Looking for advice on top end engine changes
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Joined: Apr 2006
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From: Virginia Beach Virginia
Looking for advice on top end engine changes
Hey guys, I've got a long story that I will try to make a short as possible.
A while back I had worked out a deal with an engine builder friend to help me put together a nice street strip motor for my 77. He would call me during the build process and tell me what was going on with various parts and give me options and explain them. Well in the end I have an engine that I have not started yet but don't really know any of the specs on it. He has since passed and took his secrets with him. I do know some of the basics like the cam has a really close ratio and needs to idle somewhere around 2k rpm. I know it's high for street. If I wanted to change the cam without knowing too much else, what is involved and how difficult would it be to do this? I know that it will change the geometrics of the motor but what does that intale? different push rods/lifters? complete head rework? anything else? Thanks for the read and hope someone can help.
A while back I had worked out a deal with an engine builder friend to help me put together a nice street strip motor for my 77. He would call me during the build process and tell me what was going on with various parts and give me options and explain them. Well in the end I have an engine that I have not started yet but don't really know any of the specs on it. He has since passed and took his secrets with him. I do know some of the basics like the cam has a really close ratio and needs to idle somewhere around 2k rpm. I know it's high for street. If I wanted to change the cam without knowing too much else, what is involved and how difficult would it be to do this? I know that it will change the geometrics of the motor but what does that intale? different push rods/lifters? complete head rework? anything else? Thanks for the read and hope someone can help.
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Joined: Apr 2006
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From: Virginia Beach Virginia
I meant to add as well that I probably won't be taking it to the track as much as I anticipated and would like something I can drive down the street without scaring all of the birds away and attracting the police. Thanks again
Burning Brakes
Joined: May 2008
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From: Stratford Ontario
Its much easier to go down in cam size than to go up. I would first go and pull the valve covers and check with an indicator what lift You have to start with. If the cam and lifters are new and havent been run yet then You can order a new cam but it will have to be the same type such as solid lifter or roller. Your going to need to remove intake to see, but it has to come off if Your going to replace cam. If Your running an automatic You need to match torque converter and rear gears to cam. If You don't mind pulling the engine again try it out You may enjoy what you got now. If He was really building it to what You have it should work with no problems. If You run this motor without knowing what cam you have I recomend a 3000 RPM breakin for 20 min. Imediately after engine starts. Then change motor oil and let the fun begin.
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Joined: Apr 2006
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From: Virginia Beach Virginia
Thanks for the info Timsride. I am running a 4spd M20. The motor is a 355. I have not yet measured lift. I really do want to "play" with it first like you stated to see if it's something I can work with but knowing what I do about it now I'm not sure how streetable it will be. I know it has 0 vacuum at idle. I plan on adding a vacuum pump for the headlights anyway so maybe I can tap the brakes and lights together? 2200rpm is going to be aweful loud I think too. Any suggestions on how to find out what spark gap I need and where to set the timing (stab the distributor)? Also I added a new carb and I'm not sure of any settings on it either.
Pro
Joined: May 2001
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Sorry to hear 'bout yr buddy's passin.
As far as the engine goes... is it on an engine stand, or in the car?
How far has it been assembled?
What about the bottom end? Block, crank, bearings, oil pump, cylinders, rods, pistons... Did the block get bored? New rings? etc? Or did he just set off to give you a new top end, to liven up the engine?
Did he mention what type of intake? My guess, with a 2k idle, is that he was shootin for a tunnel ram, or somethin extreme, possibly combined with a high stall torque converter. Not very streetable IMHO. I'm an amateur here, but I do know that you'll need to cough up more info to get better advice.
But- to answer your cam change question - yer gonna hafta pull off the intake, distributor, valve covers, rocker arms, pushrods, timing chain cover, timing chain, etc just to swap the cam. It'd be easier to get a dial gauge, pull the valve covers, and measure the amount of lift on the intake, and exhaust side, while turning the crank by hand. This, at least would give you an idea of what cam is currently installed.
If he passed while in the middle of the project, and doesn't have notes, reciepts, or any data converning your build... I'd make sure its kosher b4 tryin to fire her up. Wait for some more experienced guys to chime in.
As far as the engine goes... is it on an engine stand, or in the car?
How far has it been assembled?
What about the bottom end? Block, crank, bearings, oil pump, cylinders, rods, pistons... Did the block get bored? New rings? etc? Or did he just set off to give you a new top end, to liven up the engine?
Did he mention what type of intake? My guess, with a 2k idle, is that he was shootin for a tunnel ram, or somethin extreme, possibly combined with a high stall torque converter. Not very streetable IMHO. I'm an amateur here, but I do know that you'll need to cough up more info to get better advice.
But- to answer your cam change question - yer gonna hafta pull off the intake, distributor, valve covers, rocker arms, pushrods, timing chain cover, timing chain, etc just to swap the cam. It'd be easier to get a dial gauge, pull the valve covers, and measure the amount of lift on the intake, and exhaust side, while turning the crank by hand. This, at least would give you an idea of what cam is currently installed.
If he passed while in the middle of the project, and doesn't have notes, reciepts, or any data converning your build... I'd make sure its kosher b4 tryin to fire her up. Wait for some more experienced guys to chime in.
