490 SBC pumpgas 23* dyno results, need expert "power" advise

[67RS502]

The way I see it, the caveat in this exercise is the “street manners” aspect of the build.

If the goal was simply to move the HP peak from 6300 to 6500, I think it could be easily done by changing the cam........ to a solid roller with longer duration.

If the cam was changed and the power peak moved up a few hundred rpm, it would make the point that the current induction and exhaust were sufficient to support that sized engine and a higher than 6300rpm peak.

Someone here must have a sim where they could take the current build, and “swap out” a few cams to see if the peak could be moved or not, with only a cam change...... and maybe a bigger carb.

Yes I doo want some street manners, and have not run anything bigger than 25X/26X on the street.
Not a fan of solid rollers, but do run solid roller lobes with HR lifter... I'm all for that.
Not sure how much street manners I'd loose by running something around 260/270 on a 112 compared to the current cam.
a sim of a carb and cam swap would be very interesting to me.

[67RS502]

You can string her out and get 700 ish. Or buy bigger heads get well over 700 with street driving quality.

heads, that would be going way beyond the purpose of this build.
But, down the road I would consider some SB2 take-offs for it, along with the intake and corresponding cam.
that's a dream for waaaay later down the road.
that's if this thing lives on the street 1st.

[67RS502]

Just looked at the 502 dyno sheet... July 2002, has it been that long already
1.77" of vac @ 6700 (same carb)
for some reason I thought it was only .5"

[cjperformance]

That's on of the problems, I lost that somewhere, I believe it was around .130"/.120".
We did try to check it when retarding the cam, but I'm not sure how accurate this was, as the HR lifters may
be bleeding down some

Well, as streetable as we can, I want reasonable street manners putting around town at 2500.
the car currently has a tight ATI 8" and 410s (set up for my 420SB) but I would like to go back to the
ATI 10" and 373s (old 502 setup) down the road. At this point I believe I'll have to go down to the 373s
for this thing to make it the full 1/4 mile.

Its worth spending time to check PV accurately so you know for sure. Theres going to be a big difference between Max Effort and Practical Street which is very driver dependent! , you could for street with similar manners re cam with 1deg more Lsa, 6 deg more in and ex, then install it IVC@.050" almost where it is now. Pick up .020" to .050" lift if you can while at it. It will still be perfectly streetable and reliable and once the intake and carb are addressed will rpm and hp a little higher.
258*/263*@.050" ,, 111LSA/110IVC ,, .700"
IN 19/59
EX 63.5/19.5
O/LAP 38.5
Max Hp for the base combo cam will look a lot different,

yes I would love to end up with a cam that small.
do you think only a 5 degree split is enough?
I/E ratio is poor.

Depends on street exhaust system and wether you race exhaust on or off. More split wont necessarily help if the street system is on the small side and if the more duration also comes with much later EVC. If you are only chasing a small ammount more rpm and hp and want it very mannerly on the street then yes 5 deg split is fine. Theres a thousand cam specs that will get you where you want to be. You just need to decide what you really want the engine to do, slight tweek or yeeeehaaaaa

[cjperformance]

Just looked at the 502 dyno sheet... July 2002, has it been that long already
1.77" of vac @ 6700 (same carb)
for some reason I thought it was only .5"

Are you trying to run a brake booster at WOT !

[67RS502]

More in progress pics, sorry for the poor quality, thought I had better pics of the ports.
Thought I had more of the bowls and intake ports, but I cant find any better.



About as good as I could get the exhaust without a sonic tester, it was really lacking area around the guide

[67RS502]

Its worth spending time to check PV accurately so you know for sure. Theres going to be a big difference between Max Effort and Practical Street which is very driver dependent! , you could for street with similar manners re cam with 1deg more Lsa, 6 deg more in and ex, then install it IVC@.050" almost where it is now. Pick up .020" to .050" lift if you can while at it. It will still be perfectly streetable and reliable and once the intake and carb are addressed will rpm and hp a little higher.
258*/263*@.050" ,, 111LSA/110IVC ,, .700"
IN 19/59
EX 63.5/19.5
O/LAP 38.5
Max Hp for the base combo cam will look a lot different,

yes I would love to end up with a cam that small.
do you think only a 5 degree split is enough?
I/E ratio is poor.

