Just blew up my first engine rebuild due to ignorance, so I'm back to square one. I'm seeking advice and ideas for the second attempt. There's a fair amount of thinking aloud in the following piece, feel free to correct me if I'm wrong.

Vehicle:
- 72 Supreme
- 2.56 posi rear (highway cruising is 80+ MPH over here)
- TR3550 (3.27 first, .68 fifth)
- (currently powered by a '71 350/350 with a rejetted '77 Qjet.)
- Headers and dual exhaust.
This is currently used as a daily driver, and will remain as such for the foreseeable future.

Engine:
- 72 350 block, +.040 with a sleeve in #8. Needs cleaning and a hone.
- 7a heads, 3 angle valve job, 50% new valve guides. Heat crossover filled with aluminum, exhaust divider welded up for headers.
- Nodular factory crank, currently turned .010 down, needs further down-turning due to the engine failure.
- Pistons are trash, were hit by valves, two were overheated. One kissed a head.
- Stock rods, suspect they've been overheated.
- Valves have all touched pistons.
- Stock intake
- Cam was a mild Howards cam, which has bits of bearing fused to the lobes. Need a new one.
So, I have heads, block, intake and crank worth bothering with, the rest is questionable.

Extra goodies:
- Accel DFI GEN VII pro-ram Thruster package. Came with a Chebby setup, so I need an injector intake, rails, and injectors of the right size. Preferably a dual sync dist. and a crank sensor down the line. Got it reasonably cheap.

Goals:
- Mileage (daily driver, $8 a gallon over here. Some would say that I should save the money and spend it on gas instead, but I like to have an efficient vehicle, as much as possible within set parameters).
- Longevity. I'd like the engine to run at least 200,000 miles (maybe not the timing chain) before a rebuild. Can it be done?
- Streetability. I'm a pretty adaptable guy, but an engine that doesn't like traffic isn't nice.
- Efficiency. No unnecessary gas out the exhaust, not burning more oil than necessary, no exuberantly extravagant manners.

Ideas/wild-*** guessing:
- Roller cam? Pros and cons? I certainly know that I can be a lot more relaxed in my oil choices with one of those. Do they last longer than flat tappet cams?
- Lighter pistons, pins and rods? Seems that the less mass these parts have, the more power will be transferred to the transmission. Are such parts available?
- Electric fan? Is there any conclusive proof that it's less energy consuming than the traditional fan?

Torque is a physical term defined as power multiplied by distance(Newton*meter, ft-lbs), the distance being the diameter of the crank (a static size in an engine) and the power derived from the combustion. So, the torque your engine makes is changed by changing the variables and statics. BBO makes more torque out of the same air and fuel as the SBO due to stroke - or rather, crank diameter, but the two are connected.
- Stroking. As far as I can read, it's rather limited how much I can stroke the factory crank, especially since it needs to be turned down before this can happen. Something about Chebby rods or some such. I will lose RPM capacity, but gain torque down low, yes? That'd be a good thing for me, seeing as my transmission will need torque to get me started with my tall rear, and the more torque I have, the higher gear I can run without stalling out - within reason, of course. This will help mileage, and longevity by decreasing RPMs.
- Porting. Here we have the other factor. From what I've been told, Olds heads are restrictive, especially on the exhaust side. Makes sense that it'd hinder the engine, seeing as a bottle neck in that area would eat up power on the exhaust stroke(leeching off the opposite piston which is at that time firing), since it takes more effort to force hot air through a pinhole. I've also been told that the exhaust side should only flow ~80% as well as the intake side. Why? What possible advantage is there to trapping the exhaust gases in your cylinder when it serves no purpose? Not trying to be snarky, I am just trying to understand this.
Intake porting is a more controversial thing to me. Will the engine consume more when the intake runner is opened up? Presumably, because it CAN suddenly consume more. But by my reasoning, it will also add torque, meaning I can lower the RPM and thus the increased consumption per stroke will become a non-issue. Same power, lower RPM. Ahh, now we're talking efficiency. I like this.


