7t9l82

i cleaned the top of the piston , sprayed with wd-40 put a big wad of play-doh on the dome and molded it . removed it carefully then inverted it an got mu burette out and checked the cc of the dome. thats as easy as i could make it. it may be a tad off, but not much.

c3_dk

This will come in my L46 in my Corvette.

c3_dk

That is also a very good idea, and very easy to do, Thanks

scottyp99

So.....what did you get for a volume? Is it a secret, or something?

Scott

c3_dk

Maybe something like this

7t9l82

well scotty, that was over 25 years ago. but the principle applies.
i did it on several motors that way from LT-1 small blocks to LS-7 big blocks. kind of hard to remember everything. what were the names of all the kids in your second grade class? its not a secret, you probably don't remember.

cardo0

post #45 Maybe something like this

I guess that would work but i think measuring the cyl vol itself and subtracting the "swept vol" would be less prone to errors. U could always do both the resin method and the cyl @ BDC methods and compare them. I if do please post your results. Well please post your results regardless of method u use.

cardo0

cardo0

Well thinking of your 4" dia bore and 3.96" dia piston u may be able to reuse the stock pistons. It depends on the top ridge left at the top of the cyl bore. I believe the old TRW forged pistons had a generous piston to cyl wall clearance. U maybe good up to something like 4 or 6 thou inch (0.004"-0.006"). An easy way to measure the clearance is u use tape gauges - just 12" long feeler gauges. Clean the bore and piston and slide the piston down the bore over the tape gauge to find the widest clearance - dont force anything here.

I used the old TRW forged pistons before and they do have some "slap" on startup but once engine is warm they were nice an quite.

cardo0

REELAV8R

To get the volume of the Dome I would recommend using Cardo's method.
You don't even have to have the engine assembled.
Just put a piston with a ring on it (only one will be needed to keep it from sliding down the bore) inside the bore and make sure the dome is below the deck of the block.
Then measure how far down the bore you piston top edge is (not the top of the dome the edge where a flat top's top would be next to the bore) with the long needle end of your micrometer that sticks out the back.
Once you have measured how for down it is compute the volume of that cylinder as if the dome were not there.
use this clac if you want.
http://www.online-calculators.co.uk/...ndervolume.php
Since your bore is in inches and your down the bore measurement will be in inches then take your answer and convert it to cc's.
http://www.metric-conversions.org/vo...entimeters.htm

Ie. 4.030" bore 1.004" down the bore is 12.8117 inches.
convert that and you have 209.95 cc's.
This is the volume of the cylinder without the dome.

Now grease the crevice use a q-tip to do it or have it done before you measure how far it is down the bore so that it doesn't change during the greasing of the cervice.

I would suggest you use antifreeze to fill the volume. It has much less surface tension that either oil or water and will give a more accurate reading.

Use a piece of plexiglass and a calibrated syringe that can be gotten at a farm supply store.
drill a hole in the plexiglass the size of the nipple on the syringe and another very small 3/64" or so hole near the edge of the bore. Seal the plexiglass to the bore with the grease as well.
The very small hole allows air to escape as you fill the void.
You can see how I did mine here;

http://forums.corvetteforum.com/c3-t...er-size-2.html

Look at post #31.

Now if you measure 202.25 cc's the volume of your dome is 209.95 - 202.25 = 7.7cc's.

You'll use the same piece of plexiglass to cc the chambers as well and similar process.

Oops couple of math mistakes now corrected.

cardo0

U did a really outstanding job on that measurement REEL. That L-48 piston dish thread should really become a sticky at the top of the forum here. It would be used nearly daily here.


Have to go, chasing the clock today.
cardo0

v2racing

Pistons have come a long way from those old slugs. Back in the old days we used to have to fit 2618 alloy pistons very loose, in some apps as much as .010" clearance or they would stick. Black death was a common problem too. Now with the computer modeled shapes using thermal dynamics you can get CNC machined pistons that will run problem free at .002" with the same 2618 alloy.

63mako

The 268 cam with 114 LSA with 4 degrees ground in advance ends up with an intake closing point of 64. The DCR is 8.7 to 1. This would have the death rattle. He needs the slow factory ramp instead of a modern fast ramp to get the 222 duration @ .050 to run typical RPMs yet a late enough intake closing point to bled off enough compression to keep the pistons from detonating out of the holes. He needs the stock L46 cam or else, if he goes with a modern lobe, he needs a 288 intake duration with 114 LSA with that much compression and iron heads. The 288 duration cam would have a duration @ .050 of 236 or more and would not be very streetable in the 350.

v2racing

These are the old Comp lobes that have been around since their beginning. The are not XE lobes. You can get a few degrees between .000" and .006". They are slow by today's standards.

scottyp99

Boy, I feel like a jerk, now!

Scott

boat196

What's the recommend DCR for 91 octane with iron heads.

c3_dk

Thx cardo0,
I was hoping to reuse the old pistons, and only add new piston rings ec ec.
I will measure like you told me, also regarding the pistons, it is a shame, I have a packed coming from Summit (with tools) to me next week. But I don't have that degree wheel, so I guess I have to go shopping again :- )

c3_dk

Very good question Mr. B :- )
Looking forward to the reply.

c3_dk

Hi REELAV8R,
That is a very easy way of doing it, thanks for telling me about this.
I love this forum

7t9l82

im glad you took it in the spirit it was intended, getting old is hell

c3_dk

You are NOT old, you just have a lot of experience.......

The best days of your life are coming up, no matter how old you are.