84z28350

Well im trying to figure out the compression ratio on my future 350 buildup. I have a pair of GM 883 76cc heads and its a .040 punched out 350 block, Its already got federal mogul/speed pro h423np-40 pistons in it with -10cc dish and 4 valve reliefs.

Using some calculators im coming up with numbers around 8:1, does this sound about right?

F-BIRD'88

Does it matter? It's going to be too low, unless you plan on supercharging it.

Surely you can find some better head castings to start with.

84z28350

Yes it does matter or else i wouldnt have posted...

Yes, I do plan on throwing a blower on it.

I dont see too much wrong with these heads, According to d2000 these will make more power than 441 or 462s. I know they are a bit skimpy in places and prone to cracking but so is my wallet...

If i do use these heads i will definately port them to get some more out of them.

F-BIRD'88

Don;t believe every thing ya see on DD2000.
The 462's are much better. The 441's are about the best of that type of head. The 883's fall somewhere down the bottom of the list. Alot like the crappy 624's and 882's.

You can improve the port flow a good bit with lots of porting and large valves.
@ 76cc's I get 8.3:1 with a felpro gasket assuming a .025" piston deck clearance @TDC

F-BIRD'88

For a budget street blower project I'd be looking for some 441's 487's 336 or 920 castings to port.
they are all pre 1974 heavier castings.

Here
is the online calc page I like to use to calc compression ratio.

84z28350

ok so my calculations were somewhat correct i should be around 8-8.5:1 which means i can run a few pounds of boost relatively safely.

I might go dig around the junkyard on saturday, is their any specific vehicles i should look for to get some "nice" heads?

F-BIRD'88

What is the highest octane fuel available in your neck of the woods?

For a superchaged motor you want to open up the piston ring end gap large( er) Ring butting is not fun....

Sonix

iTrader: (1)

if you're in my neck of the wood soon, you can have some sweet 993 castings i've got laying around.... Real hot item there...

actually they're supposed to have thicker walls then the 882's, so they might be better then what you have...

Those heads mentioned would be put on pre '74 cars, so they'd be rare (I don't see pre-'74 cars at the wreckers too often...)

F-BIRD'88

is a 76cc large chamber head what you want?

You have to remove th valve cover and read the casting number to be sure. the above heads came on pre 1974 cars and trucks. 487,441's and 336 were "hi perf low cr heads heads
920's are very simular (same potential ported)

Avoid 882's 883 old 993 and 624's any of the light weight 350 smog castings suck. after 1975 avoid swirl port castings TBI
A 487X or 441X is the prefered blower project casting. It- some of them has 80cc chambers can be deshrouded to 83-85cc's I believe the ones from old 400SBC's are the ones with 80cc chambers.
Lower cr allows more boost.

A 7.5:1 cr allows 10+lbs boost on pump gas

84z28350

I actually finally got around to checking the casting number today and the one is for sure an 882. Oh crap i just realised i goofed on my original post these are 882 not 883.

casting number is 333882.....74-80...350/400......76cc chambers.
which pretty much pinpoints the year for my block too as it was a 70-74, so i guess my old engine is a 74.

About those 993's, Got some specs on them?

The highest pump gas avaliable here is 91 octane but i can easily attain 120 octane for not much more per litre which should allow some crazy boost!

F-BIRD'88

I'd go real conservative on boost with 91 octane. 5-6psi.

Like I said lower cr allows more boost. So does water/ methanol injection.

84z28350

i would consider water/meth injection but is it practical for street? i doubt it unless i have a 100gallon tank replacing the back seat... lol

Does a water/meth injection have to run all the time or only under high loads/rpm?

F-BIRD'88

This off the shelf Crane Cam

Makes for a nice street blower cam.

F-BIRD'88

No you don;t need a 100gal tank.

yes its very Practical ya just got to fill the tank

last time I checked tap water was fairly inexpensive.

you mix it 50-50 for best results. you only inject it while accelerating. More boostand rpm ,,, more water.

A 1-2 gal under hood resivour is all you need. ( windshield washer bottle) In fact winter formula windshield antifreeze (mostly distilled water and methanol) is almost ideal for a "anti detonation fluid".
Do a internet search do some research on it. lots of info available. you can make your own or buy a kit.

Usually you will go thru 1 gallon / tank fill up. Depends on how much ya hoof 'er...

84z28350

Well with the ammount of driving i do at a time (usually 2-5hours of cruising at a time) im not concerned about cost of water/meth but i dont want to have to pull over every 10min to fill up the water like im running a steam engine


I do like my hard acceleration so maybe i would have to get a big jug lol.

F-BIRD'88

Do the research... Running racing gas on the street gets real old in a hurry. Water/ methanol injection is very practical and effective for blower motors on pump gas.

Allows much more boost and less ignition timing retard while under boost.

84z28350

Well i have looked a little into injection, i see jegs has ones from snow performance wich are just a c hair under $400us

I looked on holleys site but didnt see one listed there, I would like to keep the thing somewhat one brand to minimize headaches on install. am i just looking in the wrong places on their site?

F-BIRD'88

yes

Do a google search. there are many kits and lots of build your own plans.

http://www.aquamist.co.uk/ to start.

many of the Buick GN turbo V6 sites have good info.

Go to the public libarary and find a book By the Author : Ricardo....
(water injection internal combustion reseaarch cra: 1930's)
Still very relivant today. the laws of Physics hasn;t changed.

84z28350

Ok i just had a really funny thought, what if i put ice cubes in my water tank would i get better results?

Sonix

iTrader: (1)

ice cubes? well, doubt it, the gain is when the liquid water is pumped into your intake, and vaporizes, taking some heat with it (heat of vaporization), and cooling the intake charge... So if it's ice cold water, or hot bath water, won't make a huge difference, it's when it becomes vapor (boiling) that you get the gain.


My 993 heads are heche en mexico ones from an old crate motor apparently. I've stripped them down. They're kinda like 882 heads, but *apparently* are thicker castings, which make for better to port, and stronger heads in general.... Just what i've heard... I'm not using them 'cuz I want to use 416 castings to have higher compression.
I was going to take 'em to a garbage dumpster nearby soon... Or practice porting on them... So far i've pulled two rocker studs and tapped the bosses (for mr gasket collarless studs), but they could also have the boss milled down for collared studs... or just put in screw-in studs for those two, and pin the rest....

84z28350

I would be glad to take them off your hands if you dont want them. but after their ported j/k

I can see what shipping will be to get them up here, i can get crazy ship rates through work. I might be down there the end of october for a few courses but im not sure what airport security will think about 200Ilb chunks of iron

Sonix

iTrader: (1)

haha, yea, I was thinking of practicing porting them, then junking them... If you want me to *carefully* port them, I could charge you for the grinding stones or something...

Yea I don't think they're valuable enough to send them, but if you're in the area, let me know, and I won't throw them out soon...
*you want the rocker studs pinned? I bought a bag of 500 roll pins, since that was the min quantity...*

84z28350

I wouldnt mind paying for the stones as long as you dont mess up the heads

Now what the heck are you going to do with 500 roll pins lol, sure if you wanted to try pinning those heads first i could give you something for it.

Ill have to give my dad a call he lives in Lethbridge and does insurance appraisals so he drives all over southern alberta, and usually makes a couple trips a month to calgary. Maybe i could get him to pick them up for me sometime if thats all cool.

Sonix

iTrader: (1)

k, we can take this to PM then.

I'll be playing with them (carefully), and just let me know when you want them, and I can "finish" them by then...