low compression 548 dyno testing has begun!!
 

Finally got 548 on my dyno, this is going to be a LONG , extensive dyno test comparing the merits of different intakes, carbs, manifolds, throttle bodys, stock 500efi intake, highly modified 500 intake, speedmaster chinese open plenum intake, edelbrock 454r victor intake, cams, cam timing etc. The "mule" motor is a 8.5-1 548 w afr 315's that been re-cnc'd to flow over 400 cfm. The first test which is 80% complete is to establish a baseline using the chinesium intake which is similar or same as what tim full force had on his 540's. I bought a 180$ speedmaster efi rectangle port intake and efi rails to use for this. Overall at first glance intake appeared to be a nice piece for the money.

When i ran the inside calipers thru all the ports to get a idea of how uniform it was i found 6 of the runners to be fairly uniform in CSA and #2 and #7 to be approx 10% smaller. As far as "core shift" and other alignment, i found zero problems. I spent about 6 hours w a die grinder and polishing rolls port matching intake to heads and opening #2 and #7 up to match, i'm no rick lappoutre or jim valeko but i do my best.
For first test i used a holley 4150 850 that has been modified by my dyno partner norm schenck that has 40 plus years of modifying holley carbs.
http://www.compfuelsystems.com/
This carb is highly modified and flows well into the 1100 cfm range. The manifold has a dominator 4500 bolt pattern, we mounted carb with a 2" tall 4150 to 4500 adapter and a 1"phenolic open spacer to straighten out airflow. As far as dyno dress of motor, no accessory's , 2.25 dia race car headers, 4" collectors going into 5"tailpipes w gibson marine mufflers clamped on to keep neighbors happy. Our depac sofware uses J607 CF which most other shops use and it does yield slightly higher numbers thsn sae1349 like mercruiser uses. We have had pretty good air so our CF has been around 3%. We started w 93 octane, after some tuning we made 674 hp around 6200 and 620 ft lbs tq at 5000.
5800-662.8
5900-667.6
6000-671.7
6100-672.6
6200-673.8
6300-672.6
6400-668.3
6500-665.4
6600-657.6
Tuning is NOT complete as we ran out of big enough carb jets to get mid range where we want it and timing is all in by 3500 rpms at 38 degrees which is doing torque no favors (when we test with efi on and can tailor timing curve i expect tq gains,as this motor previously liked 30 or 32 degrees in mid range). Switching to 89 octane picked up hp to 677 and torque to 627
58-664.2
59-671.7
60-674.5
61-677.3
62-677.6
63-672.7
64-670
I will be testing also with 87 octane once efi is bolted on and knock sensor is present and working.

After switching to 89 octane and pulling i then removed mufflers to see IF there were and gains to be had, hp went to 687 and tq went up to 639.
587-666.6
58-672.0
59-676.1
60-678.1
61-680.4
62-683.2
63-687.1
64-679.6
65-673.1
The cam, motor has a cam motion hyd roller previously spec'd by Bob M for the blower motor that was in my Baja. 252/259 duration at .050, 114 ls and .660/.654 lift. Running isky red zone solid roller lifters at .010 cold, haven't played with lash yet but hot intake changed to .006 and exhaust went to .012/.013, td 1.7 shaft rockers w aluminum intake rockers and steel exhaust rockers. Springs are isky tool room at 225 seat and 525 or 550 open (cant remember for sure anymore)

I then swapped on a 454rVictor intake with port matching and slight plenum divider work. With mufflers on it made 2 to 10 more ft lbs tq from 3200 to 3900, was almost identical from 3900 to 4300, the speed master pulled away from it from 4200 to 4800 by 8 to 10 ft lbs, they were close to even from 4800 to 5300, from 5300 to 5600 454r made 3-5 ft lbs more. With 454r tq peaking at 5100 and speedmaster tq peaking at 4900/5000. From 5600 to 6100 speedmaster made 5 to 10 more hp then from 6200 up hp was almost identical with speedmaster making 677.6 at 6200, 454r making 678 and change at 6400. So they were overall pretty close.

Speedmaster intake is back on and we are testing a modified dominator next. I also advanced cam timing 3 degrees since cam is obviously too big for such low compression and surprisingly motor gave up 10 to 12 ft lbs of torque and hp on the upper end and at peaks, i expected hp to drop but thought it may help lack of upper midrange torque , it did pick up 10 to 15 ft lbs torque from 3100 to 3900 where i DONT need it.

Duplicate post

I plan on testing retarding cam and going richer with carbs in midrange to see if it picks up some more torque. My goal is to try to make 700 reliable hp on 89 or 87 octane gas, we are already close. When done i plan on cloning what ever combination works the best and putting these in my 33 scarab avs. It already pulls 30 merc labbed props to 5600 and 84/85 mph with stock 500 efis so i dont need 700 ft lbs of tq to get boat moving, i need a high rpm motor that pulls on top. I have pulled this to 6700 on dyno and we were still in the 650 to 660s. I previously dynoed this with modified 502 mpi intake and 8.4-1 at 627 hp at 5600 on my dyno and less peak tq, fwiw the open plenum intake and carb makes about 75 to 80 less ft lbs of tq at 3400/3500.

Any flow sheets on heads? or pics of the intakes?

Impressive

it is, with low compression and too big of cam, if I am around them numbers with new builds in marine trim I would be super happy, gives me some hope....