SBC Dyno results, where to go from here

[rustbucket79]

Not saying it would happen, but I have dealt with cars that were fussy when getting on the converter.
(Big headers/induction/cam for the displacement)

[randy331]

Is the pull posted the best pull ?
The cam in 2* retarded. Is that 2* retarded from the cam card suggested installed position, or 2* vs LSA ?
Pulls to compare the cam positions tested could be helpful.
It looks like peak TQ RPM is below the dyno start rpm and peak HP is above the dyno finish rpm. That's a big spread between peak TQ and peak HP.

Randy

[rustbucket79]

Cam is a custom grind carry over from my previous build, only with a bunch more rocker ratio. It's ground straight up 109 ICL and 109 LSA. Testing was done +2 and -2 with small intake and carb, -2 (111 ICL) with the big intakes including this run, and also tested at a later date at -4 (113 ICL). This run was an 1100' day and the subsequent runs were on a 2000' day, with the backup run being down a few numbers making it tough to compare to the previous tests. I think it needed a bleed change leaner, however it's not my carb so I didn't want to mess with it since it was reasonably close. Retarding the cam to -4 resulted in a 3 # loss of torque in a narrow range down low for an average HP gain between 7000 and 7400 of 1.6, totally worth it!

These tests were run to find out what I had, and to explore trends of what the engine liked or disliked rather than a final tune to put in the car. I appreciate all the thoughts offered from fellow ST members.

[rustbucket79]

Oh this "best pull" matches one other, and in regards to how the lead in spike of the torque curve, it's quite likely a result of not letting the engine settle out long enough before starting the test.

[rustbucket79]

T R Overlay.jpg

Here is the overlay comparing my Super Victor 4500 and a Holley 1150 (red traces) and a Victor Ram and two Holley 950 HP's. (black traces)
What curves would you rather have?

[In-Tech]

Hello, can you overlay AFR traces for the same red and black traces above? When I see a power dip like the black trace with a tunnel dual 4 it is usually from not enough HSAB and the signal is starting to come in hard making the AFR go rich with RPM. It is not uncommon to have larger HSAB and emulsion with a dual 4bl setup once tuned.
my .02

[F-BIRD'88]

Put in all the gear it needs. Then when dial in et racing rpm limit the last 200ft of the run to limit rpm and MPH. When you are "on time". but if you "leave late" let it rpm thru the traps to catch up. The big step headers will react to the bigger duration cam. Moving a cam by only 2deg is useless. Start with the cam well advanced and then progress towards straight up. On that cam try tighter lash and advance it.

Nice if you can borrow/rent a set to try. Not just bigger, but step header.

Gear change,, the rpm will not change as much as you think as with the lighter gear the converter will Lock up better. I'd go to 4.56. ( it probabily actually needs more) To me the power curves look like it wants to rev rev up.
The tunnel ram may need 2x750's instead of the 950's I don't like the 950's.

may need a plenum fill too. If you get a chance don't be afraid to play with that
to dial in a tunnel ram. ( plenum fill+/- and carb height+/-)
On our old 406 we were right where you are and going to custom built big step headers AND the big cam it suprisingly HELPed Everwhere. It wanted to eat.

A tall tire and a short tire choice also allows you to play with trap rpm with steep gears. Also adjusts for bad air good air days.
Yours it like ours, It really wants to rev. Do you have a front chin spoiler? really gets the MPH up. Get the front end down thru the traps too.
What is the 1/8th mph and the 1/4 mph's? Its free engine power.


X2 re: In-Tech's post. usually the trend is the opposite.. It started out great but then got all choked up.

[vortecpro]

You need to be looking at your drive line instead of the engine. How come no one does this?

[vortecpro]

You need to be looking at your drive line instead of the engine. How come no one does this?
133 MPH @ 3250=589 HP

[user-9274568]

All I will add is with that bigger cylinder head and a 406 your going to need some stall and gearing.

Like more of both than you think.

[Frankshaft]

Car only has 1 3/4’s, bought them in 1992 to go on a 327 with iron Bowtie heads. They also only have a 3” collector compared to the 3 1/2” on the dyno headers, plus they have evac u pan nipples. I would consider 1 7/8” but one thing always sticks in my mind, Joe Sherman stated in a magazine article that those headers don’t seem to work on any small block.

Well, I can tell you what, the 1st thought I had, was I would try bigger headers, run a vaccum pump, bump compression and run Q-16. I bet it goes over 700.

The header thing, I did a 331, 327 based deal for a road race engine. Engine wasn't making the power I though it should, we started with using some 1 5/8 hooker competition headers, nothing great, but not total garbage. We finally said lets put your headers on. They were 1 7/8 with a 3.5 collector. It picked up over 50hp and made more tq everywhere. We said WOW. The 460hp 410 ft lb ho pooch, went over 500hp and made almost 440 tq. They were really nice custom headers built by the owner, to fit his chassis. I have seen 20-30 hp from good 1 3/4's to 1 7/8's numerous times on sbc's.

Headers can have a way of humbling you. Ive seen header changes that should have done a bunch do nothing. And headers that shouldnt do crap make you look stupid when they do. Blanket statements on headers from people set of my bullshit alarm because of that.

I am not disagreeing with you. It's not the norm. But, there can be those gains, depending on what you started with, and ended up with. The 327 example, most guys would say, 1 7/8 with a 3.5 collector is WAY to big. Maybe they were, but it certainly came a live. Believe me, I have A LOT of back to back header testing on a lot if different applications. Sometimes you say, that sucks, waste of time. Other times you say WOW. Try a set if cheap ass 3 tube headers on a Pontiac 455, then back to back it with a good set of headers, you want to really say WOW try that. I should add, I think this is one of those engines that may pick up a fair amount. If it was some 550 hp 6400 rpm deals, not so much.

[user-9274568]

I just recently had a customer dyno a 13-1 421 with a 227cc head. I would post up the sheet if you would like to see it as long as folks don't think it's some sinister plot. lol

[Stan Weiss]

scanpwr.jpg
406, Dart Little M, AFR 245's, 12.5:1, 266/271 @.050, 109 lobe separation, .449"/.437" lobe lift, 1.7I/1.6E rockers, 1 3/4 dyno headers, Super victor 4500 port mached and plenum work, Holley 1150 HP. (best numbers but ultimately not the carb that will be used)

I tested with 4 different intake manifolds, 4 different carburetor configurations, with and without a vacuum pump, and different cam timing. This test happens to be with the camshaft 2 degrees retarded. This is an old build (bracket racer) that will ultimately be torn down and freshened before it sees the track in another year. Thoughts are a bit more compression, possibly a different cam, and maybe even a bit more stroke.

The engine is solid but ultimately, is there much on the table here or am I chasing just a few numbers?

Is the 4 column on the dyno sheet not really the A/F ratio?

► 212.4 / 0.426 = 498.59 Un HP ----------------------
► 212.4 * 12.6 = 2676.24 Mass Air Flow
► 2676.24 / 5.59 = 478.75 Un HP ?????

612 SCFM is roughly 2790 lbs/hr Mass Air Flow
► 2790 / 5.59 = 499.11 Un HP -----------------------

Stan

[Stan Weiss]

I just recently had a customer dyno a 13-1 421 with a 227cc head. I would post up the sheet if you would like to see it as long as folks don't think it's some sinister plot. lol

Chad,
Please post up your dyno sheet.

Stan

[treyrags]

I just recently had a customer dyno a 13-1 421 with a 227cc head. I would post up the sheet if you would like to see it as long as folks don't think it's some sinister plot. lol

Chad,
Please post up your dyno sheet.

Stan

Yes please