Is there anyone hear who can help me figure out what the CR would be of my motor if I give you the specks of what I got to put in it? I have changed my mind from what I originaly planned to do and this has trown me for a loop and I have NO idea where the CR will fall out now?


This is what I was thinking of doing?
Lt1 with 383 Stroker (3.75) crank, 5.7" rods, Stock CC heads (about 55CC), .041 head gaskits, pistons with C.H. > 1.268, Bore size 4.030, CC's > Negative dome 35.000. Has anyone got any clue what CR this would give and if it would work?

What I had previusly was.
LT1 stock stroke (3.48) crank, 6" Rods, Stock CC heads (about 55CC), .041 head gaskits, pistons with C.H. > 1.268, Bore size 4.030, CC's > Negative dome 35.000. AND this build resulted in a 8.5 to 1 CR.

The things I am trying to changing would be the stroke of the crank and the Rod length. I want to see if its possible to build the stroker with the piostons I have and what CR it would result in?

Please point me in the right direction if you can help! Thanks a TON, Lata, Ark

PS - I can get more specs if they are needed?

 

GV (Head Gasket Volume) = Bore(in) X Bore(in) X 12.87 X (Head Gasket Thickness in Inches) = 8.5698

DV (Below Deck Volume) = Bore(in) X Bore(in) X 12.87 X (Inches Below the Deck) = -1.67216

HV (Head Volume) = CC's = 55

VV (Dish, Valve Pocket, Dome Volume) = CC's = -35.00
(Minus for dish or valve pockets, Plus for dome)

PV (Volume displaced by Piston) = Bore X Bore X Stroke X 12.87 = 783.8264

Compression Ratio = (GV+DV+HV-VV+PV) / (GV+DV+HV-VV) =
(8.5698-1.67216+55+35.00+783.8264) / (8.5698-1.67216+55+35.00) =

9.08:1

Assuming that your deck height is -0.008 like mine.

 

SEE now that all just gives me a head ack!

What I think I understand is that you are saying the stroker crank and 5.7" rods with my set up will give me right at 9 to 1 CR? If that is corect than I think I can live with that!

I dont mean to bother you BUT using your formula would my original build be 8.5 to 1? If you fealin frisky would you or could you confirm that for me? STock Crank with 6" rods?

Thank you SOOOOOOOOOOOOOOOOO MUCH for the hep. Lata, Ark

 

OK - LET me try this on My own,
The original set up was this I think. Using your formula

Compression Ratio = (GV+DV+HV-VV+PV) / (GV+DV+HV-VV) =
(8.5698-1.67216+55+35.00+727.3909) / (8.5698-1.67216+55+35.00) =

8.5068 CR which is what I expected to get from my Original Build. BUT where do the rods come in to play or do they not matter when it comes to working out CR? I guess they just dont hu? Thanks for the HELP! Lata, Ark

 

Looks right to me. Yeah, I don't think the rod length comes into it for CR.

 

Thanks again bro! I am thinking that I will be able to use My pistons which is GREAT news. ALL I gota do is sell my 6" rods and get me some 5.7" rods, that and my new stroker crank and I will be all set! I will keep this formula handy for sure! Thanks, lata, Ark

 

Yep, according to Ross piston's web site compression will be around 8.95:1 witht he 383 (assuming zero deck height) and the 355 is around 8.38 (3.48 strock) all else being equal.

http://www.rosspistons.com/calculator.php

Later,
Dave