My 75 has 100,250 miles on it and it still runs good. It doesn't use any oil and seems to be a good strong engine once it is around 3K rpm. The problem is it doesn't have any low end torque. I am thinking about replacing the heads, cam, and intake. Plus add headers and true duels on it. What I am wondering is what will this extra power on the top end do to the low end? I didn't really want to pull the engine if I don't have to.

:flag
Ron

 

Ron,

I rebuilt my 350 in my first '69 while it was in the car, so don't let anyone convince you that you have to pull the engine. Granted... it's not the best way to go as you will not be able to change out the front & rear main seals and the rear freeze plugs, but you can do everything else that is necessary without pulling the block. The radiator has got to go though when you change the cam. With the intake, heads & pan off you can do just about anything.

 

Ron:

Before you make any modifications to your 100K mile engine, you should do a little recon on it's overall condition. I'd recommend that you go to AutoZone and invest in a good compression testing guage. Take the time and do a test on all engine cylinders and write down what pressure you got on each cylinder. Trust me...write it down. When you are finished, inject a ounce of motor oil in each cylinder and retest. Write down you second set of readings.

These types of tests isolate various systems in your engine. The test outlined above will eliminate the possibility of compression leaking by your 100K rings and allows you to access if you have leakage occuring in your valve area.

Unfortunately many of us make the mistake of adding performance components to our aged engines only to find that we accelerated the death of our engine, sometimes in a non repairable manner (thrown rod/bent rod/etc).

Did not mean to scare you Ron, but amke cahnges cautiously when you exceed 100K miles on a engine.

Good Luck.

 

:iagree:

 

This is of concern to me too. Hmmmmmm

 

Most people are like you and alittle afraid to pull your motor. Beleive me, it's not that bad. I pulled mine out twice know. The first time to rebuild it and the second time just to put new heads on it. Putting it back in was easier than pulling it out. With that many miles on it you will be better off doing a full rebuild. Do it right the first time and never have to worry about it again.


[Modified by redwingvette, 3:53 AM 12/27/2002]

 

Ron,

I don't agree with any of the above, but that's what this forum is all about. Maybe I was a bit simplistic with my answer above, but any engine with 100,000+ miles needs to be re-ringed & re-bearing. And that is what I was suggesting if you took the intake, heads & pan off. Maybe it was just me assuming that everyone would do that if they decided to go into an engine with those kind of miles on it. If you have the compression gauges I do agree it is worth your time to find your problem areas before you take the engine down so you can research those areas, but it is not a necessity to tearing down an engine if you are planning on doing it anyway.

Were it not that I was changing this engine out for more horsepower I wouldn't listen to anyone about pulling the motor. Not everyone has the equipment, space or resources to go that route and if you you just have normal wear you can do everything needed with the engine in the car. Everyone needs to look after their own needs and not listen to the forum that might attempt to give them advice otherwise. My '69 engine was probably better than most on this forum and I never pulled it. And had it not been that I bought another engine, this L-48 with 74,000 miles would be rebuilt in-car and would be good(better) for another 75,000 miles.

You can hop up a motor without going to extremes.

 

It sounds like you had a good experience, but if anyone ever told me they were going to rebuild an engine with it in the car, including a ring and bearing job, I'd say they are nuts. The heartache, time, and knuckle-busting (not to mention you can't properly inspect the block, or have it cleaned) isn't worth it in the long run. Pull it, period. If you can't, then have someone else do it.

Brian

 

Brian....

Where are you getting to knucklebusting on anything with the block still in the car? I completely disagree with your analogy. It is much more simplier and the basics(main & rod bearings, hone, ridge ream, cam bearings & cam, piston rings, freeze plugs) can be done much easier in the car no matter what you have heard. I don't disagree that it would be better to pull the motor. It's just not necessary for everyone. A good set of ramps to pull the car on to and you can go to town without an engine hoist.

Looking for real horsepower? I agree... pull the motor. But, it's not for everyone and I bet everyone can do what I am suggesting if they have the correct tools and take the time.

 

If you're going to put a camshaft in it you might as well pull it. What I'm doing is keeping the L48 stock and building a different motor to drop in. Allows me to keep original parts for the future (granted I'll NEVER sell, but just in case), and lets me use a four bolt main and everything. It just isn't feasibly to go and change the heads, intake, carb, and put some headers on when so much more power could be had by spending the extra DAY to do a motor swap. Once you get the block back from the machine shop and have all the parts, it may take a week to assemble and then a day to pull the old and install the new. Maybe another day (or sometimes weeks) or troubleshooting and tuning. It isn't that big of a project.

 

Thanks for all of the responses. That is what is so great about this forum. I get so many different choices to make. :lol: I plan on doing the compression check this weekend and go from there. If I have to pull the engine then I guess I can take it over to the military base here and use the auto hobby shop and they have all of the tools to pull the engine. Like I said though I just don't want to hassle with that if I don't have to. Again thanks for everyones thoughts on this.
:flag
Ron

 

Ron,
Thats what this forum is about,opinions and choices and for the most part experience.Myself I would rather build my own engine than buy one from Gm or Harry`s mail order.Lots of people go the crate motor route and I agree it is eaiser.But in responce to your question,there is no way you can do a quality rebuild with the motor in the car.Once you get all the parts off that are required to remove the pistons,all that is left is 2 motor mount bolts,6 trans to engine bolts,2 fuel lines,and the starter and the block comes out.You will be way ahead to do it right the first time.
Bgrice
You made a couple of statements that I have to question.First you CAN change the front and rear seal on a sbc with the motor in the car.Second I don`t know of anyone that can change the cam bearings with out knocking the rear cam bearing plug out.Sure you could drop the trans to replace it but I think it would be eaiser to pull the motor to begin with.And the one thing you seem to forget is you have to pull the radiator if you leave the motor in and change the cam.I have removed my radiator a few times over the years and can say I`d rather have my n--s in a vice than pull it if I didn`t have to.In mho you get a patch job at best if you don`t pull the motor.And that was a bold statement about your 69`s engine being better than most on this forum.From what I`ve seen in the sign ons,yours pales in comparison to what a lot of these people including myself have.
Ron the choice is yours.Good luck on your rebuild.

 

For the back ache bending over the fenders,and the $100. bucks you save by not pulling the whole engine,I'd say you're nuts.However to each his own.

 

I would pull it. Even if you don't want to do it or don't have the means to do it, take it to a mechanic with an engine hoist and have them pull, it won't take them long or cost you very much. It'll be well worth your money to pull and do it right the first time than to be back in however many miles doing it all over again. This post is the first I've heard a lower end rebuild being done in the car. The top end can be done in the car pretty easily, but like was said before, you have to make sure the bottom end is holding up first. I'll be putting my AFR heads on with the motor in the car (maybe, my buddy just bought a hoist and engine stand :D ), but the engine will be pulled the following winter for a complete bottom end rebuild/stroke to a 383. Good Luck with whatever you choose to do :cheers:

 

If it were me, I would certainly do all the tests I can before yanking and rebuilding a good running engine. I drive a lot of miles each year, and have seen many 200,000 plus mile engines that still run just fine. I had a 68 Pontiac Catalina with over 350,000 miles, still going strong, all depends on how you treat them. Do you feel as though the low end power has been gradually getting worse, or has it always been a little sluggish? If you are still running the standard 3:08 rear axle on your L48 you could see a big low end improvement by changing that. Don't expect miracles from adding headers, but if you decide to do all the other things you have described they would not be a bad idea.