355 Poor Performance

[VileZambonie]

1 full turn of the rocker arm nut from zero lash will be just right. Yes the rockers will still be able to move. Let us know how you make out after you have them set

[78ScottsdaleK20]

Will do Vile, thanks again for your continued support. I said this before, but it really helps out when we have a site such as this willing to help other people out.

I will set the lash again this afternoon, might squeeze in a comp. test as well. This will only verify the possibility of other issue I may be having.

Now that I think of it, I can tell the difference in how the power band reacts with the way I have the lash set right now, compared to previous. Now I have very little low end and its all in the late mid to upper RPM power with a lot of fade towards the very top.

Will check back later after all is done. good thing I installed those Fel-Pro $45 rubber gaskets  under the valve covers for a quick on and off.

[78ScottsdaleK20]

So the valve lash is set. I rummaged through some of my Chevy High Performance mags and found the latest one on valve lash setting. With your advice Vile, and all the others I read on how much to turn, the rockers, rods and how it feels against the lifter, (you can feel it preload) I set it on 3/4 turn from when I felt just the slightest resistance turning the rod, once lash was at zero. This should be about the same as what you suggested with 1 full turn. I wasnt far off as the typewriter sound is very minimal. Drives like it is a little better.

I think it might have been a little off before I set it the first time. Still having metering problems with carburetion, but that is a whole seperation issue, that I will regretfully say I can fix with about $400 from Holley Unfortunately thats gonna have to wait until I return from Hawaii in March. At the same time the top end will get replaced with better heads and maybe an Intake. Should be a screamer after that!

BTW, I noticed when replacing the dist. cap, I had #1 at TDC and rotor in position for #1. When I put the cap on, I noticed the rotor tang didnt exactly line up with #1 on the cap. Could the be due to the advanced initial timing of 12 degrees? Or should the tang on the rotor match perfectly with the #1 on the cap? Maybe the dist. is off one tooth as you suggested before? I have tried numerous times during misc. wrenching, and the dist. would only drop all the way in one way. But I have heard other people having their dist. off one tooth. Also, when I pulled the plugs, #'s 1,7,4, & 6 were black and sooty=rich. The others were clean... Not sure what this could amount to, other than maybe my carburetion.

Anyways, I have said it before, but thanks again Vile. This thread is long, but maybe it can help others as well.

Mike

[Captkaos]

Depending on how advance/retarded you timing is the rotor will not be pointing at the #1 post.  If the distributor is off a tooth, or you need to move it a tooth to get more advance, you have to pull it out and turn it and drop it as far down as it will go to engage the camshaft and then have someone bump the motor over so the oil pump shaft will align to the new posistion.

What is you timing set at now?   How much vacuum are you getting at idle?  What is you idle speed set to?

[78ScottsdaleK20]

Initial timing is set at 12 BTDC. Currently I am getting approximately 14-16" hg vacuum at idle. It drops down to around 8-10" hg at part throttle, then up to 20" hg when you come off the throttle decelerating. The idle speed has always been set at 800-900 RPM's.

Each time I re-jet the carb to improve A/F, I set the idle air mixture screws with the vacuum gauge plugged into direct manifold vacuum. I have found for best vacuum it likes idle air screws 1.5-2.5 turns out. This is way too rich as I get the lack of performance, and black sooty plugs.

If I back the screws in the lean it out, then the vacuum drops to around 14". I have also noticed some oil accumulation at the rear corners of the block, looking like a slow head leak. Could be from the valve covers too though. Its pretty popular to leak at  the corners of the covers.

If the head is leaking, even a little in the lower corners, could this cause weaker vacuum readings? I doubt the head gasket is failing, I dont get the milky oil.

[78ScottsdaleK20]

Drove the truck around, and it drives like a dog. Stumbling, hesitating, no power, running really lean-then really rich...

I thought of something after reviewing the carb manual for the umpteenth time...

If the carb operates according to engine manifold, should direct manifold be applied to the front main orifice located at the center of the carb? I have the PCV line hooked up to this. This line is from the valve cover, and would it provide enough or if any at all, vacuum to properly operate the carb?

I am thinking that direct manifold vacuum should be applied to that center orifice. I feel a little silly right now, not thinking of this before, but that was how the old engine was hooked up. But it was a quad-jet with some other provisions hooked up to the carb.

If this is the case, I need a different area to put the PCV line to. It basically comes down to this...This engine is as basic as it gets, as far as there is no smog equipment, no EGR, or heat riser, or vacuum lines besides the vac advance. The crankcase ventilation off the pass side valve cover is going into the bottom of the air cleaner (open element 14"x3") and the PCV line off the drivers valve cover into the front of the carb. I know I should inclulde a pic...slow computer would take me a week to upload a photo.

Soooo...I will have to test this change out to see if there are any improvements. I stopped by the Dyno shop of the guy who referred me to the engine builder, and I balk at throwing them $300+ to have the engine tuned. I know that they will do a tremendous job, since one of the guys teaches advanced auto at the local community college and drag races, and he was my teacher at a vocational skills center.

Well, I will fiddle around with it and post any results I find.

