I had my block decked and am running 10 to 1 comp.
I do have detonation issues which I have not really looked into yet.
I think my gaskets are fel-pro but cannot say for certain.

I'm not exactly sure on the pistons either but there nothing special just a run of the mill brand.

I will check when I get home hopefully next weekend as I'm working out of town and do not go home.

I've been working 7-12 hour days since the first week of sept.

To find out what the compressed thickness of a head gasket is, place a small lead pellet in an appropriate location and torque down the head. Pull the head off and measure the pellet.

I had cast pistons (can't remember brand or part #, again nothing special) with very little chamfer around the top, zero deck, "normal" valve pockets, file fit rings, Fel-Pro .039" thick gaskets, ported #16 heads, RA IV cam and 1.5 rockers, stock 4 bbl intake and Q-jet, recurved dist., three tube headers, 2.5 duals and Sonic Turbo mufflers, three core rad with shroud and five blade stainless flex fan, TH400 and 2.56 gears in one car, T10 and 3.23 gears in another. 3000 feet above sea level, premium unleaded, no overheating or detonation problems ever, lots of highly illegal top end blasts for a few miles and extended highway runs averaging 85-90 mph in mostly 80 - 85 F temps max, engine made good power and mileage, 36 degrees total all in by 3000 rpm.

vikki,

i didnt know your gear was sooooo looowwww! you should get into the higher range. it will DRASTICALLY improve the power you feel. while in there you should install a posi. i'd go with a 3:08 and posi carrier for it. while the 400 can lay rubber with the 2:76's you have now when it happy, its not always happy is it? the higher gear will set you back in your seat better without the need for added power to do it!

Yes, Drew, I know. But the car is destined to rack up a lot of highway miles. I commute in it in fair weather, go to distant shows and cruises, and drive it around like any other car when the weather is fine. The numbers matching gears (factory posi) will stay in the car.

I want to address the engine issues. I do not want it damaged by detonation. It's easier and cheaper to prevent damage than to cure it.

why not do as you said you would and build the engine i brought you to build as you said you planned? damage to that engine wouldnt matter much now would it?

The '69 will stay numbers matching, along with the '68 400 4 speed. What good would it do to put the engine into storage in less than optimal condition, and if I was to pull it out later for use it would have to be rebuilt anyhow, so I will just do it now. But I don't want to alter the block.

I have two more that are not numbers matching. I also have another fine 400 block if I decide later to build something else to thrash.

I'm looking for a '67 vert for that '67 engine.

I'm not trying to be a smart a$$ because I know I have a lot to learn, but they do talk about zero decking on Jim Hand's book. P95.

Yes, they do. I think it was quoted a few pages back, too. But the measurements he decked to correct don't exist in an original block with original pistons, so more than a "deck the block" decree is needed. I have no doubt it will do wonders for a poorly designed set of replacement pistons. But is it necessary for a custom set of Ross or Diamond pistons? Probably not.

TOHCan posted the optimal quench distance and compression height. Armed with that, with compressed gasket thicknesses per manufacturer, and with piston-below-deck measurements an educated decision can be made regarding decking the block.

I have a lot to learn too, hence the start of this topic.

Every advice I read and discussed by PM from capable engine guys is to deck the block. I understand not wanting to grind down 20 thou on a numbers matching stock block. That's why a mentioned perhaps moving the piston top up with a custom piston instead of grinding the block down. Custom rod will do that too, but I figure the piston will need dishing for a lower CC head anyway, for pump gas. Especially after I just bumped cr up a bit by decking the motor. A custom piston will do this all in one purchase. The $500 Ross custom piston will be lost in the total expense. At the same time, the custom piston can be dished to lower CR a bit, depending on the head. I'm not sure how that effects quench and detonation. I have not found much discussion about that.

I guess my problem is a bit different. I have a 71 GTO motor with '96 heads. I need more compression not less and I don't mind milling zero deck or reducing the chamber volume on the heads to get to the sweet spot. My motor doesn't numbers match anything now.

