Rebuilding a 304

[kb'sforme]

I agree. And gasket matching is all I will be doing. As bill pointed out anything more on these motors is overkill.

[jauringer]

Got the drain back holes done as well as the casting flash around the spark plug holes. It looks good and went very smooth. I've got to get my gasket kit in before I can do any more grinding so I'll take pics when It all finished.

I cleaned up a couple pistons just to see what shape they're in. They're pitted pretty bad and just don't look like something I would want in my new engine. It may need bored anyhow, but even if it doesn't, I'll be getting new.

I take it this is from pretty sever detonation?



My dial bore gauge and my Micrometer set has shipped and should be here early next week. I'll start taking measurements and recording data on the black and crank as soon as they come in.

Jason

[jauringer]

Originally Posted by Bill usn-1

I always gasket match during my builds. It's cheap and fairly easy so why wouldn't you.
I blend both sides an inch or 2 into the ports.

Do the heads, intake and manifolds.
Wouldn't hurt to surface the exhaust manifolds if their pitted.

Porting/gasket matching is one thing but polishing is something else. There is no real benefit on these engines.

Thanks for the info Bill. You've obviously done this with good results. Like I said, I couldn't tell what information I was reading was quality and what was crap. I recently did run across a guy a few times on justIH (here too but not as much) that seemed to know quite a bit about the subject. I imagine you've had few conversations with this guy-Username-71scout2


He seems to have access to a flow bench, a bunch of heads, and a little bit of time. There's a a lot of information on JustIH.org about this. He's got flow bench numbers, cut away heads, and a lot of cool info. Some of his older posts indicate that some gains could be had as long as what you're doing is correct and a lot of the info seemed to be talking mostly about further into the runner by the valves. I'm not sure any of the info had anything to do with just the first inch or two of runner.

Then later on down the line, he seems to tackle the gasket matching question directly and it didn't sound very promising. Things like knocking down the air injection humps do next to nothing for performance and are a wast of time. (not that I have that to worry about) Then in 2009 he actually states NOT to do any gasket matching.


Here's a thread that I found most interesting. (and the most recent info I found from him)

"Which 345 to rebuild"

For those that don't like reading. (Even though you should read it all)

Don't gasket match any of the ports, neither intake nor exhaust. You'll gain nothing, with a possible loss in torque/hp. Not to mention time/money wasted. If you want to, take the intake manifold and radius the sharp edges inside the plenum.

Since I found very little info from the main guys I trust on this site (such as yourself) This guy seemed the most knowledgeable and had data to back it up.

Conflicting data: check

Confused: check (what do I do when I'm confused and have no means to obtain the data myself, keep it simple and leave it alone. )

The only consistent message I've seen is that this is a perfect example of how IH's are nothing like the big three and treating them like one can be a big mistake.


On a side note. I've been doing some more research on bumping up compression. Most folks run with the flat tops so there's a lot of data regarding the procedures there and I've come to have a pretty good understanding about how to set those up.

Unfortunately I'm having a hard time translating some of the info over to the contoured piston. CC'ing my heads will be the same but obtaining a zero deck height seem to be a little confusing here as the contoured piston already comes out of the hole. Plus, I can't seem to find any numbers regarding the volume of piston that comes out of the deck stock as well as the volume for the valley.

Can someone elaborate on the variables that come into play when adding contoured pistons to the mix, or point me to a thread? Keep in mind that I've been searching "contoured piston". If there is some other slang or term for this piston that would bring up more results, that would be great to know as well?


Jason

[jauringer]

Reset the crank and inserted the #1 Piston. Put the dial indicator on it and found TDC, here's what it looks like.

Lens is a little fogy, sorry.

@ the pistons highest point, it looks to be roughly .350" out of the hole.

[Bill usn-1]

From your previous post I don't think the gasket matching is all that conflicting.
I don't do it to try to make big improvements in performance.
I recommend it and do it on all of mine so that each cyl operates the same.
You can physically see different amounts of material sticking into each port. So by gasket matching you now make them all the same.
There have been sooooo many engine/head threads over the years and i have post pics of my work many times.
I do blend the bowls and i gasket match.
The one variable that isn't really discussed is flow numbers on the 304 head. The intake posrts are 1/2 the size of the 345/392's.

