I just got done putting my motor together and tried to start it the most I can get is a backfire my buddy told me to get the motor to top dead center pull the cap and see where the rotor is pointing I did this and I had it exactly 180 degrees off I flipped it to where it should be and still I'm getting nothing he told me that if the cam gear on the disributor is off even one tooth it could mess **** up... I'm lost any tips or hints would be helpful.... thanks

 

With cyl 1 at TDC. Position the distributor on the cam gear so the rotor is pointing to cyl 1. Then before you start it, turn the distributor cap to the right about 30-40 degrees (you'll have to spin the oil pump drive with a long screw driver to line it up), try starting while slowly moving the cap to the left (advancing timing). Once it's running use a timing light and set it to factory spec. Is your distributor mech or electronic advance?

 

But it has to be TDC on compression stroke ; not exh stroke

https://www.thirdgen.org/forums/post...921-post3.html

 

compression stroke.

 

Yeah my buddy actually came over and we repeated the process at least 15 times... my only guess would be the timing chain being installed wrong.... oh well I'm done with it for the night I just dropped my fiberglass cowl hood on my fender and messed both the hood and fender up so I'm content with being done with the car for a few days

 

i also had that question, if the timing chain is off by 1 tooth, would it hurt?

 

If the dots line up, it can't be installed wrong. If the alignment was off, you'd know it for sure.

 

mine are but i dont exactly, like 1 tooth off

 

I flipped the distributor a few more times this morning still nothing do you guys think it would be worth my time to take the front of the motor apart and check the chain? Cause from my understanding correct me if I'm wrong I could installed it on the wrong stroke?

 

This is the first motor I built so I'm not ruling anything out I just need some input before I start ripping this thing back apart.. it seems like somethings completely backwards when I crank the motor gas shoots upb out of the carb

 

You shouldnt need to tear it all apart, just the chain cover. now when you look it over the dot on the crank gear should be at 12 oclock and the cam gear should be at 12 also. some people will say dot to dot but in most cases that is for number 6 firing posistion. thats just my 2 cents.

 

Really? For Cyl 1 At TDC on compression stroke I thought the dots always "touched"? I could have sworn that's how I did my last one... if it was TDC on the exhaust stroke I could see it happen...

 

Dot-to-dot is #6 firing, #1 exhaust.
Both dots on top is #1 firing, #6 exhaust.

 

Apeiron bet me to it. When you do dot to dot then install the dizzy while it may look to be at #1 it is really at #3. Remember you are turning the cam to line up the marks. The crank is already at #1 tdc when you have the dot at 12oclock on the crank gear.

 

Is that true for big blocks also?

 

 

Hey guys I don't know if anyone remembers me or my problems but I let the iroc sit for. Good 8 months and yesterday I pulled her out of storage and dove back in I ripped the front of the motor apart and the timing chain was all jacked up that thing might as well have been put in by stevie wonder it was off that bad so I fixed that put her all back together and she fired right up and boy did she sound nice ran her for about 10 minutes everything looked and sounded good so I buttoned it all up.pulled the timing gun out started the car and right as I started to set the timing I heard some not so good noises so I shut her down pulled the valve covers. I overtightened a lifter and snapped a pushrod s to be safe I checked em all 6 were bent and 2 broke. This was the first time I built a motor so I was expecting something to happen. Now the odd part is. All the bent and snapped pushrods were on the exhaust side and the intake side was still perfectly fine. What would cause this?

 

You installed the timing set wrong.

 

If it was wrong again the car wouldn't run though right? I mean it fires right up now I just put brand new pushrods in so please explain before I go try to start this thing and fry another set. comp pushrods aren't exactly cheap

 

The other alternative is you didn't check your valvetrain clearance and you have too much lift for your heads.

 

Did you install a larger than stock cam, and did you check for retainer to guide boss clearance, and spring bind clearance? Dual pattern cams usually have more lift on the exhaust side. Or as mentioned above, if the timing set is still installed a bit off you may have pistons kissing valves.

Apeiron - beat me to it!

 

the cam is a bigger cam than stock by a lot but im leaning towards it being a timing issue because this exact set up was run on my friends 350 in his iroc for about 300 miles and he rolled the car.. it ran perfect in his car the only part re used on my motor was the stock crank and pistons but thats the same as his too. so my guess is the timing is off im gonna tear it down again and see whats goin on

 

The fact that it ran on a different engine means nothing about whether it will run on yours. Evidence now suggests it won't.

What cam did you use?

 

im goin with it being the timing set i used because there are 3 notches where it can be installed on the lower gear so im gonna put a standard timing set on that can only be installed one way and see what i get... i mean there is literally 0 difference between my motor and the one it came off besides the timing set i think i have it on wrong

 

And besides a whole stack of manufacturing tolerances.

 

Same heads? And valvetrain in its entirity?

 

Yes it literally came off his motor and on to mine. We played with it some today and the car is running awesome I haven't driven it yet we put in new pushrods and a new timing set. We ran it for about half an hour with a few revs to 3k or so and maybe one to 5k the only problem is we bent one pushrod not really bad but bad enough for me to wonder how it would work under load and revving higher than 5k for more than a few seconds. My guess is I would run into more problems so I'm taking the cam out instead of tearing it all apart and overhauling the motor again I'm gonna run a smaller cam and see what happens. awesome part is my buddy has 3 350's and a 327 with with all different combos the cam I have in is a magnum 292 I really wanted it to work but I'm not going to jump through hoops to make it work. The next cam were gonna try is the comp xe274 and see what happens... any cam suggestions?

