[ztwntyn8]

I have a 1971 Pontiac 400 which I have replaced the cam and bearings in twice now. The first time for more power and the 2nd because a lifter mushroomed and took a lobe with it. I did notice that the original cam had a nearly flat exhaust lobe on one cylinder. The last cam died the same way but faster. Both times I used clevite bearings. The first time a street/strip (from what butler performance said) and the other bearings I got from Summit and were a stock replacement.

When I first replaced the cam and bearings I noticed that the stock bearing fit really snug on the cam's bearing surface whereas the new clevite bearings fit on really sloppy. I'd say that there is about 3 times the clearance. I know this is dropping oil psi. and causing my valvetrain problems but not sure how to solve it.

I have been told by a local well known engine builder that there may be 3 different cam bearing sizes for 400 ci. Pontiac engines. He wasn't sure which engines had what or what year etc. I have never heard of such a thing and have read everything Pontiac related that I could in the last 20+ years.

Has anyone ever heard of such a thing? One other thing I notice about the engine is when I replaced the timing chain (which is the only part of the engine that I could tell had been apart before I took it apart) the new one was just as sloppy as the old one. I have been told that some blocks are machined to closer tolerances than others explaining my slop in the chain.

So, I'm confused. The bearings seem to be consistently the same size and cams bearing diameter seem to be consistent.... even in comparison to the original cam which I still have. I'm about rob some bearings out of another engine I have sitting around. I'm kidding but I'm about that frustrated. Hate half assing things. Thanks, Nate.

 

[ztwntyn8]

Thanks for the good info. I am installing the bearings myself with a universal cam bearing instalation tool. I was very careful to mark the bearing so that the hole is lined up as close to perfect as possible. I am a professional mechanic however, I don't know everything but try to be as informed as possible.

Break-in:
-Cam has all of the lube they gave me in the kit on cam and lifter bottoms.
-As soon as it fired I made sure it stayed around 2k rpm... a little higher than the fastest fast idle setting.
-The engine stayed at that rpm fluctuating only slightly when I was checking timing and making sure all of the push rods were spinning.
-All push rods were spinning.
-Oil was not squirting on the wheel wells. Rather it was oozing out of the rocker arms. I am used to oil squirting all the way to the wheel wells from the rocker with valve covers off and that's at idle not 2K rpm.

As for the different cams:
-stock has the same size bearing diameter as the other summit cams.

Cam bearings:
- all that I have ordered (3 sets now) are the same diameter.
-the replacement bearings fit much much more sloppily compared to the ones I removed form the engine.
-the cam turned much much more freely whith the new cam bearings. Almost no effort at all in comparison to trying to turn the stock cam in the stock bearings.

Engine:
-started with me stock down to brake linings and original exhaust you could put you hand around, showing 43,800 mi. on the clock. No machine work ever. The cyl walls still had cross hatch patterns with no obvious wear.

Car:
- 1971 Formula 400.
-Ram Air heads and cam
-3.42 posi
-TH 400
[email protected] till cam later died.

I'm wondering what the clearance should be. The clearance is so much larger with the new compared to the stock bearings that I know it's bleeding allot of oil psi. The second cam died much quicker and I used Rhoads lifters that actually bleed off to help vacuum with larger cams (which both I have installed are within the accepted spectrum of the stock replacement springs.

Thank you for your interest and input.

 

[ztwntyn8]

To clarify, Ram Ari III #48 heads and summit blueprint HO, RA III, or 068 cam. It's good idle to 5K rpm. I usually shift around 5200 but it pulls to 6K rpm hard not dropping off if you aren't watching the tach.

 

[ztwntyn8]

I agree that I have"D" port heads although, a RAM AIR III engine is a "D" port engine so, not sure why you say they aren't RA III heads. Enough of the semantics.

The only evidence of the engine being apart before I took it apart was marks on the timing cover where the chain had been replaced.

I have stock rockers, push rods and valve springs. I used a summit blueprint HO or 068 cam the first time.

I just don't get why the all of the bearings that I have bought feel so much sloppier than the original bearings that I removed when I have them in my hands and place them on the cam which is also in my hand and that is the stock cam and the summit cam. So, the camshaft's bearing surface is the same diameter stock vs. summit. The bearing it's self has a much larger diameter in the replacement Clevite SH-292S vs. the original bearings that I removed when the engine was all stock.

Any oldschool hotrodder that I ask says they are surprised that I have any oil psi. I was reluctant to put the new bearings in long ago when I did the first cam swap.


Thanks, Nate

 

[ztwntyn8]

Because aluminum alloy bearings are harder and less forgiving to can tunnel misalignm

This sounds like my best bet so far. A sprint car guy said that maybe the bearings would change diameter as they were pressed into the block but another guy said if it shrunk that much it would prob need align-honed. I realy don't think I have any wierd block issues etc.

