489 BBC

[Airflow]

Hi there.
I've had a 489 stroker built. We've been discussing on a norwegian Forum about the AF ratio from the dynotest done on my engine. The engine is built and tuned on one of the best engine builder/tuners here in Norway. The readings show that it runs a little lean. I've asked the enginebuilders about this and they say they tune their engines after what the engine likes, nice curves and the most power. Then the number becomes what they do. They say some engines are better running a little on lean side and some on the rich side. What do you guys thing?

Here's some info on the engine.


Scat stroker kit 42310BI
Edelbrock topend kit 2095
Holley streetavenger 870 carburettor
MSD ignition.
9,0:1 in compression.

 

[grumpyvette]

first let me say, congratulations on having a big block built under conditions that Im sure are far from ideal or cheap,Im sure you will enjoy the results.
its true that each engine combo will need to be tuned to what it likes best and thats usually found on a dyno or the track, mostly by trial and error but obviously experience has a great deal to do with what you will find works best.
Ive built at least two dozen 489-496 big blocks and its not hard to build a 550hp-600hp combo.

viewtopic.php?f=69&t=5123

viewtopic.php?f=69&t=6125

viewtopic.php?f=69&t=3153

viewtopic.php?f=69&t=189

http://www.dragzine.com/tech-stories/engine/ultimate-guide-to-budget-bbc-cylinder-heads-under-2000/

yes its possible that that engine runs best on a leaner fuel air ratio, but I rarely see engines run best on ratios leaner than about 13.7:1.
now on a fairly high compression engine its been my experience that a fuel/air ratio in the 12.5:1-13.3:1 range usually produces the best results , but factors like quench distance, cylinder head temperatures and ignition advance curve obviously need to match the fuel air ratio used.
your running a fairly low static compression ratio, which tends to run better with a slightly leaner fuel air ration and a slightly slower ignition advance.
now Im not saying that thats the absolute only useable correct fuel/air ratio, because changes in the ignition advance and other factors can easily effect the results.
If it was my engine Id try to richen the fuel/air mix up to keep it consistently richer than 13.7:1 as I seldom see leaner mixture ratio than that produce best torque
Btw heres a tip learned through experience , if your 496 -540 displacement BBC combo includes an engine with at least 10:1 compression and a cam with at least 240 duration at .050 lift, and oval port heads, youll almost always find a single plane intake has some advantages over a dual plane intake.
https://www.holley.com/products/intakes/single_plane_manifolds/parts/7620

viewtopic.php?f=55&t=109

viewtopic.php?f=70&t=4683

the best solution from a performance perspective is to do the required calculations to select the longest length connecting rod and the lowest weight piston,
of a decent design that will reduce the reciprocating mass significantly more.
the tall deck has a 10.2" deck height, a good dual plane aluminum high rise intake manifold will tend to provide the best compromise if you use a low compression and mild cam duration,
while it might seem like a waste of time, now, reading the links and sub-links will provide a good base to work from, later and save you a great deal of wasted time and money
you have a choice, you can slap the components you own together, now and live with what you have built regardless of the results , or you can put some real thought into making the result perform and carefully select parts and significantly boost power... yes that routes more expensive up front, but in the long term it tends to get better results and cost LESS.
common BB CHEVY piston compression heights are
1.270"
1.395"
1.520"
1.645"
1.765"
remember the blocks deck height, minus the piston pin height minus 1/2 the crank stroke will equal the required connecting rod length
OR
the blocks deck height, minus the connecting rod length, minus 1/2 the crank stroke. will equal the required piston pin height

if you wonder why I suggest using SCAT (H) beam style cap screw connecting rods vs stock or most (I) beam designs this picture should show the increased cam to connecting rod clearance

notice the pin height in the pistons pictured above allow a longer or shorter connecting rod length

heres a selection of commonly available big block chevy connecting rod lengths

https://www.uempistons.com/index.ph...e=deck&zenid=823ce2c9e2ffa691864d832c10107df0

https://www.uempistons.com/index.php?main_page=calculators&zenid=823ce2c9e2ffa691864d832c10107df0
1.765 compression height, pistons in standard 9.8" deck block, a 10.2" tall deck requires a longer connecting rod
most likely a 6.535" aftermarket connecting rod

threads you should read through carefully,and the sub links in them are below,
the tall deck block is put to much better use building a 496 with a 4.25" stroke and a .060 over bore and 6.385" connecting rods

http://garage.grumpysperformance.com/index.php?threads/another-496bbc.5123/

http://garage.grumpysperformance.co...g-block-head-comparison.319/page-2#post-61658

http://www.maliburacing.com/patrick_budd_article.htm

http://garage.grumpysperformance.com/index.php?threads/427-tall-deck-bbc.14451/

http://garage.grumpysperformance.com/index.php?threads/big-block-chevy-info.710/#post-60299

http://garage.grumpysperformance.co...-displacement-street-engine.10961/#post-50668

