88 coupe

Same pressures on both banks show the cam is correct for that lifter angle.

At this point, finding the cause of the higher pressure in #1 is top priority. Normal(?) pressure in #2 shows the "stroke" and "clock" on the crank, is not the cause.

Pull the left head, and compare #1 and #3 cylinders, as far as piston to deck (at 9 and 3 o'clock) and "dish" (diameters and depths).

I am sure that it would make captjim happy.

There are several ways to work around a poor piston choice. Find the actual source first.

Norm

captjim

Originally Posted by ijasond
Should I stick the stock cam back in and see how it runs? ........
I am sure that it would make captjim happy.

ijasond being satisfied with his vehicle's performance would make me happy. IMO if his Cr is low, coupled with high gears in a heavy car, a cam closer to stock will accomplish that better than the cam he now has in it. Could be that the Cr is higher and that there are other issues, we will find out when he begins his inspection.

dan2286

Could the higher compression in one cylinder be caused by something messed up in the valve train like a bent push rod, worn cam lobe, or something else that would not cause the valve to open all the way? I am sure it really doesn't matter any more since the engine has other problems, but it might be something to look for when taking the engine apart.

ijasond

Could excess fuel in the #1 cylinder have caused it to have a higher compression reading? It has obviously run far richer than the other 7 cylinders based on the fact that it was black and the others were not, so I thought that maybe fuel was being dumped in there during the test??

When I pull the head, how can I accurately measure the piston dish while it's in the cylinder? Also, should I measure the combustion chamber volume?

ijasond

Just posted a couple of new pics over at Builds and Projects.

https://classicoldsmobile.com/forums...html#post94528

88 coupe

No.

Less valve lift = less flow = less cylinder fill = less cylinder pressure.

Do you think more fuel found its way into #1 than into the other seven?

http://www.harborfreight.com/cpi/cta...temnumber=5658

Easy to do, when it is at TDC.

Couldn't hurt to "CC" and record the numbers for future use, but unless you see a difference visually, I doubt they are the cause.

Remember: At this point, you are only looking for differences between #1 and #3.

Norm

88 coupe

Here it is, again:

One of those "ways" is to use an RV (recreational vehicle) cam.

The same "RV" cam I learned about, from a "competent machinist".

Norm

ijasond

I have 20-25 pounds of oil pressure at idle but that number only increases another 5 pounds from idle to 2500 rpm, then drops to about 5-10 pounds as it warms up. Started hear tapping under the valve covers so I pulled a cover off and found no oil pumping through the pushrods. Drained the oil and it's very black/gray after I changed it about 60 miles ago. I've only put about 350-375 miles on it since the build.(They should have one of these little faces throwing wrenches in the garage or laying under an oldsmobile so no one can see him crying) When I moved I left my engine stand at my buddy's shop because I didn't have room to store it at the time. Looks like I'll be going to pick that up saturday morning. I guess I know what I'll be doing this weekend.
After a trip to harbor freight of course

jensenracing77

sorry to hear about your troubles. i built a 350 6 years ago and had a cam failure. it sucked real bad. i had built many engines before that one with no trouble. later i found out that the lifters were all junk coming to the US at that time. also the EPA made the oil companies change there oil additives. if i had used more cam lube and primed the oil system better it may not have happened. between the lifters and bad oil it cost me big money. i only got about 80 miles on mine. at least i got a free set of lifters from the manufacturer. that was hard to believe.

citcapp

Sorry to here that, will you be taking the engine back to your builder to find out why the engine failed? Best of luck hope everything works out ok. When my 455 blew the head gaskets less the 250 miiles after I had it built my machine shop stood behind their work and fixed the problem at no cost.

ijasond

If the problem is in the machine work, I'm sure he'll take care of it. The only problem is that the machinist didn't build the engine. I sent him the block, heads, crank, 1 piston with rings, the rods and the camshaft. Then when I got it back a friend/neighbor who runs a towing service and mechanic shop next door to my body shop helped me assemble it. They do mostly diesel work and know their way around chevy motors really well, but they are not engine builders. He's offered to do whatever he has to to help me with it again, but I'm no longer next door to him. I just want to make sure everything is right this time, so I'm going to start by doing the tear down & inspection at home. Once I know where the problem originated I'm sure I'll feel a bit more at ease and know which step to take next. I just hope it doesn't turn out to be too costly. If it does, I'm going to have to put it on hold indefinitely.

