JesseShredd

Would 70cc heads be a problem replacing my 76cc 882 heads? I have domed piston making 10:1 compression.

sofakingdom

iTrader: (1)

If iron, yes; very bad.

If aluminum, probably not so much.

Be assured though, your compression probably isn't 10:1 with those heads, even with the domes; to get a .030" over 350 with .045" deck clearance, .039" gaskets, and 76cc heads to 10:1 would require domes about .250" tall. While it's possible you're in that situation, it's not all that likely.

JesseShredd

Good to know. what would the situation be If I got 64cc aluminium heads? And if a bad idea, Howso?

sofakingdom

iTrader: (1)

Too much compression.

It's not much fun driving a pinging, detonating, premium-gas-sucking pig that you have to back the timing off so far just to make it bearable that the gas mileage gets even worse, it runs lazy, and overheats.

All in all, NOT a recipe for anything most of us would consider "fun".

That would depend on the details.

What pistons are they? Part #s ONLY please.

What's the deck clearance?

What heads?

DeltaElite121

What you have now is right within acceptable limits. Unless you want to be running race gas in the tank at $8 a gallon like I have had to do, I highly suggest you don't go pushing your luck. Your compression right now is fine where it's at, and I wouldn't go trying to get more out of it because you're going to need to change a lot more than just your heads if you start doing that (with much more than what you've got now, anyways).. There's better ways to see power gains.

JesseShredd

Thanks for the replies. Well, i honestly have no Idea what the part numbers are on the pistons, just believing what I was told from previous owner who rebuilt it.. Came to the conclusion that if my compression is 10:1, then I must have domed pistons but haven't physically checked. My 882's are holding back a lot of hp, but I don't want to invest more than I need to in order to get better flow. If all said is true, what would be the best path to tale to do this?

scoflaw

iTrader: (2)

Until you pull the heads off, and start measuringeverything, it's all speculation.

DeltaElite121

This. You don't know anything for sure right now, so don't go out buying parts until you pull those heads off and figure out exactly what you're working with. Once you figure that out, then formulate a gameplan.

sofakingdom

iTrader: (1)

That can lead almost anywhere... before buying parts, you gotta know what's in there. Otherwise who knows what kind of mismatches and misfits you could run into. Time to start checking, it would seem.

cuisinartvette

Lots of "11:1" motors really sitting at 9.5
teardown first measure then go from there

JesseShredd

Found out I have the 3998993 993 heads instead of the 882s which I was informed of due to the block casting. Trying to research some input on these. Seen that there were some with 1.94 - 1.50 and 2.02 - 1.60. Anyone aware how I can specifically identify which I have by the casting numbers?

sofakingdom

iTrader: (1)

Nope...

Valve size is a matter of machine work. You can take ANY junk smogger casting such as 882, 993, or 624, and graunch the larger valves in it. It'll still be a crappy smogger POS casting, won't run noticeably different in any way, won't make the slightest difference to the overall outcome.

Gotta LOOK AT THE PARTS to know what you've got though. There really aren't any substitutes.

But you already know you have garbage heads, so it doesn't matter at this point what valves are in em, they're still garbage. Frankly, if they were mine, I wouldn't even bother to waste the 10 seconds that finding that out would take, if the heads were already laying on the ground. No sense delaying their trip to the recycler by those precious seconds of my life that I'd throw away uselessly and couldn't ever get back.

cuisinartvette

Amen on not fooling with iron production heads.

JesseShredd

Okay, thanks for the replies. I read about them putting out 300-350hp but sounds like I'd be better off spending 2 grand to get the results that I am looking for. Looks like I would have to pull the heads, see what I got then PUT THEM BACK ON to keep myself rolling which sounds like the biggest waste of time and discouraging. Smart approach to take must be buying a new cam (since I'm unaware the specs), new heads, and pistons to match a setup that would work for me. Any recommendations on where to go with this situation will be considered.

JesseShredd

how would these dart's be for a direct replacement?

http://www.ebay.com/itm/360534636687...84.m1438.l2649

sofakingdom

iTrader: (1)

Depends on what pistons you actually have, what the deck clearance is, etc.

Don't start trying to buy parts until after you know what you're buying parts for.

Tear down.

Measure.

Evaluate.

Plan.

Purchase.

Assemble.

Tune.

In that order.

DeltaElite121

You're going to have quite a bit of change sunk into those before you can bolt them on and go. Better off getting an assembled cylinder head and save yourself the headache of chasing parts. That, and the SS heads suck in comparison to DART's other cylinder heads.

