350/383 swapout

[76-C10Strokin]

I am brand new here and joined the site b-cuz it seems that people here are willing to share Knowledge and seem to be understanding. There also seem to be alot of Texas members. just a few details: I have a 1976 Chevy c10 L vin with 400 tranny, that I bought in September I think. Drove pretty well till the begining of november. Shifted a little late somtimes. It had a 350, the block, a piston, crank, were bad, I found a REALLY nice 383 stroker motor w/roller rockers, forged rotating assembly, blueprinted and balanced, but i cant confirm that b-cuz the machine shop is no longer doing business. new EVERYTHING Edelbrock carb and intake included, just used my old Accessories, Dizzy and wires, New NGK plugs, gaskets were new of course, and dropped her in everything seemed great, started up nice, we ran it a few minutes but we went back and readjusted the valves and then ran the cam at 15-25000 rpm for 20+ mins. FIRST Drive at first did not engage gears properly, I added more (lots more) tranny fluid, that seemed to help that, but it lacks power and shifts late, Heard what sounded like clicks in the tranny at first, (maybe from me readjusting the linkage?) but then sounded like backfiring around 30-40mph or in park at 3-4,000 rpms. the balancer does not have numbers on it only degree marks in one small section and a few other marks around it......After a bit of research... Ive got an idea how to try to mark it to check the timing just too cold the last couple days. other things im going to do, maybe bring the idle back down around where it was at first (750possibly before, 900now) going to put clamps on some of the vac lines that dont seem snug enough namely the vac advance on the HEI Dizzy. Current vac hookup, brake booster to the rear of the carb, PCV to front, port above throttle plate plugged, below throttle plate goes to the trans modulator. No A/C just Alt. and Power Steering. I hope this is not too confusing, Im sure Ive left somthing out, and i need to get this going very quick,and i been at it since mid-late november, so ne1 that can help thanks i will try to update often and check up very often. muthazbutta@hotmail.com 512-623-0979 HELP!!!!!!!! LOVE THE SITE and the fact that you guys have a squarebody club, I just joined. Tried to edit for Clarity. please, any questions just ask, i will try to answer.

[Slonaker]

Welcome to the board from a San Antonio member!

That was really hard to read, and I'm still trying to figure out what your questions are, but my TH350 shifted late and hard when there was no vacuum to the modulator. I thing mine gets its vacuum from the back side of the intake manifold. It may be that it gets vacuum at the wrong time where you have it hooked to the carb, or it might have popped loose and be getting no vacuum at all.

Just a thought...

Slonaker

[76-C10Strokin]

Yeah sorry I always have too many thoughts fighting to get out at once, and I was trying to give as much info as possible. Part of that post was taken from the other forum that i joined. I always forget something too so bear with me friends. my issues are the lack of power that this 383 should have, and the late shifting. this baby should melt my tires and on the <10 mile ride home, all highway, I had a really hard time getting it to 50 mph, partly cause i was so worried about all the popping at around 3-4k rpm. I really dont want to screw up the break-in, and hope I havent screwed thatup already. Thanks in advance for any insight. EDIT: What else would be helpful? Video pictures? and how do I post them here? and also is this the best place for this post? Thanks again, a Big Noob.

[SCOTI]

You need to identify or verify vacuum issues. The popping sound is concerning. If you are not sure how, I would immediately take it to a shop & have the valve settings & timing verified as correct.

Non optimal timing will cause it to run like a dog....
Valves not adjusted correctly will cause it to run like a dog or make a bunch of noise (rattling under the v.cover when loose).

[OJOE]

welcome to the board from montgomery al. now to thre problem. i don't think we are going to help you real easy, just in my small mind i am thinking your valves are way out of adjustment or you have rocker arms off or bent push rods. any of these would screw up your vacum. sorry for the little help. joe

[cableguy0]

first things first. A fresh engine should NEVER be ran at all until break in is complete. you need to stay above 2k rpm for 20 minutes. running for just a couple minutes at idle is enough to wipe a cam out. The first 20 minutes are the most critical time for a fresh cam. First thing to do is slow down. take things one at a time. you need to start back at the beginning and work forward. rushing will get you nowhere and will only cause severe wallet pains.

[76-C10Strokin]

Cableguy and OJOE thanks for the input, Everyone please forgive me if my post-speak is not up to par of if i confuse you. What I did today, wrapped a wire at the starter that had melted and grounded out on the header. Discovered and tried to remedy an exhaust leak at the headers, its a bit better but still hear it through a length of tubing held to my ear, more at the middle two and front of pass side, maybe a little at front of the driver side. what i did, loosen the collectors and retighten on the pass side. made a little bit of difference. I also lowered the Idle from around 1k to about 600. when I throttle it i dont hear the backfire through the carb any more, maybe just a little "burping" out the rear.felt a bit more power on a run around the block. still wont burn the tires or shift at about 20mph (Where i think it should) doesnt shift into P or R as hard as it has the last two days ive tried to work on it. checked the vac at the dizzy modulator before and after i changed the idle 13 before and jumpy between 13-15 after.
now for the responses: when we first started the motor we did only run for a few minutes, at 2000 rpm, then heard some rattlin so we killed it and came back a few days later and readjusted the valves. then ran 20+ mins varying the rpm from 16k-25k, only then did i try to drive. I dont think any rods are bent being that is is a completely new engine but then i could be wrong, dont think any valves are loose cause i would think that i would hear them, dont think theyre too tight but again could be wrong, pretty sure we adjusted them correctly but my money is made at the poolside not in an engine bay.
All help and comments are greatly appreciated, also please check out this link if you are any where in TEXAS and Esp if you are near austin

