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Old 09-15-2011, 12:22 PM
Ocean-Angler Ocean-Angler is offline
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Originally Posted by cobalt327
To start with, having no cam specs and not knowing what the real compression ratio is, along w/no idea (I'm guessing) what the quench distance is, there's gonna be a lot of guesstimating going on here...

Having a vacuum advance has far more advantages and basically no drawbacks on a street driven engine. It aids economy, it will allow a cooler running engine, at idle especially. It can help smooth the idle. Definitely a good thing to have.

Basically, you want as much timing advance, as soon as possible- w/o the engine detonating at all. Detonation (pinging) will kill power the moment it begins and in severe cases will ruin an engine outright. To answer your question, no- 2800-3000 RPM is not to low of an RPM to bring the total in by. BUT, this will depend on a lot of things: vehicle weight, use, fuel octane rating, gear ratio, carb tuning, etc. There is no number that's correct for all engines. The numbers given are a starting point from where you will add and subtract timing as required to keep the engine out of detonation and making the best power.

First, there is no amount of main or rod bearing wear that will ever be great enough to cause a significant change in the compression ratio.

To compute the CR you need to know the head gasket and cylinder bore diameter, the stroke, the piston deck clearance (how far down the hole the piston is), the head gasket thickness, the piston volume and the chamber volume. If you don't know these figures, you're guessing and the difference could easily be more than a 12% variation.

The large chamber SBC heads are crappy flowing and the chambers are inefficient. Given that, the work you did may or may not have actually helped flow- w/o a flow bench, this is a crap shoot once you alter the stock port profile. Just cleaning up the ports and port matching the heads to the intake can help.

I seem to get that you didn't get a valve job done. And that means that likely the guides are also untouched. These two areas are wear points that have to be addressed on every used SBC OEM head I've ever seen. The guides always wear and are loose after being used for any real length of time. The seats being done correctly w/a multi-angle valve job and back cutting the valves will give you more flow increase at the lifts where it matters most, than most anything else a home porter could ever hope to accomplish unless the home porter has a lot of experience and/or has served under a pro.

What are the specs from the cam card?

Always use long tube headers any time they CAN be used. The shorter headers leave power on the table.

I doubt seriously you need a billet torque converter! Use a good TC builder and get a TC that has a stall RPM that about matches the torque peak RPM of the engine, or slightly lower. That does not mean the TC will rev to the torque peak every time you pull away from a stop sign. It will mean that when there's traction and you mat the throttle, the TC will flash to where the engine is making the most torque for the best launch.
Hey thanks for all the help and answers -

Looks like the amount of money I spent on this motor, I shot myself in the foot.
THe origional idea was just to give it a little power, till IU bought my LS2 motor and built that a little. But after everything, Ive overspent on a motor that wasnt properly tuned it looks like

Cam specs -
.050 duration - 204 intake 214 exhaust
sae duration - 278 intake 288 exhaust
valve lift .422 intake .444 exhaust
Lobe separation - 107 int 117 exhaust

.050 timing BTC -5 ABC 29 BBC 44 ATC -10 (??)

engine is a goodwrench crate 350 with stock 8:1 compression ( if that helps for compression calculation)
I didnt get a valve job done, I spent quite a bit of time lapping the valves, also cleaned the valve bowl really well.

I couldnt fit long tube headers, theyd be about 1.5" off the ground if I put them on

car weighs 3600 lbs

I dont know if any of this helps..

With that non vacuum advance diz, do you think its really gonna kill me on gas? and rough idle?
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