Author Topic: 440 compression ratio question (Read 12296 times)

high perf mopar · « **on:** July 06, 2012 - 11:20:00 PM »

after reading about the heat loss/compression with switching to aluminum heads im beginning to wonder..

current motor is
440 .030 over,,milled just for truing
six pack replacement pistons,,speed pro i think.
six pack rods.
906 open chamber heads..not decked..all ref says appx 90 cc volume..heads r from hughes perf. big valves..
according to my machinest with this combo my c/r is 9.5 to 1..

just bought a set of 60929 rpm's off craigslist..84 cc's chamber volume..now in my book that should bump my c/r up to appx 10.1-10.2..each cc equals appx .1 c/r..i think..-6 cc's.

is this c/r enough for the aluminum heads to operate o.k.//appx 10.1ish "static" or do i need to think about bumping the compression up some way..pistons/milling the heads.. iv'e read where the heat bleedoff of the aluminum's will lower it to non eff levels?

?or is it a non problem..

pump gas 440..car shows,,no racing..91 octane calif..

no

Chryco Psycho · « **Reply #1 on:** July 07, 2012 - 02:19:13 AM »

That will work OK , I recommend Cometic steel head gaskets to allow for the different expansion rates between the iron & alum .
You should dyno it before & after the swap , last time I did this we gained 3 HP

dodge freak 2 · « **Reply #2 on:** July 07, 2012 - 10:45:10 AM »

I've heard about HP lost by switching from iron to aluminum heads. Heat is HP, the iron heads hold more heat inside. Now if the newer aluminum heads flow much better, then it should gain HP

high perf mopar · « **Reply #3 on:** July 07, 2012 - 12:34:55 PM »

Quote from: Chryco Psycho on July 07, 2012 - 02:19:13 AM

That will work OK , I recommend Cometic steel head gaskets to allow for the different expansion rates between the iron & alum .
You should dyno it before & after the swap , last time I did this we gained 3 HP

yeah, thats what i thought,,the c/r will be probably higher than the 10.1 because of the cc diff between the 2..both lunati and c.c. want the ratio to be 9.5-10.0 for the cams im looking at..

the dyno action would be fun,,but unfortuneatly theres none any where near..r u talking about the cometic MLS gaskets..no steel ring to inbed into the head after torquing,,unlike the 1009 felpro edelbrock req..

Chryco Psycho · « **Reply #4 on:** July 07, 2012 - 09:44:44 PM »

Yes Cometic MLS

high perf mopar · « **Reply #5 on:** July 08, 2012 - 12:55:36 PM »

Quote from: -Sledgehammer- on July 08, 2012 - 06:12:06 AM

at best you are only gonna gain about 1/2pt in compression from current setup... im pretty sure cutting .010 of the head you need to take .012 off the intake side to make everything still line up intake wise but double check on that. you'd have to get them heads to 75 cc to make me happy for that setup adding a 4.150 stroke to those heads would take it to upper 10's without touching the heads

at this point I would get the heads off and find out how far the piston is in the hole... use a deck bridge to find true TDC, once that is done move the deck bridge onto the block and zero the indicator out then move the indicator to the edge of the bore and rock the piston to the highest and lowest point. add those 2 numbers together and divide by 2 then you will know how far the piston is in the hole. at that point you can determine what thickness cometic like neil suggested(see what your quench is also) and what your going to do with the heads... I worry more about dynamic that static ratio's also and the XR286R will hold that valve open longer ABDC and will lower the dynamic also putting cranking in the 150 ballpark and dynamic in the midish upper 7's. yea no problems on 91 but won't be optimal.

lots to consider here in the combo as a whole...

this one is a consideration .almost the same specs as the xr280r cc..but the abdc intake timing is alot tighter..
Solid roller, rough idle. Good cam for street/strip applications, has good mid range and upper RPM torque and horsepower. Works well in 383-440 cubic inch engines. Needs 2800-3000 RPM stall converter or 4 speed transmission. Needs 10:1 compression ratio and 3.90 rear gears.
�Advertised Duration (Int/Exh): 273/279
�Duration @ .050 (Int/Exh): 243/249
�Gross Valve Lift (Int/Exh): .578/.585
�LSA/ICL: 110/106
�Valve Lash (Int/Exh): 016/016
�RPM Range: 2800-6800
�Includes: Cam Only
#60332.

abdc timing 47.5 intake valve closes.that should raise the dynamic up to more acceptable levels?
most of my specs meets the cams requirements..

high perf mopar · « **Reply #6 on:** July 10, 2012 - 08:46:35 PM »

Quote from: -Sledgehammer- on July 08, 2012 - 02:06:41 PM

that will raise your cranking compression up 30psi and over a point in the dynamic... all of this figured at altitude now and higher elevations will be a little easier/lower numbers...