Don't go cheap on cylinder heads. They're the most critical part of the engine when it comes to making power. A cam is worthless if the cylinder heads can't feed it properly. Save up some change and buy a set of complete heads that ARE ready to bolt on.

And like Sofa said.. you don't go buying parts until you know what you have. That's just dumb, and you're throwing money down the drain by doing that.

JesseShredd

Valid points, Thanks guys. Appreciate your time and putting up with my inexperience. Really don't know what I would do without this extremely resourceful website.

DeltaElite121

That's what we are here for. We were all new to the game at some point, and it's only right to pass that information along to the next person. Just be smart about your build, and more importantly - be smart with your money.. because in this hobby, when it's gone it's definitely gone.

JesseShredd

Oh and deltaelite, regarding your first post on this thread, what would be some significant upgrades to get more power other than swapping heads that you were referring to? I've been looking into upgrading my ignition setup to a msd 6al with msd coil and msd distributor, getting some 1.6 rockers (builder told me I can go 1.6), an edelbrock rpm performer intake and possibly a bigger carb than my 1406 edelbrock. Are these all going to make some more power alone, or should I be looking to upgrade elsewhere?

cuisinartvette

All most street/strip motors need are a good quality HEI and a decent coil thats it. I only used the MSD as I run a pretty large cam and plan on spinning it well over 7k' dont want low speed fouling-
I know that one day that lousy box will leave me stranded somewhere.
Keep it simple.

Savage388

Without good heads and a cam those mods are pretty much worthless because an rpm intake and big carb on smog heads is a waste itll be a total dog on a 350. Adding 1.6 ratio rockers to those heads is also a waste of time, just save up for some new ones. For a reference I've got 882's on my 383 with a performer and 750 edlebrock and even with the extra cubes the parts arent good for torque and top end isnt there with the heads. Dyno's of the almost the exact same engine made 335 hp and 390 ftlb of torque so the heads need to go for sure.

JesseShredd

Wow, That just blew my mind. Guess it is time I start saving for another car, then new heads.

Savage388

whoa no need for the sarcasm I'm just trying to help, I have almost the same thing as you do now and have looked at different ways to go.
If you want heads I would seriously consider summits aluminum head after you measure your domes.

JesseShredd

I apologize, no sarcasm was intended. Just surprised how much these smog heads hold back even with the goods you have on the top end in your situation. I will look into those, thanks for the recommendation. Any idea who makes them for summit?

Savage388

Yea no problem, It has been said by many many people that brodix makes the summit heads so they are some good pieces for the price. Oh and Like it was previously said I seriously doubt it has 11:1 compression with a 76cc head, that would be a huge dome.
Heres a thread that might help you a bit, They are for my 383, but hey its only 23 cubes
https://www.thirdgen.org/forums/tech...uch-hp-my.html

sofakingdom

iTrader: (1)

First thing you gotta do in order to understand how to make more power, is to understand how an engine works.

First thing to understand about THAT is, power comes from fuel. Each incremental amount of fuel you burn, releases energy, in the form of heat. The engine's job is to turn that heat energy, into mechanical energy. It accomplishes this by allowing the high-pressure hot gases produced by combustion to expand by pushing the piston down, which cools the gas and takes the heat out and turns it into the mechanical pushing action.

Note that AT NO TIME does it make THE SLIGHTEST DIFFERENCE exactly how the fuel (a) gets into the motor, or (b)gets set on fire. Which ultimately means, the brand or size of carb makes NO DIFFERENCE WHATSOEVER to the engine's power output, as long as it delivers the correct amount of fuel at the correct time; and similarly, the ignition system makes NO DIFFERENCE WHATSOEVER ("gimmick" spark plug ads notwithstanding) as long as it sets the fuel on fire properly, just like th efire in your fireplace doesn't burn hotter because of the brand of match you started it with.

Once you get those myths and "fog of war" cleared out of your mind, THEN you can begin to understand what DOES "make more power".

Since power comes from fuel, and subsequently the conversion of heat to mechanical energy, it is immediately obvious that to "make more power" you have to (a) burn more fuel, or (b) do a better job of energy conversion. Eh?

Energy conversion is controlled by the compression ratio - which has another aspect that's MORE IMPORTANT than "compression" itself, which is, EXPANSION as the hot gas pushes the piston down; and, the "leakage" of heat out of the conversion process, either into the cooling system, or into the exhaust. Engines with higher "compression" make more power because the gas expands to a greater multiple of its original volume during the power stroke, thereby extracting more of the heat and converting it ot mechanical energy. Too much compression though, and other BAD things happen. The maximum compression ratio you can use is controlled primarily by the fuel you run. As a result you can't change it very much.

