SBC Dyno results, where to go from here

[rustbucket79]

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.

[JoePorting]

Headers are over rated. If you're lucky you might pick up 3 hp with a larger header.

Saw a Hotrod magazine video from the Road Kill guys recently where they smashed the primary header tubes to a 550 hp sbc by 50% and only lost 1 hp on a Dyno.

[F-BIRD'88]

What was the best MPH? I don't think you are trapping at a high enough rpm.
You are not even hitting peak HP rpm at the stripe.
If the MPH was 138 MPH or less you need more gear in that car.
you want to be 2000 rpm (above the flash stall speed), thru the traps
so 7600rpm+
IMHO a bigger duration cam 277-284in 284-290 ex and 1-7/8 to 2" step headers
will give more peak HP and more "afterpower" . Thus the trap rpm will come up a bit and it will carry the top end. The carb is small once you buzz it like this.
Needs a 1350cfm (worked) Dominator or go for the Victor Ram.
Not that crazy about the supervic. You can make a better more powerful intake
starting with something else.

is that 3250 ish with or without driver? Nut as it sits now I;d say that car needs a lot more than 4.10 gear. MPH is???

[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.

[hoffman900]

You guys need to find a real header builder.

[CGT]

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.

[AMXstocker1]

The first thing i would do is forward those results to whom ever builds your torque converter.

[MadBill]

it's a nice flat power curve as far as it goes, but looks like it might peak at ~7700 RPM. Best performance would likely be gained shifting at ~8,000, if the bits are up for it.

[rustbucket79]

What was the best MPH? I don't think you are trapping at a high enough rpm.
You are not even hitting peak HP rpm at the stripe.
If the MPH was 138 MPH or less you need more gear in that car.
you want to be 2000 rpm (above the flash stall speed), thru the traps
so 7600rpm+
IMHO a bigger duration cam 277-284in 284-290 ex and 1-7/8 to 2" step headers
will give more peak HP and more "afterpower" . Thus the trap rpm will come up a bit and it will carry the top end. The carb is small once you buzz it like this.
Needs a 1350cfm (worked) Dominator or go for the Victor Ram.
Not that crazy about the supervic. You can make a better more powerful intake
starting with something else.

is that 3250 ish with or without driver? Nut as it sits now I;d say that car needs a lot more than 4.10 gear. MPH is???

Averages 133 MPH with a best of 134. IIRC trap RPM was 7200 or a touch more. Car weight is estimated with driver, last accurate weigh was with a GM block and iron heads, TH350 trans, at that time it was 3245 with me.

I’m well aware that the car needs more gear, and will be addressed before it sees the track since the 10 bolt axle is way overstressed. I was considering a 4.30 gear since I’m not super pumped about 8000 RPM as a bracket engine. FWIW the cam on this run is retarded 2 degrees, will need to retest straight up with this setup to see if the average numbers warrant running it that way.

Not sure why I would need a 1350 com carb, in the 18 pulls I did not once did it exceed 880 CFM through the turbine.

I did finish up with 2 pulls with an Edelbrock Victor Ram with 2 950 Holley HP carbs. I will post a run overlayed with this setup and the first post, possibly later tonight. Care to hazard a guess on the results?

My ported Super Victor 4500 was worth 11 HP over an out of the box one.

[rustbucket79]

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.

Engine will go back on the dyno this year, one of the tests will be to compare my small collector headers to the dyno large collector headers. At some point I will need to replace my headers, I just wish I had a set of 1 7/8’s to try. I’m concerned that a very small gain in peak HP might be offset by a large loss in numbers at the bottom of the on track powerband.

[midnightbluS10]

Well your heads are tapped out at 5600 rpm, but where do you actually shift the motor at 7200 to 7400?

It would be nice if that dyno print out also stated how much VE the motor made as I don't know what those heads flow , but it took 320 cfm to produce your 662 coreccted HP.

How do you figure 5600?

Without looking over the data again, the only thing I found earlier that's correlating to 5600 was BMEP and it hits its max right around that rpm, IIRC.

[MadBill]

...Not sure why I would need a 1350 com carb, in the 18 pulls I did not once did it exceed 880 CFM through the turbine....

There's no magic in having the turbine numbers matching the carb rating; that would just mean that at least theoretically, the manifold vacuum at that point would be the 1.5" Hg. at which the carb is rated. Many race engines use larger carbs that operate with as little as 0.5" Hg. vacuum, giving significantly more airflow and power, albeit at the expense of much more sensitivity to tuning.

[rustbucket79]

The first thing i would do is forward those results to whom ever builds your torque converter.

Interesting bit of trivia here. I could footbrake hold my previous iron headed combo in high gear to about 5400. The first time I whacked this engine on the trans brake, it hit 6000 which surprised the hell out of me. 195 cc runners to 245 cc runners, approximately 2 points LESS compression, I was fully expecting to have to restall higher.

First weekend out at a lower altitude track, running my ported Victor JR intake and a 850 double pumper, 2 step set at 5400, car ran a 10.06 at 134.x (VP113 fuel) with a 6.39 1/8 mile.

[rustbucket79]

[quote=rustbucket79 post_id=716531 time=<a href="tel:1517884718">1517884718</a> user_id=1136]...Not sure why I would need a 1350 com carb, in the 18 pulls I did not once did it exceed 880 CFM through the turbine....

There's no magic in having the turbine numbers matching the carb rating; that would just mean that at least theoretically, the manifold vacuum at that point would be the 1.5" Hg. at which the carb is rated. Many race engines use larger carbs that operate with as little as 0.5" Hg. vacuum, giving significantly more airflow and power, albeit at the expense of much more sensitivity to tuning.
[/quote]

it's a nice flat power curve as far as it goes, but looks like it might peak at ~7700 RPM. Best performance would likely be gained shifting at ~8,000, if the bits are up for it.

I just meant that with both the 1150 and the pair of 950’s that the airflow didn’t exceed 880 CFM. Early in the dyno session I tried my old Victor JR with a 950 Holley UHP, it pulled 807 CFM and 1.4” Manifold vacuum. Didn’t check manifold vacuum with any of the other intakes.

What do you consider a long term safe upper RPM limit for a Scat H beam rod with replacement ARP 2000 bolts? Wiseco pistons in the low 600g range with pin.

[statsystems]

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.

Engine will go back on the dyno this year, one of the tests will be to compare my small collector headers to the dyno large collector headers. At some point I will need to replace my headers, I just wish I had a set of 1 7/8’s to try. I’m concerned that a very small gain in peak HP might be offset by a large loss in numbers at the bottom of the on track powerband.

If the bigger headers are the correct length and you play with collector length you won't lose bottom end. You have enough converter and a high enough shift speed who cares what happens below 5k anyway?