Depends on street exhaust system and wether you race exhaust on or off. More split wont necessarily help if the street system is on the small side and if the more duration also comes with much later EVC. If you are only chasing a small ammount more rpm and hp and want it very mannerly on the street then yes 5 deg split is fine. Theres a thousand cam specs that will get you where you want to be. You just need to decide what you really want the engine to do, slight tweek or yeeeehaaaaa

Exhaust (on the 420SB) currently is 1 7/8" headers, merge collectors, 3 1/2" pipes to 1 common terminator box just behind the trans cross member (keeping collector length as short as possible) 3 1/2" pipes to 3 1/2" ultraflows, removable 3 " tail pipes for the street.
So for the track I just leave tail pipes at home.
New combo will be the same with the 2" headers.

I'd like to keep the cam relatively small, but not sacrifice much power under 7000, so another 5 degrees with more carb should have it peak around 6500, and shift upper 6000 range, I'd be happy with that.

[Stan Weiss]

Stan will your program predict what head flow he would use for 490 cubes and his hp goals?

It does have a rough calculation. Larry's software will give you a better answer.

Stan

Code: Select all

Bore_=_4.2_____Stroke_=_4.42_______________Rod_Length_=_6.2_____RPM_=_6500
Intake_Valve_Size_=_2.14___________________Exhaust_Valve_Size_=_1.6
Intake_Valve_/_Bore_Ratio_=_0.509524_______Exhaust_Valve_/_Bore_Ratio_=_0.380952
Intake_Valve_Area_=_3.596809_sq._in._______Exhaust_Valve_Area_=_2.010619_sq._in.
Intake_Valve_Stem_Size_=_0.3415____________Exhaust_Valve_Stem_Size_=_0.3415
Intake_Valve_Stem_Area_=_0.091595_sq._in.__Exhaust_Valve_Stem_Area_=_0.091595_sq._in.
Valve_Lift_at_which_the_Valve_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=_0.535_Inches___________Exhaust_Valve_Lift_=_0.4_Inches
Throat_CSA_(0.91)_Intake_=_2.8869_sq._in.__Throat_CSA_(0.91)_Exhaust_=_1.5734_sq._in.
Effective_Throat_CSA_=_0.8959______________Effective_Throat_CSA_=_0.88462
Valve_Lift_at_which_the_Throat_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=_0.42941_Inches_________Exhaust_Valve_Lift_=_0.31302_Inches

Crank_Angle_of_Max._Piston_Velocity_=_72.288______Volumetric_Efficiency_=_0.954
Choke_RPM_______Minimum_Intake_Lift_=_0.8030______Minimum_Exhaust_Lift_=_0.8013
________________Maximum_Intake_Lift_=_0.9200______Maximum_Exhaust_Lift_=_0.9181

_Valve___________________Minimum_CFM_@______CSA_@_300_____Throat_Velocity____CSA_@_280
_Lift____Choke_RPM______28_Inches_Water___fps_Velocity_____fps_-_User_CSA___fps_Velocity______L/D_Ratio_
_______Intake_Exhaust___Intake__Exhaust__Intake_Exhaust___Intake__Exhaust__Intake_Exhaust__Intake_Exhaust
_.600____4857____4867___218.71___154.26__1.7497__1.2341__181.820__235.309__1.8746__1.3223__0.2804__0.3750
_.625____5059____5070___227.82___160.69__1.8226__1.2855__189.396__245.114__1.9528__1.3774__0.2921__0.3906
_.650____5261____5272___236.93___167.12__1.8955__1.3370__196.972__254.919__2.0309__1.4325__0.3037__0.4063
_.675____5464____5475___246.05___173.55__1.9684__1.3884__204.548__264.723__2.1090__1.4876__0.3154__0.4219
_.700____5666____5678___255.16___179.98__2.0413__1.4398__212.124__274.528__2.1871__1.5426__0.3271__0.4375
_.725____5868____5881___264.27___186.40__2.1142__1.4912__219.700__284.332__2.2652__1.5977__0.3388__0.4531
_.750____6071____6084___273.39___192.83__2.1871__1.5426__227.276__294.137__2.3433__1.6528__0.3505__0.4688
_.775____6273____6286___282.50___199.26__2.2600__1.5941__234.851__303.941__2.4214__1.7079__0.3621__0.4844
_.800____6475____6489___291.61___205.69__2.3329__1.6455__242.427__313.746__2.4995__1.7630__0.3738__0.5000
_.825____6678____6692___300.72___212.11__2.4058__1.6969__250.003__323.550__2.5776__1.8181__0.3855__0.5156
_.850____6880____6895___309.84___218.54__2.4787__1.7483__257.579__333.355__2.6558__1.8732__0.3972__0.5313
_.875____7082____7098___318.95___224.97__2.5516__1.7998__265.155__343.160__2.7339__1.9283__0.4089__0.5469

[Stan Weiss]

700 HP @ 6500 - .469 BFSC - 12.5:1 A/F ratio would be a 99.112 VE

Stan

Code: Select all

Bore_=_4.2_____Stroke_=_4.42_______________Rod_Length_=_6.2_____RPM_=_6500
Intake_Valve_Size_=_2.14___________________Exhaust_Valve_Size_=_1.6
Intake_Valve_/_Bore_Ratio_=_0.509524_______Exhaust_Valve_/_Bore_Ratio_=_0.380952
Intake_Valve_Area_=_3.596809_sq._in._______Exhaust_Valve_Area_=_2.010619_sq._in.
Intake_Valve_Stem_Size_=_0.3415____________Exhaust_Valve_Stem_Size_=_0.3415
Intake_Valve_Stem_Area_=_0.091595_sq._in.__Exhaust_Valve_Stem_Area_=_0.091595_sq._in.
Valve_Lift_at_which_the_Valve_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=_0.535_Inches___________Exhaust_Valve_Lift_=_0.4_Inches
Throat_CSA_(0.91)_Intake_=_2.8869_sq._in.__Throat_CSA_(0.91)_Exhaust_=_1.5734_sq._in.
Effective_Throat_CSA_=_0.8959______________Effective_Throat_CSA_=_0.88462
Valve_Lift_at_which_the_Throat_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=_0.42941_Inches_________Exhaust_Valve_Lift_=_0.31302_Inches

Crank_Angle_of_Max._Piston_Velocity_=_72.288______Volumetric_Efficiency_=_0.99112
Choke_RPM_______Minimum_Intake_Lift_=_0.8030______Minimum_Exhaust_Lift_=_0.8013
________________Maximum_Intake_Lift_=_0.9200______Maximum_Exhaust_Lift_=_0.9181

_Valve___________________Minimum_CFM_@______CSA_@_300_____Throat_Velocity____CSA_@_280
_Lift____Choke_RPM______28_Inches_Water___fps_Velocity_____fps_-_User_CSA___fps_Velocity______L/D_Ratio_
_______Intake_Exhaust___Intake__Exhaust__Intake_Exhaust___Intake__Exhaust__Intake_Exhaust__Intake_Exhaust
_.600____4857____4867___227.22___160.27__1.8178__1.2821__188.895__244.466__1.9476__1.3737__0.2804__0.3750
_.625____5059____5070___236.69___166.95__1.8935__1.3356__196.766__254.652__2.0287__1.4310__0.2921__0.3906
_.650____5261____5272___246.15___173.62__1.9692__1.3890__204.636__264.838__2.1099__1.4882__0.3037__0.4063
_.675____5464____5475___255.62___180.30__2.0450__1.4424__212.507__275.024__2.1910__1.5454__0.3154__0.4219
_.700____5666____5678___265.09___186.98__2.1207__1.4958__220.378__285.210__2.2722__1.6027__0.3271__0.4375
_.725____5868____5881___274.56___193.66__2.1965__1.5493__228.248__295.396__2.3533__1.6599__0.3388__0.4531
_.750____6071____6084___284.02___200.33__2.2722__1.6027__236.119__305.582__2.4345__1.7172__0.3505__0.4688
_.775____6273____6286___293.49___207.01__2.3479__1.6561__243.990__315.768__2.5156__1.7744__0.3621__0.4844
_.800____6475____6489___302.96___213.69__2.4237__1.7095__251.860__325.954__2.5968__1.8316__0.3738__0.5000
_.825____6678____6692___312.43___220.37__2.4994__1.7629__259.731__336.140__2.6779__1.8889__0.3855__0.5156
_.850____6880____6895___321.89___227.05__2.5752__1.8164__267.602__346.326__2.7591__1.9461__0.3972__0.5313
_.875____7082____7098___331.36___233.72__2.6509__1.8698__275.472__356.512__2.8402__2.0033__0.4089__0.5469

[MadBill]

Since you've stepped up to a solid roller lobe, presumably you've also checked out the number of recent advanced design and/or short travel lifters?

A shop I frequent builds several dozen big Hemis yearly. A few years ago he did up a 572" for a TV show. They wanted 700 streetable HP and preferred hydraulic rollers. With a big aggressive HR cam, it initially dynoed a disappointing low sixes and was short on revs. He spent a couple of hours working over the plenum plus dropped a set of solids onto the same cam with the same springs. That stepped it up to ~760 and added 1,200 RPM to the usable power curve. He figured all but maybe 20 HP was the lifters. (This was before the widespread availability of the 'New Tech' crop of hydraulics.)

[GARY C]

More in progress pics, sorry for the poor quality, thought I had better pics of the ports.
Thought I had more of the bowls and intake ports, but I cant find any better.



About as good as I could get the exhaust without a sonic tester, it was really lacking area around the guide

You don't hear much about the port intruder heads these days, I remember when Self Racing introduced those to our local Drag Radial class here in Dallas.

[econo racer]

like your combo as is. Would be cool in a full size Chevy step bed street truck. Do you happen to have a picture of the block clearancing for the rods? This is the biggest sbc I have seen.

[Orr89rocz]

https://www.chevyhardcore.com/tech-stor ... ck-part-2/

Heres a 440 inch with a 254/266 hyd roller .579” lift. Small head 215cc. Peaked at 6200, was down 6 hp at 6500.

I ran a 246/252 .640 hyd roller in my 400” sbc with a bigger 245cc head. Peaked in mid 6000’s.

[RevTheory]

Do those intake ports have any throat left in them?

[Steve.k]

More in progress pics, sorry for the poor quality, thought I had better pics of the ports.
Thought I had more of the bowls and intake ports, but I cant find any better.



About as good as I could get the exhaust without a sonic tester, it was really lacking area around the guide

I did a 438 sbf last year. Heads pretty much mirror yours in terms of flow. Cam was 266-276@050 and 728 lift. The difference i had was 13:5 comp and dual 1050's. Peak power was 703@6700 and 621 ftlb @ 5100. The exact same combo with one 1050 made 651 at exact same rpm. So with your lower compression but more cubes not sure if cam swap get you over hump. I think because you want streetable power you need a head thats a little bigger than what typically would be required. Or you cam and carb bigger and take a little hit in drivability department.I guess what im trying to say if you don't have higher compression and dual 1050's as option you have to get the extra power from somewhere. Heads that seem overkill on a 400" chevy likely not so big on 490"