ijasond

Worked for a couple hours when I got home today and got everything up top unhooked and out of the way. Tomorrow after work I'm going under it to take the exhaust and transmission loose. Should have the diagnosis by the end of Saturday. Fingers crossed, but not too crossed.

ijasond

Wrong pistons. As soon as I pulled the head and saw that dog bowl I knew without even measuring. I can add this to the list of lessons learned the hard way.

gmrocket

i doubt they would cause low oil pressure. you have more than one problem,,like excessive fuel wash&could explain how the oil looks? it would be more economical at this point to get the correct cam if the pistons are useable. stay away from guys who say "i'm real good with chevies" but these oldsmobiles with eight pistons, two heads and an intake manifold really screw me up! didnt you say you helped him assemble it? and didnt you remember what the piston looked like when you took it to your machinist? i'm just trying to understand how it can be so mixed up..

ijasond

I realize this. I intend to correct the fuel wash problem as well.
I did, but I've never done an engine before. You don't understand how a guy with absolutely no experience could assemble an engine with the wrong pistons? Seems pretty simple to me, no matter how stupid. As far as the cam being "incorrect", a couple of guys have said that they are running this cam and it works well. What would the "correct" cam be??

captjim

I said this earlier in the thread. Unfortunately, piston choices are pretty limited for us, even more so with a 425. Was the assembly balanced? Before you remove them, see how far down in the hole they are. Then mewasure the dish, if you can.

ijasond

I've been looking, 455 pistons everywhere. Not so much on the 425.
It was
I can, and I will.
I got all my new fancy tools and I'm ready to continue learning.

dan2286

Did you find anything that would cause the higher compression readings in the one cylinder?

captjim

The problem with the 425 is the pin height is 1.605, same as the small blocks. 455s have a different p/h, so they are not interchangable, even though the bore is the same. See where the pistons are, you might end up with a manageable compression ratio by milling the heads a tad and decking the block and using a thin gasket to achieve your .040 piston to head. That way you can keep the lower end pretty much the way it is, if the crank and bearing clearances end up being OK. Read this if you feel like it, it is how I go about choosing parts,
http://www.oldspower.com/vb/showthread.php?t=36717

442scotty

I say...find a good machine shop...drop it off and tell them to start from scratch...too much going on with this thing...you could but putting her together and pulling her apart over and over.....Start fresh...costs more...less headaches in the end

ijasond

As much as I would like to at this point, It's out of the question. I've spent about all I can for a good while on this project. If it's going to get done anytime soon, I'm going to have to do it myself. I used the wrong pistons, no more machine work is going to fix that, nor the fuel wash problem.
I hate that this happened, but at the same time I don't believe I could have acquired such a vast amount of knowledge in such a short time other wise. It's caused me to educate myself as much as I can.

citcapp

These pistons are on e-bay right now for a 425

http://cgi.ebay.com/ebaymotors/8-new...Q5fAccessories

ijasond

Seeing this really makes it a bit clearer. I have the dish like the L2213.
I have about .042 from the top of the piston at TDC to the block. I'm not really sure how to measure the piston dish volume, but I made an attempt an came up with 25cc, does this sound right?

ijasond

You think he's got another set of .040s lying around? I'm usually not that lucky. The .040s will show up on ebay real cheap the day after I fork out the dough for the expensive ones.

captjim

" I used the wrong pistons, no more machine work is going to fix that"

Not necessarily. For $200 to deck the block and mill the heads, you can regain almost a full point of compression. If not, a cam change will at least make the car fun to drive. Any ideas yet on the low oil pressure?

ijasond

The 1 plug looked like it was far richer than the others. Now seeing the #1 piston, it looks that way as well. A lot of fuel carbon build up on it already.
Everything else looks ok, had to be the carbon + extra fuel causing higher reading on that cylinder. Any other ideas or thoughts on this??

ijasond

just went out and tore down the bottom end. Here is what I found.
4 rod bearings look good. 3 have a groove down the middle and one is toast.
3 main bearings have grooves.
the cylinder walls look great.

