Blown 327

[glljr]

Here is the Dyno graph from the last pull on my blown 327. Air fuel is a little fat but better safe than sorry. Timing is set at 32 degrees all in by 2500 rpm's. Numbers seem a little low to me any suggestions would be helpful.

[Marv D]

What boost and cam?
Curious why you stopped at 5500?

I don't know blower motors that well but 8.2 a/f and dropping seems like it's MAJOR fat not 'a bit'

[glljr]

Boost gauge was showing 8 psi and the cam is a summit k1103. We stopped at 5500 cause doesn't really make any power after that.

[AJII]

Originally Posted by Marv D

What boost and cam?
Curious why you stopped at 5500?

I don't know blower motors that well but 8.2 a/f and dropping seems like it's MAJOR fat not 'a bit'

It looks like it's staying above 10 the whole time. Not incredibly rich.

Any detonation at all? Did you try backing off the timing and giving it more RPM?

[glljr]

The air fuel doesn't get under 10 unless I am reading the graph wrong. I could lean out the secondaries a bit and shoot for 12 if that will help. What about the lean dip in the beginning?

[glljr]

No detonation. Just hooked up my msd 6btm for the timing retard just to be safe. The cam is only rated to 5200 rpm. Also has aluminum heads with 195 intake runner 64cc combustion chamber with 1.6 roller rockers long tube headers and full 3 inch exhaust.

[Blue Rat]

Originally Posted by glljr

No detonation. Just hooked up my msd 6btm for the timing retard just to be safe. The cam is only rated to 5200 rpm. Also has aluminum heads with 195 intake runner 64cc combustion chamber with 1.6 roller rockers long tube headers and full 3 inch exhaust.

That is at least HYD Roller Territory an high RPM with those heads an the small CI's.

[vin63]

Originally Posted by glljr

Boost gauge was showing 8 psi and the cam is a summit k1103. We stopped at 5500 cause doesn't really make any power after that.

Did you have a target power range before starting your build? What type of supercharger (my apologies if it is posted somewhere else)? Did you select that cam as part of the complete blower combination, or were your top end components chosen in stages, and are you willing to change cams at this point? Also, is 8 psi of boost your goal, or were you looking for more? Just trying to get some clarity on your combo.

[glljr]

The blower is a weiand 177 with a holley 750. Had a comp 292 in there at first went with the smaller cam to go with the stock converter and the 3.08 gears. Drive it daily was shooting for closer to 400 rwhp.
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[Captainfab]

I don't know that much about boosted engines, but that looks like a mismatch of parts. Heads with too big of intake ports for the cu in of engine. Too small of cam for power goal. Too big of carb for size of engine.

Is this an engine dyno, or a chassis dyno?

[Marv D]

Originally Posted by AJII

It looks like it's staying above 10 the whole time. Not incredibly rich.

Any detonation at all? Did you try backing off the timing and giving it more RPM?

Yeah it's time for new specticles I guess. I couldnt see the img that well and it looked like the line it was hovering around was 8.2.. but but it's 12 (DUH!!)

[Super73]

Lean spike.. I am not the best carb tuner but from what I understand that could be an accelerator pump issue. Perhaps too small, but I'd have a few others comment before taking my word on that one.

AF... Sorry, but from the hit I think it is too rich and only getting worse. Some motors like more fuel and some don't. But we are talking less than .5 of AFR. My finding is most don't. I have seen some pretty big gains getting out of low 11/high 10 AFR and putting the motor where it likes it. Some like 12.6 some like 13. The old saying that "fat is safe" is being proven untrue more and more every day. What happens to the extra fuel in the cyl? Once it gets past the first ring in to the second, build enough heat and you could be lifting a ringland.

I have watched a budy of mine tune carbs on a dyno and he does it similar to how I do EFI:
Keep timing mild
Get fuel curve right, IE get it flat fast and find where the motor makes most power.
Then start adding timing back in at 2* increments until it does not make any more power. Then back it off 2-4 degrees.
Less advance is always more safe than more fuel.

I bet there is 40rwhp in that tune. But 100rwhp, probably not.


The reason for going with a smaller cam would definately be justifiable if you were still NA, but being blown, it is probably hurting you.

I personally don't think the heads runner size is an issue, being boosted will definately over come any short comings there.

You are seeing 8lbs of boost? Did you double check with a boost gauge while making pulls?
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[vin63]

Originally Posted by glljr

The blower is a weiand 177 with a holley 750. Had a comp 292 in there at first went with the smaller cam to go with the stock converter and the 3.08 gears. Drive it daily was shooting for closer to 400 rwhp.
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Gotcha...based on this, I think the power band is right in line with what I would've expected. I select my cam more based on the cylinder heads and induction type as a combination. I then select my torque converter last based on the power band the final engine combo makes, and the chassis weight.

