Oldsproject

We are finally putting together our 425 Rocket Motor but ran inot a concern today when installing the cam and timing chain (Cam is a Comp Cam 270H -10 shows fits into a 1967 425 and the timing chain is a Cloyes Roller).

When I first placed the timing gears and cam in I lined up the two "O's" 6:00 and 12:00 as instructed. Put when I went to check the degree (using Mondello Degree kit) it was out of spec. So after trial and error (and hours later) I've got it as close as I can but now I'm thinking it's the wrong cam even though it's specified by Comp Cams?

Here's what I've got using the degree kit on the odd side:

#1 Intake 17 BTDC Open, 29 ABDC Close, Max 313
#1 Exhaust 55 BBDC Open, -11 ATDC Close, Max 313 (yes, these are negative numbers on the exhaust close side)

#3 Intake 20 BTDC Open, 35 ABDC Close, Max 313
#3 Exhaust 60 BBDC Open, -15 ATDC Close, Max 313

#5 Intake 15 BTDC Open, 30 ABDC Close, Max 313
#5 Exhaust 55 BBDC Open, -11 ATDC Close, Max 313

#7 Intake 15 BTDC Open, 27 ABDT Close, 313 Max
#7 Exhaust 55 BBDC Open, -15 ATDC Close, 313 Max

Comp Cam Specs

Intake 29 BDTC Open, 61 ABDC Close, Max 313
Exhaust 69 BBDC Open, 21 ATDC Close, Max 313

If I advance it one position I get the following:

Intake 33 BTDC Open, 12 ABDC Close
Exhaust 72 BBDC Open, -27 ATDC Close

(There are negative numbers as it doesn't get to the begining of the ATDC side)


What is going on here? I'm marking every piston at TDC with a gauge to ensure accuracy, performing the test without the heads using the plastic lifter gauge that came with the kit, rotating the engine clockwise from the front of the crank, then reading the numbers. I'm using the first hole (looking front to back) as the intake holes for piston #1 & #3 and the second hole (or closest to the dash) on #5 & #7. Is it possible that I'm dealing with the infamous do I have a 45 degree or 39 degree cam bank, am I screwing it up or are the readings OK? Helppppp!! Thanks.

88 coupe

what type gauge are you using and how is it set up?

Didn't your shop verify the angle, before they ordered your cam?

If the cam were correctly ground, the numbers would be the same for all cylinders on the same bank, regardless of the lifter angle.

Odds are, the cam was ground correctly.

Norm

Oldsproject

It's the CDK-455 Camshaft Degree Kit sold by Mondello. It has a 1" dial indicator, lifter bar for .842 & .921 bores, degree wheel and fixture that bolts onto the block or head (I'm using it without heads attached bolted to the block).

The readings are very close so thats probably an operator error as there is some play at TDC (3-4 degrees when the piston goes over center).

Based on the numbers I would guess the actual numbers are as follows:

Intake at 15 BTDC Open and 30 ABDT Close.
Exhaust at 55 BBDC Open and -11 ATDC Close

I will check with the machine shop tomorrow on the angle but as most people know, there are a lot of Chevy guys and few Olds.

Any tips on what I might be doing wrong or what I can check to verify?

88 coupe

At least.

There is nothing exotic about an Olds engine. If a shop cannot find a 6° difference, they won't be working on any of my Chevs.

You need to make, or buy, a “piston stop”. Then you can follow these instructions.

While you're there, it's a good time to verify the timing mark, on the balancer, matches #1 TDC.

Norm

joe_padavano

Since all your readings were on the same bank, the bank angle difference won't show up. Try checking #1 and #2 and compare.

Oldsproject

Thanks for all of your help guys. As it turns out it wasn't an operator error after all. I rechecked the timing using the centerline method, was able to get the #1 Piston at 107 (reccomend was 106) but when I put it on #2, I got 96 on the center lobe. I broke down and called Comp Cams and sure enough and after some pursation, found out that they were not aware of the 45 degree banks on the "67" 425's and the grind was for a 39 degree bank (They were insistant that all 67"s were 39 degree until they found an ole timer that worked there, he set them straight). I pretty much wasted all day yesterday and today, my hands are sore as heck from turning the motor over so many times in the last couple days. I told my wife I probably put 50,000 miles on it while on the motor stand . The good news in the whole thing is I have becoming a timing degree expert of sorts and Comp Cams does have cores they can grind for the 45 degree bank in the 270 or 280H. So we live to fight another day. Thanks for your help on this and I hope whoever reads it learns a lesson on 45 and 39 degree cam bank angles. Check, check, check ( I thought the machine shop would!)

