to much exhaust duration

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to much exhaust duration

Post  nitro717 on November 3rd 2011, 11:05 am

I have ran this for a couple years now, going to pull the heads off and have a valve job and the short turn and bowl work done on a stock set of A-460 heads.
Everyone I have spoke with says it has atleast 10* to much exhust dur. @.050 . Its a 521 A-460 heads 13-1, 1150 carb. Whats it going to do with smaller duration? What i am trying to get is about 75 more HP out of what I have now. Thanks


Last edited by nitro717 on December 11th 2012, 4:01 pm; edited 1 time in total
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Re: to much exhaust duration

Post  Lem Evans on November 3rd 2011, 11:08 am

What's the duration @.050" on the intake side and lsa?

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Re: to much exhaust duration

Post  nitro717 on November 3rd 2011, 11:14 am

260 @ .050 and 112, lift was 750 and 725 and advanced it 4* this year which seem to help a little
car just seems very lazy down low, will go mid 5.90s at 118 and low 9.20s at 148 and if i shift it eairly like 7000 not 7400 it will slow down about a .10


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Re: to much exhaust duration

Post  Lem Evans on November 3rd 2011, 11:23 am

21* split with only 13:1 is too much i.m.o ......I'm not sure it's 10* too much. Less exh. duration and close the lsa. Where does the conv. stall?

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Re: to much exhaust duration

Post  nitro717 on November 3rd 2011, 11:31 am

glide with 1.80 first gear and 5400-5500 at 3100lbs.
what the benefits I could see by doing this?
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Re: to much exhaust duration

Post  rmcomprandy on November 3rd 2011, 11:46 am

Lem Evans wrote:21* split with only 13:1 is too much i.m.o ......I'm not sure it's 10* too much. Less exh. duration and close the lsa. Where does the conv. stall?

I agree ... up the compression ratio a point or take about 5 or 6 degrees from the exhaust side: (or both).

You're NOT going to find 75 horsepower with just a camshaft change unless you were WAY off now.

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Re: to much exhaust duration

Post  nitro717 on November 3rd 2011, 11:55 am

You're NOT going to find 75 horsepower with just a camshaft change unless you were WAY off now.
Agreed
So with adding the help of getting the heads worked on going to ge it there?
Not really needing anymore HP, just earlier. I tryed to hit it with a 100 shot couple weeks ago so figured probable made another 75 at the motor after being very safe with the tune and taking 10* of timing out. Car left real good tripped the 60ft beams with the back tires and went 124 in the 1/8 dont remember the exact time,was just testing. But never left that good before so figuring if i could find a way to get 75 more around 1500 rpm sooner would work great and no need to have to spray it to race in the class trying to go into.
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Re: to much exhaust duration

Post  Lem Evans on November 3rd 2011, 4:22 pm

More compression and better heads will help a lot.

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Re: to much exhaust duration

Post  richter69 on November 3rd 2011, 5:19 pm

sounds like it needs a barrel valve and some M5............... Razz
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Re: to much exhaust duration

Post  Lem Evans on November 3rd 2011, 6:40 pm

richter69 wrote:sounds like it needs a barrel valve and some M5............... Razz

A magic Lem cam cures all tongue

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Re: to much exhaust duration

Post  richter69 on November 3rd 2011, 6:47 pm

make sure the wheels are rated for a Lem cam............
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Re: to much exhaust duration

Post  nitro717 on November 3rd 2011, 6:59 pm

Lem I will give you a call tomorrow, is there a certain time good for you?
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Re: to much exhaust duration

Post  Curt on November 3rd 2011, 7:22 pm

After 11:00am. That'll give him time to wipe the sleep out of his eyes.
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Re: to much exhaust duration

Post  cool40 on November 3rd 2011, 10:56 pm

if your heads are "stock" A460's you can do a lot for them.
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Re: to much exhaust duration

Post  dfree383 on November 3rd 2011, 11:42 pm

Lem Evans wrote:
richter69 wrote:sounds like it needs a barrel valve and some M5............... Razz

A magic Lem cam cures all tongue
Now where going to start the Lem "Magic Stick Series"...... and If your looking for that 70's street lope sound it would be a Lem "Disco Stick Series"..... Laughing Laughing Laughing cheers

OP on a more serious not Lem does damn mean kick ass cams for BBF's... Trust what he tells you, ts all backed up with years of experiance and a whole lot of dyno time. king
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Re: to much exhaust duration

Post  Tennessee Bullitt on November 4th 2011, 7:00 am

dfree383 wrote:
Lem Evans wrote:
richter69 wrote:sounds like it needs a barrel valve and some M5............... Razz

A magic Lem cam cures all tongue
Now where going to start the Lem "Magic Stick Series"...... and If your looking for that 70's street lope sound it would be a Lem "Disco Stick Series"..... Laughing Laughing Laughing cheers

OP on a more serious not Lem does damn mean kick ass cams for BBF's... Trust what he tells you, ts all backed up with years of experiance and a whole lot of dyno time. king

When he built my cam he said it was a "good guess".... lol!
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Re: to much exhaust duration

Post  Lem Evans on November 4th 2011, 9:44 am

nitro717 wrote:Lem I will give you a call tomorrow, is there a certain time good for you?

Send me a # and I'll call you.

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Re: to much exhaust duration

Post  nitro717 on April 16th 2012, 2:02 pm

Ended up not changing cam, just a little intake runner & chamber work on the heads and a good valve job and port matched the intake. Car ran average 5.98 to 6.02@ 117 and low 9.30s in 1/4. with a best 1.34 60ft. Well first pass out this year 5.79@121 with a back tire 1.31 60ft. guessing in 1.28. then a 5.80 same 60ft. Next pass not leaving as hard goes a 1.30 and 5.80 run it out to a 9.11 at 150. WOW what a difference a little head work will do. I think i need to jet up a bit now it has gained 4mph in 1/8 and about the same in 1/4 I would think it should be maybe 6mph in 1/4 if gaining 4mph in the 1/8?
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Re: to much exhaust duration

Post  rmcomprandy on April 16th 2012, 3:20 pm

nitro717 wrote:I have ran this for a couple years now, going to pull the heads off and have a valve job and the short turn and bowl work done on a stock set of A-460 heads.
Everyone I have spoke with says it has atleast 10* to much exhust dur. @.050 with 298. Its a 521 A-460 heads 13-1, 1150 carb. Whats it going to do with smaller duration? What i am trying to get is about 75 more HP out of what I have now. Thanks

I think it would be have been whole lot better for your power goals to try and get another point and a half of compression ratio to go along with the headwork.

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Re: to much exhaust duration

Post  nitro717 on April 16th 2012, 3:36 pm

yes IF I were after it all I simple was wanting 75HP and got that and some ,without uping the compression and cam change
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Re: to much exhaust duration

Post  meandad on April 20th 2012, 8:07 pm

"disco stick" now THAT is funny s#%t there! Laughing

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