 

Yeah, wouldn't run it anymore till you find out. Pushrods don't just bend, something is hitting something. Instead of just throwing random new cams at it - really should measure things and find out what the max lift is you can run. Then fix it for your current cam, or select a new fitting within that.

The magnum 292 would be a pretty big cam. I haven't had any first hand experience with big cams, but if your valve timing is wrong - you will have a smaller margin for error with piston-valve contact due to the increased duration.

Are you sure you installed the timing set right? Crank at No 1 TDC exactly. To install 'straight up', crank sprocket goes on with the keyway that allows the dot or '0' (not the '-' or '+') to point directly up. Cam get rotated so that cam sprocket dot point straight down, so the dots are directly next to each other. Using your 2 pairs of hands, wrestle the chain on and finagle the sprockets so its all on, without losing the relationship. This sets the motor to no 6 tdc compression stroke. Rotate it exactly one full turn to get back to no 1 firing, with both timing dots facing straight up. You should, I imagine, be able to feel any piston clearance issues at this point.

Another thought - old chain? Stretched too far?

On a personal note - how come everybody's pushrods seem to bend first and act as fuses for the rest of the valvetrain, except mine! I have lost 2 cams, various lifters, 2 rocker studs, a spring damper and couple of retainers due to minor interferences, unnoticed by me and the PO - but the bloody pushrods are like the rock of Gibraltar!

 

What we think is in the higher rpm's the valves are jus barely kissing the pistons the timing set is brand new and the second set we used lol.. from everything we've done and looked into that's our conclusion so were going to run a slightly smaller cam and hope it solves the problem if it doesn't I'm pulling the motor and were gonna go through it top to bottom and I'm gonna get the 292 to work.trust me your not the only one running through parts I feel blessed that th pushrods gave way first that's the entire reason I'm going through all this hassle I had a completely stock 350 with a slightly bigger cam just to give it a little rumble well I was out beating the **** ou of my car and wiped out three lobes on the cam and four lifters. But now I got the motor gone through bored.30 just rebuilt the bottom end stock. I have pro topline heads set up to take .550 of lift with an edelbrock intake and holley carb plus now I have brand new hooker headers into true dual with spintech drag mufflers a stage 2 clutch and a few other little uprgrades here and there. It should make a fun weekend car if I can ever get it working again.lol

 

You like buying parts so much you'd rather thange them at random than spend a few minutes checking and measuring to find out what's actually wrong first?

 

Yep measure measure measure! When I bought my car, the top end was basically a bunch of mis-matched old and dissimilar parts thrown together - amongst many many other problems caused by previous owners just doing random stuff. It eventually ran fine, but a couple of binds under 10 thou was enough to destroy parts in the long term.

The good thing was, this forced me to look in-depth at how all this works, educate myself, and get lots of tools. I have been keeping old bangers running all my driving life, but nothing's given me problems like this motor! You've got an opportunity here to make this a good learning experience.

 

Ok I'm gonna try to explain the situation I'm broke I can't afford to dig back into it and start paying for any work to make the current set up work. The cam is free and will take an hour or so to swap instead of pulling the top end apart and measuring everything when I already have a good idea of what is happening in there ya know? I mean if it doesn't work then I'm gonna have to start measuring and figuring this problem out. Trust me I would love to go the right route spend tons of money and have an awesome motor but I'm just ur average joe with no money tryin to make ends meet. That and my car is dead in my buddies shop and he doesn't want it sitting there much longer.

 

You don't have to disassemble to check cleance... You do have to disassemble to replace the cam...

 

I've taken the cam out so many time its easy now. How do I measure clearances with the motor still together I'm lost I'm sure I've said somewhere this is the first motor I built.

 

Um... how are you pulling the cam out without pulling the intake and valvetrain? Is there a trick I haven't learned yet? How'd you get the lifters and springs etc to levitate? If a cam swap takes you an hour, I'd say thats your problem right there!

I'm also an 'average joe', and cant spend tons of money buying endless new parts in the vague hope it might randomly work out somehow. I don't have an 'awesome' motor, but it's solid. I need my car to go to work, and when I started with my car I'd never encountered a SBC before. Education is free. A heads-on spring compressor, spring mic, vernier caliper, and crank socket are way cheaper than buying endless cams, pushrods, gaskets, etc etc. Guess you got more money than me!

Measure clearances: Get a piston to tdc or close, retain the valves using the rope method. Pop a the spring off, hold the retainer and locks in place with one hand. With the other, stick the vernier between the bottom of the retainer and the top of the valve stem seal/boss. There's your max lift, minus about 50 thou for safety

Get your spring mic, install it under the retainer, and measure the installed height. For stock type springs should be 1.7". If it's low, you'll need machine work or just some offset valve locks. If high, just shim it. So no spring bind, provided you're using the right springs for the cam.

That takes care of the two major sources of valvetrain binding. These descriptions are simplistic however... it is difficult to work out how to do all this the first time but its like anything - just gotta learn it once. Now I've measured stuff so many times it's easy!

As for piston-valve contact - if the timing set is installed ok, I shouldn't think there would be a problem unless your block was decked, and heads super-shaved or something. If you turned it by hand, I would imagine you could feel the contact. Might have to pull a head to check for witness marks.

In the end, the parts don't really care if you reckon they should work together and don't want to spend $$. If something hits it hits, and you gotta find it. Or buy shares in Comp's pushrod division.