88fbird

Sometimes it is a backfire, sometimes it is a pop pop pop. The new engine runs great. But when I let off the gas, I get the pops, or the backfire. I guess it is dependant on how much gas I was giving it. I know If I rest my foot on the gas, just above idle, while it is in gear, It will pop until I let off. Then everything is normal. So, what do you guys think. Here's what is different from before
350
Headers
no cat
10*adv. timing
305 inj & chip (old but working)
I think that is about it. Like I said, it runs like a dream. Just makes the noise when you let off of it. Thanks
FBird

Vader

Have you changed the cam or valve timing for any reason? Are you getting valve sealing problems, or valve sticking (can happen on a fresh build)?

Red Devil

What did you replace the cat with? What is your fuel pressure? That 10º is the base timing you set correct? Are running really rich? What type of gas are you running?

It sounds superficially that you are running a tad rich or your timing is retarded. Post up a bit more info and hopefully it'll clear it up for someone to answer.

88fbird

The cam is the stock LB9/L98 cam. I installed it when I built the engine. It has about 1500 miles on it now. I replaced the cat with a 3" piece of pipe. Yes the base timing is 10*. I'm not sure what the fuel pressure is, but I didn't change the settings from the 305. I basically just removed the intake and fuel rails and reinstalled them on the other engine. The problem is there no matter what fuel I run. 87, 89, or 91 octane. Hope this is enough.

Red Devil

Is that 10º total or base? It really sounds like your timing is retarded or you're running really rich and combustion is still happening in your exhaust (pop,pop,pop). How are you setting your timing? Are you throwing any codes?

88fbird

I unhooked the brown/white wire. Set the timing on the balancer to one notch above the -8 on the cover. Someone told me it was because of my freeflowing exhaust. I agree with you. I think it is running rich. I'm getting horrible gas mialage. I don't know if that is because of the small injectors though. I don't know. Oh yeah, I'm not throwing any codes either.
Thanks again

Red Devil

K, this'll be a fun one. Check your timing after the EST is connected again. Also check to see if you are running in closed or open loop when it happens, but I'm assuming it happenes all the time.
Popping does happen now and again, but not like you described. You may want to increase the timing a tad more, the timing tabs have been known to be off now and again, BUT, before you do that, pull your plugs and take a look.

After re-reading your original post I'm thinking you may be missing on one cylinder or have one injector leaking or some such artificial enrichment. Of the times when I've had the popping, it was always on deceleration, either rapid, or by using the engine for assistance, so I was provoking a rich condition. The only other time was for lack of tune and that would only happen when taking any load off the engine, not putting it under load.

88fbird

You are right about this being fun. To start with, I don't have a timing light. I borrowed one when I set up the engine. So, It might take me a couple days before I can check it with the EST hooked up. I don't know how to tell if I'm running in closed or open loop. I have heard of it before, but I haven't really messed with my computer stuff much. It pops most of the time when I change gears. If I let off the gass all the way! One big pop. I know what you mean about the timing tabs and balancer marks being known to move around. That is possible. I didn't change the balancer when I built the engine. I don't think it is missing any cylinders, because it runs really good. It pulls real hard, and doesn't sound wierd doing it. It may be the tuning thing though.
I cleaned the IAC. Set the TPS. And set the timing over and over until it was all right. I don't know. Sometimes it surges at idle. Not much, but it does. Well, let me know what you think.
FBird

Red Devil

Well, I have been known in the past to set my timing by ear. Never very accurate, but it should get you in the ballpark.

You may want to do it this way prior to setting the light on it to see if the tab is off. Also get the total timing if you can when you get the light. If you get a chance try a compression check as well to make sure your valves are seating correctly.

IMO fuel is getting into the exhaust so that's where I'd be concentrating.

Some other info I scabbed off some guy wearing a phallic symbol style metal can on his head. Gave off some evil vibes too. EEEEvviilll....

Red Devil

Oh yea, field service mode is what you want to look at to learn how to check the computer's mode.

88fbird

Well, I'll see what I can find out. If I ever get any extra time. Too much time at work and not enough time at home! As soon as I come up with something, I'll let you know. Thanks Devil.
FBird

88fbird

I think I had the valves set too tight. I loosened them all up 1/2 turn, and it runs alot better now. It still pops a little, but It idles and runs better. The pop now isn't anything like it used to be. I messed with the timing some, but that didn't really help much. That is why I tried the valve lash. Thanks for the help.
FBird

BOTTLEDZ28

iTrader: (9)

im having the same problem with mine. I was told at the dyno that my valvesmight be stuck open or something since the engine seemed to be shaking more then normal at 1500rpms. how did you reset your lash. engine running or not?