Heat can escape from the hot gases in the chamber, and pass into the piston top and the castings. In point of fact, the majority of the heat that escapes directly from the chamber, does so into the head casting. Which is why the cyl head material affects things: heat passes more readily into aluminum than iron, meaning aluminum automatically "cools" the mixture (a LOSS) more than iron, meaning you NEED higher compression with aluminum than iron to get the same results, if all else is equal. (yes I teach math in college) You can use ceramic coatings on things to further reduce heat loss, which is common practice nowadays in about all forms of competitive motorsports. So, assuming you have the mechanical compression optimized for your fuel and head material, there's not much more you can do to make the engine "convert" the energy more efficiently. It was pretty much baked into the design of the motor long before it was built.

Just as a FYI, in a properly working engine at its max HP RPM, about 1/3 of the fuel's heat energy goes into the cooling system, about 1/3 out the tailpipe, and about 1/3 into mechanical work (useful). Keep those #s always firmly in mind: 2/3 of the energy in the fuel is thrown away, and you can't do anything substantial about it, once the motor has been designed and constructed. But even just a little bit of efficiency improvement at design time results in a MANY % increase in power, so every little bit helps. That's the kind of thing that makes supposedly "equal" engines run so differently; why a Reher-Norrison or the like can build a motor out of the same parts somebody on this forum would, but will get 20% or 30% or even 50% more power out of the identical same parts list.

Which leaves, burning more fuel. Each unit of mass of fuel releases a specific amount of energy. (spark plug, ignition system, or carb brand DOES NOT change this) Energy = work. 2 words for the same thing. (yes I was a physics and math major my first time through college) Power, as measured in horespower or watts, is the time rate of doing work, which is to say, the time rate of energy release, which is the time rate of burning fuel, which would be measured in units like lbs per hr or the like. But... fuel requires air to burn, no? and as we all know, it takes almost exactly 14.7 times as much air as fuel, by mass, to produce complete combustion. So in the end, the time rate of burning fuel that an engine can burn, is limited by the time rate at which it can move air through itself.

Well that makes life pretty easy, doesn't it? The time rate of air movement has a word to describe it: we call it FLOW. It is usually described in cubic feet per minute, or in grams per second in the case of computer tuning... basically the same thing, just a larger or smaller chunk being measured at a time.

So what have you learned?

1. "More power" isn't made by an ignition system, as long as the one you already have is adequate. Don't waste your money.
2. "More power" isn't made by carb brand or size, as long as it can deliver as much air and fuel as the engine can consume. Don't waste your money.
3. "More power" IS made by careful choice of compression ratio, to get as close as posible to "optimum" for the fuel you are using, without going over. If you were to graph power against compression for any given fuel, the curve would look like a rounded-off saw tooth; a gentle rising ramp as compression increases, increasing more slowly as the "perfect" spot is approached, levelling off as it's reached, then PLUMMETING as that spot is passed, from all the "compensation" that has to be done.
4. "More power" depends on FLOW, which is DOMINATED by the heads, cam, and exhaust. The intake is a relatively minor tweek, and the carb is nearly irrelevant.

And even more important, what can you do with what you just learned?

1. Find out what your compression is, so you can optimize it for the least amount of money. Replacing pistons might be necessary, but is EXPENSIVE, and should be reserved as a last resort.
2. Don't waste money on things that won't get you closer to your goal. Big shiny pretty eye candy sitting up on top of the motor in plain sight like carbs, intakes, brightly colored spark plug wires, "chrome" such as air cleaners, etc. are for people of weak will and limited understanding but who are easily distracted by the shiny things beside the path. Don't be one of those people.
3. Concentrate your money, time, mental focus, and effort, on WHAT MATTERS. Right now you already know the heads you have are GARBAGE and therefore are your first and most immediate need to upgrade. Keep your money in your pockcet until you have enough to buy them. Don't get all hung up just yet on which ones you need to buy, if you don't already have the money for them; start saving the $1500 or so that you KNOW you will need.
4. Don't buy a cam yet; if the one you have works, use it, and at the time you buy heads, buy a cam that suits THEM.

Any questions?

JesseShredd

Shew, good information sofakingdom. It's good not feeling like a dumbasses on this site anymore. Looks like I have a lot of work to do and money to save.

DeltaElite121

Your best weapon when it comes to cars is being informed. Notice how he explained how and WHY things work the way they do? That is someone who has a very clear perspective on engine operation. You will find many people have their biased opinions based on things that are false, and they will try passing that along to you. This is why you need to do your research, read, and do as much as you can for yourself.. and most importantly, ask questions.. because ultimately - it's your time and money on the line, not ours.