Finally decided on engine specs, opinions needed

[peej410]

ok im building a 350, heres what i got so far

GM Forged nitrided indexed and min stroked crank, 3.493 stroke, it came out of some sort of oval track car but its been checked and its good to go

bore 4.030

rod 5.7

head volume 76 (882 casting 1.94 intake 1.50 exhaust)

piston to deck 0

piston -6.6 cc (valve reliefs)

 

cam 274 intake 286 exhaust .490/.490 110 lobe sep

@ .050 230 intake 236 exhaust

 

i calculated a 8.14 dynamic compression, which is pretty much where my engine buddy told me i should be.

 

intake manifold is a weiand single plane similar to the xcelerator.

exhaust is shorty block huggers (for now) and 2.5 dual all the way back

 

i dont think i left anything out, i realize this isnt exactly a perfectly matched setup but it will leave room for improvement down the line and i think the cam is the right choice. critiscise away

[grumpyvette]

Id bet that with that combo the RPM AIR GAP DUAL PLANE intake would be slightly superior! now Im not saying your intake wont work but the cam specs , or those that are very similar to yours , that your suggesting ive used in several engines including my current corvette

 

look

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5

 

and I think youll find that the dual plane intake more correctly matches the RPM band as it tends to be pretty much out of breath by 6300rpm while the intakes designed to run higher up,look over both intakes designed rpm band and youll see that the dual plane tends to cover a higher percentage of that rpm band and will usually produce better low and mid range power

[Savage42]

That's pretty low compression. Are you planning on boosting it eventually, or just want a motor that runs on regular? Compression is power and efficiency and I've always built my motor with 10:1 to 10.5:1, which requires super unleaded, but more power and better mileage works for me. Just curious.

[grumpyvette]

http://www.wallaceracing.com/dynamic-cr.php

 

dynamic & static cpr differ YOU may be thinking of STATIC vs dynamic compression, dynamic may be about 8:1 but that puts the STATIC COMPRESSION at about 9.5:1 with that cam

 

http://kb-silvolite.com/calc.php?action=comp

 

 

http://www.digitalcorvettes.com/forums/showthread.php?s=&threadid=32358

[peej410]

Id bet that with that combo the RPM AIR GAP DUAL PLANE intake would be slightly superior! now Im not saying your intake wont work but the cam specs ' date=' or those that are very similar to yours , that your suggesting ive used in several engines including my current corvette

 

look

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5

 

and I think youll find that the dual plane intake more correctly matches the RPM band as it tends to be pretty much out of breath by 6300rpm while the intakes designed to run higher up,look over both intakes designed rpm band and youll see that the dual plane tends to cover a higher percentage of that rpm band and will usually produce better low and mid range power[/quote']

 

yeah i was looking at the rpm air gap, if i can find one at a swap meet ill definitely use it. but for now i might have to just use the weiand. so you think thats a good setup grumpy? what heads did you use on those motors?

[grumpyvette]

lately Ive been useing heavily ported TRICKFLOW or DART PRO 1 heads

on most engines

I find they are an excellent value and take well to minor clean up work

[peej410]

lately Ive been useing heavily ported TRICKFLOW or DART PRO 1 heads

on most engines

I find they are an excellent value and take well to minor clean up work

 

hrm well i know the 882's will kill power but they are all i have for now. if i put it together with those and upgrade later, what unforeseen problems might i have?

[grumpyvette]

you heads have 76cc chambers, depending on what your replacement heads have the combustion chamber size could change the compression ratio, but generally the better aftermarket heads may require differant head bolts or head gaskets but thats about all, but the increased air flow will usually make a noticable increase in power

be aware that the plug angles could cause problems with the headers if the angle changes on some applications

IF you had POP-up pistons instead of flat tops,that may be a potential source of problems as the dome/combustion chamber shapes might be a differant and clearances may not be compatable

[peej410]

if i went to a smaller combustion chamber later couldnt i just retard the cam ? or is that a bandaid fix ?

[grumpyvette]

you may not even need to retard the cam or the ignition timing at all if they are quality ALUMINUM heads simply because aluminum pulls heat from the combustion chambers far more efficiently than iron, making a increased compression far less likely to get into detonation

I sure would not worry about that untill the time came to purchase the new heads and even then boosting the static compression up to about a full ratio (from 9.5:1 to 10.5:1) may not cause problems that simple tuning may cure.

example my current 383 runs 11:1 with a very similar cam and it runs fine on 93 octane high test

[peej410]

hrm, alright, in the dynamic and static compression software i used i came up with a 10.4 CR where are you getting this 9.5 number from? also the cam that you linked me to has a whole lot more lift than the cam i mentioned. whats the correlation?

[grumpyvette]

your building a 350

the thinnest head gasket comonly available is about .015-.017 thick

and has a 4.060 bore

stroke 3.48"

bore 4.030

rod 5.7

head volume 76 (882 casting 1.94 intake 1.50 exhaust)

piston to deck 0

piston -6.6 cc (valve reliefs)

 

thus the EFFECTIVE combustion chamber is 76cc plus 6.6cc plus 6.44cc for the head gasket=89.04cc

cylinder voluum is 714 cc

thats effectively only 8:1 cpr really

 

cam 274 intake 286 exhaust .490/.490 110 lobe sep

@ .050 230 intake 236 exhaust

 

your cam has 230/236 durration mine has 230/238 durration

mine with its similar cam timing

 

durration timing is quite similar, durration not lift has the most effect on when the valves open an close thats what effects the dynamic cpr.

 

HERES YOUR CAM SPECS

http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=12-246-3

 

http://kb-silvolite.com/calc.php?action=comp

 

run youR specs thru the calculator...

 

YOUR STATIC COMPRESSION IS CLOSE TO 9.5:1 using the calculator

 

YOUR DYNAMIC IS UNDER 8:1 using the calculator

[peej410]

why does the program take into account gasket thickness and valve relief volum if your adding it into the combustion chamber volume figure? that doesnt make sense, that would put those two variables into the program twice wouldnt it ?

 

nevermind i figured it out, my friend told me to put the piston dish volume in as a negative figure, im using patrick kelleys DCR calculator