88fbird

I set it with the engine off. I tried to do it with it running, but it didn't work for me. It still isn't perfect, but it is alot better. I'm going to change my wires and plugs when I get a chance. I'm still using straight plug wires. I just bent them away from the headers. Hopefully it is just a bad connection. I'll see when I finally get a chance to work on it.
FBird

sellmanb

In my experiences, when there's no cat there you sometimes get a crackly sound that sounds sorta like a pop?

88fbird

On my way home tonight, It started missing some around 2200RPM. I thought it was another burnt wire, so, I changed them. The car seemed to idle better, but the drive was horrible. Around 2200-2300RPM, it just dies. When it sputters to about 2500-2600RPM it doesn't sputter, but it isn't as strong as normal. I can't mess with it right now, but tomorrow I'm going to check the plugs. That is the only place I can think of to start right now. I'm really starting to get frusterated here. I've put close to 4000 miles on this engine now and can't seem to get it right.

yugi-master

All this info is assuming you have a non roller hyd lifter cam.

with that said, this is how i have set rockers for the last 15-20 yrs with very few 2nd adjustments needed.

1st disable your coil/ign so that turning the engine over will not start the car.

after pulling the valve covers and getting setup bump the engine over (with key if you have help, or with a 5/8 socket on bottom crank pulley) until you see the number 1 intake valve close (give it a little extra to be sure its off the cam lobe, this will be the compression stroke) at that point grab the pushrod with 2 fingers and rotate it (might need a rag for grip) if it doesnt rotate back off the rocker nut until it just starts to rotate with your fingers, (if it already rotates then loosen it 1/2 turn) next ease the nut back down slowly and stop as soon the you cant rotate the pushrod (make sure your socket isnt pushing down rocker and giving you false indications) then simply give the nut 1/2 a turn clockwise (tighten) and your done with that valve ( you can go 1/2 to 1 full turn and be in spec, but i always go the 1/2 turn only and its always been enough and gives you enough preload that it wont click, big cam guys may want to push to 3/4 turn for the extra lift but i would'nt go all the way to 1 full turn just because i hate to chance going to tight).

now do the same to the number 1 exhaust valve since your on compression stroke it will already be in position to set.

continue down that bank of the engine setting each cylinder to compression stroke, setting preload, and then do same for other bank.

replace valve covers, re-enable coil/ign, start engine, have fun.


As a side note, if you rotate the engine and check each pushrod and they all rotate (even slightly) when you when you check them your for sure not too tight, and if they are not clicking then not too loose. I can get further into detail on these instructions if needed, just ask.

88fbird

I believe all 86 and up have Roller cams. I know my 88 does. Thanks anyway

yugi-master

being the factory rollers are still hydraulic i would say the process is same, but since i dont mess with rollers much i dont want to say it will work when i am unsure.. i would say plenty of members here set thier valves the way i do and could tell you if the process is the same.

RB83L69

Whatever you do, DO NOT follow this "advice". This is a sure way to a stripped crank or a bolt broken off in it. We see this "advice" given here all the time, and then usually have to counsel the victim on how to repair a damaged crank.

They make tools for that. One is a socket that slips over the crank snout, and another is a crow's-foot looking thing that bolts to the pulley bolts and accepts a square drive. You can also use a strap wrench or a chain wrench around the perimeter of the balancer. If you're going to turn the crank by hand, get one of these tools, as it will save you money in the long run.... and the long run isn't really very long.

There is no difference in valve adjustment between a roller and non-roller, or between roller rockers and ball-fulcrum rockers, or any of that. If the lifters are hydraulic, then they'll all adjust the same way.

It's a whole lot more reliable, if you don't have the understanding of what the lifter is doing as you adjust it and the experience to be able to identify it, to adjust them with the engine running. Use any of the "on the stand" methods to adjust them; but then once it's running, do it that way.

Just back each one off until it begins to clatter, and slowly re-tighten it until it just stops. Go all the way around the engine doing just exactly that, NO PRELOAD, until you get all 16 done. Then shut the engine off, and add your desired lifter preload to all 16.... ½ turn is good. Then re-install the valve covers and so on. That way, you avoid the problem where the engine runs terrible for a while after preloading each one, and you end up having to run it without valve covers for longer then you really need to, and the mess just gets bigger.