Saying the original engine wasn't decked from the factory and ran fine with original pistons back in the day doesn't address the concerns of todays octane fuels. Lets remember that the stock block didn't and couldn't run decent on today's pump gas. My 350 I had in 1968 required Sunoco 230. I ran many tanks through above and below 230 and that was the best choice. Otherwise it pinged. Or a grade higher I paid $2.60 instead of $2.45 to fill the tank. My mom's '67 Olds 88 350 Rocket had to have Sunoco 260. Without 260, it could drive for miles around town with the ignition off.

Zero decking helps reduce detonation by permitting less advance for the same sweet spot on power. It reduces heat also. Since what isn't heat is more output, you get more power. I think zero decking is just about a given for a rebuild on a car one wants to drive. The question is my mind is to do it in the pistons (more cost) or machine the block (damage no's matching block). Since you can make new pistons but can't replace metal on an original Pontiac block, I would tinker with the pistons.
In other words, I would consider having the block decked flat and no more. Perhaps the machine shop will come back with advice the engine is adequately true without any milling. I read Mr P-body of Central Machine, Va saying align bore should not be routine, but rather the engine checked to see if it really needs it. That flys against notion of blueprint everything, grind it to spec and make it all new, but grinding stuff down isn't renewing, it's refurbishing, right? Anyway, then knowing what brought the engine true at the machine shop, define the pistons and have them made to suit.

I think the second half of the issue is to get down between 9.2 and 9.5 compression ratio (assuming iron heads). Then you can enjoy the car on pump gas and not trailor it around or baby it or need to feather the throttle because marbles are bouncing around under the hood. You then don't need to be within a hundred miles of racing fuel and your home mixing gas containers. To me, that is what the car is about. Driving the car, WOT at times, no worries and filling up on pump gas where you find it is the win.

To me, the ideal is to run on pump gas and enjoy the car. And pump gas is a loose term that I think will deteriorate even more in the next ten years. Newer cars run on 89. Eventually that will be what you can buy.

If a 400 won't produce the desired power at 9.2-9.5 CR, then its time to stroke it with an eagle crank or a turned 455 crank. I know it's not no's matching stuff, but if you don't grind down your engine and don't throw away the original crank, you have a path back to originality. That is what I see as most important... to not throw away history. So I don't see that ross piston or different crank as horribly important because it's out of view. At least not when driving and enjoying the car is at stake. I think that custom pistons and even an Eagle crank is better than closing the hood at car shows because you're wearing aluminum aftermarket heads. It's better than milling off metal you can't put back too. Aluminum heads let you run more compression, but they just don't look right on a restoration. A ported iron head or port matched intake isn't strictly no's match, right? It looks right, but it's an improvement at least from many peoples viewpoint. I guess with my faulty reasoning, you could say store the iron head and install the E heads and move on. Or even store it all and run Cheby box stuff. I guess we all have lines drawn in the sand. Life is full of compromise. We all have tough decisions. Trade off is between totally original and drivable and how to get there? If you buy Sunoco 230, all the original stuff will work perfect when it's up to spec.

[quote] [/q At the same time, the custom piston can be dished to lower CR a bit, depending on the head. I'm not sure how that effects quench and detonation. I have not found much discussion about that.
uote]
68Bigbird, You are right on your post on 0-deck but you seem to have misted the point that if you use 0-deck to get the proper quench height by cutting the block or by using taller pistons you CAN run 10 to 1 compression on pump gas with no detonation.
If you go to all the trouble of 0-decking and then dish the pistons to reduce compression you just lost the power gain you wanted in the first place.

The other part is being careful with the cam you use. Need one with late intake valve opening to help with dynamic compression, Should be around 170 LBs per cylinder.

The cam may be why Vikki will have trouble with 0-deck. (she wants to stay original).

Whenever I read these long tech posts about zero deck I get the impression from the writer that there is a problem running an exactly stock Pontiac engine. I want to assure you there is no problem at all. They run perfectly. I drive mine around three times a week at about three hours a stretch. I do have to pay a little more for fuel. The fuel is readily available here because there are so many of us here that use it. I talked with the gas station owner and he says that he has no plans at all of discontinuing selling the racing fuel because he has a great source for it and he sells a lot. I'm a firm believer in "If it ain't broke don't fix it".