Red Delta

Crummy. Well, at least you know where the oil pressure went.

gmrocket

i think we've all been kinda waiting for a piston top pic. if you got the one on the left in that pic, they are not to far off. with the correct factory steel shim gasket&a little head cut you'll be ok on compression, even with that big cam. you will want a true 9:1 min if you plan on using the same cam..i wouldnt though, a smaller cam will work much better. by the looks of the crank, it may need turning? did you measure yet? i think you need someone to help you put it together..take your time&dont rush it together in a couple hours..if it takes a week to get the crank in the block...correctly, thats ok. do it slow&the right way. you have to disect every piece now so you can learn&find out why it went bad. dont put it back together untill you know 100% what the cause of the failure was.

gmrocket

i had this on my "to do list"

the above statement by norm is false. if the engine was put together with all the correct parts&the only "wrong" part was the cam bank angle mix up..the engine will run&actually run fairly strong. one bank will be advanced, the other bank will be retarded. they kind of balance each other out as far as power is concerned&it will have a strange idle.

i know of a car that has been running for a few years now&it runs mid 13's ,,heavy four door loaded cutlass 455 internals in a 45deg 66 block.

cfair

When I got my recently rebuilt 455 back, my engine installers hadn't put the throttle rods in the right place so the carb was only opening about 40% of the way when the pedal was floored.

I got it home reconnected correctly, tweaked & instant power.

Here's a pretty easy possible fix: Disconnect your throttle rod or cable from the carb, see how far back the throttle plate will go. Look down the carb and hopefully you'll see the primaries and secondaries open 90 degrees. Then it's fully open.

The question is whether or not your cable or throttle rods can open the carb to 90 degrees. To check, floor the pedal with the carb disconnected and see how far back the cable / rod goes, if it doesn't go back far enough to open the carb to a full 90 degrees, that's at least part of your problem.

The other way you can check this without flooding the car is to leave your throttle cable or rod connected, but disconnect the accelerator pump so you don't flood the motor. If you're using a qjet, I find a standard hanger wire bent just so is the perfect thing for driving the pivot pin out of the pump arm & airhorn. Push it from the inside out.

If you're using a Holley, I seem to recall it's pretty easy to disconnect the accelerator pump, but I can't recall exactly how. Thing with the Holley's is you can see _everything_.

Once you've disabled the accelerator pump, you can see how your whole throttle system works -- the key question is how far the carb opens when the pedal is on the floor.

In my case I had to drill a new throttle rod hole lower than factory to get it to work right. Basically the geometry changed between 1966 and the 1978 800 CFM qjet I'm using. Had to correct for that by putting the hole lower and closer in toward the center of the primaries.

cf

ijasond

I took one, I guess it didn't upload. I'll post it as soon as I can.
definitely... again
This is definitely worse than I expected. I'm trying to pull some favors so that I can actually afford to get the machinist to build the short block for me.

88 coupe

If the valve timing on one bank is advanced by 3° and the other is retarded by 3°, Where would the ignition advance be set?

3° or 6° of retard would cause a significant power loss.

Norm

gmrocket

i've never been on a more frustrating forum than this...why do i get kicked out&have to sign back on if it takes more than 1 min to type what i have to say??

i had a real long explanation norm but i'm not gonna try again..in short, the dist has nothing to do with the lobe phasing. on a solid lifter motor you can duplicate the same affect as this by opening up the lash on the odd bank&tightening it up on the even side... leave the dist in the same location&see how it runs. and it will be 6deg per side diff, not 3

88 coupe

Glad you brought it up. Warhead had the same problem and I forgot to answer him.

The CO server has some sort of timer. Has to do with conserving bandwidth.

"Copy and paste" the quote into your favorite word processor, do your thing, log back on, then "copy and paste" it back to the edit page.

Norm

88 coupe

In this case, the right bank would have been advanced (more compression) and the left would have been retarded (less compression). Would optimum ignition advance and fuel mixtures be the same for both banks?

If so, in "theory" the power at the flywheel would be the same with either cam but, in an A-B comparison, will the "practice" actually follow the "theory"?

3° on the cam = 6° on the crank. Thanks for the clarification.

Norm

ijasond

Just for the record, I've been on FAR more frustrating forums and none of them as helpful as this one.

gmrocket

correct on the compression difference. in theory? i would take a wild guess&say that if you dyno'd identical motors except for the cam bank cam thing, the motor would have less peak tq&hp numbers and have a broader power curve. compression balancing(actually unbalanced is the more correct term) isnt new, its been tried in nascar years ago&i'm not sure if its still going on? differennt comp ratios per cyl&or lobe specs per cyl is a way to broaden the power band.

in my opinion there is to much emphasis put on making everything the same as far as compression, cam timing, intake port flow&shape, intake manifold flow&shape, header pipe length&size..99% of the engine we are concerned with are not symetrical in these areas. if your dealing with symetrical port heads&a tunnell ram intake, thats a different story.

sorry for getting of track

ijasond

Here's a shot of the piston.

88 coupe

Welcome to the Internet.

Norm