The amount of preload has nothing to do with how "big" the cam is. Above all, one does not increase it in proportion to lift. All it does, is to locate the plunger in the lifter body farther down; such that it can take up more slack as things wear out. But, it also increases the chances that if there is any slack in the valve train at high RPMs, such that spring tension on the lifters is momentarily lost at some point in their operation due to valve "toss" or whatever, the lifters can "pump up" to take up that additional slack, and then they won't allow the valves to close when they're supposed to. Most experienced people with "big" cams leave their preload set as low as possible; 1/8 to ¼ turn being typical.

All of this about the various tuning issues, seems to be just that, tuning. Tackle it one thing at a time, and move on to the next, don't get frustrated; this is normal with a new engine if it's modified from stock. Set your timing to the stock spec and then leave it alone. It isn't the problem. That is, twiddling the distributor won't solve whatever problems you have, so once it's right, leave it alone. Set the valve lash with the engine running and then leave it alone. Make sure you have a good set of plugs and wires installed, and that the wires are off of the headers and secure.

If you have the original 305 injectors, you'll never be able to get it to run right; they simply don't flow enough fuel. They're sized to feed a smaller motor, which requires less fuel. In fact, your original question about popping in the exhaust on deceleration, is probably caused by an excessively lean mixture, which is directly caused by the wrong injectors. Get the right injectors; 22 lbs/hr, or very slightly larger, but no larger than 24 lbs/hr.

Then get a more suitable chip, since as is well known, the fuel and spark curves in a 305 chip aren't right for a 350; a stock 350 chip, and a few blank PROMs and a PROM-burning setup, would be the best place to start. You're going to have driveability issues as long as that mismatched and inappropriate chip is in there.

yugi-master

well i got RB woke up, I guess the 5/8 to the crank wasnt the best advice for a novice, i too have seen them strip from that as well, but i have turned them for years with no problems that way so i mentioned it. (the tools they make for this are great but assume that you have the crank pulley off in most cases) BTW every aftermarket repair manual maker will tell you in their books to turn the crank when needed with a 5/8 on the crank bolt so it is a tried and true way to turn the engine when fully assembled and no power to the starter to bump it over. (as a side note i didnt mention in my instructions, i pull all my spark plugs to make the engine spin easier by hand, and can make a huge difference in the stress on your crank bolt)

as far as setting your rockers with the engine running, this works fine but since we are worried about breaking crank bolts, lets also worry about an oil fire (just as likely for a novice) because i have seen my share of them while rockers were adjusted engine running.

either procedure will get your rockers set proper for you which is the end goal of the process,(doing them engine running is 90% foolproof since you can hear whats happening as you go, i dont like the mess and have done them the way i listed for years with no problems) if you ask 50 mechanics about rocker settings you will prob get 15-20 different ways of setting them.

personally i set preload the same for all cam sizes, i have been told a little more preload for larger cams, and we was just told the opposite by RB, who is right? i think it goes to the tech's preference with both of us being in "spec" just more or less total preload.

thats some of the best advice your gonna get towards tuning, once you set something move on and be patient.

RB83L69

For keeping the oil mess to a minimum, take a pair of stock valve covers, and either hole-saw 8 holes in them or cut a long slot in them right above the rocker nuts, and put those on for the adjustment process.

88fbird

Well, thanks for the info. However, I don't think my valve lash setting procedures are the problem. I appreciate all the help there, but it isn't really helping. I agree with RB. I know my setup isn't ideal, but it is what I have right now. I just wanted to know if my problem was caused by the injectors/chip or something else. I'm already planning on changing them. I just want to know if I'm barking up the wrong tree or not. Thanks again,
FBird

USA_Rally

BINGO!

88fbird

I have to fix the current problem before I can keep going on the backfire thing. It just started. It idles fine, and goes fine, but when you floor it, it falls on it's face. I've checked the plugs and dist. cap. Changed the wires, and fuel filter. Once I get this problem fixed, I'll get back to the original problem. I know the injectors aren't causing this. I already have close to 4000 miles on this combo! Thanks,
FBird

357T/A

When I had my 305 in my car the engine ran fine for a long time until i floored it one day. At around 5500 rpm i heard a loud pop so I let out. From then on, after 3000rpm, I would hear this terrible popping noise. I tried everything like you did but nothing worked. My Dad's engine builder said I had wiped the cam. Sure enough, I pulled the cam and one of the exhaust lobes was almost perfectly round! Don't know if this is your problem but it is something to look into.

My suggestion would be to pull the valve covers, disconnect the fuel pump and ignition, crank the engine and watch how far your rockers move. I know it is a lot but if you are that desparate.

88fbird

It doesn't really pop more than normal after 3000RPM, it just stops going. If I'm going pretty good, it will surge, then start to pull some. It isn't as strong as normal though.