548 CI BBC Advice

General engine tech -- Drag Racing to Circle Track

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TBART1970
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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Aug 08, 2017 12:14 pm

If you look at my original Dyno sheet it made 663 hp and 720 tq. Engine builder said it is a stingy Dyno. Those higher numbers are with a 4 percent fudge factor. The new numbers are not with the fudge factor. I am happy with the numbers as printed.

Fudged 4 percent. 769.49 hp 756.91 tq.

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Re: 548 CI BBC Advice

Post by cstraub » Tue Aug 08, 2017 12:29 pm

Can you post the new dyno sheet?
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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Aug 08, 2017 12:37 pm

engine.png
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Re: 548 CI BBC Advice

Post by cstraub » Tue Aug 08, 2017 12:41 pm

Old dyno sheet....
barton555.jpg
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Re: 548 CI BBC Advice

Post by cstraub » Tue Aug 08, 2017 12:53 pm

You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

You put the old smaller cam in it the butt dyno will feel better.

Old Cam
.650/620
242/252
108 LSA

New Cam
.672/.672
252/261
110 LSA
Last edited by cstraub on Tue Aug 08, 2017 1:16 pm, edited 1 time in total.
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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Aug 08, 2017 12:56 pm

cstraub wrote:Old dyno sheet....barton555.jpg
Yes old sheet.

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Re: 548 CI BBC Advice

Post by cstraub » Tue Aug 08, 2017 1:05 pm

cstraub wrote:You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

Latest dyno sheet has a correction factor of 6.5%
Old dyno sheet has a correction factor of 5.3%

You put the old smaller cam in it the butt dyno will feel better.
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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Aug 08, 2017 1:32 pm

Ceralli's cam recommendation,

262 intake
267 exhaust

.710 lift

112 lobe separation.

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Re: 548 CI BBC Advice

Post by cstraub » Tue Aug 08, 2017 1:41 pm

TBART1970 wrote:Ceralli's cam recommendation,

262 intake
267 exhaust

.710 lift

112 lobe separation.
Bill's a customer of mine. We talk weekly. Based on your goals for power you don't need a large camshaft and the dyno sheets prove it. At the end of the day it's your engine and as long as you are happy that's all that matters. What's interesting is your dyno sheets prove once again bigger is not always better.
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Re: 548 CI BBC Advice

Post by MTENGINES » Tue Aug 08, 2017 2:07 pm

cstraub wrote:You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

You put the old smaller cam in it the butt dyno will feel better.

Old Cam
.650/620
242/252
108 LSA

New Cam
.672/.672
252/261
110 LSA
you put in a bigger cam, and he will never think of putting the smaller cams back in it. how is the butt dyno going to tell you anything while your tires are spinning and you aren't moving forward?

I saw a shop take out a mid 270@.050 cam fom a 632bbc, they put In a 242@.050. the engine lost 300whp and picked up 200ft torque.. the car was not easy to drive. tires would just blow up in smoke at the crack of the throttle. this was a big tire car. 33x18 hoosiers.

Big engines need big cams to be streetable. I know because I build them. I work with certain cam companies when necessary, and they normally fall where my gut instinct tells me.

heck my work truck had a bigger cam in it than both of those and it was just a tiny 496 both lift and duration.

The Dyno looks like it wants more Carb.

But if the customer is happy, hes happy.

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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Aug 08, 2017 2:42 pm

MTENGINES wrote:
cstraub wrote:You lost average power under the curve with the larger camshaft. Street engines need broad flat power. Peak numbers are great but these engines rarely see those rpms. The do see 2000 to 5000 pretty regularly.

You put the old smaller cam in it the butt dyno will feel better.

Old Cam
.650/620
242/252
108 LSA

New Cam
.672/.672
252/261
110 LSA
you put in a bigger cam, and he will never think of putting the smaller cams back in it. how is the butt dyno going to tell you anything while your tires are spinning and you aren't moving forward?

I saw a shop take out a mid 270@.050 cam fom a 632bbc, they put In a 242@.050. the engine lost 300whp and picked up 200ft torque.. the car was not easy to drive. tires would just blow up in smoke at the crack of the throttle. this was a big tire car. 33x18 hoosiers.

Big engines need big cams to be streetable. I know because I build them. I work with certain cam companies when necessary, and they normally fall where my gut instinct tells me.

heck my work truck had a bigger cam in it than both of those and it was just a tiny 496 both lift and duration.

The Dyno looks like it wants more Carb.

But if the customer is happy, hes happy.
Injected in the car.

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Re: 548 CI BBC Advice

Post by TBART1970 » Mon Sep 04, 2017 6:36 pm

In the car and running, vacuum is up. Now time to tune with the Holley EFI.

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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Nov 07, 2017 7:45 pm

I pulled the distributor to check the gears, everything looks good. Oil pressure is good, car runs good. 130 miles on it, still tuning.

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Re: 548 CI BBC Advice

Post by CharlieB53 » Tue Nov 14, 2017 8:00 pm

It is interesting to note that the 'smaller' cam can produce more torque in the usable street RPM range while more cam can produce more HP at higher RPM.

Learning how to drive either one on the street and keep tires connected may be difficult, but certainly put a lasting grin on your face.

TBART1970
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Re: 548 CI BBC Advice

Post by TBART1970 » Tue Nov 14, 2017 9:24 pm

BK8K0014.JPG
Cut open oil filter and found metal. Adjusted the valves, no problem found, decided to stick my scope in to look at the cam gear and noticed this lobe.
Sent pics to Bullet cams, I can't win.
IMG_20171114_185611549 (2).jpg
old cam 600 miles hydraulics 52 miles solids

Have not pulled apart yet, any suggestions what to look for?
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