Some of these people think that larger than normal tolerances wouldn't hurt lifters or cam because it may not be directly feeding the lifters but any psi. drop is a a drop accross the board.

Thanks for turning me onto measuring a pressed in bearing. I will try that.
Nate~

 

[ztwntyn8]

Measure the oil clearance of the cam journal to cam bearing by fitting the bearing on

My friend who is a toolmaker is out of town and if the measurement needs to be that accurate, I want him to do it.

Tonight I pulled the cam out of my 73 455 TA (71 Formula is to other) which I have previously installed stock replacements from summit and same part # as the ones that I last installed in the formula's 400. When I got the cam out (only after break-in for 20 min. (and this was last year but not started since) and the cam bearings themselves were scored in from the 6 o'clock postion to the 12 o'clock. The one bearing that I didn't replace (that I couldn't unless I pulled the engine and it wasn't scratched by the cam comming out by the dist drive gear) looked realy evenly worn compaired to the new bearings. All new bearings were worn irradicaly. It was already digging into the bearing. I can't feel it but can def see it.

I also tried the cam in the front most bearing on the way out and I can feel the same slop that I can when I test an uninstalled bearing on the cam. I'm fairly certain that I have a tollerance issue.

I'm about to order bearings from another co. and see what I get. I guess they are cheep enough it's just spending the couple hrs. to get to them.

 

[ztwntyn8]

Right on Jim. Now I have some measurements to compair to. I still need my buddy to stop by or get some good calipers or mics myself.

Yeah, I realize they could be 350 HO heads. I was just trying to discribe my combo. I guess the RA III is the only "Ram Air" engine that has D ports huh. That's kinda a trip. I guess that was more of a marketing strategy?

I'm gonna get after it this weekend. Have a good weekend.
Nate

 

[ztwntyn8]

I just went through the "exercise" of measuring all these things.

Ok, I had engine builder from the 60's and 70's came by my body shop yesterday. Today he showed up with inside and outside mics. It seems that my out of the box vs installed and then removed or "crush" is .006 OD. He was concerned and I asked shouldn't it be about half that. He said yes and was concerned. He went to the shop he used to work at and took my engine info with him. He says that my OD on the bearings is correct and measured my block's bore for the cam bearing and said that they were fine. The thing he didn't like is that the replacements were skinnier. As in they don't cover as much of the bearing surface. I think I remember the stock bearings being wider.

His concerns are all about my oil psi. Obviously if my crushed ID is too big it will bleed off psi. and kill everything. I can't believe we didn't measure the id. of the installed bearing or even the uninstalled bearing. I just forgot to mention it because I was trying to shut up, respect and learn from him.

This guy is in his mid 70s but he looked realy confident with measurements and took his time but it didn't take him long.

His measurement on the uninstalled OD was 2.035.5" He verbaly said 2" and 35 and a half thousandths and to put a decimal point there. I supose it was a significant digit sort of thing but that was his way.

The installed bearing OD was 2.029.5"

So, there is .006" difference in OD but not sure about ID.... dang it.

When he had the installed in his hand measuring he laughed as he remembered the cam journal size and said "I could probably put this in with my hand" and walked over and put it about 1/4" in by hand. Then thought about how much it is crushing and said that is way too much.

Then he wanted to see my instalation tool.... It's a universal with an expandable center made of 4 pieces and a rubber 1/8" rubber sleeve that contacts the ID of the bearing. He said that the ones he used were metal. I asked the obvious about the rubber giving and letting it crush too much. He nodded as in yes but not too quick to say that's the problem.

He asked me about the heads and springs. The blueprint 068 had that small barely over .400 lift and think that's why it lasted longer but the summit 2802 cam has .488 or so lift and he is concerned aobut coil bind. My cam card was blank where the recomended springs place is. I was told and accepted the idea that stock springs are good up to .500 lift. Since I had one lifter fail.. not all of them he said that he suspects coil bind on that spring or possibly valve touched a piston bottoming the lifter and destroying the cam. He was also realy concerned about breakin. Saying that if 1 lifter or lobe is scared it will fail. So, I have alot to think about. Also, he said that the tolerances aren't always that great and that if I had the original bearings they would have been marked as to how much larger or smaller they were to accomadate the cam journals. Keep in mind he was a builder of ford, chrysler, pontiac, chevy, honda. Which brings me to another tolerance learning experience. He said Honda auctualy measures to tenths of thousandths and can have several different sized main bearings according to the colored markings and if you were to install all the same sized replacement bearings the engine would run but wouldn't last nearly as long as if they were more precise.

