Timing??? Either too low or high? I would think that the shop would check it.
Aggressive lobes? How aggressive????

 

Fred we tried 34, 36 and 38 deg. it liked 38 the best - did not want to go any higher. Agressive per Mike Lewis - his design, not sure on the lobe design, 292/300 242/248 @0.050 with .621/.616 lift

 

292/300 242/248 @0.050 with .621/.616 lift

I think you are asking a lot of a 242* cam to go much higher than about 5500 in a big 496. You're doing good to get it peaking at 5700 IMO.

 

Well, I guess it's carb time. Jetting played with? Did the two engines have comparable carbs? Still think a bigger cam would do it. What kind of use for the engine are you planning?

 

Fred - its a street car that will hit test n tune a few times a year.

My carb is QF 850 - ran best with 78/84 jets. When we jetted up it ran rich and lost HP. Strange because most of the 496's here run larger jets.

Marks 489 is running a ProSystems HP1000. Hard to believe my 850 could be that far off?

 

Tom if it helps you at all heres my carb specs for my 498

 

Maybe, just a maybe, you're at the limits of an 850. Anybody else out there making over 600 hp with an 850????

 

thanks Skip, wow 972cfm
is that the carb you went to the dyno with?
Looks like the ProSystem HP 1000 got it done!

when we jetted up to 80/86 it ran rich and I see you're running 84/92

Fred, I think theres a few Mark Jones 496 here with 850 Holley DP running 650hp. My QF 850 has annular boosters. Maybe I should flow this thing to see what I really have?

 

thanks Skip, wow 972cfm
is that the carb you went to the dyno with?

when we jetted up to 80/86 it ran rich and I see you're running 84/92

Fred, there are plenty of Mark Jones 496 here with 850 Holley DP running 650hp. My QF 850 has annular boosters. Maybe I should flow this thing to see what I really have?

Yes Sir.... Same carb with the same jetting on the streets. Had plenty of tunning problems but it wasn't the carb... Tom i would slap 1000hp on there to see what it likes:thumbsup:

 

What's the full combo - cam, heads, intake, distrib

Edit- I found it:

496 Merlin III
4.310" Bore
4.25" 4340 Forged Ohio Crank
6.385" H-beam rods
18cc SRP forged small domes
Total Seal rings
Federal Mogul Bearings
Brodix 270 RR Ovals with CNC 115 chambers
Comp billet hydraulic roller 242/248 .621/.616 on 112
Edelbrock RPM Air Gap
Quick Fuel 850cfm
Pertronix III
60412 Moroso pan w/Melling pump



Should be an easy 625+hp motor. Was a AFR meter hooked-up? Carbs can make a big difference...if there's something wrong with it. I ran a regular 850DP on my 509, easily made 650HP+.

 

What's the full combo - cam, heads, intake, distrib

Merlin III
4.310" Bore
4.25" 4340 Forged Ohio Crank
6.385" H-beam rods
18cc SRP forged small domes
Total Seal rings
Federal Mogul Bearings
Brodix 270 RR Ovals with CNC 115 chambers
Comp billet hydraulic roller 242/248 .621/.616 on 112
Edelbrock RPM Air Gap
Quick Fuel 850cfm
Pertronix III
60412 Moroso pan w/Melling pump

 

I would think pk power should be higher - like around ~5900-6000. Did you put the motor together? Compression test/leakdown? Carb is really the only easy thing left, after that, really need to start taking a closer look at things.

 

Agree it should be peaking around 6000rpm or so. Local builder. I need to do a hot leak down, I did a cold test today and showed about 12%, 9 pulls on the dyno and zero miles so far.

 

I ran a 850dp for a while and it had no problem making power for me either.

 

I know one thing, Brodix heads need a valve job right out of the box, but that alone isn't costing you 70 hp.

12% is to high.


May I ask what your rings were gapped at?

 

May I ask what your rings were gapped at?

good question, I can't tell from my build sheet, I'll find out.

 

Carb to small.

 

I would put more cam in it. My 9.5 to 1 498 went 10.86 at 127.96 in a 3500# car with me in it. TKO 600, 4.11, 36 total, flat tappet cam 260-268 at .050 .637 lift 950QF Q series. I drive it everywhere.

 

I would put more cam in it.

Sounds like you have a nice combo:yes: -

on the dyno looks like it could be running out of cam -but there is at least one other BB (same heads & cam) making 635 hp at 6,000 rpm, mine is peaking too early.