You would roughly be
8.80 Dynamic / 10 to 1 static
180 cranking

Your pushing it on 91 octane "at 10 to 1 compression " which most will tell you that's pump gas friendly with aluminum heads.... and we still don't know your quench yet either... I like to plan my junk at altitude cause it's safer overall on pump gas junk.

BTW I crank at 170 with 11.89 to 1 static in summertime heat
0 Altitude (cooler weather) I'm at
8.84 dynamic / 11.89 to 1 static
180 cranking
I race on local 93

Now all most hear/ and the concensus mostly is you would be fine at 10 to 1 and I wouldn't stand a chance on pump gas at 11.89 but i'm safer than you would be and my stuff is already proven good

find out how far the piston in the hole for starters...figure out what you actually wanna accomplish, get cam last

I'd up the compression and have good quench with the 286cam (for a shelf cam) and find the happy medium for gasket thickness and how much to take off the head... Like I posted before a custom ground cam can really help you out also.... Lower compression with bad quench and the wrong cam can cause disaster

just so you think Im not fibbing or anything...
Cylinder Pressure

after reading your post and now this i understand what i need to look for ABDC intake is the key,,

Why it matters: A 355 engine with a 9:1 static CR using a 252 cam (110 LSA, 106 ICL) has an intake closing point of 52� ABDC and produces a running CR (DCR) of 7.93. The same 9:1 355 engine with a 292 cam (having an intake closing point of 72� ABDC) has a DCR of 6.87, over a full ratio lower. It appears that most gas engines make the best power with a DCR between 7.5 and 8.5 on 91 or better octane. The larger cam's DCR falls outside this range. It would have markedly less torque at lower RPM primarily due to low cylinder pressures, and a substantial amount of reversion back into the intake track. Higher RPM power would be down also since the engine would not be able to fully utilize the extra A/F mixture provided by the ramming effect of the late intake closing. To bring the 292 cam's DCR up to the 7.5 to 8.5:1 desirable for a street engine, the static CR needs to be raised to around 10:1 to 11.25:1. Race engines, using high octane race gas, can tolerate higher DCR's with 8.8:1 to 9:1 a good DCR to shoot for. The static CR needed to reach 9:1 DCR, for the 292 cam mentioned above, is around 12:1.
This lowering of the compression ratio, due to the late closing of the intake valve, is the primary reason cam manufactures specify a higher static compression ratio for their larger cams: to get the running or dynamic CR into the proper range.
http://www.empirenet.com/pkelley2/DynamicCR.html

that lunati is right there..what i want to acomplish is a good running motor for the car shows with that big cam solid roller sound..once i get the current cam off the bottom rpm range it pulls hard..more than enough to put me in the ditch with the rears breaking loose at 65 mph..

now the lifter chose for street longevity,,the comp rep said on the phone today that in order to run there endure-x rollers i would need to groove the lifter bores,,,there has to be a better way...mrl's?still time to figure it out..

high perf mopar · « **Reply #7 on:** July 10, 2012 - 10:31:19 PM »

current combo with 9.5 c/r,,79 degrees ABDC=6.64 dynamic compression ratio...no wonder the thing wont run in gear at idle with 6 1/2 to 1 compression:(

new combo with 10.1 c/r eddy heads
xr286 r 69 ABDC intake 7.74 DCR,,,,286/292,,248/254@50,,576/582
lunati 60332 47.5 ABDC 8.95 DCR,,,273/279,,,243/249@50...578/585..
lunati 60333 50.5 ABDC 8.81 DCR,,,,279/285,,,249/255@50,,585/600
xr280r 66 ABDC 7.93 DCR 280/286,,242/248@50,,,570/576
all end numbers r dynamic compression rations based upon 10.1 static..
7.5-8.5 dynamic appx is where i would need to be running on calif finest 91 octane gas..
if one is to err i would have to say on the high side,,common thinking is an aluminum motor can run a point higher compression than steel,closed chamber also hinders det..
forged pistons r a factor also..none of them r "ideal" but real close..
i want that nasty a$$ roller sound just like on cc website with the xer-287 hr -12,,cam sounds..
any thoughts on which one,,not trying to beat a dead horse..but those lunati's r looking really good.more geared towards street applications...............

TinCuda · « **Reply #8 on:** July 11, 2012 - 01:27:23 AM »

Look into Rhoads lifters. See what you think. I love them.

.,

high perf mopar · « **Reply #9 on:** July 11, 2012 - 08:26:44 PM »

Quote from: -Sledgehammer- on July 11, 2012 - 12:51:28 AM

of the choices above I still like the XR286r for a shelf cam! (your on 91 remember) customs really aint that much more ya know. still need to figure out your quench though... tighter quench can help out with detonation.... find out how far that piston is in the hole!

as far as mike roths lifters are they are new and I have never ran them! I am sure they are good! comps are a decent choice! crane has some nice stuff also!

price is not an issue here at this point in the game for a cam,,knowing what ones talking about (me) when i have them on the phone is,,iv'e called comp twice now and until todays call and specificly asking about changing the ABDC intake timing on the xr286r to raise dynamic c/r i was told off the shelf should be good to go.and after i thru around there competitors cams already in the 50 range on intake timing they started punching numbers..
until the motors out in a couple of months piston to deck height cannot be measured,,but,,they did tell me they can change the intake timing down to around 53 but the lsa will change to 112 from 110 and the centerline will change to 108 from 106,,ideal intake timing at this time is 58..that would give me 8.47 dynamic..of course that could change when the rest of the measurements r takin..