THE only problem is in order to gain hp you must change the configuration as a whole or else the sum of its parts will not matter! vikki has a gear that is not suited for what she sdesires! the stock block doesnt need to be decked in order to offer bteer performance. in fact she could gain 30+ hp just by having the engine balanced as it is assembled! you'd be surprised what an engine feels like when it doesnt have to fight itself to work! better response, quicker off the line, over all well mannered and for just a few ponies more, you too can have one just like it

I want the car back to stock performance. That does not require a gear change from the stock gear. Yes, I could make the car quicker. I don't care how quick it is as long as it's not a slug. I have other toys to play with when I want to drive hard. But I do need to stop the engine's self-destruct cycle and can't embalm yet another 400 for a 20 year nap. Restoring factory performance should not require major changes on an engine that has not been modified previously. If it does, something is wrong with the plan and the process. I have faith that Pontiac knew how to build an engine in '69 just as they did in '68.

most people here wont agree with you vikki.most have tried to modify what gm did but all they ever do is shorten the life of a motor.i always put my cars back to stock but i am only a certified auto mechanic,maybe if i was a plumber or an air traffic controller of a layman i would know more than the engineers at pontiac

At the risk of alienating a few people, engineers aren't gods and even if they were, they aren't allowed by the Powers That Be (accountants) to build what they'd like.

There are lots of ways to improve the performance and fuel economy of a factory built engine and at the same time improve the life expectancy and reliability. Most of them were probably on the engine designer's wish list before the cost cutting for production.

GM offers crate engines that they can't put into cars that they sell. They know how to build better engines - and they're not alone.

I would have no more problems with my conscience decking a numbers matching block than I would boring it for .030" pistons, installing new guides, grinding the crank, line boring the block, sizing the rods, balancing the internals surfacing the heads, grinding the seats - all of which remove "original" metal that can't be put back - in the interest of building the engine to run the best that it can. I don't worry about duplicating some of the compromises that the factory made for the sake of saving a few pennies per car.

But that's just me. Everyone is allowed to do things their way! Now for a teaser: wouldn't taking .020" off the block with stock pistons be closer to factory than a set of custom pistons in an uncut block?

There are some good reasons to zero deck a block. The reason(s) for zero decking do not include making a stock engine run great. That can be done with the pistons slightly in the hole.

Jim, they do include making a stock engine run better. That's the whole idea.

I understand that opinion. It's valid in certain circumstances. But they run great without it.

And they run better with.

Just to clarify, I'm talking about the correct piston to head clearance, not cutting the block just for sake of saying "my engine is zero-decked"! This isn't questioned, it's a given - in all circumstances.

My main point was to address detonation problem of the original design operated on widely available pump gas by setting zero deck and dishing the piston. That way you drive the car where ever you want without concern for finding fuel that won't harm the motor. This idea is supported in the article at:

http://www.speedomotive.com/t-showbymodel.aspx

With the concern of milling the deck on an original motor, I proposed the alternative of moving the pin in the piston (taller piston) so zero deck is still obtained without cutting the deck. The stroke and compression remains the same for either way of setting zero deck. I don't see there is any real difference in outcome for either approach.

You can argue the original motor design ran fine. And it did with fuels commonly available in the day and when the engine was fresh and had good oil control. The point of this discussion in my mind is to return the engine to reliable operation while running it on widely available fuels. If the engine is detonating, the reliability will be poor. We have a few here with engine failure caused by detonation.

Another thing to consider is as the engine wears and had poor oil control, oil consumption will lower the effective octane. That may be why some combinations run okay at 10:1 while someone else building the same recipie has problems. Taking the compression down to 9.2-9.5 gives you more margin than 10:1 for fuel variations, tuning error and wear.