 

Tom, does your builder have the capability to set the dyno up for charting BSFC and AFR during the run? While AFR is certainly good at seeing how well the carb is set up, the brake specific fuel consumption number will show you how efficiently the engine is turning fuel into power. It may give some clues as to what's going on. I don't have near as much engine, but my peak hp came at 5800 with only a 224 cam so something is up somewhere.

 

Tom, does your builder have the capability to set the dyno up for charting BSFC and AFR during the run?

I'm not sure I believe these readings with the new springs.

The initial pulls (with the original springs) are the second attachment.

 

Thanks, I am still trying to get used to it. I wanted it on video, but I was running behind getting to the track as it was. The first pass I let off when I saw the shift light come on, so it was 10.91 at 126.89. Its never turned the shift light on before the finish in fourth gear before. This 498 loved the port work. 2 1/8 super comps running through the mufflers, and Cedar Falls Raceway was working great. I was only letting the clutch out at about 3000, I should of tryed 4000. I gotta get my 2 step hooked up. Dont laugh at my reaction time, I was checking out the guys tubbed wagon I was running.

 

Whoa, that first one with the thumbnail is rich if it's accurate. There's a good bit of power getting drowned out there. Typical BSFC numbers for a normally aspirated engine with a carb are more in the 0.45 to 0.55 range. AFR should be more around 12.8 or so at wide open full load with good heads. That excessively rich mixture explains why you couldn't get any more with the extra timing. Like you said though, there is a big disparity between the two.

Here's mine for comparison:

 

I am believing the original BSFC values - I made no changes to the carb on the second dyno pulls. The plugs looked good, if was really running that rich I would think I could hear it. both runs were 850 with 78 pri/84 sec jets

I am leaning towards trying a different carb and see what we get.

 

Are we looking for consistency in the BSFC across the entire rpm range? Yours looks pretty consistent. My second set looks all over the place

 

You should see the lowest numbers in the fattest part of the torque curve, and higher numbers above and below that. It's basically an efficiency indicator, not like mpg of course but rather how much fuel it takes to make one hp. That's why the range is fairly consistent for an engine type. A 300hp SBC and 600hp BBC should both have relatively close BSFC numbers when tuned properly. Nitrous engine will have a higher number, and turbo/supercharged will have a higher number still.

If those numbers are accurate, then something is amiss. Weird how the one looks good and the other is way rich. Do they have a dyno carb at the shop that they can try out on it?

 

im no expert on big block hp by any means, but if you think its got what it takes to give more in the upper rpms, could valve train stability be a cause? would a rocker girdle help in that situation?

 

im no expert on big block hp by any means, but if you think its got what it takes to give more in the upper rpms, could valve train stability be a cause? would a rocker girdle help in that situation?

From I have learned, Morel makes three series of BBC lifters. Street, Sportsman and Ultra Pro. These are sold under many "brand" names and there is more than a few BBC running them with good results.

I upgraded to the Sportman series, direct from Morel. These hyd. roller lifters can take 150-160# on the seat no problem and 450# open. I don't think asking for 6,0000 rpm from these lifters, PAC beehives, 3/8" pushrods w/guides and roller rockers is unrealistic. If I was looking for 6500+ I would have went with a solid roller.

Not saying a rocker girdle wouldn't help, but I don't think thats my problem at this point

 

n/m

 

I spent time checking installed height of all valve springs.

Intakes were 1.850" range and exhaust 1.880". Both too low. The PAC 1255 Beehives should be installed at 1.950"

looks like the Beehives are dangerously close to coil bind on the intake side. I am using 0.060" thick locators and have new +0.050 retainers and locks on the way to get these set to spec.

Question - Would coil bind (or very close) be holding back the upper rpm HP?

Also have a new ProSystem 1000 ready to go :thumbsup:

 

who said they have to be installed at 1.95"?
shim them! as long as your atleast .060" from coil bind youre ok.
whats the spring pressure? I'm guessin too low

 

160# at 1.950"
425# at 1.300"
408# spring rate

coil bind at 1.220"

1.220" + 0.060 + 0.621" lift = 1.90" min.

 

+.050" lock would put you at 1.90"
I'd put more spring on it tho, around 200# / 500#, and rev it

 

Ha! not sure the Morels would like 500#
which springs are you running in the 502?