Anyway....the Vortec fast burn chamber will allow for 10.2 to 1 on pump gas....especially with that cam....no problem.
The reason I like compression is two fold.....first it is more efficient and easier to tune....secondly, it sounds better!!!!

Jebby

 

Can't remember if a denser fuel/air charge burns slower or faster to inhibit or increase detonation. But combustion chamber shape and temperature sure do. I recall it's the hot spots and poor flame travel that cause detonation. Just never heard anyone worried of too much or too little VE causing detonation. What I'll say is the DCR calcs are the best indicator we have as a novice without a full laboratory and dynomometer for testing.

 

Mahle-Clevite Hyper Piston pn 244-3940

I phoned mahle clevite (Kyle) because I could not find CD/CH or dish volume published for their hyper replacement piston for iron head Vortec 5.7L 350 as found in Chev-GM lite trucks '96-2002. These motors also known as RPO code L31 VIN code R

L31 pistons are a very good piece with the desirable thin metric ringpak (1.5mm, 1.5mm, 3mm).

Kyle pulled up Mahle print for 224-3940 and told me CD/CH is 39.5mm and he converted that to 1.555" inches; I confirmed as 1.5551181"

Kyle also told me dish volume is 11.4cc

repeat:
224-3940 CD = 1.555"
Dish Volume = 11.4cc

oversizes are listed metrically
so, a 0.030" oversize is 0.75mm

pn 224-3940-0.75mm

pretty sure Mahle also offers these as a set, or as a set with rings

These are rather pricey but maybe a little less than the very nice wiseco forged piece.

-edit-
with above thirty-over piston, 64cc chamber, stock 9.025 deck and 3.245cc shim ... I see 9.56:1 SCR with Quench = 0.045"
nuthin's perfect but that looks pretty good.

 

What were you using your cars for when you installed your kit? Were these drag cars or just weekend warrior type vehicles?
Why did you feel the need to install them?

 

Thanks for finding these!
I couldn't find any that were 0.030 or 75mm overbore. I searched for that part number, but nothing came up. But honestly, for the price, it seems like the forged pistons are only $50 more and i like the idea of buying the rings as a kit.
Piston dish is what I'm looking for though...

I'm not much of a businessman, but I would say there is a business opportunity here for the piston manufacturers.

 

So if i putt in my 62cc vortec heads (because they were shaved 0.020) i get 10.51 static compression and 9.06 DCR using the same cam and 6cc for flat top with valve relief.
This seems like too much compression for iron, no?

What would you say is the upper limit is on iron heads in terms of CR and DCR?

 

w/ 62cc iron chamber, wiseco 15cc dish, 0.025 in hole, 3.245cc shim.... I see 9.51:1 SCR with Quench = 0.040" ...

I would Not run a flat top ... I'd stick with your wiseco choice. The more resilient forged is alloy 2618. Your wiseco is 4032.

FWIW, jegs does sell that mahle, but I see it as only a single. ... likely some more shopping would turn up a set/kit ... but the wiseco kit is a very good value.

FYI, some years back I bought a new set of wiseco protru d-dish for 6" rod 406 ... forged 4032. Probably much same as your choice. Mine were very well made & looked like jewels.

 

...So you think I should install the crank sprocket advanced, then?

 

Here is what I came up with using the following data and Pat Kelly's program.

Howard's Cam - as ground:

Adv duration: 266/270
LSA: 112
ICL: 108

Advertised Seat Timing:
IO: 25
EO: 71
IC: 61
EC: 19

Overlap: 44 degrees
Ground in cam advance: 4 degrees

Piston Dish: 15cc
.025 Deck
.015" gasket
Quench: .040"

SCR: 9.51
DCR: 7.83

If you want to advance the cam an additional 4 degrees you will end up with a DCR of around 8.0 which is still safe for pump gas.

You could advance it more but its your call. Some times perfection is the enemy of good enough. Tail wagging the dog. You could be able to run cheaper gas with the cam run "as ground".