Just as TOHCan says you don't zero deck so you can say you did it, you don't cling to factory CR and all original parts just to say you did it when the sacrafice is not enjoying the car because you can't take it out of range of good fuel.

Quote; you don't cling to factory CR and all original parts just to say you did it when the sacrafice is not enjoying the car because you can't take it out of range of good fuel

No sacrifice here. That's my only point. I sacrifice nothing by using the original engine configuration. You don't need to accent a negitive viewpoint to bolster the zero deck idea. One thing that you can't do is make an argument that you can't enjoy driving your first gen with the original engine configuration. Not around here anyway. I can drive as far as I want to. It runs great. Perfect. Not a ping. Plugs are clean.

bottom line it's about fuel?

Exactly!!! If you can get it then your golden. If you can't then start modifying.

It's not only about the fuel/detonation issue, although it is definitely important on a street/octane-challenged engine. The engine will make more power because it will need less spark advance (because of the extra turbulence during the burn caused by the squish). That means that there is less negative work - the piston doesn't see as much cylinder pressure before TDC. The quicker the burn, the less advance the engine needs and so less power is taken away from the output.

This is SOP on racing engines where the octane level of the fuel is not an issue - maximum power output is.

Like I keep saying, if you have good fuel there isn't any problem to fix. Just like back in the day, they run perfect with just the right amount of power. At least my 400 does. And that's just my opinion. I'll take some video and you can decide if it runs good in your opinions.

id say rebuild it to stock and if you dont like it, modify it! simple as that!

Well, I thought we were discussing what to do with an engine that was headed to be freshened up. I surely wouldn't rip open an original engine just "set deck at zero" as a vague claim if there weren't any issues with the motor. But when you are spending new dollars on an old engine, one is faced with lots of choices. These choices involve difficult selections between current fuel, future fuel quality, trips to buy racing gas and the planned use for the car. Originality is also a concern, but I surely wouldn't search out NOS main bearings, cause no one will ever see them. Many of these choices have only minor impact on the final cost for the engine rebuild. For instance, $200 on pistons vs $500 on custom pistons will be lost in the final price on an engine rebuild that you won't see completion of for less than $3000. I know the difference is a few hundred bucks. But I'm looking at longer term use of the car with fuels we can expect to buy.

To be sure, Pontiac didn't screw up when they set deck height for their production engines. They had different concerns. One was production tolerances, where avoiding collision piston to head (or valve) was essential and had to be avoided with the cheap OEM rods. If the deck height wandered from spec on a mass produced motor, it couldn't be allowed to clash into the head, even with some wear during the warranty period. These are production choices that engineers make all the time. Engineering choices made nearly 40 years ago don't have a lot of relevance for a motor being reworked today. Yes they did a great job back in the day, but that has nothing to do with 2007. This is especially true when the motor gets precise machine work from an accomplished shop rather than being manufactured en mass.

I figure we are talking about an engine that is headed for freshening up in a car that will be driven. I surely didn't suggest Jim tear apart his motor to make it "run better" with lower CR, zero deck and all that. Jim says he can buy decent gas where he goes. I expect he is fine where he lives. I can't buy good fuel around here in the nation's capital, without burning half a tank during the trip. Here, the gas stations dump octane boost into the tank when the county comes down on them for failing testing after complaints.

We're talking about choices for a new project. To me, that means the car needs to take fuels you can buy on the road, not what you can mix at home after a trip to buy racing gas that you store and mix at home. I guess there is racing gas around here somewhere if I search, but mostly I can buy 91 octane at best. Everywhere I go now posts notice that the fuel is contaminated with 10 percent ethanol. I would rather get 10 percent less fuel for my money.

Add to the concerns that the engine needs to be numbers matching so not machined to zero deck on the block is why I brought up special pistons. No's match dismisses notions of bolting up aluminum E-heads, milling the block to zero deck, or even installing other heads from the early 70's low compression smog engine where CR might be set where you want (need) it. I understand that, but in any engineering puzzle, you can't optimise everything at once. A milled '96 head or a later head won't numbers match this car. I really understand the concern.

