alright this is my first post as well as my first engine build.its a 400 that has been completely rebuilt . Block has been bored and honed with torque plates. decks have been squared. new cam bearings and freeze plugs. new **** forged crankshaft , GM PM rods resized , speed pro forged Light weight LW2606F coated dished pistons balanced.9.78:1 compression Crane hydraulic cam .516 .525 lift 244 252 dur at .050. 110 lobe sep.all internally balanced patriot aluminum heads. 195cc runner 2.02 1.60 valves 5 angle grind ss valves springs to match cam. cnc bowl blended port and polish. set of shaft mount aluminum 1.6:1 full roller rocker arms.+.100 long comp cams moly pushrods.hardened guideplates. speed pro moly rings. true roller timing chain. felpro gaskets.holley street dominator intake manifold.holley 670 avenger carb. MSD pro billit dist . all ARP bolts. heres the problem... cant get it timed right. i have read every post and still cant get it. ive verrified my tdc and checked the dampener its marked correctly. set it to tdc rotor facing #1. i can get it to run but with 18 deg innital and then it wont idle good and lotsa spark rattle under load. i can only get 10 -12 inc of vacuum but was told with this cam thats ok. i can get it to idle but when i put it in gear it drops about 400 rpm and cycles two or three times then almost dies diesels a little jumps back to life and cycles again. if i go below 16 deg innital it dies. it is a vac adv dist but i am adjusting with all vacuums pluged. when i connect the vac adv to full manifold vac it jumps to around 38 innital and major spark rattle any ideas would help im pretty much stumped and being new to engine builds dosnt help oh and i live out in the middle of nowhere with no help in site.....
throw an hei or points dizzy in. Get the carb set right, on the edge may be right next to way above sea level. it could be lean, you may have the valves too tight, etc. sounds like an aweful big cam, you have a stall converter, right?
You've got more carb work to do. Set the timing based on TOTAL advance - rev the engine to 3,000 or so (where you're certain all the timing advance is in) and set it at 34 degrees. Let it return to idle, and check where the initial timing is. It should be around 12 or so. Once your timing is set correctly, snug it up and leave it alone. It will be hard...you will be tempted to mess with it....but DON'T. Now, on to the carb. You will have to fine-tune both your idle and idle mixture screws to get the idle you're after. In your case, with that cam, it should be about 800-850 rpm. Set the idle rpm screw on the linkage so it'll idle there, and then focus on the idle mixture screws. Start by setting all four idle mixture screws about a half-turn out. This should be really close. If the engine refuses to idle smoothly when the timing is set correctly and the carb idle rpm screw is set correctly, you've got other problems. I've tuned a couple fresh engines in my day, and if I understand your writings, it sure sounds like you've got a vacuum leak to me. Spray some starting fluid around the intake and carb base while the engine is running. If the rpm level suddenly goes up, you've found your vacuum leak. If it's not a vacuum leak, I'd also be su****ious of your valve lash being too tight. This can play havoc with idle too. Double-check to make sure you've got the right lash on all of your rockers. Otherwise, the engine should idle nicely with the total timing set at 34 degrees and the idle rpm screw set to 800-850 rpm. Good Luck with it. ~Scotch~
it is an hei, 3000 stall converter, carb claims to be adjusted out of the box. adjusted the valves to 0 lash then 1/2 turn
for sea level in the dyno room on a properly timed motor, yes. In your driveway, with humidity, at al***ude, not so much.
i have tried the starting fluid spray no noticible leaks.. will idle at 1000 but put it in gear and it dropps to 600 and rough. so i can try adjusting the total to 34. is that with the vac hooked up or dosent matter. im gonna try that now....
tried the 34 at all in that helped. have to keep the vac line hooked up or she shuts down. still when i put it in gear it goes from a smooth idle at about 1000 to about 400 and shuts down if i idle it up it has to be at about a 1700- 1800 curb to not die when i put it in gear it has a 3000 stall conv. any ideas? why would putting it in gear change the idle? its not trying to pull the vehicle or anything i dont have to be on the brakes. truck dosent surge....
"total" advance that scotch described should be checked with vacuum advance disconnected. what kind of gas is in it? premium I hope?
