434 sbc?

[grumpyvette]

Hey guys, i was an active member on here prpbably 8 years ago but was out of hot rodding for awhile but now i'm getting back into our disease.....So I'm putting together a 408 w/ a solid roller and I've got pretty much everything besides the cam, putting this motor together with parts from a ex nitrous motor, but i'm not going to run the fogger so i'm swapping pistons and cam.

Here is what i have and wont change:
-434 with lunati splayed main caps
-4340 forged crank and 6.0" H Beams
-Dart Pro 1 230cc with just light clean up work
-matching dart single plane w/ fogger(removing fogger)
-Erson roller rockers, comp stud girdle
-MSD pro billet

Application:
'51 f100 pro street, back halved w/ 9 inch, 4 linked, 18.5" mickeys, th400 w/ 3500 stall, low 4ish gear


Up for decision:
Compression ratio and Cam, I want to easily be able to run on 91 octane, not have to de tune to run pump gas and be on the edge of destruction

I was thinking around 11.5 and this cam

http://www.compcams.com/Company/CC/cam- ... d=308&sb=0

Any help appreciated, should i lower the CR, is the cam too big?

below some pics of where i'm at now

because the goal is to run street high test gas,and produce killer hp, Id suggest dropping the compression ratio to 11:1 MAX
BTW for anyone who doesn,t know a 434 is a 4" stroke crank in a 4.155 bore 400 block (thats .030 over bore)

and Id strongly suggest going with a BILLET CORE on this lunati cam below and installing it split overlap

http://www.lunatipower.com/Product.aspx?id=1995&gid=290


a 11.1 cpr 434 sbc the cam 4 degrees retarded ,with those components and a 4.11 rear gear and the 29" slicks will be a nice TRACK/occasional street combo
youll want 1 7/8" headers with about 37" primarys and about 16" 3.5" collectors

heres a DD2000 wild guess at power levels with a bigger carb.(Id just use a 2" open spacer to increase the plenum volume with the current carb and intake)

 

[Indycars]

Won't both of those cams provide a DCR that is a bit too high?

I made the following assumptions:
Chamber Volume: 72cc (The other choice was 64cc for a Dart Pro 1 heads)
Deck Clearance: 0.040"
CompCams IVC: 72 ABDC
Lunati IVC: 67.5
Pistons: Flat Top 5cc Valve Reliefs
Bore x Stroke: 4.155 x 4.0 (I used the bore and stroke from Grumpy Dyno Graph )


Below are my calculations for Dynamic and Static Compression Ratio. Did I make a wrong assumption or is the DCR really a bit too high for pump gas (91 octane)???

What do you think???

 

[grumpyvette]

your correct if the cams installed 4 degrees advanced(dot-to-dot)and flat top pistons are used that are using the correct quench (.040) but like I stated Id limit the static compression to 11:1 max (dish piston)and install the cam 4 degrees retarded
but thats I nice catch! because your correct I forgot to retard the cam in the dyno
splayed 4 bolt

heres a corrected dyno

 

[Indycars]

That's right you said retard the timing 4 degrees. I figured I was missing something, but wasn't sure what it was.

In your last dyno graph, I'm not sure what you are using for the intake valve closing IVC (seat timing). I can't read the numbers in the green box, is that the seat timing???. Am I getting the right IVC in my calcs at 67.5 degrees for the Lunati???

 

[grumpyvette]

Its the valve timing at .050 lift for that cam, retarded from its dot-to-dot factory install timing , remember I stated 11:1 cpr that may require dish pistons with about a 8cc dish

so you would subtract, or delay by 4 degrees from the intake open and add 4 degrees to the intake closes,etc

Intake open 18.5/Intake close 56.5

exhaust open 62.5/Exhaust close 20.5

http://www.kb-silvolite.com/calc.php?action=comp2

given a start point of 11:1 static cpr puts you at about a 8.3:1 dynamic which should be ok running a 12.7:1 fuel air ratio, once you get the timing curve correctly adjusted and assuming your keeping the coolant and oil temps on the lower edge of the range and know a few tuning tweaks, remember the object on a race engine is usually to try for max average torque so the higher cpr is almost mandatory.
or put a different way, Im running almost 11:1 cpr in my 383 with a milder cam and 36lb injectors and once the tunes correct I rarely see problems
viewtopic.php?f=32&t=430

 

[Indycars]

I went back to run the IVC again and I came up with another question......image that !!!

When you say retarded 4 degrees, then that's relative to the numbers provided by Lunati. At first when I went to the calculator in the pics below, I entered -4 degrees, but that's not right it should be zero as shown. Would that be correct ???

If it should really be zero in my calculator, then I do get the same SCR and DCR that you get.

 

[grumpyvette]

lunati ,crane,comp,isky and some other cam manufacturers grind cams so that if installed in the typical DOT-TO-DOT install they are ADVANCED from SPLIT OVERLAP by 4 degrees,
this in my opinion is a band-aid fix to a problem that started many years ago because most guys years ago, ordering cams knew very little about cams and tended to think bigger was always better,most customers tended to select a cam that had to much duration for the application, the manufacturers knew that but were reluctant to buck the trend, during the muscle car era I saw cams advertised with listed durations of 350 plus degrees(obviously thats B.S.) and the muscle car era manufacturers found that advancing the cam moved the power band down about 200 rpm giving a resulting boost in low and mid rpm power so they got fewer customer complaints, the upper rpm power was rarely a problem simply because the cam selected was already a bit larger than ideal for the application.
by the late 1960s it had become accepted practice for most manufacturers, I think youll find installing cams at split over-lap and selecting the correct cam for the application tends to give better results



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