|01-23-2013 08:09 PM|
|techinspector1||Use the Comp 280 cam. With 10.3:1 static compression ratio, it will make 8.746:1 dynamic compression ratio on the KB calc. Should be just right for aluminum heads and pump gas.|
|01-23-2013 06:40 PM|
Well, the weekend is coming up, the short block has arrived! Took a few weeks after it arrived to get everything situated back at my house, had to pick it up from my work in order to get the good shipping.
One final question before I begin the build and start a thread on that. For some reason I did not think to request the type of cam for the engine builders to install, so it came with an Engine Pro MC1730 with Duration @.05 = int204, exh214, and int.422, exh.444 Lift. The duration seems a little low for 10.3:1 compression, would it ping with this cam, or am I ok as I will have a good quench and aluminum heads?
For just in case that cam will not work, I purchased a comp cams, and cam assembly lube (that I can return) CS 280H-10 Duration @.05 = 230, Advertised Duration 280, valve lift .480.
I can also get an Edelbrock RPM series, and I believe that one had about 245 duration at .05 and 305 advertised, but I figured that would be a bit over-kill.
Let me know what you all think, I can return this comp cams next week for a different one with even more duration, or less, I simply got one so if it is correct I can get my pushrod length measured, and next week can have things moving along smoothly.
|12-11-2012 10:07 PM|
|trillobite||All true, I will use the cam the engine comes with, I keep forgetting to ask him what cam it will come with, and yes, it comes with pistons, rods, crank, timing chain, lifters and the cam.|
|12-11-2012 09:57 PM|
The 0.0035" variance is reasonable, considering that he may not want to spend the money to equalize rod lengths, etc. Like Cobalt said, make sure the tallest stack is at zero and the shortest is 0.0035" down in the hole.
Any used flat tappet cam and lifters are junk. You would have to re-use the very same lifter in the very same lifter bore, not in a different block. What do you think the chances are of 16 lifter bores on block #1 being bored exactly the same on the x and y axis and each one the same distance from the flywheel face of the block as 16 lifter bores on block #2?
Why would you spend 62 bucks for a Fosdick 5-quart oil pan? I doubt that it'll seal as well as a bone-stock production pan. If you want to make a difference, use a larger pan. 7-quart is a nice size for a street motor. Get the windage tray and crank scraper. Be very cautious about fitting the screen to the pan. You will need about 3/8" clearance. Less clearance can cause the pump to suck the bottom of the pan up against the screen and cut off oil supply to the pump. More clearance can cause the pump to run out of oil.
|12-11-2012 09:23 PM|
|12-11-2012 07:35 PM|
Thanks a ton, makes perfect sense, I shall let him know!
A .060 bore will bring me to 10.36:1 compression, crossing my fingers that everything will come together perfectly, all the numbers look excellent.
I will send him this: "Ok, looks good as long as the margin of error is with the piston below the deck, not out the top; Both decks match, each corner of the deck is the same, and the final cylinder bore will be .060."
|12-11-2012 07:29 PM|
|12-11-2012 06:42 PM|
Got an interesting email from the builder.
"Just left the shop and wanted to run some things by you. The only 79 down 4 bolt at the shop is a .060 over, let me know if that's alright. Also, the owner (Barry) said that with the stock block, crank, etc. He can only guarantee a 0" - .0035" margin between cylinders on zeroing the block. Shoot me a note when you get a chance."
Usually I would think that a .0035 margin as insignificant since it is such a small number. Is that good, bad, or ugly?
I asked him if .060 will be the final bore, if it is, I don't see it as a significant issue, I have a triple pass aluminum radiator, high-flow aluminum water pump, and I assume aluminum heads will help out a tad too.
|12-10-2012 03:26 PM|
Ok, with a quench of .040 I will have 10.3:1 compression.
Bore: 4.040 (diameter)
Cylinder Head Volume: 64
Effective Dome Volume: 6
Use (-) for Dome and (+) for Dish.