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I do not claim to be an expert, I'm just looking for ideas and answers to my musings. Feel free to comment. Thanks for your time.

 

- Electric fan? Is there any conclusive proof that it's less energy consuming than the traditional fan?
=======================
I work with fans. Rather larger, on the order of 36 to 55" fans. We are all about efficiency, cfm per Watt consumed is a major factor in selling fans. We generally operate at pretty low pressure across the fan, up to 0.15" water column. Many variables affect the efficiency- prop speed, number of blades, pitch. shape of blade... etc. Tight fit to the orifice is essential, more so at higher pressures. We spend a lot of time at a giant calibrated air flow chamber at the University to alter variables and get verified publishable efficiency figures. That said, it seems to me that an electric fan, presumably optimized for automobile cooling at its one given speed [they have not yet implemented brushless motor variable speed technology], should have great efficiency compared to the best clutched mechanical driven fan, which is still more or less tied to the engine speed. Proof? No, I do not have that.


- Porting. Here we have the other factor. From what I've been told, Olds heads are restrictive, especially on the exhaust side. Makes sense that it'd hinder the engine, seeing as a bottle neck in that area would eat up power on the exhaust stroke(leeching off the opposite piston which is at that time firing), since it takes more effort to force hot air through a pinhole.
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there's little doubt that easier exit makes for better efficiency. Some dragsters use short pipes angled away from the motor a bit.



I've also been told that the exhaust side should only flow ~80% as well as the intake side. Why? What possible advantage is there to trapping the exhaust gases in your cylinder when it serves no purpose? Not trying to be snarky, I am just trying to understand this.
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One possible reason- the driving force on the intake side is a PARTIAL vacuum as developed by the piston, with a MAXIMUM possible pressure differential of oh 14.7 psi. Whereas the exhaust is dashing out as soon as the valve opens, with hundreds to thousands of PSI forcing it along, then furthermore being chased out by the rising piston. MUCH greater driving force, regardless of the size of the exit door.

 

So, electric fan is definitely a good way to up the effectivivity (effectivize?). Thank you. Proof or not, you know a LOT more about it than I do.

So we've concluded that everything I can do to open up the exhaust side of the heads is worth doing, short of making them bigger than the headers and thereby choking it up. Excellent. The rule of thumb still confuses me, since it'll still be hindered more by a restrictive exit door, no matter the force behind it. In an ideal world the exhaust port would be so big that the opening of the valve would result in near-instant 1 BAR in the cylinder, before the piston ever start moving upward. I hope you get my point.

You point about the intake being very restrictive in comparison is also interesting, since it contradicts the snipped I picked up about exhaust being the restrictive part of the Olds design. What a mystery.

Shorthand? 2 valve throttle position pumping losses? Makes no sense to me.

 

The intake flow results from only atomspheric pressure (14.7 psi theoretical, less in reality) across the port. The exhaust flow sees greater than atmospheric pressure from the piston pushing the gas out on the exhaust stroke. The higher delta pressure across the exhaust port doesn't need as large a port as the intake side to get the same mass flow rate. CFM is easy to measure but mass flow rate is what matters.

 

Ahh, so modify my statement to 'need only flow 80%' and we're good, yes? I was worried I could port my exhaust too much and create an imbalance. Doesn't seem the case.

 

A high performance shop wants the exhaust 72-75% of the intake flow. This is for any brand of engine and told to me by a few mighty successful race engine builders.

 

Your interpretation of torque is a little off.
Peak torque occurs when the cylinder is filled most efficiently. Overall torque is the ability to fill the cylinder efficiently throughout a range of rpm.
People say "Olds make more torque". No they don't, they make more torque earlier because of the smallish ports. Big block Olds make more torque earlier because of the smallish heads not necessarily the increased stroke over most other Detroit big blocks.
Fact, Olds BB has a 4.25 stroke, known for it's torque. But explain this, a 455 Buick is also known for it abundant low end torque but only has a 3.900" stroke, less than a 454 Chevy, hmmmm. Optimum Cylinder filling is the key, and when it happens.