Squirrel is right, as usual. It drops rpm when you put it in gear because it's being loaded. This is typical to a degree, but you're experiencing too much rpm drop. It means the engine isn't tuned correctly...seeing 100-150 rpm drop when you put it in gear could be considered 'normal' . You should have about 850 rpm idle speed in neutral/park and about 750 rpm idle speed in gear with that camshaft and the rest of your engine setup. Disconnect the vacuum line (and plug it) while you're tuning. The vacuum advance shouldn't matter yet, and if you can't get it to be smooth and right without the vacuum advance hooked up, it's not right. The only times I've seen an engine do what yours is doing is when it's had a vacuum leak. Are all the ports in the intake and at the base of the carb plugged? It's tough to do this online, but we'll keep trying... ~Scotch~
all ports on carb andintake are plugged 1 for modulator 1 for vac adv 1 for pcv all on carb 1 for power brakes on manifold. i just re adj all valves when not running. re checked tdc reset timing and still does it!!! could it be a vac leak on the valley side of the intake where the spray wont reach? still only getting 10-12 inc of vacuum at the full manifold port on carb. anyone in south central va or northern nc? i think u are right scotch, this is too hard online and im a f@#$in newbie to this...
oh and yes i run premium 93. is pulling the intake and regasket and retorque my next logical step? i have the af mix good i think. i was told the blocks will be ice cold when your mix is correct
running a msd box as well? if yes, on the leads from the distributor to the box, what color goes to what? and just for ****s and grins, swap them. Buzzard and I went round and round trying to get his 327 to run- and the entire time, it was because the leads to the dizzy were installed wrong from the factory. they aren't made in the usa anymore, and quality control has taken a poop. - my buddy that ultimately made the discovery said it was the 3rd one he saw that way this summer alone!
couldnt get it to run with my msd 6al i think the box is bad, it was a donation to the cause... so i am currently just running with the msd hei pro billit dizzy only. would this be a factor?
I am leaning towards yes- is it the one with the "built in box" inside it? quick-n-dirty way to check it- somewhere in the directions is how to convert it to a standard issue hei, without the "most impressive" msd guts. it would cost you about 13 bucks for a module- which you could promptly throw in the glove box in a ziplock with the jumper wires for the "just in case" factor if it proved to not be the problem.
Are you doing all the timing with the msd box connected? I thought I read about the msd boxes messing up what the timing lead reads off the plug wire. If so disconnect the box all together does that change it? Guys correct me if Im wrong on this. ok just read your last post, nevermind
the dizzy i have already has the stock module. to connect the box u just remove the module and connect an adaptor to the box. i am running it now with the supplied gm hei module and no box. has some new msd hei coil that is supposed to be real strong. is 10 vacuum way low with this cam and the 1.6:1 rollers? next step is to pull the intake (again) and reseal.
10 doesn't seem all that low to me, simply due to cam size and duration. I still can't help but wonder if it isn't related to the ignition.- but Brush pointed out some really valid points by of timing, also- that is how we do it here, and everything always seems to work out peachy. what carb? oh yeah...with the timing light on, (this is gonna sound so dumb) does the flash from your light get a weird, erratic flash every once in a while?
Ive Done The Tdc Thing Like 5 Times Each Time Works Out The Same. Install Dizzy, Ingaging Oil Pump Shaft.rotor Points Twords#1 Install Cap With Rotor Pionting To Tower For #1 Wire Check Firing Order On Cap And Trace Each Wir To Approp. Cylinder. At Tdc I Adj Valve Lash On Recomended Valves. Rotate To Tdc#6 And Adj Remainder Of Valve Lash. All To 0 Lash +1/2 Turn. Disconect And Plug Vac Lines At Carb. Fire It Up. Can Get It To 18 Innital No Lower Or It Wont Run Just Dies Out Unless Idle Is 2000. Can Set Total To 36 All In But When I Let Off It Dies Can Get A Surgie Idle At 1200 But Put It In Gear And It Drops To 500-600 And Dies ..holley 670 Street Avenger Carb And Holley Dominator Intake. No Wierd Flash Of The Timing Light.
