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Discussion Starter · #1 · (Edited)
I've attached a video of the dyno...looking for some opinions on the dyno results...I was pretty happy with the numbers, but surprised by one aspect of the results. Results are at rear wheel..I came in with 408HP at 5800 rpm and 442 torque at 4000 rpm. The torque #s were impressive even at low rpm with 375 at 2600rpm. The thing that I'm looking for opinions on is this....this is a solid roller motor, I was surprised to see the HP start to drop at only 5900 rpm, at 6700 rpm I was down to 350HP. Specs are:
406 cubes, Dart SHP, scat forged crank, Mahle H Beams and pistons
10.2 CR with quench of .045
AFR 195cc intake runners
Comp Cams 12-770-8 solid roller cam .564/.570 236/242 @ .050 power range of 2200-6500
AFR 8019 springs 155lbs on the seat, 420lbs @.600
Proform 750 on an Edelbrock RPM Air Gap

Dyno was performed by the guys at Jesel valvetrain, their thoughts were that the power dropped off so early due to the size of the intake runners. I have a suspicion though that the relatively light spring pressure that is recommended for this cam may be causing a float as I approach 6000rpm. These pressures were what Comp recommended for this grind, even though they are much less than most other solid rollers. When you are in the car driving, it feels like it just does not want to wind up past 6500.

So even though I'm satisfied with the numbers, assuming an approx 20% loss thru drivetrain puts me around 500HP, I really was hoping to make more power in the 6000-6800 range. Opinions wanted!!
 

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looking for some opinions on my dyno results...I was pretty happy with the numbers, but surprised by one aspect of the results. Results are at rear wheel..I came in with 408HP at 5800 rpm and 442 torque at 4000 rpm. The torque #s were impressive even at low rpm with 375 at 2600rpm. The thing that I'm looking for opinions on is this....this is a solid roller motor, I was surprised to see the HP start to drop at only 5900 rpm, at 6700 rpm I was down to 350HP. Specs are:
406 cubes, Dart SHP, scat forged crank, Mahle H Beams and pistons
10.2 CR with quench of .045
AFR 195cc intake runners
Comp Cams 12-770-8 solid roller cam .564/.570 236/242 @ .050 power range of 2200-6500
AFR 8019 springs 155lbs on the seat, 420lbs @.600
Proform 750 on an Edelbrock RPM Air Gap

Dyno was performed by the guys at Jesel valvetrain, their thoughts were that the power dropped off so early due to the size of the intake runners. I have a suspicion though that the relatively light spring pressure that is recommended for this cam may be causing a float as I approach 6000rpm. These pressures were what Comp recommended for this grind, even though they are much less than most other solid rollers. When you are in the car driving, it feels like it just does not want to wind up past 6500.

So even though I'm satisfied with the numbers, assuming an approx 20% loss thru drivetrain puts me around 500HP, I really was hoping to make more power in the 6000-6800 range. Opinions wanted!!
Ron, I'm sure you will get some better opinions than I can offer.. but.. that is one STOUT runner! I almost wonder if you were getting a bit of tire slip on the rollers when really "winging it".. This said, I suspect the 195's might be holding it back just a bit. Congrats on some great numbers.
 

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Discussion Starter · #3 ·
thx Mike, yeah the car will give you a little thrill if you really lean on it, t-56 with 3.90 12 bolt...trying to post up a iphone video of the dyno, cant get it to load yet, will keep trying...
 

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Here's my thought.

You're making the kind of power that you should be at the rpm you should be with this combination. Congratulations, most don't get this good because some piece of the puzzle is holding them back. You probably have the timing and jet pretty close.

So I think their thoughts are correct. You need a bigger head. You may also need a bigger cam and bigger headers to get to the level you're thinking of. Maybe more carb too. The reason I say bigger most everything is that I think you're pretty balanced right now. To go up a significant notch may mean more of everything.

But you only gave us the peak numbers. It would be interesting to see the entire torque/hp curves in more detail, as well as anything else they recorded. But I don't see any dips or obvious areas to work on. It all looks pretty good. If you had a serious valve spring problem, it would drop off more when that occurred.
 

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Discussion Starter · #6 ·
Thx Rick, here is a better pic of the results,like I said the torque at as low as 2500rpm is what impressed me the most. Maybe that is a result of the smaller 195cc heads combined with the larger 406 ci?
 

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Thx Rick, here is a better pic of the results,like I said the torque at as low as 2500rpm is what impressed me the most. Maybe that is a result of the smaller 195cc heads combined with the larger 406 ci?
I think you are right. Those 195's will certainly make the torque down low.. which BTW, is really right for a street cruiser anyway. Really how often are you going to hit over 6K rpms? I think your combo is just right... plenty of power, great parts, well thought out... Not too many street cars will be able to mess with you.
 

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Sounds about right. Mine is sort of similar, Dart 406, 11:1 comp,similar lift cam but mines not a roller. Main difference is I have 230cc Pro 1 heads that work really well on the combo. 448hp at the wheels.My shift light was set at 6500 but it zings past that real fast still pulling hard. We had people saying the heads were too big but we proved them wrong. It ran 11:8 in full street trim first time on the 1/4 but had carbie problems. It should be good for a low 11 when sorted.Yours should too. Would be good to see it run on the track. That is the real dyno. Cheers
 

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Discussion Starter · #10 ·
Wow those are nice numbers 55dart, yeah I put alot of thought into those 195's and the Comp ratio and wound up going more on the conservative side for both. I was concerned with detonation with the higher comp ratio and having it lug at lower rpm with the bigger heads. But looks like as you said you proved the bigger heads may work well. Do you have any detonation problems? And what gear and trans are you using ...how'd you get it to hook up?
 