Furthermore use a piston that's light and has a smaller ring pack. Program the EFI to run as lean as possible at cruise. Limit the cold start mode and optimize the spark at every rpm and load. That will help as much as anything.

Hope this helps.

 

Yep, there are a lot of SBCs running fast with 2.02 intakes and 1.5 exhaust valves.

 

380: So it's a nigh-universal rule that has some deeper reason. Without a flow bench I'll be flying blind anyway, so I can only follow a DIY recipe and hope for consistency between ports. Nice to know, though; thank you.

Mark:
- No used RPM intakes over here, not that I've found so far anyway. I'll keep looking. The engine can always run carbed for the first while anyway - the Qjet runs very well for a carb.
- Roller cam: I assume you haven't suggested one because that's the last part of the combo to be chosen, once I know compression, intake, etc.
- Recommendations for light pistons with a small ring pack? "Hypereutectic" gets thrown around as the "new thing", more modern, longer lasting and less wear, etc. Overkill for my application? Factory rods the best thing to go for?
- Sizing for my pistons? Should I be on the safe side and go for a .060" overbore, or? I can certainly measure the bore if that helps. It's theoretically 4.097".
- Optimizing the spark at every RPM: Don't I need crank sensor for that, and a dual sync distributor?

I'm very much learning here, but I'd rather ask than blow up another engine.


As for my understanding of torque, you just pointed out that flow efficiency, thus how well you fill the cylinder, is half of what makes torque - stroke being the other half. The Buick must be better at filling its cylinder at low RPM, because evidently it makes more torque than a BBC, despite having a shorter stroke. They have nigh-identical displacement, so the Buick must be better at filling the cylinder to make up for it. I didn't invent the definition of torque, Archimedes did, so there's two ways to make torque - fill the cylinder (add power), or add stroke.

Why does a smallish head lead to more torque at fewer RPM, though?

 

No it doesn't, it makes more torque sooner.

A smallish head will make more torque sooner because of mixture velocity. It will fill the cylinder more efficiently at lower rpm. But at the same time hinder hp on the other end for the same reason, limited flow.

By the way, it's never been proven definitively that say adding 50c.i. via a longer stroke will give you anymore torque than the same c.i. increase via a bore increase. In fact quite the opposite may be true. A larger bore normally enhances flow by further unshrouding the valves. And you don't have to contend with increased piston speeds from the longer stroke.

 

I'll have to research the Chevy rod/Chevy piston thing. If it's lighter, cheaper, easier or any of the above, it's certainly not a bad idea. Thin/small rings sounds to be what makes modern engines wear their cylinders less, so that's desirable for sure. Is it a "standard package", specific rods with specific pistons that work? Compression height and rod length would need to be close to work, if I understand correctly.
Boring is not something I'm opposed to at all, but I'm concerned by the lack of experience with Olds motors over here, and the lack of torque or bor-tru plates on this continent.

Good thing about the spark control, then I'm happy.


When I say half and half, I'm referring to those two elements being the determining factors - not a 50/50 distribution between the two elements. If that's not what you were correcting, then you've lost me.
I would have thought that mixture velocity was part of the 'filling the cylinder' cover-all. Does it go as far as meaning I should limit my intake porting to make sure I don't lose low-end torque?

The stroke vs. bore increase argument is interesting, and I have no reason to contend it - it makes perfect sense. I only stated that the same power applied to a piston with a longer stroke would make more torque than the shorter-stroked version, with factors like valve shroud discounted. A healthy dose of real-world experience is appreciated.