On the build I am doing, the next move was to actually measure the head chambers. Got a significant change there. Caused me to remove my cam retard from the original game plan. The actual chamber sizes were much more important than the cam advance in my case. Could be the case here too. No way to tell without actual measurements.

 

15 minutes of typing wasted , I'd use a higher compression than 9.5 for several good reasons that I don't have time to re-type.

 

so i decided to get the Wiseco forged pistons and they are currently at the machine shop getting pressed onto the rods. hopefully they will be done today.
In the mean time I have been trying to assemble as much as I can, so I have the crank installed and torqued to spec (70 ft lbs), and installed the new rear main seal.
I checked the clearances with plastigage, and all of them came back at 0.002 to

 

You can see i did a little bit of hammering to slightly flatten the circular protrusion on the water pump plate
Before buying the Cloyes timing cover with the end play button I read a lot of info about people who have issues with the short corvette water pumps. Most of the posts I have read said to grind down the bolts on the back of the pump to get the clearance needed, but that didn't give me enough clearance. The bolts dont seem to be a problem, its the plate on the back of the pump facing the timing cover is not getting enough clearance.

I did replace this pump about a year ago, and I can't remember if I bought a "high flow" pump. Is it only the high flow pumps that have a big of a protrusion toward the timing cover?

I opened it up to see how close the impeller or pump wheel was to the plate, and it seems flush with the body of the pump, so not sure why they added the extra room there inside the pump.

Has anyone ever just used a hammer to pound on the plate to give just a little more room where the water pump and timing cover meet?

Since this isn't the original pump, I whacked on it a little bit, not totally making the protrusion totally flat in the area needing clearance, but just a little bit. After doing this the water pump seems to fit, after torquing it down with the WP bolts.

Is there any reason why the water pump won't work with this tiny bit less space inside the pump behind the wheel?

Should I go buy a regular output water pump?

 

you can see the pump wheel is flush with the body of the pump

is there any reason why i cant put some RTV on the old WP gasket and reinstall it with the plate slightly hammered in?

 

Did you not degree (check) the cam?

Jebby

 

I think it is kinda crude but effective on the water pump.....I think I would have taken the cover to the machine shop and had it milled down in the offending area.
That way if you ever put another pump on it it will just bolt right on.

Jebby

 

You better pour that Vortec head - every one I've cc'd came in at either 62 or 63cc's. If it's cut .020, they'll be closer to 60.

 

x 2 ...??

 

I know I'm going to get some flack for this, but not I didn't. I installed the crank gear advanced based on the cam card specifying 108 ICL if installed straight up.
How common is it to have a cam with incorrect cam specs? Different ICL than specified for example?
How much are they usually off?

 

That's a good point. I've read they can be as higher as 65cc and as low as what you say, 62cc.
Maybe i'll pick up one of those kits to measure it exactly. I did get these heads from a remanufacturer, so it's possible there are differences in volume between the 2 heads. I mentioned this to the machine shop guy, and he measured the bolt whole depth and shaved them to match. Not the most exact method, but I trust the guy; apparently he makes the majority of his money working on high end ferrari, porsche and other exotic motors. You know...the ones where there is still money in doing machine work vs just replacement.

If it is as low as 60cc after taking 0.020 off, I think I will still be safe at 9.71 SCR with 8.09 DCR with the crank gear installed advanced. When i originally outlined my plan for this project I was hoping to use 91 octane gas, and I hope with 8.09 DCR I will still be able to do that. Many people say 32 degrees spark advance with vortec heads at 2800 rpm, so I'll probably run 29-30 just to be safe. Maybe even run it at 27-28 when I'm breaking it in.

 

For how much i paid for the timing cover, I think I'd rather beat on my existing water pump or replace it with the regular flow one. I may do a little more tapping before I paint it again and install.
Are there any risks or pump failure or cavitation by using it with the plate slightly bent in?
Anything i should watch for other than leaks and quickly rising water temps?