As for the CR measuring...your on your own. I did some research also when I had the contours. But unless you can get an accurate measurement of the dome and the dish it's will be just an educated guess.
The CCing the heads is straight forward and I have shown how I do it.
You could even cc the dish. but getting a cc of the positive dome would be a little difficult. maybe use a water displacement method in a measured beaker?

I went zero deck with flat top pistons and ran the composite gaskets for my squish area.
I originally ran the isky 25/26 cam and you knw i always run EFI.

[teenbmxer]

well we have all read conflicting ideas as far as the heads. If i were builing it id probably zero deck the block and resurface the heads to bump up the compression. gasket matching should just be done.period. run a split duration isky cam, with appropriate springs. definitely shim the oil pump. balance and blueprint as well. i cant help out to much, all the research i have done is aimed more towards forced induction power, but the best basis for a boosted engine is a well built na engine with less compression haha

[jauringer]

Wow Bill, you did do some bowl work. Very cool!

I thought I was going to get that answer regarding the cylinder volume. Let me ask you this then, how did you determine how much to deck the block? BTW: I posted this very same info over at IHON in the hopes that Robert Kenny would chime in. He's got some very informative threads over there and seems to know what he's doing as well. maybe he's got a cylinder volume somewhere he can give. I guess you could say this is another disadvantage to using a contoured piston. It's not as simple as measuring the piston in the hole and zero decking the block. I need to do a little brainstorming and see if I can come up with a decent way to measure this volume at home. .

I actually cc'd the chambers this evening on one head. They came in lower than I anticipated and I've guessed that it was because these heads don't have the recessed spark plug hole.

Made my own setup, thanks to Microsoft works and my kids old medicine cups/syringes.

I cleaned the combustion chambers, drilled a few air holes in the CD, surrounded the chamber with Vaseline and inserted 20cc's @ a time until I got to 80 and then used a 3cc syringe. Keep in mind since there were so many holes that this could easily be a hair on the high side. Doubt it's much but water did create a small surface tension "dome" at each hole.

Cyl 2: 84 cc's
Cyl 4: 83 cc's
Cyl 6: 83 cc's
Cyl 8: 85 cc's

[Bill usn-1]

So what if you measured and marked the piston at the top of the deck and then filled the combustion camber with water. (water displacment method)
Then inserte the piston to the the line into the chamber to displace the water.
Then remove the piston and measure the remaining water. Subtract from you chamber CC.
The dish may hold air so you may have to tilt the psiton or fill with vaseline and measure it separately.
Then the gasket volume will need to be subtracted.

The chambers are actually less then I remember. maybe mine had the recessed sparkplugs?

Joe....he has contour pistons. if you looked at his pics, there really isn't a zero deck.
So the volumes must be measured separately.

[jauringer]

Playing around with the piston and water, I'm coming up with ~7cc's positive material.

In other words, an area that's known to hold 350cc's of water is requiring 343cc's to fill including the piston volume.

I took a paint measuring container and filled with 350cc's of water. I marked my line around the container and then flipped it over on the piston (I coated the piston with Vaseline just below my line to make it air tight) and lined up the 350cc mark with the mark I made at TDC on the cylinder. I then drilled a hole in the bottom of the container. (now top) and filled it with water. I was able to fit 343 cc's in it. With the piston now being the floor I was able to make certain that there wasn't an air pocket in the "dish" portion of the piston.

I knew this would be crazy accurate but I figure it would get me close. I'm not sure it did as the CR calculation with this figure seems odd to me.

Cyl bore: 3.875
Stroke: 3.21875
Head gasket bore: 4.00
gasket thickness: .020
Combustion chamber volume: 83cc's
Dome volume : 7cc's
Deck clearance: ??

Compression ratio: 8.19:1

So backing into these numbers give me a deck clearance of +.O33 give me a CR of 8.196

Being that we've got 7cc's of positive material above the deck, shouldn't deck clearance come out to a negative number?

Thanks,
Jason

[Bill usn-1]

Are you planning steel gasket or composite?
IIRC the composite is closer to .030-.035 compressed.

Decking will leave more piston above so it might be as easy as using the same calc as the head gasket since it will affect the fuel diameter of the piston.

A lean up cut on the block just to square the decks and then surfacing the heads to the desired CR may be better.
You may have to play with your measurements of both to see how much each affects the CR.

.030 shaved from the deck vs .030 from the heads.