He also told me that with the thousands or so engines he has built that ones like mine that were running well before a build typicaly had more problems than a worn out engine that auctualy has to be rebuilt. I see that now since now you have new machine work and you get bearings etc. that match the new cut. That makes alot of sence.

Told me one other thing I want to share. On a ford road race engine he was having problems with them lasting and a known ford guru built an engine with him. I think he said the rods had .004" clearance and mains .006"....... could be vice versa but much larger than what he is used to. He also said that you can block the bypass on the oil pump which they did. Had to use a special oil filter so it wouldn't blow off. The psi. was 200 lbs! and once the engine warmed up it ran at 35 psi. He said he couldn't believe it but it worked many years ago and is still capable of running but is sitting under a bench.

IDK, but I think he can get me straitened out. I may buy a pro cam bearing instalation tool but still want the factory replacement bearings and to instal correctly. I'm going to post pics of the 455 that didn't fail but was broken in for 20 min. @ 2000 and you won't believe the amount of wear on the cam bearings in that amount of time. It was (goiong clockwise) half of the bearing scored and worn from 6 o'clock to 12 o'clock pretty bad concidering the run time. He also said it should if anthing wear in the bottom half not one side. I'm still trying to process all of this and make scence of it. I think I'm going in the right direction though. Thanks for the help. I have been realy frustrated and have 2 cars down over this ****. Anyway, if you have any differences in opinion lmk. Thanks again, Nate.

 

[ztwntyn8]

I have read soooo much. And sometimes feel that I am realy well informed. Now, I am humbled and also inspired. The older fellow said "it's just a challenge". I have so much respect for the guys hotroddin or rebuilding successfully in the 50's and 60's. They are responsible for so much unpaid R&D. I am happy to see the other side. There are so many variables and I have come to find out that you have errors and then epiphanies. He said and I believe it... "when you have these problems you never forget". You've spent your last dime and all of the thought... then it fails. That's part of hotroddin I guess. I just wanna do it right and make it last. Thanks so much for all of any or you guys's input. I was so dissapointed bc I have 2 cars down right now bc of this. I am going to get to the bottom of it and when I do I want to tell everyone what happened to correct so others don't stay down for half of a year scared to buy more parts knowing it's going to fail again. Have a good weekend guys and I'll be talking again soon if you are interested. Does anyone else know of people having these problems?

Nate

 

[ztwntyn8]

I feel ya. That is something that I wasn't getting right off. I thought people meant cutting on the cam journals when they would mention honing. I didn't concider cutting the bearing it's self until I talked to him the other day but hadn't mentioned that yet on here. But good point and now I gotchya.

 

[ztwntyn8]

Ok, this is nearly embarassing. It's not as bad as it could be (on my cred lol). The 2 things that the older engine builder had concern with but wouldn't condem right off as a problem.

1. He used an instalation tool that was metal on the end that the bearing sits on as it's driven into the block. Mine cam bearing tool is a universal. So, I have 5 different sizes to choose from. They expand as you tighten a bolt that wedges apart and gets a firm hold on the bearing. Well, The part which expands is metal but there is a rubber sleeve around it vs. the all metal tool.

2. He didn't like seeing .006" "crush".

Ok, I thought about it all day after the measuring went down. He has confirmed that I have a suitable bearing for my application as well as the journal size that it's suposed to have.

I ended up bing *** backwards. He said they are crushing too much. Eventhough that was OD, I know that the ID has to be decreasing by too much aswell.

Yesterday, I thought wait a minuit. I thought these things were loose but he is saying that they are auctualy smaller than they should be after instalation. I thought damn, he said (with a removed bearing that I installed in his hand) I bet I could put this into your engine with my hand. Then he did get it started but that was his point. The bearing crushed so much it could likely end up spinning. I'm hoping like hell that none are spun in my 400. This 455 I'm on I only tore down to prevent failure since I put the same cam/bearings that I did in my 400 in it..... dang it!

Here's where I'm at now. That cam tool is ****. The rubber that contacts the bearing and is giving. A professional tool with a metal driving end will have to be a pretty close fit and also isn't going to give like rubber thus holding my crush to a less dramatic shrinkage. It sounds good and i'm sticking with it lol Well I ordered the tool last night. Had a few beers and went through with.

I know clevite is selling these bearings to alot of people. As a matter of fact you have to try to find another co. on google. With that, my Summit cams have the same bearing diameter as the factory cam. He confirmed that my block and bearings were appropriate. So, I think my universal cam bearing tool is junk. When I picked up that bearing that he started in by hand and put it on my cam I about ****. It barely went on! Too tight. You guys are right on by letting me know that you never heard of a pontiac having too loose of bearings. I had no idea that a cam bearing crushed when I drove them in. Hindsight..... Anyway, even when I was told by a couple of guys that they will crush I though there was no way it's going to get that much smaller. What I was guessing in my mind is that there must be like .015" or so when I tried the new out of the box bearing on the cam in my hands. That estimation of .015 was bs (aparently I havn't had enogh time with dial indicators, calipers and mics).

