dallasite21

I have installed a rebuilt 455 in my 1971 Cutlass, but I seem to be having some vacuum issues or something. I have compression tested all of the cylinders and got readings of 160 to 180 on all. I also set it to top dead center and lined up the distributor. It will fire up but idles rough and is only getting 14 to 15 in/lbs of vacuum. The other weird thing is that when I put my timing light on it, the balancer mark is almost dead center of the balancer on the top... Not even close to the timing mark even though I know that top dead center is at the timing mark... what would cause it to do that. I have sprayed around the carb and intake for leaks but have not found anything... What else could cause this issue? Any ideas on where else to look for a vacuum leak? I do know I have a header that needs to be torqued becasue there is one screw I cant reach, but I would think this wouldnt cause the vacuum issue. By the weigh it is a 9.5:1 compression ratio with a very mild cam, nothing that should cause a vacuum issue though.

Gary's 2 442-S

You just might not have a vacuum issue could be something else. I had basically the same problem as you are describing but I think a little worst because once the engine was warm up, it would be sluggish on turning over. It would also not idle correctly. I spent many, many hours and dollars trying to figure out what was going on because I just knew that they engine was good. Here is a thread I posted about my rebult engine. I hope you dont have the same problem that I had.

https://classicoldsmobile.com/forums...d-rebuild.html

dallasite21

I really hope thats not the problem, but it sounds similar to my issues. Mine has problems trying to start after running too, however I do have headers that are right next to my starter which I believe is probably causing heat issues. I just dont understand why my timing is so far off. I have a comp cams 3712 cam and lifter kit and I have the high compression pistons with 9.5:1 ratio. I just cant think of anything that would cause timing to be that far off.

dallasite21

Im sorry... I meant an edelbrock 3712 Cam kit

dc2x4drvr

Are you using the original balancer? When you bring #1 to TDC, where is the timing mark, and where is the distributor pointing?

dallasite21

Yes I am using the original balancer. Here is what I am doing. I use my electric starter to turn the engine over untill I feel air push out from the number 1 cylinder.Air normally starts pushing out when the timing mark is between 12 and 1 oclock on the balancer. Then I manually turn the engine over to line up the timing tab and balancer mark which is at about 2 oclock. Once I get it to the timing mark I set the rotor to point at about 5 oclock so I can line up the #1 plug wire. All of this makes sense to me and the car starts just fine, but once it starts instead of the timing mark being near the timing tab, its sitting up around 12 o clock on the balancer while running. I just dont understand what could cause that. Should I start feeling blow back at the timing tab or before?

dc2x4drvr

Manually turn over the motor to bring #1 to TDC, I use a screwdriver through the plug hole to verify the piston is all the way up, the timing mark should be around 0 on the timing tab..pull the distributor up and position the rotor to point at #1 with the distributor fully seated...if after doing this the timing mark is still at 12 o'clock running, check to make sure the vacuum advance is plugged..are you running a known good distributor? Was the cam degreed?

Highwayman

If you have a points distributor you can go the extra step of turning the distributor until the points start to open. That should preset the timing to within a few degrees.

dallasite21

The cam was not degreed and it has an electronic advance distributor which ran perfect on the 455 that was in the car before this one. I can take that distributor out and put in my hei with vacuum advance and see if it changes anything. Would a bad PCV valve cause this issue?

dc2x4drvr

No the PCV valve doesn't have anything to do with timing. What is the idle RPM? Have you tried to turn the dist., with the engine running? Electronic advance...what kind of distributor?

firefrost gold

Are you sure the wires are all on and good and in the right order? How did you brake it in? or is this still on first start no break in yet?

m371961

With the electronic advance dist you need a timing light that has a advance ajustment on the light. The same with a mechanical advance dist. This light allows you to see the timing at all RPM. It has a adjustment on the light that you can turn and when the marks align at zero the light tells you what the advance is.

oldcutlass

I am sooooo confused at what your trying to do?

dallasite21

The distributos is a Mallory. Im at work and dont remember all of the details of of, but I have attached a picture of it. It idles around 1600 RPM. I have not checked the wires becasue they were working fine a month ago when I took the old engine out. They are definetely in the right order, and when I turn the distributor to try to adjust the timing it appears that it runs smoothest where it is. Here is a video of it running a month ago before I took that engine out. As well as a pick that shows a small part of my Coil on the firewall.

http://www.youtube.com/watch?v=Syor5fHcozs

dallasite21

All I am trying to do is get my car to idle properly and have the proper vacuum. Right now it is doing neither.

TripDeuces

Are you disconnecting the vacuum advance while timing it?

m371961

Edelbrock and Summit websites lists that cam for 350, 403, and 400 motors only, not 455
You cannot time an engine at 1600 rpm unless you have a timing advance light and know the distributor timing curve.

dallasite21

There is no vacuum advance on this distributor set up.

oldcutlass

First reduce your idle speed to 600-700 rpm. Hook your timing light up and rotate your distributor until you have 15* btdc. Set your a/f misxture screws for highest vacuum. Readjust your idle speed to what the engine likes.

m371961

here is link to cam card.http://www.edelbrock.com/automotive_...3712&submit=go
Vacuum at 1000 rpm-16
There are a lot more people on this site that are more familiar with Olds and can help more then me, but I do not understand why you have a cam in a 455 that is not listed for that motor. The instructions for this cam also talk about not using a set of gears and chains that is used on late model emission engines. Also, any aftermarket cam should be checked with a degree wheel.

TripDeuces

Is it idling at 1600 rpm because it's on the fast idle cam for the choke? It should not idle that high. All Olds cams use a common core except for the 45* bank angle ones so the cam should work fine. You need to find out why it's idling that high first and correct it. Since it has no vacuum advance I'll assume this is a Mallory 32 Series distributor with mechanical advance only? http://store.prestoliteperformance.c...p-208-cap.html

Here are the instructions for it: http://store.prestoliteperformance.c..._32_series.pdf

See if any of this helps. There are several other series that don't have a vacuum can so if the 32 Series is not it find yours on that sight and look up their instructions. It will be at the bottom for that particular distributor.

m371961

Teach me something about Olds. I know the cam will fit and the engine will run, but why would a major manufacture like Edelbrock only list it for those engines and make a different one for the 455?

TripDeuces

Bigger engines will make the same size cam milder for lack of a better word. So a 214* cam in a 350-403 would act more docile in a 400-425-455. You'll notice on the Edelbrock site the 350-403 cam is 204/214* at .050 while the 400-425-455 cam is 214/224* at .050. If you read the description Edelbrock is shooting for 10-12 inches of vacuum in the engines. The 3712 in a 455 would produce much more vacuum but a lot of torque. One drawback of using a cam that is too small is excessive cylinder pressure which would tend to rattle the thing apart on today's gas. Edelbrock is just trying to match components here for best results. It's not a matter of it not fitting. Obviously it fits as he's running it now.

As an example the cam in my engine is 242/242* at .050 but the engine is a 496ci. In a 455 this would probably result in a rough idle but the 496 dumbs it down.

Highwayman

When you started this thread you seemed to believe that you had a vacuum issue. Pull it out of the valve cover with the engine running, plug it with your thumb and see what happens.

I don't know why you couldn't just temporarily plug it while you troubleshoot the problem. Or just replace it if you have any doubts about it.

joe_padavano

And many vendors say that their headers won't fit Supremes, so what's your point?

The reality is that the same cam works fine in a 400 and a 455. As noted, the larger the displacement, the "smaller" the cam will seem, but it WON'T cause the problems described in this thread.

m371961

Thats why I said to teach me something.