Mark71

Hey Everyone,

Happy New Year!

I am in the middle of a '70 455 build and trying to make some decisions. I ran into a couple of questions. Any help is appreciated...

1. Can I reuse the timing cover (see pics for detail)? It is kind of pitted, but I'd like to reuse it if I can, just to keep as many original parts as possible. The last pic has some arrows showing the worst pits I've found in it.
   
   
2. My machine shop says I can safely reuse the main bearing bolts in my build, but should swap the rod bolts for some solid ARP's. Does that sound like good advice? I am a little concerned about the original 1970 main cap bolts and was thinking of replacing them, too.
   If I do replace them, I won't be able to use the original oil control baffles that mount to the main caps...
   
   
3. I was recommended to use forged pistons. Are they really better than cast (or hypereutectics)? I am not planning on running power adders or crazy high compression, so am I am just adding weight (and cost) by going with forged slugs?

Thanks,
Mark

Fun71

1. Timing covers are timing covers and a replacement won't be any different than the one that came on the car from the factory. Use one that won't leak coolant into the crankcase.

2. I think the use of ARP bolts depends upon your intended usage of your engine. My engine has had all factory bolts since it was built at the factory, then rebuilt in the '90s, and I spin it to 5500 all the time. Can't say yours will hold together or not, so do what helps you sleep at night. With that said, quality fasteners are always good insurance.

3. I thought forged pistons were available in much less weight than cast pistons. I guess it depends upon WHICH forged pistons you are thinking of using.

Gary M

The cover will only get more pitted over time. Would be a pita to go back later to replace it.

On on my last 455 I was told by the builder forged was the way to go but not the hyper- whatever they're called. Others may disagree on that but the forged worked fine for me.

joe_padavano

All Olds timing covers from 1964-1990 are exactly the same. Brand new GM 307 covers are still in the parts system and are sold by many vendors. If there's any question, get a new one. Of course, having said that, I have dressed many pitted covers from daily drivers with a disc sander and had no problems whatsoever.

The stock bolts will work. ARPs are stronger. Depends on your build and intended use.

Replacing the main caps requires align-boring the block.

Forged pistons are much more resistant to damage from pinging and are always a better choice.

wr1970

Joe he isn't changing main caps! The op is talking about changing main cap bolts. There is no reason for align-boring with a bolt change.

joe_padavano

You're right, I read that too fast.

cutlassefi

When changing bolts or going from bolts to studs it's always a good idea to align hone the main saddles. The aftermarket bolts and studs don't pull the same as the stock ones.

VC455

I agree with Cutlassefi. When you use bolts that have a different torque specification (ARPs) the caps and saddles become different shape and align boring is recommended.

wr1970

I would love to see you warp cast Iron Main caps!Sorry i am not buying this.

83hurstguy

Bearing clearance gets measured to the 0.000x". Cast iron blocks do move around, and changing torque on the main caps will change the shape of that bearing housing. If cast iron doesn't move, what's the point of torque plates either?

wr1970

Luke you Mark whom ever vc my answer stands. That i have never seen cast iron main caps warp from a bolt change. Now you can accept my answer or you guys can argue about it. I have used studs on more than one engine on main caps. I have used ARP bolts on more than one engine on main caps and have had zero problems.If the op wants to take Marks advice yours vc i could care less.

firefrost gold

wouldn't the proper answer be clean block install bearings in block and cap torque to speck then measure the crank and go from there. Or use plastigauge to see how it all measures out ?

wr1970

I will try one more comment. I am talking about a basic build not a high performance engine. Firefrost gold your post is good enough for a basic build. Some guys don't like plasigauge.

Mark71

Hey All,

Thanks for the responses. My goal with this build is to basically do a slightly-better-than-stock build. It'll be a hydraulic flat-tappet cam with a modest profile and a focus on torque production. I may go with the Edelbrock heads (spendy, but good, I hear), but that also depends on total cost...

@Joe, Gary, Fun71 - Point is well taken, both about the timing cover and the forged pistons! Machine shop recommended align honing, so I'll end up having that anyhow.

So, as long as we are on this topic:

• What about oil pumps? The shop recommended a standard volume one, primarily (I guess) because I am planning on doing roller-tip rockers. I was thinking of going with a high volume one, though, just for safety's sake.

Thanks,
Mark

classicmuscle442

Have not used high volume oil pumps in my Olds builds. These pumps can pump pan dry at high rev's.

ELY442

That is a very common myth on this site. I have it on my 455 and it never ran dry.

joe_padavano

X2. I always use a HV pump. Never "sucked the pan dry", ever.

wr1970

X3 all but one engine i have built are high volume pumps.

Mark71

Ok, so seems like we're getting a consensus on HV pumps. There are apparently such things as "high pressure" pumps as well, but I am not sure how that works. What I mean is, increased volume through a restriction would create additional pressure... or so I figured.

Anyhow, I am learning a ton talking to you guys and my machine shop. I just got the following numbers back from them:

• Worst bore measurement was 7 thousandths too large ()
  
• Suggested new bore size: .030 over
• Suggested new crank size: .010/.010 under

They are suggesting .030 over on the bore because it is much easier to find them than .020 over pistons.

They also asked me if I wanted to go to a full-roller top end, either with the "E" heads I have or aftermarket ones. Does someone have experience with this? I think I would need tall valve covers to run full rollers... right? That means my stock brackets for AC and so on will not fit over the covers, right? I may just have to do roller tips because I like AC.

