Newold1 wrote:Before we get into hydraulic versus roller cam conflicts, lets talk about your power and torque expectations.
The horsepower expectation you have in my opinion is very achievable and the power limiting factor on this engine will come from, believe it or not, the intake manifold and throttle body. The CFM this engine will consume at about 6000 - 6500 rpms with a good camshaft will either eclipse or come very close to exceeding what a 90 mm throttle body on that small plenum EFI intake from Edelbrock may be able to supply. This manifold is really about a 600-maybe 650 hp combination on a 548 BBC with good compression, good camshaft and a good set of flowing heads. The challenge here may be getting it to a point where it will flow the air required, You might do some research as to what others have achieved with this setup as I have no direct experience with this setup and I am just doing some simple calculations on PipeMax and its' may be a challenge with what I know a 90mm throttle body can flow. It might help you if you happen to be able to identify the heads here and specs. as well as any flow data you may have. It will also help with a camshaft choice.
http://www.edelbrock.com/automotive/mc/ ... -723.shtml , I have this intake and kind of what I was shooting for power wise, the cam is smaller than both of my cams.
Newold1 wrote: As for compression increase and combustion chamber burn patterns, its' my opinion that compression in this engine can only help to a point. Most likely the Holley EFI control system you have has some great tuning capability for both fuel and timing and that being said I don't think its unreasonable to try to use 10.5 to 1 in this aluminum headed BBC in this street type use as long as you have 93 octane fuel available in your area. If you stay with your current pistons then obviously you've got to decrease combustion space CC's to get to that point and that might be doable but it will take some work depending on your dome volume now, deck height of piston when reassembled, head gasket thickness.
Can you give find and give some input here as to those questions so a compression calculation can be done to determine where the engine is now on compression (really) and where with some simpler changes may get close to a higher compression ratio.
We are going to mill the heads, I don't want to touch the pistons because I don't want to re-balance the assembly. Chambers are 131cc, felpro 1073 gasket I think. I forget what the dome is, 9.7 to 1. We are going to redo all the numbers again before the heads get milled.
Newold1 wrote: Also keep in mind that some compression changes might be doable with camshaft design as your requirements on power and rpms leave a little more flexibility of where intake closing and exhaust openings can be adjusted to deliver more dynamic compression and sort of lessen the effects of your current lower cranking compression.
Newold1 wrote:As for milling heads and intake to fit that's a lot more expensive and involved and I am not sure there is enough easily possible there to make a real cost versus benefit. I would not advise going there unless you feel you must.
Newold1 wrote: Glad to hear the oil pump distributor conflicts did not totally wipe things out with metal. Have you carefully determined how this took place and what the exact cause was. Your post on that is a little short on the details.
Newold1 wrote:When you first fired this engine up with either pump what was your cold and hot oil pressures at idle and at higher rpms when measured on your gauge. When did it start dropping and if so did it drop significantly? Did the lifter and valve train noise show up initially or did it happen after the oil pressure drop?
I had so many different sets of lifters in it I lost track. Last time I drove it 19 psi hot at idle and never went over 50 psi even at 6000 rpm.
Lifters were always noisy, got worse with time. Distributor was not in far enough.
Newold1 wrote:Another piece of info missing here is the specs. on your valve springs - spring pressures closed and open, type beehive versus duals and sizes.
195 seat, I don't remember open pressure. Dual spring, all came from Straub with the Hydraulics.
Newold1 wrote:I am not a huge fan of hydraulic roller camshafts in some high performance racing big block applications, but in extended street use and certain other moderate power and rpm applications they are fine if the camshaft is a good build and design, good hi-performance hydraulic roller lifers and proper valve train matches are used. This is even more true when a lower rpm use such as yours is being built and reasonable spring pressures are usable in the application. So don't throw in the towel on a hydraulic roller here yet. If you can use one well they are definitely going to be longer lived and easier to maintain.
Newold1 wrote:Hope some of these questions and thoughts here can help you get to a better place with your re-build and end up with a nice satisfactory result.
Lots to learn here on both sides of this post!
definitely getting me to think
found this online calculator
your 2 has an Overlap of 32.00 degrees and has in Intake Duration of
242.00 degrees.
The Exhaust Duration is 254.00 degrees. Your Lobe Separation Angle is
108.00 degrees.
The Inlet Cam has an Installed Centerline of 103.00 degrees ATDC.
The exhaust cam has an Installed Centerline of 113.00 degrees BTDC.
Your 1 has an Overlap of 31.50 degrees and has in Intake Duration of
247.00 degrees.
The Exhaust Duration is 256.00 degrees. Your Lobe Separation Angle is
110.00 degrees.
The Inlet Cam has an Installed Centerline of 108.00 degrees ATDC.
The exhaust cam has an Installed Centerline of 112.00 degrees BTDC.
Inlet Valve Speed of Sound (MACH) Index
Your bore size is 4.600 inches with a stroke of 4.125 inches and has 1
inlet
valves with a diameter of 2.250 inches. Running a Mean Valve Flow
Coefficient
of .336 inches at 6200 RPM, the inlet valve mach index is 0.736 .
The mach index for maximum volumetric efficiency is .6 . Beyond .6 the
volumetric efficiency falls off. As the mach index rises beyond .6 the
volumetric efficiency can be increased by later inlet valve closings
(60 to 90 degrees ABDC).
Camshaft, Rod Length, Boost and Altitude Correction to Compression
Your engine summary is as follows: Bore 4.600 inches,
stroke 4.125 inches, rod c-c length 6.385 inches, with a static
compression ratio of 9.7 :1.
Your camshaft specifications call for an inlet valve closing of 44
degrees ABDC (after bottom dead center).
Your chamber volume is 129.13 cc's. With this camshaft your dynamic, or
effective stroke is 3.71 inches.
Your dynamic compression ratio is 8.82 :1 corrected for cam timing,
altitude, and rod length.
Your dynamic cranking pressure, corrected for cam timing, rod length and
altitude is 180.31 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam
timing, altitude, and 0 PSI is 8.82 :1.
Camshaft, Rod Length, Boost and Altitude Correction to Compression
Your engine summary is as follows: Bore 4.600 inches, stroke 4.125 inches,
rod c-c length 6.385 inches, with a static compression ratio of 9.7 :1.
Your camshaft specifications call for an inlet valve closing of 51.5
degrees ABDC (after bottom dead center).
Your chamber volume is 129.13 cc's. With this camshaft your dynamic,
or effective stroke is 3.55 inches. Your dynamic compression ratio is
8.49 :1 corrected for cam timing,
altitude, and rod length. Your dynamic cranking pressure, corrected
for cam timing, rod length and altitude is 171.68 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam
timing, altitude, and 0 PSI is 8.49 :1.