rebuild - need advice

[kridgley]

hello all,

I am finally getting around to pulling the basically stock 350 from my 75 and I am going to rebuild it, well ... my dad and I will. I am looking for advice as to what you all think I can do to pick up extra power in the rebuild. Already figuring on boring 30 over, this will require new pistons ... so what do you all suggest for pistons, cams, intakes, heads, etc ...

Thanks, kev

 

[Jack]

more info please

Tell us which 350 L48 or L82? ... which trans auto or 4spd? ... which rear gear ratio? ... does it or will it have true dual exhaust? ... approximate budget?

 

[kridgley]

Yep, true duals - its an L82, and an automatic with 3.08 gears. not sure about a budget - just looking to take the opportunity to get ird of the 75 power while rebuidling the 350, but if i had to put a value to it it i would say ... 4k.

 

[goingballistic]

I just finished my rebuild, getting the car ready to take the motor.

I'm about $8K into it and not finished yet, wife is going to kill me. Still need headers and pipes, that's another $1200.

Basically the advice I'd give you BEFORE you start is decide what you want to accomplish with the motor/car. What type of horse power do you want, torque etc. These guys on here helped me a lot to get through this but I made several mistakes ( which equates to wasted $$$$$) in being too hasty with what I wanted to do.

I've built the motor from the ground up, internal balance and spared no expense but "wasted" almost $800 in parts I can't use, crank, cam etc. I started external balance and went to internal, crank and cam are worthless to me, so I ate the cost.

Do some basic research on building a 350, I spent over 200 hours reading stuff before I even started and I'm still reading stuff. I ended up with an internal balance crank, 6 inch rods, bored 60 over, new cam, AFR 195 heads, Ross pistons, Edelbrock RPM air gap intake, Edelbrock 650CFM carb, MSD ignition etc etc. I also paid to have someone assemble the bottom of the motor, crank, bearings etc..........too much money involved for me to make a mistake at that level of the rebuild and I didn't have all the "right" tools. Keep that in mind as you move forward, tools are not cheap.

If you are planning to just drive the car and not place a huge amount of torque on the back end ( drag race ) I'd suggest external balance crank, stay with the current rods length, 30 over, new cam, new pistons and rings, something like DART heads, new ignition, new carb.

There are compression ratio calculators all over the web, use one and decide what CR you want to push. High CR needs high octane gas, high octane gas means $$$$ out of your pocket. If you are worried about how much money your car drinks, design the motor for a lower CR so you can stay on pump gas at 90 octane or below.

Good luck.

 

[GTR1999]

As the others said you shoud really think about what you're planning on doing with the car and how much you're going to drive it. It used to be you build the car then drive it all the time but today the high gas aand insurance rates you may find you're not in a position to dirve as much as you thought- unless you're weathly.
A 75 is good crusier, just installing good 2.5 duals will wake up the engine another 20-30 hp. Add a cam,intake and carb and you'll be in the 30 hp range-nice for a driver. Add a shift kit,2400 stall, and 355's and you'll feel the difference.
You can very easily get caught up in the add more power game and end up thousands into it.
If you want to cruise add the cam, intake, and exhaust. Leave the 308's in and drive it. Are you sure you need a rebuild and does it need .030? I rebuilt my 72 last year and only went .020 over- why remove more then you need to? I also sent out our 75 L-82 and the guy wrecked the block. So I'm off to court with him. If you machine it be sure to check it yourself or by someone other then the machinist. This guy never guessed I had measuring tools and knew how to use them, be aware.

Good luck sounds like a nice car.
Gary

 

[kridgley]

Hey,

I do still want this as a driver, not looking for anything to tear up the local drag strip - just something to show that its still a vette. But as i driver .. not daily of course, just something to drive when the weathers good ... 5-6 months of year around here. As I understand the stock L82 is only 200 horses ... so I'd say it would be nice to have at least 300 but no more than 375 for drivability but torque enough to smoke the tires if desired ... something it cant really do now too easilly. Back in '75 the motors were really turned down and I want to rebuild it with some better performance parts to get more out of this motor. Trying to get ideas really to if its worth the upgrading ... finding parts and prices ... just a solid game plan. This might sound dumb - but i want the cam to sound mean too ... not a crazy 11 sec car lope or anything, just want it to be meaner than it is now.

So now its looking like cam for sure ... what sizes?
new carb ... 650 cfm should be plenty right?
bore 30 over and new pistons, etc ... flat/dished?
heads for more power ... what size?
intake? right now it has the edlebrock performer ...
and as long as theres no damage, the stock rods, crank, etc should be fine right?

Thanls for all the help so far,
Kev

 

[Jack]

Yep, true duals - its an L82, and an automatic with 3.08 gears. not sure about a budget - just looking to take the opportunity to get ird of the 75 power while rebuidling the 350, but if i had to put a value to it it i would say ... 4k.