Thanks again,
Mark

cutlassefi

No, you can fit a full roller rocker under the stock valve covers. May also want to consider a roller cam as well. That way you can use just about any oil you want.

classicmuscle442

Looks like I have received bad info from my engine guy, do remember a issue with #7 connecting rod bearing being the weak spot. I stand corrected, sorry for the bad info.

Mark71

The reason I ask is that a friend from the local Pontiac club told me that even doubling the gaskets didn't get him there. He had to move to tall valve covers and that kept him from using the original brackets, etc. Now, I know that Pontiac motors are a different beast from Oldsmobile motors, but... If you are sure about it with Oldsmobile engines, or at least with the 455, that would be great news for me.

So no one reacted to the one bore being 7 thousandths out. The machine shop guy said "meh, I've seen much worse", but didn't elaborate. Can I assume that 7 thou is not that big a deal?

ELY442

X2, I got in my 455 without doubling the gaskets.

Troys Toy 70

X3, no cutting on baffles, thick gasket though.

joe_padavano

Why would the #7 con rod bearing be different from any of the others?

VC455

My full roller rockers on a air conditioned 455 fit under the valve cover as well. I used stainless steel rockers; perhaps some varieties of aluminum rockers are taller.

oddball

Timing cover: That one does look fairly bad, but enough RTV will seal it. Like Joe said, they are available new, or several folks on here have stockpiles for sale.

7 thou bore: Frankly, it doesn't really matter since you're doing a rebuild. I'd want to pay extra attention for any other damage, but that's across the board anyway. Standard oversize bores are 30 and 60. 20 and 40 pistons can be found, but selection is larger and cheaper at 30 and 60.

Crank at 10: This is pretty normal, no big deal.

Main bolts: Olds main bolts are high quality reusable parts. As long as they're not damaged you're good to go. At some power level folks switch to studs and/or straps and/or girdles, but it doesn't sound like you're there yet.

Rod bolts: Same with the mains. Depends on how much power you want to make. If it's staying somewhat near stock then the original rod bolts are fine. Switching to aftermarket bolts will require resizing the rods, which can bring in its own problems. If the rods are straight and the bores are round, and you're not building a race motor, then I'd stick with the stock bolts.

Rockers: My full rollers fit under the *small* Oldsmobile script covers with a 3/8" spacer, and those things are much smaller in the corners than the normal covers. Still fits under the A/C bracket. The key is the polylock and stud - not the rocker. Need to use the short 1" polylock. Regardless, the utility of this change depends on the rest of your combo. It doesn't have much value until you're talking about higher power and more agressive cam profiles. The roller tip kit is cheap, cheery and effective. Just throw away the pushrods and locknuts that come in that kit. I'm very serious about the pushrods. Depending on your cam - and therefore the spring pressures - you may need the shop to drill out the mounting pads for a larger stud. Mild cams with stock-ish springs are fine for the Comp conversion studs (5/16" in the head, 3/8" on the rocker).

Oil pump: High pressure units just have a higher tension bypass spring (or just washers to load up the spring). This is of no use to an Olds engine. Maybe other makes that have spectacularly terrible oiling configurations? HV or standard is fine. Something has to have gone terribly wrong for the pan to get sucked dry. It can happen - happened to me, when the engine was burning 1 qt of oil per tank. Wasn't because of the oil pump though. If you have an oil pressure gauge then it's easy to tell - pressure will flutter as the pump starts getting air, and it can sit in that state for a little while before it actually runs dry. In any case, one big benefit of the HV pump is a bolt-on pickup. Milodon has a nice stock style pan with matching bolt-on pickup. Still measure clearance though. Mine sat on the floor of the pan when I bolted it together.

Pistons: Depends on what you want to do. Forged are stronger, but require more clearance which can make them noisy. That's why it's important to pick the right mufflers. Stock-replacement cast are fine for mild builds. Hyper tend to be inbetween regular cast and forged. There's other considerations, like piston weight and ring package. But it depends on your goals. If it's a mild rebuild then just about anything is fine. The shop will need to inspect your pistons before they bore the block. Ideally, at least.

Roller cam: It's a good idea, but adds quite a bit of expense.

classicmuscle442

Have had two of my engines spin #7 bearing. Used Cheby rod to replace #7 rod and was able save crank.

wr1970

Chevy rods or one rod.

Troys Toy 70

I thought Chevy Rods were 7, and not 6.75 rod length. How does this work? Why #7, what would make it different?

wr1970

Now i am really What about rod journals being different. Then there is the balance of rotating assy. He must have changed all the rods to chevy.

GOSFAST

Just a tip, but running the retro-hyd-roller gives you an add'l 30 HP by design. Slightly harder build overall though!

Thanks, Gary in N.Y.

P.S. I would most definitely NOT use a hi-volume pump, first, it really isn't necessary and second, it's harder on the timing chain and the oil pump driveshaft! Just my opinion, we rarely use any HV pumps, most builds here get hi-pressure pumps only!

Mark71

The HP gain is really from the more aggressive cam profiles, though, right? The only problem I have with a roller cam is that they seem to be pretty spendy. Gotta keep a watch on the budget, but I do appreciate the info.

You guys have me convinced of a few things, though:

1. New timing cover, definitely
2. Forged pistons, definitely - sounds like it is worth the cost, especially on a first-time build.
3. Roller rockers, probably - machine shop says I don't have to decide right away.
4. HV Oil pump, maybe - gotta do more research on this; seems like both sides of the argument have their points.
5. Hydraulic Roller Cam, maybe - need to check out costs on this.

I will have a lot more questions coming up about this rebuild. I will try and remember to add them to this thread to make it easier to track.

Thanks,
Mark