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RPM

The intake cc may be a little small for a 406 but you could try pluggin your number into Desktop Dyno or similar program and see if retarding the cam 2 or 3 degrees to see if that would be enough to satisfy you if not send the heads back to AFR for their compitition port job. That would be cheaper than a new set of heads, I tried the computer trick and mine picked up 10-15 hp upstairs while reducing tire shredding low end with a 700R4's deep first gear,
 

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Wow it makes it look easy and doesn't sound like it was revving hard at all.
Mine was all twisted up and wheel spinning . Pretty scary to watch ! I wished I took a video.We had ours on my engine builders Dyno Dynamics rollers. I use 275/15 ET M/Ts on the track that hook up well and use 295/15s on the street that don't. I run a th700 and 4:11 diff gears. I have no problem with detonation and 11:1 comp. Our BP ultimate 98 fuel is not too bad.

Was yours on a mobile dyno ?
Should be a good tough cruiser. Nice looking car too. Any more pics and specs?
Cheers
 

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Discussion Starter · #13 ·
thx 55dart Here are a couple of recent pics, just put in some pretty cool HID projectors...biggest prob for me is getting it to hook. 255/50 on rear and it just eats them. But with it as low as it is just cant get any bigger tire under it, I have to drop the rear to get those in!
Thx 56 owner I'd like to look into that idea, do you have a link to any desktop dynos?
 

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fifty five it's the tall K&N 14"..why do you ask?
Just to scratch off too small of an air cleaner. I was curious if maybe it was running out of air because of a small cleaner. Our engine builder, and others have commented that a cleaner that's too small could drop as much as 100 hp, depending on application that is.
 

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midnight, your car is amazing, not a damn thing wrong with it. your just a 125 shot away from being a 10 second car.bowtie-trifive
 

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very impressive!

you will give up low end HP and drive ability for more top end HP.
larger heads, bigger cam, bigger headers , all make for poor low end perf,
and alot less fun to drive at normal speeds.
at the HP levels you have now, I'd be delighted and would enjoy it!
 

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Discussion Starter · #19 ·
I kinda like 56owners idea of retarding the cam ...really all I am after is to still make power to 6200-6500 rpm, with my 3:90 rear and 2:67 first gear and a built up bottom end I would like to be able to wind it up a bit more...from chart you can see my power starts dropping at 5900...as you can see from results I have loads of low end torque and just shred the tires, I know if I go bigger everything I may give up a bunch of that low end, so I don't want to do that but I like the cam retard idea to just give up a little and get a bit more top end...whats opinions on that?
 

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I've attached a video of the dyno...looking for some opinions on the dyno results...I was pretty happy with the numbers, but surprised by one aspect of the results. Results are at rear wheel..I came in with 408HP at 5800 rpm and 442 torque at 4000 rpm. The torque #s were impressive even at low rpm with 375 at 2600rpm. The thing that I'm looking for opinions on is this....this is a solid roller motor, I was surprised to see the HP start to drop at only 5900 rpm, at 6700 rpm I was down to 350HP. Specs are:
406 cubes, Dart SHP, scat forged crank, Mahle H Beams and pistons
10.2 CR with quench of .045
AFR 195cc intake runners
Comp Cams 12-770-8 solid roller cam .564/.570 236/242 @ .050 power range of 2200-6500
AFR 8019 springs 155lbs on the seat, 420lbs @.600
Proform 750 on an Edelbrock RPM Air Gap

Dyno was performed by the guys at Jesel valvetrain, their thoughts were that the power dropped off so early due to the size of the intake runners. I have a suspicion though that the relatively light spring pressure that is recommended for this cam may be causing a float as I approach 6000rpm. These pressures were what Comp recommended for this grind, even though they are much less than most other solid rollers. When you are in the car driving, it feels like it just does not want to wind up past 6500.

So even though I'm satisfied with the numbers, assuming an approx 20% loss thru drivetrain puts me around 500HP, I really was hoping to make more power in the 6000-6800 range. Opinions wanted!!
The heads and intake are your biggest restrictors, The push rod pinch area is tight on those heads but will produce good torque numbers and with that cam you moving a lot of air and with that intake and small runner head the air speed is very fast which = torque. GREAT NUMBERS

Built a 421 last month and dynoed with the 220 AFR heads as the customer had a set of new crower SS stud mounted rockers or I would have used he 235 AFR's with a set of jesel shaft rockers. That being said the peak torque was at 4800 which was 574 and peak power was 604 at 6400 RPM.

Talked to Tony Mamo at AFR during the build and he was right on the money on my numbers but if I had gone with the 235 heads I would have given up about 30 plus foot pound of torque but would have made around 660 horse and the peak HP number would be around 7000 RPM.

http://www.chevelles.com/forums/showthread.php?t=481081

Again great numbers.
 
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