Deck Clearance: .025
Compressed Gasket Thickness: .015
Number of Cylinders: 8
Compression Ratio : 10.31 : 1
Total Displacement (in.3) : 356.88
Total Displacement cc's : 5850.49
2 FEL Pro Head Gaskets Rubber Coated Steel Shim 4 100" Bore 015" Comp | eBay (head gasket)
New Small Block Chevy 350 IMCA Claimer Racing Oil Pan | eBay (oil pan)
PRW SBC 305 350 Chevy Sportsman 8" Polished Harmonic Balancer | eBay (damper)
350 Chevy Short Block Assembly High Performance w Forged Pistons | eBay (they may be in the build process as we speak, they are willing to do any deck height I choose)
I can either use that .015 gasket (sounds too thin for aluminum heads) or I can tell them to deck the block to .000 for my Fel Pro 1003 .041 gasket.
|12-09-2012 08:28 PM|
|12-09-2012 08:20 PM|
Some things I forgot to say. Main thing: Stick to the fundamentals.
Insist on a torque plate final hone. A good, round cylinder w/a piston that has the correct piston to wall clearance, along w/the correct ring end gaps will do as much for performance as a LOT of other "racing" tricks. What guys fail to realize is, while a loose piston to bore clearance may have less friction, the rocking motion this allows causes the ring seal to go away.
Follow the manufacturers specs for piston clearance, ring end gap, etc. Measure the piston where the manufacturer says to measure it.
Use a three angle valve job. Backcutting the valves is sometimes a cheap way to increase flow where it'll help on a day-to-day basis (look at what GM did w/the Vortec valves- they do NOTHING "just because" ).
• Break in the cam correctly.
There are other things but these are fairly important IMHO.
|12-09-2012 07:54 PM|
While it's true you can usually get away w/more compression using aluminum heads, this is only because aluminum sheds heat easier into the cooling system. There are no free lunches- if you build w/alum. heads, the added compression is needed just to stay even w/an iron head- not that aluminum magically allows you to run more compression. I don't much care for aluminum heads on a SBC daily driven vehicle myself, I like good ol' cast iron. That's not to say the good aluminum heads aren't good- they are- but you do pay for the privilege.
In the same vein, I also never build a street engine right on the edge, compression-wise, either. The general rule of thumb on compression is one point- like going from 9:1 to 10:1- will net you about 4% more power, all else being equal. Now, that IS 16 hp on a 400 hp engine, so isn't exactly insignificant, but the down side to the added compression can be a huge loss of power if you misjudge things and you end up needing to retard the total timing from what gives you the best power- just so the engine doesn't detonate. And it has other downsides as well like less tolerance to a bad tank of fuel, or something that causes the coolant temp to rise past normal. At least in the last two cases you can stop, get out, and turn the distributor to lower the timing to limp home w/o ruining the engine- as long as you caught it soon enough.
My bottom line is: There have been a LOT of VERY strong running SBC 350/360s built using 9-9.5:1 CR. A properly spec'ed and assembled engine w/that CR can expect to make more power than you can safely use on the street. A racing engine is another animal altogether and the two (racing engine on the street) seldom meet happily in the middle, in my experience. Again, that's not to say there aren't 10:1-plus iron head or 11:1-plus aluminum head engines being driven on the street every day, w/o issue. But it IS to say that if you choose to run on the edge, it can bite you.
So I cannot in good conscience advise anyone to build a 11:1 aluminum or 10:1 iron head engine for street duty. When the parts on hand absolutely HAVE to be used, sometimes this means compromises must be made- I understand this. But if at all possible, hedge your bet to the safer side rather than the "faster" side.
|12-09-2012 07:42 PM|
iron makes more power hands down.
alum is easier to cast/machine/etc and why they use it..
pore the same heads in both, iron will win everytime
heat = power, alum transfers it, iron holds it..
with a fuel that not pre ign. iron all the way..
r09 engines heads where taken by nascar that where iron.. because the walked over the field
team fined 100k
|12-09-2012 06:13 PM|
Are you talking about bowtie heads certainly not nascar worthy but used in all types of circle track racing.
Aluminum is not easier to cast it also is much more expensive. Alum heads transfer heat way batter than cast so you can run higher compression on hotter day out and still avoid knocking if its tuned right of course. Cast is usally a full point lower in compression and still stay in the safe range.
|12-09-2012 05:46 PM|
but a 12 to 1 iron headed and the same engine with alum heads..
if both the same in everyway other than heads casting material..
the iron wins everytime..
if you got the fuel..
e85 if they'd cast say dart pro ones in iron.. would rock
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