On top of that, Vikki is determined to not mill metal from the original motor deck. I can understand that too, cause you can't put it back. That leaves piston design as the only option. There are folks who build one-off pistons, so lets look there. If that is out of the question too, there ain't any solution other than good fuel. I don't see good fuel in our future, without a lot of effort. Blueprint the motor, put gas equivalent to what we bought in 1968 and you're golden.

But life is full of compromises. You can put the engine back to blueprint specs, but if there is wear that doesn't clean up with a hone, it's .030 over already. Now the engine isn't no's perfect anymore. How many of them are left not worn? Worse, the engine has lost .030 and has only one more clean-up before it's trash. I never accepted bore it out as a remedy to get a bit of power through the small increase in displacement. These are tiny gains while limiting the functional end of life for the motor. But then I don't race, so to me it doesn't matter. I guess Chevy motors are cheap and this is a worthwhile choice for that last tenth. But we're not talking about the last tenth here.

I might be lost here, but I thought the puzzle was what is the best thing to do with a '68 motor without grinding down more original metal than necessary. And I thought this was a car to be driven often. That says you don't drive back home for more hundred octane or home mix of racing gas and 93. To me, that says drop the CR, deck the motor and only rework (grind down) what is necessary to make the motor run as planned. A good cam choice might help too, but I'm not started in my studies about cams.

Jim is pretty adamant about how good his motor runs. But he can buy good fuel, according to his own description, post 83024 where he says

.

Well, we are talking about fuel you can buy on the road, not what is available in a few choice locations.

There ain't racing fuel where I plan to drive MaybeI redefined the question with my own concerns and hijacked the topic, but there's not much high octane for "drive up" and "gas and go" around here. I stick with Exxon here because they are one of the few suppliers around town where 91 even works right in my vehicles. I expect it to get worse. Reworking my motor, what I can readily buy, vs what is possible plays a key roll in choices.

Larry

Here's an overview on Sunoco racing fuels. Also, there is a station locator.
http://www.sunocoinc.com/site/Consumer/RaceFuels/

Larry,
I see there is a station in Elkridge, MD(among others).

There are other alternatives to dealing with low quality fuel other than zero decking too. I have dealt with it simply by purchasing a stock 428 lower end and installing 6x heads on it. I used the lower compression 6x's. The engine only had 8.5 to 1 compression. It was a very simple engine that you could put together in your garage without any extra machining. It was very powerful and burned the lowest octane I could throw at it without a ping. I used to take it to the track and burn Nitrous Oxide when I wanted a great time slip. Fast on the street and super fast at the track with Nitrous. It's a very dependable engine because it's still in the 69 that I sold it in. After I beat it for 5 years and now 10 years of cruisin' the owner still raves about how good it runs on the 'even worse' gas now.

if someone were to choose to bore the engine, they could sleeve it to bring it back to original bore specs. thus the block wouldn't be trash if they reached the point of needing a 3rd rebore!

That's the approach with "Project '68 Driver", it has a 400 with 6X heads and will run plain old pump gas without a whimper. I'm not into nitrous as I can't afford to go back to the track (too competitive for my own good and budget).

'69 needs a more stock approach. With low mileage it may not need more than hone and rings, I hope. If it needs a full rebuild I have my choice of restored stock #62s or 87cc heads, ready to bolt on. Choice of stock logs or factory long branch or ceramic coated repro long branch. But my inclination is to leave this car as close to factory as possible.

'68 resto has a 4 speed trans and will retain stock config.

Here's an example of what you can expect out of a stock engine. Please excuse my clumsy shifting. This takes a while to load. Full length version on country cruisin' thread.
VIDEO LINK:

Elkridge is 100 miles round trip and two hours driving from here. The others listed are that area also. My plans are to drive this car to Ocean City, Maryland, Hershy PA car show, etc. I'll need to have no worries over octane.

