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Old 04-26-2004, 02:27 AM
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Engine & transmission -HELP!

Fellow hotrodders, please help me a bit with this

To make a long story short, I tore my engine apart and rebuilt it because of different issues.

It has the following specs:
283 +.30
11:1 pistons
462 heads, 1.94/1.5 valves
SSI cam, 304 adv, 230 0.050", .453 lift for both valves, installed straight up
torker 1 intake
2" ram horns
575 vac. sec.speed demon
Pertronix ignitor 2 ignition and coil with MSD wires.

Gear box: TH400
JEGS 10" converter (2700-3K adv stall, stalls by : ~2000 by ear measurement...) Didn't measure rpm with the timing light (my rev counter is broken...) (stupid me... )

Problem 1: only 8-10" vavuum at idle (~900 rpm), = low vacuum for the modulator = high transmission pressure = gearbox slams into gear.
Converter did help a bit, but not very much.

How can I fix this?
Is there a T/V cable modification that will work with the 400, in order to lower the pressure at idle?
Will a dual plane intake create more vacuum/ enough for the gearbox to work?
I already have an adj. modulator adjusted all the way out.
Is there a cheap trick to modify the modulator?

Problem 2: Engine idles fine, but sometimes when put into reverse or drive, it will idle for a few secs, before rpm drops and it dies.... but not every time...
it did NOT have this problem before the rebuild...

Problem 3: High rpm pinging/knock
Plugs are hot ones, AC Delco R45's
Timing is set at 35 at 3000rpm, static+ mechanical.
I expect that this one will be solved by changing the plugs to R43's, along with a fine tune of max mech. adv. at 3000 rpm.

Problem 4: Driveshaft yoke leak at gearbox
When engine is idling, car stationary the driveshaft yoke leaks badly, but then engine is stopped it does not leak

Now before the rebuild I had the #1 problem, #2 and #3 are new.
I did have an unidentified gearbox leak before, so it could be the yoke, but I for sure know that the rear and front seals were leaking and maybe also the pan, but all those are now exhanged...

Any help appreciated!


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Old 04-26-2004, 08:10 AM
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problem no. 1: 230 @ .050 cam= low manifold vacuum.
cure: milder cam
no. 2: also cam related
cure: you could possibly drill the primary throttle plates
no.3: colder plugs
n0.4 possibly the wrong yoke.
cure: if yoke has vent hole in the center, try replacing
the o-ring on the trans output shaft. If no o-ring
on shaft try welding up vent hole in yoke
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Old 04-26-2004, 08:20 AM
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problems 1 & 2 & 3
Am I reading this right?
304* advertised duration cam in a 283 and you are asking why vacuum at idle is low?
You are probably lucky that it even idles at 900 rpm in neutral, much less in gear.
I dont believe a dual plane manifold will help your vacuum situation, it also wouldnt do you any favors as far as performance is concerned. According to cam specs I am looking at, the power band for a cam that size in a small block doesnt even start until about 4300 rpm +or-. Most dual plane manifold rpm ranges are from idle to 5500 or 1500 to 6500 +or-.
Not sure on cable mods, not really familiar with that trans.

problem 4
Check to see if you have excess movement at the driveshaft yoke or output shaft on the trans. Check the yoke for wear at the sealing area.
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Old 04-26-2004, 02:12 PM
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BOBCRMAN, galaxieguy3 , Thanks for your input

I know that I would have a low manifold vacuum, this is not a surprise, but everyone already thinks that my vacuum is too low, and I cant figure out why.
Heck, I even tore the engine apart and I still have this da***d problem.

cam change is not an option atm, with 11:1 I will need a cam with some overlap later intake closing, to make it run on normal octane ratings.

Not happy about drilling the throttleplates, don't wanna spoil a brand new carb.

Now everyone tells me that I should have more vacuum but I don't, and it p***** me off that I cant figure out why.
Atm I spend all my time reading all info I can about carbs, manifolds, cam and vacuum, to see if I can find out something.

There is no o-ring on the shaft, gonna weld up the yoke then...

Still looking for good ideas
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Old 04-26-2004, 03:11 PM
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1. the cam has too much duration = low vacuum.

2. Maybe vacuum issue, dont expect an engine with a cam like that to idle.

3. If your running 11:1 you will have to use race gas, no real way around it. Try smoothing the chambers, and using different plugs, but will have to use race gas.

4. I would guess a seal problem, did you mean where the driveshaft goes in to the tranny?

Anyways get a smaller cam and lower the compression, almost no way around it unless you want to always use race gas. This is NOT a street car setup, I can tell you that right now. You also should NOT have more vacuum with that cam and setup, sorry. Maybe get a vacuum resiviour
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Old 04-26-2004, 03:31 PM
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With your combo you don`t have a lot of cubic inches and you`ve got a big cam, what you have is a high revver combo, the cam would be somewhat more tame in more cubic inches, but is considered wild for a 283. First thing I would have did was got rid of the torker intake, it`s making the problem worse idle wise, I would go with a dual plane intake to get back some low end torque, it would probably give it enough back to idle half way decent and it would also help vacuum being it has less plenum area, it would also aide in tuning wise. I`ve always heard about the original Torkers, there great high revver intakes, but not worth anything down low, the torker II was a improvement because the runners are longer and narrower, so it goes to show the torker isn`t really needed on a street machine, this was why Edelbrock replaced the Torker with the Torker II. How about advancing the cam 4 degree`s at the timing chain, and going with a dual plane intake and see how it runs? advancing the cam would lower the power band by about 200 rpm, and the dual plane intake would help low end power and the car would likely idle without shutting off. also by doing these 2 mods the car will still have plenty of high end power so there`s no worry there, but if this is a street machine, then I don`t see the need for high revver stuff in a street car, engines don`t see over 3000 rpm on the street, it`s torque that moves the car around, not horsepower, and anything you do to aide in low end torque will help the problems your dealing with, as a last band aid resort, you could use rhoads lifters, they bleed down at lower rpms, making the engine "see" less duration, therefore they`ll increase vacuum at low rpm, as rpms increase the oil demand overcomes the lifters ability to bleed it off in time and the cam is restored to full lift.
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