 

This is just my opinion mind you, but I would first learn to walk before you run. You bring up some alarming points, for instance no torque plate when honing and "the lack of experience with Olds shops over there. I would be very uncomfortable with just a "hone and cleaning of the block". Before even considering Chev pistons and rods, thin ring packs, Efi etc, I would concentrate on the manditory machining and checking all the basics; rods, crank, block, etc. You talk about porting the heads, but make no mention of guide/valve damage, magnafluxing, stem heights etc. Without experience under your belt and no experenced machinest and proper equipment, I would stick to the KISS principle, keep it simple, don't skip essential steps and always remember there are lots of ways to do it wrong, only one way to do it right.

 

Just my 2 cents... Mark built my engine for me. (bored and stroked to 380) We discussed what I was looking for as far as performance and drivability. The horsepower and compression were very close to his predictions. The Torque is amazing! (proven in dyno testing) I plan on going on long trips with this car so drivability is a big factor for me. the ability to use 89 octane fuel was another strong consideration. Not every area I plan on going to has 92 octane fuel available. He will steer you in the right direction.

 

1970-W30: I'm working on my own shortcomings and HUGE areas of lacking knowledge - that is what part of this exercise is about. The craftsmanship in the machine shops over here is very high - the knowledge about Olds engines is non-existent 99% of the places. The first time they renovated this engine, I was asking them what they thought needed doing, and that was the biggest mistake - I should have been telling them, but I didn't know at the time.

None of this is coming together, or even being ordered, before I'm sure my block is okay. But I can certainly lay down a long-term plan for this (or another) engine, no? There's no sense checking factory rods if I don't intend to use them, for example.

When I rebuilt the engine the first time, I measured stem height - it was uniform with new valves across the board, and within tolerance. Springs were good too. The guides are questionable at the moment, due to possible heat damage.

I've been tipped off about a old-time machinist that lives relatively close by, who has experience with classic engines. Have been meaning to call him one of these days.

The lack of torque plate is an unsolved problem as of yet, though. Will have to work on that.


Kitfoxdave: I've seen many references to his work, it's very impressive. Not arguing, but trying to learn by understanding.

 

Mark is a very helpful resource on this site. He will help you understand. Your English is quite good and I am sure folks here will try to be as helpful as possible. If you need something clarified, please ask!

 

Seff, as far as the torque vs porting question, it is helpful to look at the airflow through the engine as a liquid rather than as a gas, because at most speeds, it behaves more like a liquid anyway.

Think about how the air feels when you put your hand out the window at 70 mph - it feels like when you put your hand in the water when you're in a motor boat.

The same thing happens inside the engine.

The mixture flowing through the carburetor, intake manifold, heads, valves, combustion chamber, valves, exhaust manifolds, pipes, and mufflers behaves more like water than like air. It has a hard time going around curves and past sharp edges, forms eddies and back-flows, and has significant mass and therefore inertia.

The same amount of gas flowing through a narrow tube will have more velocity, and therefore more inertia, than flowing through a large tube. This means that it will tend to keep moving even when its flow is interrupted, such as for a closed valve - because it's a gas, it's compressible, so the portion in the beginning of the tube can keep moving forward even if the portion at the end of the tube has been stopped by a closed valve.
this means that when that valve opens, the gas near it will have been pressurized by the gas behind it in the tube, and will flow into the cylinder, and chase exhaust gasses out of the cylinder, faster than it would if it were in a larger tube.

That is why you get better torque from narrower tracts.
Of course, for absolute power, the larger the flow the more the power, and the larger the tracts, the larger the flow, so racing engines, which will be operated wide-open most of the time, will have huge intake and exhaust tracts and valves, but these same characteristics would make those engines dogs at part-throttle, which is where anyone with any common sense, driving on the street, drives 95% of the time.

Every engine is designed with specific power and torque band characteristics in mind, and all parts must be designed with the same set of characteristics in mind for it to run well.

- Eric

 

Completely agree with what Eric said in above post, especially the 95% of street driving is not anywhere near full throttle.....

