|12-13-2012 10:04 PM|
|12-13-2012 07:37 PM|
|SPEED MASTERS CC||
|12-13-2012 07:35 PM|
|SPEED MASTERS CC||
|12-13-2012 04:49 AM|
Your current compression is 11:1
0.04" head gasket=8cc
deck height= 0
(785 + 64 + 8 + 6 + 0) / (64 + 8 + 6 +0) = 863/78 = 11.06:1
if you use 76cc chambers then the cr should drop to 9.7:1
(785 + 76 + 8 + 6 + 0) / (76 + 8 + 6 +0) = 875/90 = 9.7:1
I would use a good aftermarket 76cc head with a 200cc or less intake ports with a set of headers. However, if you plan to use stock exhaust manifolds then using the 882 heads would work ok.
|12-12-2012 07:06 PM|
The biggest factor will be the fuel quality you use in the tank.
You won't get far with crap pump gas in the tank.
Avoiding spark knock is all about keep the combustion pressures and temps and mixture uniformity.
The higher the mechanical compression ratio is the closer to the edge it will run.
That means that n ordder to avoid detonation you have to keep a closer eye on the engine operating
condition parameters that effect spark knock tolerance. Pressure, time, temperature, load.
Keep the engine cooling system temp in check.
Keep the spark timing in check. Proper timing curve.
Keep the air charge temp and AFR variation in check.
have the ability to detect detonation-spark knock and do something about it
eg reduce timing, reduce cylinder pressure (throttle)
change cam timing events ot adjust instantaneous cylinder pressure at that throttle load
( change the cam, move the cam)
Change the induction and or exhaust system tuning and or combine with a cam/valve event change adjustment
to a excessive cylinder pressure. ( eg choose a different intake manifold)
A method if being able to change the ignition timing on the fly ( a knob on the dash) would be nice.
A method of detecting engine spark knock, on the fly ( knock detector, driver warning device) would be nice.
|12-12-2012 11:20 AM|
|12-12-2012 10:26 AM|
|12-12-2012 06:19 AM|
882 are crap buy votec 061/L31 or buy camel hump heads or another that flows as well. also after market aluminum heads will work with 10:1 on the street without issue. If cast iron heads a border line then aluminum will usally solve your issues. But cant be sure without running all the numbers. Flat tops can be 0 cc to 12 cc thats a big jump also heads vary alot from head to head. so no real assurance they meet the 64cc mark either.
Is it knocking now when you drive it. Most engine builders try not to build motors that will knock on pump gas in the 10:1 or 11:1 range usally with race gas and good cam 12:1 is easy to get and makes alot more power in most cases. Since the DCR will change the way the compression acts a larger cam could also resolve the issue.
|12-12-2012 04:06 AM|
You`d be better off using a vortec head and taking a few degrees timing out of it.
The vortec head will run efficiently with modest spark advance because of its much better
`fast Burn Chamber` May make max power at 36deg BTDC, but will run very well with 31-32deg.
Then tune the vac advance rate so it is not agressive, no more agressive than nessessary.
You will end up way a head of the game. Use a Dual pattern cam with a wide 114 LSA to avoid peak
midrange cylinder pressure. Your cr will be 10.77:1 with a -7cc flat top and 0 deck height and a .041
It will be more detonation resistant than if you used the old crappy 882 head on it
and way more powerfull and fuel efficient, even with a few deg less timing than absolute optimum.
The new much upgraded powerfull Bow Tie Vortec cylinder head is 66cc which will get you a 10.53:1cr
Thats fine on premimum pump gas and correct tuning on your 383.
Get the Big Port version for max power on your 383.
These are sold assembled and ready to rock for .530`lift and high perf cams.
EG isky 280H Mega or Comp cams XE 284H-10 cam. It will GLH
|12-11-2012 11:19 PM|
You could always keep the comp ratio you have with a 64cc head and convert to E85 it really a simple procedure cost around 300.00 and you can run almost any comp ratio up to 15/1 and they are selling E85 at almost every speedway,meijers,costco. We are running a 14 1//2 to 1 383 on E85 and it runs awsome just buy the carb conv kit for 140.00 and for your build you could use a mechanical compatible fuel pump 120-140.00 or an allstar black with proper reg im building almost every street car that we run at this time to use E85 do some research Its def an option, MIke
|12-11-2012 10:13 PM|
A pair of 441 heads would be marginally better but I wouldn't go chasing them, either.
Anyway, even w/a "perfect" 0.040" quench distance, the CR is only about 9.75:1 w/76cc heads. Measure how far down the piston is at TDC and choose a head gasket accordingly to maximize the quench.
And it's always a good idea to CC at least one chamber from each head you plan on using to be sure they're equal to each other and that they've not been milled excessively.
There are guys here who'll give you recommendations on cams, I generally don't, except to say the 280 Mega is not what I would use. A cam having a faster lobe w/less duration @ 0.050" lift will give you better power under the curve than that old-school stick. Think Lunati Voodoo series, for example. If you're going to use the 882 heads, especially w/cast iron exhaust manifolds, use a dual pattern cam. The 280 Mega will want a bit more CR along w/a loser torque converter (if AT) and lower rear gears than a shorter duration cam w/the same lift.
Use a dual plane intake like the Performer RPM or Weiand Stealth p/n 8016. A squarebore 650/670/700/750 cfm vacuum secondary carb will work well w/this. So would long tube headers.
|12-11-2012 06:30 PM|
383 comp drop
Either head will work the steam holes only play in on the 400 sbc you will not even notice they are there on a 350 with 350 head gaskets the 882 is a good at best budget head just because of the hardened seat they have but as far as performance they will do what you will need with the exaust and induction you are planning to use if you are planning on a good street toy and the cam you mentioned keep the valve size to the 194/1.5, it will help keep the torque you'll want ,be carefull not to sink too much cash in the heads any more than 300-350.00 would almost not be worth it you can get several deals on heads on line already done or new ones from aftermarket companies for around 400-600 for better flowing and better castings that will already come with screw in studds and guides just keep the runner size on the 170-190 to not over build the engine with your parts of choice, hope this gives you some information that will help, mike
|12-11-2012 05:27 PM|
|SPEED MASTERS CC||
Need to lower comp. 383 sbc build
I purchased a new 383 short block with a zero deck and flat tops. (Cheap price, could not pass up...) I need to lower the compression into the low 10-1 range so it will run on pump gas. I have 2 pairs of 882 heads that are 76cc. One pair is drilled for steam. Are these heads worth using on a budget street rod build? Both pairs need rebuilding. Can the steam holed heads be used on a 350/383 block? The engine will have ram horn exhaust manifolds and a tri-power intake with a Isky 280 cam, duration @.05 is 230. Or should i look into something else? Looking for the best bang for the buck...Suggestions?