Now then, another question for my Olds experts. Reading through all the olds engine rebuilding articles Mondello says there's a 3/8" plug in the rear of the block that was originally equiped with a .040 hole in it (behind the rear freeze plug). Claims the Cam and Distributor will wear out prematurally if it isn't reinstalled? I asked the guys at the machine shop if they replaced it or used the old one. They said they replaced it but didn't put the hole in it as it is no longer required (according to some software they have). Can anyone tell me IF they are correct or do I need to have the hole drilled in? Thanks.

joe_padavano

This is the same machine shop that didn't know about the 45 vs. 39 deg bank angle????

Considering that Olds stopped building big blocks before the PC was even invented, I'm curious about this "software". That 0.040" hole is what lubricates the distributor drive gear. I think it's time to find a new shop.

By the way, is this shop building your heads for you? Do they have the Olds-unique gauge to set the valve stem height after grinding the valves? Do they even know about it?

Oldsproject

They did rebuild the heads, not sure about the Olds-unique gauge but will check. The guy working on the 425 has his own Olds (68 F85 with a 455) so I assumed he knows whats up but maybe not? Can you provide additional info on the gauges, perhaps I need to double check everything. As info, we set the heads up using Comp Cams Beehive springs, part# 26995-16. The seat load is 137 lbs @ 1.7, Open is 305lbs @ 1.1, spring rate is 280lbs/in, coil bind is 1.060. They advertise this spring for Olds applications but so was the Camshaft. Thoughts?

joe_padavano

The factory specifies a U-shaped Kent Moore gauge tool that bridges across the valve cover rails on the head and has a pad above the valve stem tip. This is a go/no go gauge. Mondello sells a copy of it. It is used to set the correct valve stem tip height relative to the valvetrain. If the valve sticks up too far (usually the case when you do a valve job) then the tip of the stem must be cut down to fit.

Oldsproject

Thanks Joe, you've been a great help!

88 coupe

And I would have an answer before he touched anything of mine.

Any competent shop would have ordered the 45º cam, going in.

First thing any competent machinist would ask: What changed? If no satisfactory answer, he would make sure the hole was still there.

Most likely, your guy didn't have a clue.

A competent shop will probably use a dial indicator. Same as they would on any other head.

Set a straight edge across the valve stems. If they are not all the same height, it's time to take your business to a competent shop. This applies to any head job, not just Olds.

Yes. Then check again.

Change in lifter angle does not change the spring requirements.

Olds used “beehive” springs in the 394, and went back with the new engines. It would be interesting to know what they learned.

Always check everything, no matter what shop does the work. And always check your own, as well.

In order to maintain the correct rocker geometry.

Norm

joe_padavano

Not sure how a dial indicator helps unless you know the required valve stem height dimension. You'd need to zero the dial indicator on the valve cover rail then swing it around and measure the height of the valve stem tip. The problem isn't the relative height of the stems, it's the absolute height relative to the rest of the valvetrain due to the non-adjustable rockers (and the need to maintain proper geometry even with adjustable rockers). The advantage of the gauge is that it's idiot proof.

88 coupe

How would someone expect to do machine work (or check it) without knowing what dimensions he is working to?

As I said above:
The operation is included in any quality head job, no matter what name is on it. For that reason, a competent shop would know the number for any head, including Olds.

Here is a short explanation. Works for any OHV GM, Ford, or Chrysler I've done.

Based on his previous information, I was assuming they would not pass the first test. I should have continued, regardless.

If they took enough time to make them all the same height, odds are, they set them correctly. The actual height must still be checked, but only on on the two end valves.

Norm

joe_padavano

Agreed, but this is the same shop that ordered the wrong cam...

That's a great link, thanks. I was not aware of the fixture for holding the dial indicator.

Agreed. Of course, I'm willing to bet that most machine shops are used to Chevy style heads and allow a lot more tolerance on the installed stem height since they assume you can take it out with rocker adjustment. I'm afraid I've just had bad luck with machine shops.

88 coupe

Focusing on my first two comments: https://classicoldsmobile.com/forums...tml?#post12762

Two clear caution flags that were ignored. Need I say more?

They have been in use since the forties that I know about. Takes less than 15 minutes to fabricate, usually using scrap material from previous projects. A “piston stop” takes less time.

Before dial indicators became commonplace, depth mics (micrometers) were used with the same tooling. I've used mics from the beginning, and see no reason to change.

During the initial audition/interview, one should expect a shop to offer a tour of the the premises. During that tour, one would be exposed to all the operations that will be performed. That would include, how the valve stem height is set.