 

Kitfoxdave: Thank you, and I agree about Mark. I'm half American, so that's where my English skills originate - though they've been honed and refined through DAYS of Internet debating.

Eric: Ahh, that makes more sense to me. This confirms that I will get more out of exhaust porting and maybe intake port matching, than I will from porting the hell out of the intake side. Bowl blend will still be done, though, and maybe valve guide tear dropping.

1970-W30&Eric: I agree - with the transmission I have planned for this car, I will be going for the highest gear possible, and thus relying more on the low-end torque than anything else.

 

Here is a thread that you may want to check out... comparison of a few different SBO heads on the same flow bench...

https://classicoldsmobile.com/forums...w-numbers.html

I hope this helps!

 

Anybody catch the latest HP TV?

400 Chrysler block based on a 4.34x3.38 Bore and stroke (Sound familiar? Can you say 403 Olds?)
"Stroked" to 451 by using a 440 Chrysler crank, 3.75" stroke.

Yes they "stroked" it. However it made 555 lbft of torque and 480hp, with a stroke of only 3.75 or a half an inch less than a 455 Olds. See my point?

You don't necessarily need a long stroke in order to make good torque, plain and simple. I think it would be fair to say the large bore helped as well by unshrouding the valves and improving breathing. That enhances cylinder filling and consequently torque as previously mentioned.

 

That's very impressive.

Never said stroking was the only way to make torque - it's ONE way, though.

 

Just my opinion, but one of the worst things you can do is hog out the intake, kills port velocity (which is the secret to torque). Also, I would not port match the intake, again you can do more harm than good. For what you are doing, a VERY good valve job with a little bowl work is all you need. JMHO. Don't re-invent the wheel.

 

Sounds good to me.

So, order of the day is to find a machine shop that actually knows something about old engines and have him tell me how big my bores ACTUALLY are, and how far he can hone and/or bore them? So I know what size pistons I can go with. Then have him measure the crank as well. Yes?

 

I called the engine shop, they agreed to take a look at it, tell me what options I have with the block as it is now. I'll bring the heads in as well for good measure, just in case he wants to see them.

Is it feasible to make a torque plate by myself? As far as I can read, it's 'only' a 2" thick plate with holes for all the head bolts, so one can sandwich the gasket between the plate and the block, getting the bores distorted like they would be when the head is torqued down. Is it wise to torque the main caps down as well, while honing?

 

If you're going to do the Chevy rod and piston thing then you may want to have them sonic check it first.

And too bad you don't have a Bor-Tru plate. That can be just as beneficial as a torque plate.

 

Sonic test will be discussed with the engine guy. Are the Chevy pistons a specific size since you suggest this?

The Bor-Tru plate is the one that makes sure your bores are 100% perpendicular to the crank rather than to the deck, yes? I'll ask him what, if anything, can be done to reach that goal by other means. Likewise Torque Plate will be discussed. I'm not having him do anything yet, I'm assessing if he's up for the job.

 

Hope this helps.

 

Alright. How about for a setup with the normal bore/stroke ratio? I'm not seeing very many Hypereutectic pistons with a CD around 1.6 and bore around 4.100, so I suspect it might be. This is merely shopping around on Summit, mind you.

I'll tell the machinist that the ideal is to have the bores perpendicular and centered over the crank journal, and see what, if anything, he suggests.

You have no idea how much.

 

Start here;
http://www.summitracing.com/search/d...c/plus-12-00cc

 

That compression distance is going to lower my compression, isn't it? Running 7a heads. I suppose it's no big deal to mill the heads.

EDIT: Ran it through the RSR Static Compression Ratio Calculator, puts me at 8.67 with the +12cc pistons. Is the 3.480 in. stroke what you'd recommend for the build? I gather that domed -3.3 cc pistons are a bad idea due to the valve angle differences between Olds and Chevy. The next down is the +5 cc, which nets me 9.22 static compression. This is with an assumed 68 cc combustion chamber and the reduced compression distance converted into added head gasket as a means of factoring it in.

