed only 4 bolts on each side of the intake manifold anyway? Who the heck designed the special intake manifold bolts that need only 11 Ft. Lbs of torque? I like the factory Vortec intake manifold gaskets.

My first two thoughts, maybe the timing is wrong, or maybe there is a vacuum leak.
dave
PS The 882's are not my favorite SBC head. Yes, there ok for a mild performance engine. Just remember to limit the exhaust gas crossover on 882's. The 882's have two exhaust valves worth of exhaust gas going into the exhaust gas crossover, which is way to much heat[img]/wwwthreads_images/icons/frown.gif[/img].

dave is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 06-20-2001, 11:29 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: New engine....spark knock, heat, and heads......

Dave, Andres, thanks for the replies.
Dave, I did have the vaccuum hose unhooked and pluged. Im not positive, but I think the hose is comming off the manifold vaccuum port of the carb but I am not positive, which would be better?
If I only have one leak (the manifold) I will consider myself lucky...after all it is a sbc lol. I used Fel-pro intake gaskets so a leak would be possiable. If it was leaking, would there be a strong vaccuum near it, could i take a medicine dropper and water and test for one?
It really has me stumped, I figured the compression ratio to be 9.11:1, I was not sure if I was doing it right but I guess I am since we came up with the same number. (cylinder volume/(piston dish+head volume))=compression ratio.
About the intake bolts, I used regular old grade 5 bolts from the hardware store. I was told 15-18 ft.*lbs. torque....there could be a problem. I do like the convience of the vertical bolts, but I am with you that only 4 per side does not make much sense.
Final thoughts about the possiable lean condition, I thought about that since I am having the spark knock problem and with a slightly bigger than stock cam. However, I had somebody follow me through town yesterday and they said you could smell exhaust really strong. Also if you touch the gas when it is idleing you will see a touch of black smoke puff out the pipes. Those things led me to assume I may actually have a rich condition.
Thanks for the help!!!!
Mike


Good Guys Wear Bow-Ties
[img]/wwwthreads_images/icons/wink.gif[/img]
post #5 of (permalink) Old 06-21-2001, 12:13 AM
Keyboard Implanted
 
dave's Avatar
 
Join Date: Sep 1999
Location: Vancouver, Washingon
Posts: 2,346
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: New engine....spark knock, heat, and heads......

With the Vortec SBC 400 I did last summer I used all factory GM parts, except the Edelbrock Performer intake. It will cost extra money to use GM parts, but I did not want to take a chance. The customer I was installing the engine for wanted a nice job and got to pay extra. I use a 3/8" bead of Ultra Copper RTV on the ends of the intake manifold instead of the rubber gaskets. I recommend using a vacuum gauge to figure out what vacuum source your distributor is connected to. "Ported" vacuum is the only vacuum source for a distributor vacuum advance canister. I set the Vortec SBC 400 for 6 degrees of advance, at 800 RPM's.

I also like to use quadrajet carburetors instead of Holley carburetors.
dave

dave is offline  
post #6 of (permalink) Old 06-21-2001, 12:32 AM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: New engine....spark knock, heat, and heads......

Had an old Diesel benz do that Temp crap to me. Turned out it was trapped air in the cooling system. It had a bleed screw atop the thermostat housing. I know you dont have that but i thought I would mention it.


"Bubba Tub" 1977 K-10 350,Th350,Np203 D60/14ff 4.56's Detroit Rear. 7" lift, 39.5/16.5 Swamper TSL's.
post #7 of (permalink) Old 06-21-2001, 11:11 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: New engine....spark knock, heat, and heads......

I changed to What I am assuming is ported vaccuum. One port you can feel vaccuum at idle, the other you cant. I retarted the timing a bit so it will start easier and replaced the vaccuum line that ran from the carb to the distribuitor since one end was hardned up and was not very snug at all on the distribuitor canastier. Ill give it a run in the morning and post back the results. Thanks again for the help!
Mike

Good Guys Wear Bow-Ties
[img]/wwwthreads_images/icons/wink.gif[/img]
post #8 of (permalink) Old 06-24-2001, 09:40 AM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: New engine....spark knock, heat, and heads......

Dave,
I have the spark knock under control. Have you ever heard of timing being advanced too far cause spark knock? I always thought the more advance the better for controling spark knock, but I retarded it a bit and that fixed it (for supreme and plus gas anyway). After I put the timing light on it and saw the mark was appearing off the tag, about halfway between the tag and the top of the ballancer, I tried retarding it out of desperation. I gained more low end power too. I am assuming that I was tinking right in the first place: the further up the ballancer, the more advance, the farther down, the less. Turn the distribuitor clockwise to retard the timing, counter clockwise to advance.
I am going to wait until I have more miles on the engine before I fine tune it, I have not treated it as easy as I would have liked when trying to figure out the spark knock thing. I didnt run it hard, just not absolutly pampered.
I am trying to get a 4 core radiator from a friend. After I do I am going to put new hoses on and flush out the cooling system and see what happens from there.
Dave, one more question while I have your attention, I poped the oil pan, intake and one head off of my old 350. It is a '76 model with 150K+ miles. Much to my suprise the rods had been stamped with numbers like they had been out before. The rod and main bearings all had markings like any other origional bearing I had ever seen and the bores are standard size. I was wondering if GM ever produced engines with numbers stamped on the rods? The thrust bearing must have been completely shot in the engine. The crand was rubbing the back of the main caps, they are shinny, and the rods on each journel have a disturbing ammount of front to back movement.
Thanks for the help!
Mike


Good Guys Wear Bow-Ties
[img]/wwwthreads_images/icons/wink.gif[/img]
post #9 of (permalink) Old 06-24-2001, 11:18 PM
Keyboard Implanted
 
dave's Avatar
 
Join Date: Sep 1999
Location: Vancouver, Washingon
Posts: 2,346
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: New engine....spark knock, heat, and heads......

Mike,
Thanks for posting back the results of your timing adjustments. You are correct, turning the distributor counter-clockwise will advance the timing. Timing can affect both engine performance and engine knock.

The Small Block Chevy does not have it's connecting rods numbered by the factory. I think you are correct in thinking the old 350 has been worked on in the past. It's not very common for the 350 to have thrust bearing failures, but they do happen. Usually a 350 with manual transmissions will have more thrust bearing failures than a 350 with an automatic transmission.

I'm glad I could help out,
dave

dave is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome