496ci revamped

Speedlink1973 said:
Hey Grumpy, where at duration wise and lobe separation angle does vacuum become an issue on low end?
My understanding of it is the more overlap the less vacuum on low end.
I don't know for sure.
I'm asking because the 4l80 I have is a manual shift and it has a vacuum actuator in the transgo valve body, I'm not 100% sure how it works, I just know it has to pull vacuum.
Click to expand...
That is a problem.
Engine needs 11 inches of vacuum at least.
 
Speedlink1973 said:
Now would the total seal gapless rings
Help me here Brian pulling more vacuum?
Click to expand...
I can not guarantee it will be enough with a chosen cam.
My experience with a full drag race profile in a pontiac V8 that pulls 3-4 inches vacuum at idle with conventional piston rings is that with Total Seal Gapless rings installed and all else the same it will pull 6-7 inches at vacuum.
Test engine idle at 900 rpm.
 
I am not up to date on 4L80E's Speedlink.
The Trans Go shift kit with vacuum modulator internal allows full automatic upshifts I heard.
And full manual upshifts starting from Low 1.
I may be wrong.
Have to find the directions and read.
 
cfm matters but its wet flow (MIXED FUEL/AIR ) not dry flow (just air at a constant velocity) on a flow bench,
that maters more and you want to keep port velocity fairly high.
of the heads listed that 300 cc looks impressive, but if I was building the engine Id personally still select the 315cc due to past experience, and thinking of the need for the larger port if I decide to install a wet nitrous plate.
as mentioned earlier, youll want too keep the piston speeds reasonable and valve train under control.
I don,t know at what point the low vacuum will become an issue ,
but neither cam listed will work power brakes,
https://www.summitracing.com/parts/...MI49uG9ZSr3AIVEdbACh0XWgzJEAQYAyABEgIN-fD_BwE

and the vacuum control on a trans or brakes set up to work on stock engine vacuum levels well . there are options to increase vacuum.

http://garage.grumpysperformance.com/index.php?threads/trouble-shooting-brakes-3.380/#post-73632
 
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Maniacmechanic1 said:
I can not guarantee it will be enough with a chosen cam.
My experience with a full drag race profile in a pontiac V8 that pulls 3-4 inches vacuum at idle with conventional piston rings is that with Total Seal Gapless rings installed and all else the same it will pull 6-7 inches at vacuum.
Test engine idle at 900 rpm.
Click to expand...
Well the Howard's cam I'm stuck with
Crane cam Grumpy suggested
Grumpy said:
cfm matters but its wet flow (MIXED FUEL/AIR ) not dry flow (just air at a constant velocity) on a flow bench,
that maters more and you want to keep port velocity fairly high.
of the heads listed that 300 cc looks impressive, but if I was building the engine Id personally still select the 315cc due to past experience, and thinking of the need for the larger port if I decide to install a wet nitrous plate.
as mentioned earlier, youll want too keep the piston speeds reasonable and valve train under control.
I don,t know at what point the low vacuum will become an issue ,
but neither cam listed will work power brakes,
https://www.summitracing.com/parts/...MI49uG9ZSr3AIVEdbACh0XWgzJEAQYAyABEgIN-fD_BwE

and the vacuum control on a trans or brakes set up to work on stock engine vacuum levels well . there are options to increase vacuum.

http://garage.grumpysperformance.com/index.php?threads/trouble-shooting-brakes-3.380/#post-73632
Click to expand...
The 290cc oval port heads I have already
The 300cc I almost bought, keep in mind I bought heads three weeks before I was on the blog, had I known what I know now I probably would have went at least to the 300cc head, I was worried about big fat lazy ports, so I went with AFR suggested for 496 to 509 ci.

I'm wondering if I could cheat my cam by going with a 1:8 rocker arm?
 
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Speedlink1973 said:
Well the Howard's cam I'm stuck with
Crane cam Grumpy suggested

The 290cc oval port heads I have already
The 300cc I almost bought, keep in mind I bought heads three weeks before I was on the blog, had I known what I know now I probably would have went at least to the 300cc head, I was worried about big fat lazy ports, so I went with AFR suggested for 496 to 509 ci.

I'm wondering if I could cheat my cam by going with a 1:8 rocker arm?
Click to expand...
Keep Your Heads.
Going to work.

Cam to work driveabilty wise to be debated yet.
Will make power no matter what.

Even at 550 HP & 500+ ft/lbs torque true its real hard to hookup in 1st & 2nd gen F-body.
2nd gen has the better rear suspension.
1st gen cars are lighter.
 
I don,t think youll have any issues with any of the three heads being discussed, and I would not go to the 1.8:1 ratio rockers,
you could gain more with proper exhaust header/collector and exhaust system tuning than a potential rocker ratio change in my opinion
 
What is going to happen without enough engine vacuum present is the 4L80 with its Transgo -3 will Bang Gears full Line pressure all the time on the street.
 
This is where it was at to begin with

597 lbs ft of torque at 4100 557hp at 5700
Single plane intake
9.86 :1 compression
 

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just because the AFR and procomp heads are both listed as having 300cc runners is no proof they flow close too similar amounts of air
 
Grumpy said:
just because the AFR and procomp heads are both listed as having 300cc runners is no proof they flow close too similar amounts of air
Click to expand...
Oh trust me I know that for sure,
They claim it but I know better now.

Keep in mind I didn't built it,
But It's how it was built.
Here are the so called flow numbers.

I did a simple leak test with alcohol
After I took them off , none of the ports
On either head would hold liquid
This motor had 2k miles on it when I tore it down
My brother in law wanted the heads he
Took them to a shop re-cut all the valves and valve seats I didn't get a number but they were really bad back to the valve guides

Flow numbers must be true
I found them on the internet:D
index.php
 

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