Only one of many reasons, the "top shop" charges the “top rates”.

Has nothing to do with Chevs. Everyone knows, for any stock rebuild, it's a waste of time because it doesn't make any difference. Just one of the many reasons why production overhauls cost less than "custom" rebuilds, and the biggest reason not to “cheap out” on machine work.

Once they have gone that far? Slim chance.

The guy that's doing the work, doesn't make assumptions, he just does his job.

Actually, I think you are the one making the assumptions.

Luck has little, if anything, to do with it.

Norm

Oldsproject

As info, I ordered the Mondello gauge couple days ago, will let you know whats up when I get it. Also ordered the 3/8" plug with the .040 hole for the rear. Good thing for this site and the other info I've been able to gather. It's costing me more in the short haul but hopefully saves time and money in the long run. At this point I want to be safe rather than sorry. Thanks again for the info

Oldsproject

PS, anything else that I ought to check on the heads while I'm at it to be certain that I'm in good shape?

88 coupe

It would be helpful if you explained the following:

Norm

Oldsproject

Not sure what they were suggesting on the valve guides at the time but it wasn't done and they did put in the hardened seats for unleaded fuel.

I don't want give the wrong impression though. The machine shop I'm using has been around since the 50's and they have been extremely helpful and reputable. The valve job looks good BUT we'll see when I get the go, no-go gauge (I'm being careful now). The Cam selection they made was advertised for a 1967 425 by Comp Cams which they (Comp Cams) admitted later was misleading when I called as they don't have stock 45 degree grinds. Therefore it's a special order (now anyway). They did miss the plug in the rear of the block though. But everything else has turned out very good (cylinder bore, crank welding and turning, etc.) and it wasn't cheap. They do have an excellent reputation I just don't think they are that familar with Old's. In any event I'm cutting them some slack for the time being. I reserve the right to change my mind though. Most of this is probably my own ignorance as this is my first attempt at rebuilding an engine and with everyones help on this site, I'm learning quickly which has caused some changes in rebuild strategy along the way. Please keep on giving advice and insight as it is invaluable and thanks for the help so far!

88 coupe

If they did the assembly, there is not much you can check. Use your “straight edge” to verify the head surface is flat.

Odds are, this is what they were proposing. It's been around since the early sixties that I know about, and is considered a legitimate repair for stock applications. I'll guess, they went with new guides because of the cam change.

Good insurance. They are a bit tricky to install but are no problem, if done right.

People make mistakes. Good example of the need to check everything before you start, then check it again during the assembly.

That's a good sign. Quality work is never cheap.

Everyone learns from threads like this one.

Norm

joe_padavano

Yes, knurled valve guides would be one option, but when I read this the first time, "oversized valve stems" is what came to mind. Either way, we're guessing.

88 coupe

Same here. Immediately followed by the thought of unnecessarily replacing 16 valves at several times the cost of 16 new guides.

Considering the source, that it was second hand, and, as posted, it did not make sense: It was the reason for my initial response, followed by my repeated requests for clarification.

Requests, BTW, that still have not been addressed. How much advice does one need to be given, before one should reciprocate? Or is the flow of information supposed to stop, just because he opted to use new guides instead?

I added information for anyone who might be interested in the subject.

Norm

Oldsproject

We finally got the Mondello gauge (HG-455) and here are the results:

Left Head - all Intake valves stems passed (-.010 to -.012)
Left Head - all exhaust valve stems were consitently high (+.023 to +.026)

Right Head - 1 Intake valve stem passed (-.012) - 3 were close (+0.00)
Right Head - all exhaust valve stems were consistently high (+.023 to +.026 range)

Based on the measurements I would say they intentionally set the exhaust valves higher?

Suggestions? Is this a problem or Ok?

If a problem: 1)take them back to be reworked with gauge in hand? 2). Can the tops of the stems simply be filed? 3). use adjustable push rods or rockers?

note: the plus range was measured by marking a line in the side of the gauge at the valve stem height then using a feeler gauge to measure from the mark to the bottom of the gauge, not an exact science but should be close.

Oldsguy

I am not a machinist and don't know if those measurements are within tolerance but it seems that a couple ways the valve stems would be "too high" is if the heads were ground too deep before the valve seat inserts were put in or if the seats were ground too deep. I don't know of the feasability of this happening as I have only actually observed/assisted in this process one time.

edit: I am no machinist but I spent the night at Holiday Inn

88 coupe

Based on all the specs you've posted, there is no problem.

If, in the future, you decided to go for more power, you could take care of it when you freshened/modified the heads.

Norm