GMPP will sell you a brand new crate with alotta torque & horsepower for around $4K ... all new with a GM warranty ... such as HT383 & ZZ4. You can make more tq & hp if you build yourself for $4K ... but then you'll likely need different rear gear and/or higher stall torque convertor ... both HT383 or ZZ4 have power bands that'll work OK with what you have ... especially the torquey HT383. Stow the OE L82 for the next buyer ... have fun with a crate without worrying about slinging a rod through the side of an irreplaceable OE matching block. Have nothing to base this on but anecdote ... but it really seems to me that the quality of our gasoline has seriously diminished in just the last 2 years ... A motor that'll run good on 87 (ie HT383) may become more important if things continue as they seem to be going.
JACK:gap

 

[VetteThunder]

Couple of Suggestions

Figuring out what you are doing with the car is the most important first step. Once that is done the rest is relatively easy. Not necessarily cheap but straight forward.

Something I would strongly suggest, is that if you haven't got a lot of experience rebuilding engines and matching parts from a bunch of different vendors, Either the GM crate engine or if you want to do some work, Edelbrock has some "packages" that have been put together to work well for a given application. Edelbrock also make complete crate engines as well as several others like Bill Mitchell (World Products) and P.A.W.

If you are going to try to rebuild the engine yourself, the best thing to do is get a reliable and reputable shop to do the machine work. I would strongly recomend speed-o-motive.

They also have kits and complete crates too.

Good luck and let us know what you decide to do.

 

[BLACKDOG]

Kevin - here's another option for you to consider. The GM crate motor, think it's the LM-1, a 290HP 350 motor can be had for maybe $1700. Toss on your intake/carb/distributor etc. , pull the 3.08's and go to 3.55's or 3.73's and you'll have some fun. It runs on 87 too. Throw on some flowmasters and you'll sound pretty sweet. Oh, nice thing about the crate motors ... warranty !! This might allow you to shuffle some of your $$ towards the custom paint you want. Good luck, and enjoy the ride !!

 

[Offbeat Octane]

Looked up the LM-1 for myself, seems very interesting... Might want one myself.
This site rates it at 250 HP @4300 rpm, but thats with iron heads and 8.5 compression ratio, so ot seems like it'd be easy to up it some more. Their hp numbers were obtained with a Q-jet and an Edelbrock performer intake.
Good price it seems too = $1,295.95 PacePerformance LM-1

 

[78SilvAnniv]

Kenny and I (and two other CAC members) rebuilt our engine two summers ago. Twice. We changed out the top end in the winter but still encountered problems and when we tore it down the second time that summer, we found that we had also bent the cam.

Anyway, two rebuilds aside...
For me, it was a great experience to see the internals of my engine and have Kenny explain the different functions so I could understand how my engine works. BUT, for the cost of the rebuilds, the parts, the tools, the time...I don't think we will ever do that again. We'll sink the money into a crate engine that is ready to go and has a warranty!
Heidi

 

[fine69]

hello all,

I am finally getting around to pulling the basically stock 350 from my 75 and I am going to rebuild it, well ... my dad and I will. I am looking for advice as to what you all think I can do to pick up extra power in the rebuild. Already figuring on boring 30 over, this will require new pistons ... so what do you all suggest for pistons, cams, intakes, heads, etc ...

Thanks, kev

Hi Kev,

I rebuilt my stock engine over the summer - and it took me every bit of the summer... and into the fall. Actually, I didn't get her started until November.

It was quite an experience, and I ended up with great engine, but I probably wouldn't do it again. Considering I really did not save much $, and the huge investment in time (learning, making mistakes - fixing them, etc.)... I would have been better off, removing the motor engine and storing it, cleaning the engine bay, and replacing with a crate motor. I could have at least been out and about driving!

Granted, I should have done the rebuild in the winter - but the time investment and the fact that the cost is not much different are things to consider.

Ralph

 

[GTR1999]

Don't let that 205 HP 75 L-82 fool you, that engine,if still orginal has some very good parts in it. The heads were 76cc 202/160 with guide plates, the pistons were forged TRW's, the cam wasn't bad, it had a steel crank,4 bolt mains, pink rods, windage tray. The bottom end was really the old LT1 add that cam and intake and you're around 375 hp. I'd take one of those over the base crate engines. The ZZ engines are good but they run more then a good rebuild if you can do the work. We have the same engine, we added WP sportsman heads, CC 268 XE cam, RPm intake, roller tips, 750 demon and 2.5 exhaust with headers and it flew- more HP then you're going to need. The 268 failed early as they have a quality issue, but a good Gm, Crane or isky cam will work.
Gary

 

[Jack]

Looked up the LM-1 for myself, seems very interesting... Might want one myself.
This site rates it at 250 HP @4300 rpm, but thats with iron heads and 8.5 compression ratio, so ot seems like it'd be easy to up it some more. Their hp numbers were obtained with a Q-jet and an Edelbrock performer intake.
Good price it seems too = $1,295.95 PacePerformance LM-1

That's not an LM1 ... that's a Goodwrench GM P/N 10067353 ... it's essentially an L48.

The LM1 is identified as GMPP P/N 12499529

BTW, an LM1 is essentially an L82 with small valve 76cc heads & dished cast pistons ... cam is same as L82 ... LM1 is basically the Goodwrench x353 with an L82 cam. krigley's MY1975 L82's power rating was determined on a different scale than today's scale for LM1. If looking for more grunt than existing OE L82 ... the LM1 is a virtual match to L82 ... LM1's a good motor at a good $ ... it would be an slight upgrade from an L48 ... but not an upgrade from an L82.
JACK:gap