If you pull the intake manifold again reset the valves, looking at the lifters to ***ure they are on the heals of the cam lobes. Go to the Comp Cams web site and read the section about checking cam timing by measuring the difference in height between the intake and exhaust lifter on #1 cylinder. I don't remember the procedure, but it is easy to find on their web site. This will ***ure the cam is timed correctly. If the head manufacturer recommends an intake gasket use it. Set the intake manifold on the engine without the intake gaskets and ***ure the gap between the port surfaces of the manifold and heads, if any, isn't excessive, because of block decking. Make sure the power valve(s) doesn't open at 10 in. of vacuum. Someone else on the HAMB will have to tell you what # power valve is good with 10# of vacuum cuz I don't remember. If I read your valve adjusting procedure correct, then I'm confused. It seems you are adjusting all the valves having the engine rotated to only two positions. There are a variety of procedures; someone here can offer a simple one, since I don't really recommend the way I do it.
I adjust my valves differently. Take two complete revolutions but ever 90 degrees another cylinder comes to TDC. That's when you adjust the vavles for that cylinder. Sounded like you're at #1 TDC and adjusting the valves on 4 of the 8 cylinders, rotating to #6 TDC and adjusting all of the rest? Or I read that wrong?
I still think it's a vacuum leak - Maybe under the intake ports or something, but it sounds like every vacuum leak I've ever encountered. If it can't maintain an idle with the timing set right, it's either a vacuum leak or the valves not closing. The ignition thing has potential too - but the mis-wired MSD's I've dealt with either wouldn't fire once the key was off the 'start' position or would run on after the key was off. Similar, but not identical to this problem. The cam/crank timing would have to be WAY off to act this way. Like "built the motor while drunk and on a meth binge" off. Not likely, but possible. I'd remove, inspect, and re-seal the intake first and foremost. It's relatively easy and this needs to be absolutely sealed before any other questions get answered. I'm glad you're not just throwing parts at it. You've got good parts, there's something else wrong here. Keep us informed. I'm still curious. ~Scotch~
this is how i was told to do it.1. Get #1 piston to compression TDC, Cam gear at 12 o'clock crank gear at 12 o'clock. 2. Adjust the intake valves on cylinders 1, 2, 5, & 7 by loosening the rocker nut until play is in the pushrod then just take the up and down play in the pushrod and tighten the rocker nut 360 degrees 3. Adjust the exhaust valves on 1, 3, 4, & 8 in the same manner. 4. Rotate crank 360 degrees to get cylinder #6 to compression TDC, Cam gear at 6 o'clock and crank gear at 12 o'clock. 5. Adjust the intake valves on 3, 4, 6, & 8 in mentioned manner 6. Adjust the exhaust valves on 2, 5, 6, & 7 All is done on a cool engine at room temperature is this not correct? i will remove the intake and try the procedure watching the lifters.not today but tomorrow. gotta get some other work done ive been putting off.the power valve is on the dizzy? i have also tried to adj valves with it running with limited success there i backed off till i could hear clatter tightened till clatter was gone then went 1/2 turn tighter locked poly locks. so when i adj valves i have to rotate the engine for each set of valves?
scotch, im not running the msd box at this time. the less i run the more i can nail it down. the pro billit hei dizzy i got should easily supply enough fire on its own. im really stumped it seems like ive done the same trouble shooting with the same results and no progress. everything seems to be right.except everythingseems to be wrong...go figure
so pulled the intake. some signs of possible leaking. re adjusted the valve lash by #1tdc adj #1 valves rotate 90 deg adj #8 valve rotate 45 and so on following the firing order. watching the lifters so they are all the way down.thank god my dampiner is marked! driving to the auto parts store(45 min away) to get fel pro 1206 intake which is what the head manu. recomends and what i used previously. new carb gasket and dist gasket. gonna pull all fitings from intake and reseal.no big gaps bet intake and head visable what gaping is there is less than .005 cant see the valley side but from the end there appears no gap there eather. any tips on intake install? i know not to use the end gasket to use rtv.what about thread sealer on the intake bolts? some dead out others go thru
Just a thought...Is the crank vibration dampner new or used? If it's used, it might have twisted a few degrees on the hub, such that the #1 TDC marker on the perimeter no longer indicates actual TDC and your initial timing would be way off. Don't ask me how I learned this...
i double checked tdc with a brazing rod in #1 spark plug hole till it stopped moving up marked dampiner rotated till piston started down made a mark. split the two marks to come up with true tdc. all new parts anyways everything.....
When you find top dead center on number one cylinder ,, the rotor in the dist. should be pointing at number six cylinder. common mistake
Nope. This is ***uming he's got it at #1 TDC firing. When the dots are lined up on the cam & crank sprockets,number 6 is at TDC firing. Another common mistake.
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