EDIT2: All Chevy rods are 2.2250 in. in the big end? Olds 350 rods seem to be 2.2495"-2.250".

 

I would not take for gospel that your heads are 68cc, it's not that difficult to cc them, a piece of plexiglass (with a small hole)and a burrette will get you a right on the money , rather then than assuming the heads are 68cc. When building an engine, do not assume anything, it will get you into trouble....
just my two cents worth.

 

It GOT me into trouble, that's why my last engine blew up, and that's why I'm calculating instead of slapping things together. The above was a preliminary assessment, so I could get a mental picture of the setup as it is currently proposed.

 

You're getting confused. The piston I listed is if you go stroker, grinding your crank to a 3.500 stroke using 2.00 Chevy journal with a 6.00" Chevy rod. That piston will round out that combo. With a 66cc head and the 12cc dish you'll have about 9.7:1, a little less if you have some deck clearance.

The deck on a 350 Olds is exactly .300 taller than a SBC. You can go from there.

 

I was indeed very confused. I'm not dead-set on stroking it, but it's attractive. 374/ 6.1 liters is very fun to think about. The bore to stroke ratio is nearly the same if I understand correctly, 1.17 is good, yes?
My biggest concern is that my crank has lost too much material to make this doable. Could oversized bearings help make up for this, if necessary?


Order of the day tomorrow is having the shop look at the block, heads, old pistons+rods, crank, bent valves and so forth. I basically packed everything, though only one of piston, one pushrod, one lifter, etc. I would have gone today, but they said over the phone that the master machinist would not be in before tomorrow. First thing they're doing after that is sonic test the block. If they can't, I think considering a different shop is in order, yes?

EDIT: As for compression, the two standard octane ratings are 93 and 95 AKI, which corresponds to 88-89 and 90-91 by US standards. The slightly more pricey stuff is 99 AKI, which would be 94-95 RON. Polishing the chambers helps combat detonation, yes?

 

I wouldn't worry about the bore to stroke ratio, not an issue. You'll just need to see how much material is left. If you can't stroke it to that they can always grind it to the SBC large journal size, then any undersize from there. If you keep the same stroke you can use a 6.200" rod and that piston in a 1.425 cd. That'll make a 363. I've done 2 of those, worked very well.

And 99AKI is not 94-95 RON, it's about 94 R+M/2, that's 1 point better than our 93. Ask me how I know that.

 

Ah, so I still have options. Good.

Hah, well, that's what I get for trusting wikipedia. You guys don't use RON?

 

The engine shop didn't have sonic testing, but I've found a company that does sonic testing. The machinist didn't think it was needed for taking off so relatively little, but I gather you've built more Olds engines than he has.

 

I would think that by the looks of those pistons/valves that heat was a definite issue. That block will have to be re-magged and cyls checked for roundness and the decks checked for warpage. Same with the heads. Could have cracked a seat, warped the deck, or ruined the guides. Sonic testing is just an insurance policy, but with only a .040 overbore, you're probably alright.

 

How about with the proposed .068 overbore? Doesn't sound as likely.

The guides are ruined on one side, I'm going to have all of them checked, at least.

Not sure the block was ever magged, and I have no reason to believe it was honed using a torque plate, so roundness was suspect to begin with. I should have never put that engine together in the first place, but oh well.

EDIT: The sonic testing guys I caught had NEVER tested an engine block before, so I'm wondering if they could even give me a straight answer. I youtube'd it and it seems that you measure the cylinder walls for thickness. No other way of doing that?

As for heads and deck, I'll run a straight edge over it as a start.

 

I think you'll be ok on the wall thickness, .068 over on an older 350 isn't normally a problem.

I'm sure you may have trouble finding a torque plate over there, stands to reason.