 

[Airflow]

Thanks again for the reply!
Is it possible that I could get burnt pistons with this ratio? I will get a good indication looking at the sparkplugs, correct?
I would like to buy a Air/Fuel gauge to install so I can monitor the ratio, but there ar quite a few for sale. Is there any you would recomend? Also where wshould I install the oxygen sensor? I know haveing one after each sylinder would be best, but it wouldn't be possible if I'll have it permanently installed. The exhaust system will have a x. Is there any gauges that could use 2 sensors so I could have one after each header?

 

[grumpyvette]

Thanks again for the reply!
Is it possible that I could get burnt pistons with this ratio? I will get a good indication looking at the spark plugs, correct?
yes the spark plug condition is a very good indicator of combustion chamber temps, in fact its usually more accurate than several other indicators

I would like to buy a Air/Fuel gauge to install so I can monitor the ratio, but there are quite a few for sale. Is there any you would recommend? Also where should I install the oxygen sensor? I know having one after each cylinder would be best, but it wouldn't be possible if I'll have it permanently installed. The exhaust system will have a x. Is there any gauges that could use 2 sensors so I could have one after each header?

THESE THREADS MIGHT INTEREST YOU.. READING THE SUB LINKED INFO, IN EACH THREAD, WILL EASILY MORE THAN QUADRUPLE THE INFO YOU GAIN

viewtopic.php?f=50&t=6174&p=20791&hilit=fuel+ratio+meter#p20791

viewtopic.php?f=55&t=6765

viewtopic.php?f=55&t=109

viewtopic.php?f=55&t=1115

viewtopic.php?f=32&t=577

viewtopic.php?f=70&t=202

viewtopic.php?f=70&t=4683

 

[grumpyvette]

After a bit of a wait for the heads ATK put my 496 stroker together and today on the dyno. The combo is MARK IV 496 BBC, AFR 290 HEADS ,10.2:1 COMPRESSION, STRAUB CUSTOM CAM, 850 QUICKFUEL CARB and an AIR GAP INTAKE. The goal was 630 and they hit it. 631hp at 5800 and 637torque at 4100. So thanks to the Brandon and the guys at ATk as well a Straub technologies. It should be a riot. Here is the dyno numbers

speed(RPM) CorrTorq (ft-lbs) CorrHP (Hp)
3500 591 394
3600 604 414
3700 610 430
3800 618 447
3900 628 466
4000 628 478
4100 637 497
4200 635 508
4300 632 517
4400 637 533
4500 633 543
4600 630 552
4700 629 563
4800 625 571
4900 626 584
5000 626 596
5100 625 607
5200 613 607
5300 605 610
5400 601 617
5500 592 620
5600 582 621
5700 576 625
5800 571 631
5900 558 626
6000 546 624

290cc oval
http://www.airflowresearch.com/index.php?cPath=68_121
300cc oval
http://www.airflowresearch.com/index.php?cPath=68_129
notice the very flat impressive torque curve, either of these larger port oval port heads would be well matched on a 489-496 BBC engine designed for max torque below about 6200rpm, notice the torque peak at about 4400rpm a larger port head and longer duration cam timing would push that higher in the rpm band but most likely kill off some low rpm torque, which on a street driven musclecar might not be an ideal compromise

 

[grumpyvette]

if you wanted more power, from a 489 or 496 big block, Id suggest you increase the compression ratio to 11:1-to-12:1, use the solid roller lifter cam linked to below... it won,t run well on pump octane gas but it will make a performance car engine with higher octane fuel run noticeably harder in the upper rpm ranges

and these 315cc heads with a good 950cfm carb and good high rise single plane intake
http://www.airflowresearch.com/index.php?cPath=68_74
yes the 300cc oval ports are a valid option. I doubt you would see, or feel a really noticeable difference, in the two power curves any place but on the dyno
http://www.airflowresearch.com/index.php?cPath=68_129
an engine built like that in a reasonably light weight car (lets say under 3300lbs and geared with a 3.45:1-3.73:1 rear gear with an auto trans with a 3200 stall speed converter or manual trans would be really fun to drive on the street)

 

[87vette81big]

The 496 BBC HAS A TREMENDOUS TORQUE CURVE GRUMPY.
I WOULD USE AS IS ON THE STREET.

DANA 60 REAR OR Pontiac Olds 9.3 Required.
4-link recomended.

Enough torque to easily explode C3, C4, C5, C6 IRS rears.
Also stock Ford 9inch, stock 10& 12-bolt GM rears also.