Texas Meet Thread Lets get it going.
http://67-72chevytrucks.com/vboard/s...d.php?t=380166
that link may not work sorry I'll try again

[78BO]

Ok, well when it comes to my 383 Blueprint engines state that you CANNOT use the vacuum advance because it very easy to create TOO much advancement creating detonation. With out a properly marked harmonic balancer it will be hard to set the initial timing and you'll need to figure out what total timing you need. Marshal engines (they build the blueprint engines) states that you should never go over 13* initial and 32 total at 4k rpms. The back firing that you are hearing might be it pre-igniting. One of my problems were that the engine idol speed is too high for the torque converter. The factory converter is set at around 800 rpms, but the engine idles best in gear at 850-900rmps. But at that speed it starts to lock up and that makes the truck shutter. When I lower the idle it goes away. But at that low of speed it isn't creating enough vacuum. When step on the gas at a stop it bogs down. Once it hits 18-2000k rpms watch out! So to fix it, I need a new stall Marshal says 2800. You sound like you are in the same boat. You also sound like you need a new non-vacuum advance distributor or you need to re-curve it. I'm going with a new one, just seems easier. You obviously are having timing issues. If you don't get the engine timed right and get it to idling right you are going to have a hard time figuring out anything.

That's just my two cents, I'll know for sure once I replace everything. lol

[76-C10Strokin]

I started worrying about the torque conv issue last night when i started reading some of your threads. didnt know about the vac advance dist. issue tho. oh boy there is 200+ bucks i may not have let alone the torque conv issue, dropping it all again, oh boy what fun. ssssssshhhhhhhhh********* great i may never get back to work hahahahahhahahah boooohhoooohoooo

[78BO]

For one, I don't know if it really matters, but the vacuum advance isn't hooked up right. It should be hooked up to the front of the carb. But I also see another line hooked up to where the v/a should be. If you have the transmission hooked up to the front of the carb you might not be getting enough vacuum. Cap off the v/a on the distributor and make sure the vacuum line from the transmission is hooked to the intake. The big vacuum line on the back of the carb should be for the break booster. That vacuum line might cure the shifting problem. Set your initial timing around 12* On that carb, set the accelorator pump to the middle setting. Then go give it a try. Don't go over 4k rmps for the first 1500 miles and very your rpms. Don't let it sit at one speed for too long. As for the break in. The rpms should have been over 2500 but under 3k for about 25-30 mins. If you didn't do that Don't drive it too long. Did you use oil additive for did you put Rotella in? Blueprint uses Rotella and states to change it at 500 miles. Then again at 3k. If you follow these you should be good to go on the break in.

[78BO]

For one, I don't know if it really matters, but the vacuum advance isn't hooked up right. It should be hooked up to the front of the carb. But I also see another line hooked up to where the v/a should be. If you have the transmission hooked up to the front of the carb you might not be getting enough vacuum. Cap off the v/a on the distributor and make sure the vacuum line from the transmission is hooked to the intake. The big vacuum line on the back of the carb should be for the break booster. That vacuum line might cure the shifting problem. Set your initial timing around 12* On that carb, set the accelorator pump to the middle setting. Then go give it a try. Don't go over 4k rmps for the first 1500 miles and very your rpms. Don't let it sit at one speed for too long. As for the break in. The rpms should have been over 2500 but under 3k for about 25-30 mins. If you didn't do that Don't drive it too long. Did you use oil additive for did you put Rotella in? Blueprint uses Rotella and states to change it at 500 miles. Then again at 3k. If you follow these you should be good to go on the break in.

[76-C10Strokin]

I think originally we had the vac advance hooked to the port above the throttle plate and then moved it back there, dont know how many things we tried, or at what point that pic was. took her to aamco this morn (was very hard for me to do) and should have it back in less than an hour from now. they will be fixing the vac routing issues and setting the timing. cant wait to see how she drives now, guy says it will be a night/day difference.

[78BO]

Originally Posted by 76-C10Strokin

I think originally we had the vac advance hooked to the port above the throttle plate and then moved it back there, dont know how many things we tried, or at what point that pic was. took her to aamco this morn (was very hard for me to do) and should have it back in less than an hour from now. they will be fixing the vac routing issues and setting the timing. cant wait to see how she drives now, guy says it will be a night/day difference.

Hope it is. Just my silly thinking, in that picture where you have the v/a hooked to would pull way too much vacuum for it. Hopefully they fix it.

[Slonaker]

Did the guys at Aamco get things sorted out? I won't claim to know much about how to sort out your problems, but I agree with 78BO about your vacuum sources.

The vacuum line for my transmission is hooked up where your distributor vacuum advance is in the pic above. That should fix your shifting problem since you didn't have the problem before the engine swap.

Your distributor vacuum advance should be hooked to the carb, but I don't know where. I would go look at mine, but I have a Quadrajet rather than an Edelbrock 1407. My understanding of how that stuff works is very limited. With the carb, you'll have vacuum at different times depending on your throttle position. You have to have the distributor hooked up to the right place so that your engine gets the right amount of timing at the right time. The vaccum advance being hooked to the port on the intake might very well be part of the problem. Hopefully someone else who knows more about this issue can help you out if the Aamco guys didn't get it straightened out.

If that stuff doesn't fix your problems, you may have to look at the engine itself. If the person who put it together didn't know what he was doing, it could lead to problems as well. Something could be damaged, as someone else mentioned (bent pushrods, a bad lobe on the cam) or the cam could have been installed wrong.

Good luck. Hopefully this bump will get you new input from someone who knows more than me.

Slonaker