Dist/carb tuning question

Yep Eric, I think our good buddy the Boat Dr is on to something here. The reference marks on my pistons are all to the front...I went back and checked my pics. Looks like I'll have to get a cam from Woody as well.

I thought I had researched this before I started...live and learn. Hopefully it won't be a season ender.

I don't mind taking it apart and putting it back together so much...I'm more concerned about the price of the cam and whether Amy will come after me with a wooden bat or an aluminum one?!!? LOL

Assuming things stay as they look now, I'll be turning the pistons around and changing the cam.

new lifters?
new rod bearings?
new rings?

If this engine is so specifically tuned, should I put the original intake back on? Maybe even ditch the roller rockers and put it all the way back to stock?

Greg, What's going on with you and the machinest? Billy mentioned it plus Joe just mentioned it. I too am wondering why you aren't asking him about the Marine cam he put in. Being a marine but gear driven instead of chain, is is backwards???

Jack chamberlin had one in stock, it was 280.00 i believe, lifters are cheap enough to replace with new, personally i would re-use the rod bearings and rings...thats me though, I dont think you have enough time on the engine. keep the rings in the same bore and the bearings on the sma spot on the crank
if your machinist recomended that cam i would definitely have a serious one on one with him...you paid him for his knowledge you shouldnt have to pay for his mistakes

I've just been taking this all in..

qvestion..did you open the throttle when testing compression? Or leave the butterflies closed? Hopefully the former not the latter.

Low vacuum at idle is a suspicious symptom, but you must verify that that is the max vacuum you can get by turning the distributer for best timing at idle. Turn til vacuum fails to rise. If after a reset on the idle speed and air screws If its still below 16"-17" I'm with you, something could be very amiss with the cam.

I think there is some confusion regarding he secondaries operation.

the vaccum you see at idle does not operate the secondaries. At WOT there is no vacuum.
But the secondaries are not a normally-open mechanism (they don't operate on the bench)....where does the vacuum come from?

I believe its venturi vacuum... meaning you need significant airflow throught the carb to generate the venuri vacuum to operate the secondaries.
this also suggest the engine is just not pumping the air is should be, and this may point to he cam again.

I agree talk to your rebuilder.
Consider taking the front cover off and verify the gears' alignment marks line up and/or see if the builder did some funky things with offset keys or dowels.

There is also a remote chance that all the carb and timing issues fould a plug or two that can't recover and clean itself. I've seen it before and took the front cover off an engine for nothing looking for a stretched chain and it was just a freakin bad plug.

Hollywood wrote: Was the engine cold when you did the compression test? If so, how much lower #s would you really expect to see?

shouldn't see any difference as long as the lifters are primed.

I did do the comp test with the throttle open and the choke held open. I bought the tester yesterday and followed the directions.

My receipt from the machine shop only says '454 kit', and the guy who ordered it is off today, so I think I'll get a cam from Woody and be done with it. I tried every combo of everything already, so I think the cam must be it.

I also heard that the engine would have a strage knock if the pistons are in the regular way, and I've had this issue and still do a tiny bit. I thought that was rockers, but I can't find any trace of contact in the covers. Everything seems to be pointing in the same direction.

Thanks for the input guys!

Here's the piston orientation. The tops of these pistons are exactly like the old ones except for the manner of reference mark. These have a round depression and the others had a notch.

At the end of the day I would probably end up pulling that cam anyway, or at least the lifters because for my money if I was a betting man you have one or two wiped lobes from the intial starting/breakin issues and thats your performance issue.

Chris, I have to pull the pistons and get them turned 180 degrees on the rod...that means taking it all apart anyway so I'll see what I find in there.

I'll find time to turn the wrenches. Did I ever tell the story of my 351 long block? It was worse than this...?!!?

Eric,
because to use the same crank the firing order has to be different.

And upon more thought, there is nothing one could do to the crank to use the same firing order, and therefore same cam.

TRBenj wrote: eric lavine wrote: All i can say is: in those years for the BBC thorough PCM there is a left handed cam and a right handed cam under different part numbers, why would they not use one common cam in both engines seeing that the cams spin the same rotation? Regardless of which way the cam spins, the firing order is specific to the rotation of the crank, no?

YES but there are differences there as well and the cam can be different since the crank is done in pairs, so 1-5, 2-6, 3-7, 4-8 are basicly on the same stroke on the crank just one is one the compression and the other exhaust so it can be changed based on the cam.

see the thing here is Gregs cam probably matches the left hander which im sure the machinist got a crane or the equivalant cam thinking the left hander will work in a righty because it is spinning the same rotation, he's not backfiring all over the place so i think he has his firing order correct. i think the right handed cams may be degreed differently or some thing strange to that effect. its not making vacuum because of possibly to much valve overlap or the exhaust is opening early or to the likes and on the other end maybe the valves are closing early and causing low compression....?????? just some thoughts
all the signs are there for improper cam timing

This is a pic from when it came apart. I didn't get the same pic on re-assembly, but I do know it went back this way. As I see it, there are only 2 ways to do this and 1 would be 180 degrees out. There is 1 dot on the crank gear and 2 on the cam gear...sorry they're hard to see.



I suppose there could be a problem...don't think so though.

eric lavine wrote: My point about the PCM cams were they both spin the same way and they are both are under a different part number and if the difference was the firing order you merely would switch the firing order not re-design the cam to match the firing order.

Still wrong! The firing order of the cam has to match the crank, regardless of which direction it spins. The rise and fall slopes on the lobes would be correct in this case, but everythign else would be off. I suspect that you cant make a RH engine run very well with a LH cam just by switching the plug wires around.