Chryco Psycho · « **Reply #10 on:** July 11, 2012 - 10:18:38 PM »

Proven true , however roller removes the lifter diameter from the equation , Comp can grind you a custom cam that works better than the chev grinds off the shelf , Everyone has their preference , Lunati & Engle have treated me very well over the years & the dynos # back it up .

high perf mopar · « **Reply #11 on:** July 12, 2012 - 03:41:53 PM »

thanks for all the input guys,,i think the abdc is a very well kept secret,,that can fix alot of problems..
hey sledge,,how's about p.m.ing me your custom xr286r specs???i promise i wont tell anyone or post them on the internet!lol

thanks tony.

high perf mopar · « **Reply #12 on:** July 13, 2012 - 08:32:54 PM »

Quote from: -Sledgehammer- on July 13, 2012 - 04:11:40 PM

no offense sorry I can't do that.... my custom grind is for me and moparal only! I don't mind giving opinions on things but just can't give that out for a few reasons! pump gas and good good power needs to be thought out right. only thing I will tell you is my valve closes at 73ish and it's on a 112! you seem to be grasping things though! when you talk to your cam grinder they can set you up with street/spring friendly lobes

hey cudaguy

no problem!i think either the xr286r or the lunati 60333 will be the choice.both r almost identical except for the abdc number..xr is 69 and the 60333 is 50.5..both on a 110 lsa..when talking to them comp says they can move it to a 52 with a 112 and lunati says they can move it to a 52.5 on a 112??what happened to the 110 that lunati was already at??more overlap from lunati creates more lsa,not less???

1st pic shows on dyno sim the new setup with torque and hp figures,,the other shows the boat im in now,,what a diff..download and zoom for the numbers..

scrag · « **Reply #13 on:** July 17, 2012 - 04:18:03 PM »

1970 Cuda Clone 440 six pack, 4 spd and 3.23 gears. Thought I would chime in here as I did the swap and was glad I did. I am running Eddy 84CC heads on my 440 - absolutely no issues, had better power than the 906's and am overall pleased with them. I also installed a Comp Cam Retro Hydraulic Roller (look it up on their web site the cam number has 712 in it). Good vaccuum and drivability. I also am running a 6 pack set up which was a lot of trouble (wasn't done correctly and I inherited a lot of problems). I drove this combo (4 speed and 3.23) for 6 years in Hawaii - used my car as a daily driver. Prior to moving to the mainland I installed a tremec 5 speed and strange S60 with 4.10 gears. Car ran 13.4 at 104 MPH with me granny shifting and easing it out of the gate. So with regard to the Eddy heads - my advice is to get them port matched and have some mild porting and polishing prior to installing. Also if you use a cam set up like I have it is pricey and requires Push Rods to be cut. Use the appropriate springs (actually Edelbrock has a different part number for heads with springs already installed for my cam set up). My next mod - just picked up my 500 Stroker and I am moving this set up to the new engine......good luck and have fun!

high perf mopar · « **Reply #14 on:** July 17, 2012 - 09:00:22 PM »

thanks for the input,,i have the burrs and sanding wheels,to clean up the casting slag on my eddy heads before they go to the machine shop for final assembly with the proper springs,etc.your comp HR should give good idle quality with 19 degrees overlap..and plenty of dynamic c/r.the ports r already at gasket size on the heads from edelbrock..
im leaning towards the lunati 60333 solid roller which with a 112 lsa should be around 58 overlap and 8.71 dynamic c/r..pushing it a little on 91 calif gas but with aluminum heads,,the cubic inch of the motor should eat most of that up..

a little pricey??to say the least..lunati says there solid rollers will live on the street with the right rollers,,900+$$

.will be looking at mrl's among others,,was considering the solids but they depend on the oils to live..the solid roller was and is the 1st choice so might as well go for it now and get it done.. it will compliment the heads and compression well..the heads have alot of other bennys like not having to use sealers on the exchaust bolts as well.. just tightened the bolts up again,,slight leak..in prep for another show this saturday..

Author Topic: 440 compression ratio question (Read 12296 times)

high perf mopar

440 compression ratio question

Chryco Psycho

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dodge freak 2

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high perf mopar

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Chryco Psycho

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high perf mopar

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TinCuda

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high perf mopar

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Chryco Psycho

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scrag

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