The original numbers match engine is nowhere to be found. I have a 71 YS engine with 96 low compression heads. Those are big valve 96cc heads, thread in studs etc. I don't think the motor has ever been apart, but I don't know that yet. It does need to be cleaned up. The compression comes up significantly in one or two cylinders a small bit of oil added through the plug hole. I think it would be foolish to do a frame-off restoration and not freshen up the motor and move it's performance up a notch too.

My dilemma is which way to go with the rebuild. I can go to a 455 or 462 stoker kit which will bring my low compression motor up from it's stock 8.2. Or I can deck the block and mill the heads and stay at 400 cubes. I want to stay original in many, but not all regards. I want to stay with the stock radiator, not some shiny aluminum job.



That's what I'm after Jim. I just want to do it on 91 octane pump gas I can buy everywhere. And I'm confident thats possible at 9.2 CR.




I see an advantage to staying with the stock high compression heads that are correct for that 69 engine. That keeps the engine appearing correct. But then the engine is subject to detonation because of its 10.75 CR because of the available fuel that is contaminated with ethanol. That issue has to be solved too. Detonation isn't just inconvenient and annoying, it's damaging. This can be solved by bringing the deck to zero while bringing the compression ratio down to 9.2-9.5 by using custom pistons that reduce compression and also achieve zero deck.

Jim Hand's book, page 28 he discusses dropping CR from,10.5 down to 9.2 by dishing the pistons. He gives to explanation of the machine work and suggests machining a D-shaped cup. Jim Hand writes of a D shaped piston relief:



I think this is more correct than putting a 1970 455 head on a 1969 car that has a number matching motor. If the motor really cleans up with a hone, put the original pistons in storage and it can always be put back.

Plug in some Compression Ratio comparisons into the script at

[url=http://www.bgsoflex.com/crchange.html][/url]

You loose 3% by dropping the compression ratio. I think you can still enjoy the car at 3% less horsepower unless the car's purpose is winning at the track. You'll likely loose much more than that detuning the stock 10.75 CR enough that it doesn't ping on 91 octane. I think it's a very reasonable trade-off.

Getting maximum power out of my engine is not a requirement. Getting proper operating condition is. If I were to lose 30 hp I would scarcely notice as the way it is running now I'm probably losing more than that (detuned).

Only a couple more weeks of good weather then my car goes down for its nap. Heads will come off if I get through with what I am working on now.

i tossed this to the guys on py in the race tech section. check out the post. the votes are to deck the block so far. nearly 90% say go for it as not many cons to this work being done other than the fact you may choose to run RA equipment which you would need a taller deck to do so with. post as follows:

http://forums.performanceyears.com/forums/showthread.php?t=536239

hope it helps a bit vikki. also you haven't really told us what your symptoms are. you've asked the point of decking the block but haven't told us why you are considering it in the first place. like we all do with the newbies, whats the symptoms and the goal?

andy

jim,

nice vid but we need a bit more footage to really enjoy it!

These videos have to be short and sweet due to the large file size. I could have made a huge one but you wouldn't have waited for it to download. In this thread, the only purpose the video had was to show that 'exactly stock'(no cutting) engines are still alive and kickin'. It's only there to show that the option is still open to those that are able and willing to feed thier stock configured engines right. Hopefully, the sound of the engine and of the acceleration gets the point across that you can leave it(engine) as it was in 67-69 and still have power to spare. This is only one option for the 1st gen Bird owner. Most importantly it 'IS' an option.

Drew, This is Vikki's post that I replied to and suggested 0-deck



"I guess I should qualify my remarks as my opinion only.

I am sick of paying over $5 a gallon for racing fuel.
I am tired of spark knock if I put my foot in it unless I compromise timing when running pump gas.
I am building a pump gas engine that will run full timing and put out more power than is needed to have fun on the street.
And it will be all Pontiac power. No aluminum heads, intakes, or aftermarket carbs or headers.

One is just done at the engine builder's. It's a numbers-matching engine at 9.8:1 compression. It'll be installed and broken in within the next couple of weeks. Once the car is back together I'll put it to a road test.

The engine for my '69 will be a bit lower compression with a head swap. I want to see what I can do with 89 octane. "
Vikki
http://thefirstgensite.