[Blue Rat]

Originally Posted by vin63

Gotcha...based on this, I think the power band is right in line with what I would've expected. I select my cam more based on the cylinder heads and induction type as a combination. I then select my torque converter last based on the power band the final engine combo makes, and the chassis weight.

With those gears an stock converter the cam matches good. Just can not help to think it would run a little better with the heads matched.

[Super73]

Am I the only one here that is of the belief bigger runners are not a big issue when there is positive manifold pressure? Under vacuum, I would absolutely agree that a smaller port that flows the same cfm is going to aid velocity and mid range tq. But when you have positive manifold pressure, you are forcing air in past the intake valve. In my opinion there is a major difference between the two.
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[T Smith]

When I was playing with blown Mustangs I concentrated on the exhaust side because the intake will take care of itself when you're forcing it in there. A split profile cam with more lift and duration on the exhaust is good, keep the centerline more along 110-112 so you don't bleed off your boost, a blower will tame a cam so go bigger than you would for normally aspirated, port the snot out of the exhaust, big headers and pipes, 32 degrees timing is plenty, and I'd consider even more carb (minimum 750)and be sure to boost reference the power valve.

I had a 302 putting 437 horses and 413 torque at the rear weels with 13 pouds of boost, B&M 177 blower with a highly modded R3310 750 Holley, gauging on a risky T5 and was running 11.7 @127 mph with 3200 pound mustang full interior, boom box, and roll cage on nitto street radials p\s, p\b,cruise, tilt wheel, cold air, and getting 16-18 mpg doing it back and forth to the track. 6 inches daylight under the left front on launch...

I was spraying a 75 shot in there under the carb straight into the blower, used that as an intercooler made things get really real then, picked up 5 tenths, nearly in the tens with a daily driver.

[T Smith]

ignore my double post!

[vin63]

Originally Posted by Blue Rat

With those gears an stock converter the cam matches good. Just can not help to think it would run a little better with the heads matched.

...I agree, but if you are stepping up to a boosted induction, why then would you select the cam based on your stock torque converter and gearing if you're looking for more power? If that's the case, stick with the naturally aspirated vacuum-based induction. In this application, the heads are not the limiting factor for a larger power band. The cam (that was selected for the stock converter), which does not take advantage of the boosted induction, is the bigger obstacle for more power.

[Blue Rat]

Originally Posted by vin63

...I agree, but if you are stepping up to a boosted induction, why then would you select the cam based on your stock torque converter and gearing if you're looking for more power? If that's the case, stick with the naturally aspirated vacuum-based induction. In this application, the heads are not the limiting factor for a larger power band. The cam (that was selected for the stock converter), which does not take advantage of the boosted induction, is the bigger obstacle for more power.

I agree totally. A larger bumpstick to go with those heads would prouce a lot more. But then I would want at least 3.73's.
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[gofastnut]

I'd have to agree with Blue Rat, T Smith, and Super73.
Of course this is my humble opinion, but, I definitely think you need more cam. Going larger does not mean you have to go into super high RPM. Look at the torque this thing is making, not bad at all! I don't think the heads are too big for the engine. Putting a supercharger on there makes the engine breath alot heavier, and mimicks a larger cubic inch engine. I'd also just build for the power you want to make, then look at stall, then gears, if you feel you need to.

[prostreetC-10]

Originally Posted by Marv D

Yeah it's time for new specticles I guess. I couldnt see the img that well and it looked like the line it was hovering around was 8.2.. but but it's 12 (DUH!!)

Will someone help Marv back to his AARP meeting? I think he is lost! LMAO

[Marv D]

LOL, 'lost' is a serious understatement sometimes

[prostreetC-10]

I am only 45 and have lost all my close up vision in the last year. I used to laugh when I would ask guys for a Holley list number off the choke horn and they would say "hang on.....let me get my glasses". I now have reading glasses all over the house, the shop, the car and my office. All down hill from here I think.

[T Smith]

Originally Posted by prostreetC-10

I am only 45 and have lost all my close up vision in the last year. I used to laugh when I would ask guys for a Holley list number off the choke horn and they would say "hang on.....let me get my glasses". I now have reading glasses all over the house, the shop, the car and my office. All down hill from here I think.

Bifocals are next!

[Marv D]

yup,,, around 45 is when things 'start' going to all to hell. You don't want to hear what's next.
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you WONT hear it is the point! LOL