[VileZambonie]

Your carburetor doesn't work like that. Manifold vacuum is at that port on your carb and the PCV hose should be hooked up to it. Sounds like you have it right already.

You keep saying you have low vauum, it's a dog etc. Now that your valves are properly adjusted I would check for either incorrect valve timing.(timing chain) Are you sure you have good fuel volume? (kinked fuel line, bad fuel pump etc.)

[78ScottsdaleK20]

Ok, I was trying to brainstorm ideas. It just made sense since there is oil on the PCV valve itself and a little on the outside, I thought maybe if this is a line that vacuum is being pulled from the carb, that maybe some oil is being pulled in too, richening the A/F...? Like you said before, maybe thats not how it works though.

I did have a set of valve covers on before ( a while ago) without a baffle under the cover and oil was being sucked into the carb running it rich. Of curse now it is baffled, but there is a little oil on the PCV.

I will not have time to rip of the front of the engine to verify the timing chain, since my son is in town tomorrow for two weeks, (could be a training session though  ). If it did stretch, this would lead to incorrect valve timing, right? It is a double roller. Has 15k - 20k miles on it, do they stretch this early?

Whats your opinion on the engine spec.
350 4 bolt main
Flat top Hypereuctectic pistons (supposed 9.5:1 CR)
Speed Pro RV Torquer cam .448" lift 214 duration @50 112 LSA.
Stock 882 heads with 1.94 Intake 1.60 Exhaust (supposedly 76cc's...questions the CR).
Edelbrock Performer EPS Intake
Edelbrock #1406 600 CFM carb

What kind of vacuum readings would you expect? I told the engine builder 14-16" hg was my idle vacuum, and he said "that's pretty good". I hear that number should be a little higher, more like 16-18" if not full 20" hg vacuum with this cam. It's certainly not radical, but no stock either. When I do get the full 20" of vacuum by letting of the throttle hard the A/F is perfect.

The way its all set up, the A/F is better, the more vacuum I have.

I am going to have to do a comp test and do some digging around. The next time I reply to this topic, its gonna have to read something like this...

GOT IT! I switched heads cam and carb. The truck just lost its paint job from pinning the throttle to the floor. Now Im on my way to the tire store, cuz Im gonna need to replace those too. Thanks Vile!

[VileZambonie]

Who installed the timing chain and gears? Has it ran like this since the cam was put in?

[78ScottsdaleK20]

The timing chain and gears were installed by the engine builder and have been the same since the motor had 0 miles. Ditto on the cam. It only started running like this recently.

Not sure if the winter fuel blend (10% ethanol) is a big factor. It certainly doesnt respond well in wet or damp weather.

I am really thinking the problem lies in carburetion/ignition. Reason is, it sometimes it runs where it should be, just not consistently. I can even hear and feel when its running rich, lean and when it runs good.

The point is, I am guessing that the timing chain, gears, cam, and valves must be working properly, it just seems that the Intake, Carb, and ignition are not communicating with each other properly at the correct time.

What I really need to do is perform substitute tests. Substitute in a known good carb. Check results. Substitute a known good dist. Check results. Clearly I am not doing the right things to get the corrected results. So some of it is testing equipment, and some of it is knowledge of which way to go for improvements for tuning.

I'll have to fiddle around with it some more in my spare time and check back.

[VileZambonie]

Well I would definitely say you have an ignition related problem if it runs poorly when it's wet out.

Make sure you have a good coil, the cap is good and the carbon button is good. Check the rotor, and check all of your plugs. Mist the wires and see if it runs poorly after you get them wet.

As far as fuel goes again make sure you have good fuel volume from the pump and then maybe you should rebuild the carb. Clean all of the passages with a piece of mig wire or mechanics wire. Blow shop air through all the passages.

[78ScottsdaleK20]

I have replaced the cap and plugs. The internal parts of the dist. have not been replaced or the wires (2 years old though).

Yeah I agree with you on the ignition problems. I rejetted the carb last night to 1 stage rich for the cruise mode from base stock calibration and the A/F and driveability is way better. Still lean and stumbles at off idle...but better.

Drove it in to work this morning, and it was raining and really wet out, and sometimes (most of the time) it didnt want to idle when coming to a stop.

I will replace the dist. and wires and see what results I get. Next would be replacing the fuel pump, since teh fuel pressure gauge still fluctuates.

Is it normal to see very little fuel inside the filter, and for it to perculate? I imagine if there is some kind of fuel starvation, the filter will not accumulate the correct amount including fluctuating pressure.

[dakota]

i had a truck that ran like that it was dampness  in the cap so i did a all out tuneup and it ran super

[78ScottsdaleK20]

Drove it to work this morning and ran great. It ran the way every engine should run. A/F was right where its suppose to be, and driveability was good. Still lean down at the bottom, but overall alot better than before. BTW it was a crisp cold, but dry morning.

I still may replace the wires, and definitely rebuild the carb this weekend. This may provide a good learning tool for the boy. He's into race cars, trucks and motors as is most 8 year olds.

[Lt.Del]

He's into race cars, trucks and motors as is most 8 year olds.

My 3 year old loves race cars, tractors, and of course, trucks.  He pretends his chair in the living room is his truck.