Now, waiting on the tool to come and ordering another box of bearings. I think alot of people just swap the cam not bearings and leave the distributor drive gear marks. I wish I would have but wanted to do things as right as I could to not have to teardown later. My current thinking is that that gear is going to scratch new bearings too on the way in. You just won't see it since the cam is now covering. It's just hotrodding man. You gotta learn some stuff the hard way and hope like hell somebody like George stops by and lets you know all of his hard earned secrets. I know it's a book but I wanted to let it all out. Rookie mistake by not using the right tool for the job. And by the way the damn professional quality tool..... is like 2/3 the price of that universal I sprung for :smash:

 

[ztwntyn8]

Oh hell.... Well maybe it's my technique somehow. It's worth it to me to buy the tool and eliminate a variable. The ole engine builder guy says he will assist me if I want him to. He said I may have somehow damaged/distorted the bearings on the way in but the only one that the cone isn't used for is the last one so, I think they went in straight. Ofcourse, I still have a problem. If the tool is my issue, what would they be doing selling them right? I thought of that too. If it didn't work, they wouldn't be able to market them successfuly. One thing that I thought was good was that the adaptor that I had to use fit fairly snugly beforer I expanded it. Something I recall is that I didn't torque the bolt on the expander verry hard. There is no flat for a wrench so I held the handle and tightened about as tight as possible that way.

I'm not counting my chickens before they hatch since I'm no stranger to dissappointment so far. Thank you for the input though. The more I know the better off I am. So, here is another thing for me to concider.

Oh, what all is involved in honing bearings? That seems to be my next step if the new tool is no help. Still it's a way out and it would probably be more true after being cut right?

 

[ztwntyn8]

Universal tool...

I'm finding that it's probably not the instal tool that was bad or half ***. I'm think ing that the tool that was not used properly. lol After we talked about how long you have had your universal tool for a long time now. That made mo go be back to me beeing the tool that was used incorrectly.

I looked over all of my instructions and if fine pring it said note: If you have a bearing wall of .065" or less use this rubber adapter and if you havae a .900 or more you must use the less thick adaptor. Well, I'm thinking I've used the wrong rubber adaptor.

 

[ztwntyn8]

Here is a quote I found and think the last few of yall are right.

Getting the bearings in is the easy part. Fitting the cam is a different story as the bores in the block are not all in a alignment. This is due to a number of things, such as a 30 year old block has had some movement, but most of all when the factory drilled the block for the cam, the did it partially from the front, and then the rest from the back. As you can guess they never lined up even when new.

Use a proper bearing install tool as you do not crush the edges. Once you have them installed with the oil holes lining up and making sure they are not cocked to one side, install the cam dry. You may feel resistance, but do not force. If it will not go into a bearing, get out some 80grit emery cloth and carefully sand the leading edge of the bearing with resistance. Once you have the cam in, it should rotate easily by hand. If you cannot, move it back and forth a bit and then remove. Check the bearings. Shiny spots are high points and need to be sanded for clearance. Once you have a good fit, remove and put some engine oil on the cam and set back in and verify the final feel. you should be able to turn using 2 ringers. Now you are ready for final wash of the block.

Pontiac's are a *** for this, and I recommend any novice to have the machine shop install them. I would say 30% of first time builders will mess this up and have a spun cam bearing that will require a complete tear-down all over again. You may be able to find a shop with a flat rate to install, however most charge by the hour that know Pontiac's take anywhere from 2 - 8 hr just to fit the cam shaft.

Think of what you are spending to build your motor. Is it worth the risk?


Read more: http://forums.highperformancepontia...haft-bearing-install/index.html#ixzz1ywTdjYek

My front most bearing I couldn't even enter. Took it out and it fit the rest nicely imo and turned realy freely. I just need to the the front bearing squared away and I may have it. The others seem to have slight rub marks too. I'll be glad when I learn and this is over.

 

[ztwntyn8]

The other thing I did is use my installation tool differently this time. There were 2 different sets of rubbers for each adapter size. One for bearings with a certain bearing wall thickness and less and for another size thickness and thicker. In all other instances I used the wrong one. This time I used the other, thinner rubber for the adapter. I think all of the bearings that I installed (except for the front most bearing) are good to go now. I could have went in crooked or something on the front bearing since I had no hole to place the cone in that centers the tool. That's where I'm at now. I suppose honing may be in my future.