Engine Rebuild

[gedmeyer]

Well, lately I've been in one of those day dreaming modes about getting roxy to where I'd like her to be... After reading this article I've decided that this guy did mechanically what I would like done to my car.

Can anybody give me a ballpark estimate on what I should expect for cost for an engine rebuild? If I was to do a rebuild on the engine, I want to do it right... My goal is to have an engine with some power, but is also very reliable and suitable for all kinds of driving. I would love if I could rebuild her and get 300-350 hp, but I'm not sure if that would start causing problems interms of drivability/reliability. I don't want to end up with one of those engines that requires me to pop the hood and spray starting fluid in the carb or tinker around with the timing everytime I go to drive it. Basically, my only requirement is that I keep using the orignal block (no crates motors) and use whatever original parts if possible (I realize a cam will probably be needed.)

I would love it if someone could give me some suggestions or ideas that I could work on so that I can develop a master plan.

 

[Dave L.]

Nice article. I like the looks of that car. I'm also going to be going down the engine upgrade road in the future. I'm not sure if I'll rebuild or go crate...I'm checking out all options at this point.

Dave

 

[mikejpss]

While you have already expressed your intentions to not go with a crate motor, it should however be stated here the benefits of a crate to use as a baseline for a rebuild in capital outlay, horsepower increase and time consumption.

I recently chose a GM Goodwrench crate for my 81. With a 4 bbrl carb, and stock exhaust manifold such as ours, it is rated for 260 h.p. and is a stock motor.
OK, so its not the original engine....... I preferred to take reliability over originality as I will use my car for an occasional driver.

COST: This crate motor was $1330 tax included- a completely new engine, minus the intake and bolt-ons. For under $1800 we have a new engine compartment, a/c compressor is the exception.
Of course, all the labor was done by yours truly which held the cost down. Had I chose a rebuild the labor cost would have been the same.
There are pros/cons to both paths forward, it's all in what YOU want. I personally could not see spending $1000 for a rebuild when a new crate was only $1330. Just a simple solution for my simple mind.
By the way- that was a nice article... one day I hope to have mine looking that good

Take care,
Mike J.

 

[gedmeyer]

To me, if the rebuild is done right, the engine would be pretty much new. I don't want to spend $1300 on a new motor and then have to leave another $500 (the old enigne) sitting in my garage (which i don't have space for.)


On a side note to this discussion, what is the cfm of our carbs (e4me)?

 

[Chris Kennedy]

I have an '81 4 spd with about 184K miles on it, and I went through the same quandry about 30K miles ago. This is my only car and a daily driver, so what I decided to do was to have the engine rebuilt. I have done this before on other cars, and there are several general rules I have found. First: Nothing will be as easy as it sounds, and whatever route you will take you will encounter a number of problems. Second: If you start changing the basics of the stock engine when you have it rebuilt, you will throw "off" many things that are calibrated for the engine in its stock configuration (this is especially true in electronic, emission controlled cars). Third: Working with engine rebuilders and mechanics (if you don't do it yourself) is one of life's great frustrations. They will take four times as long as they say to do anything, and there will be times you feel like you are trying to communicate with Martians. Anyhow, I kept everything the same, but I did have the engine rebuilder take REAL pains to balance the engine and also the clutch rotating assemblies. This gave an improvement in high speed cruising and power. The advantage of the rebuild "stock" route is that everything goes back in that came out. So, you minimize the worries about accessories fitting, emission control problems, electronic carb or ignition problems etc. Once you start modifying the engine, you will have other issues to contend with. Also, I prefer to keep the car legal, and don't want to go through hassles at emissions check time.

As to the crate engine route, I am thinking about swapping in one in the next several years when I have another car and this car is beyond the emissions control period. It will be fun to have much more power, but on the '81s I would keep in mind the capability of transmissions and rear ends to handle this. I may swap in an earlier 4-spd as these are plentiful and cheap (I use a special Richmond Gear unit, now, with better acceleration ratios than stock), and I believe the rear end is a Dana 44. I am doing some research now on the ability of this unit to take more power, and I do have some concerns about the aluminum crossmember. So, this is a long way of saying that if you go the crate motor route be prepared for lots of "issues" that also need addressing, and I would go with a relatively mild unit, out of deference to basic strength issues and the age of these cars.

--Chris Kennedy
Houston, Texas

 

[gedmeyer]

What computer problems could my project cause? The only things I'm aware that are connected electronically are the carb and smog pump... I'm planning on leaving all of the emissions gear on.

 

[Chris Kennedy]

If you don't change the basics of the engine (e.g., compression ratios, cam etc.) then a rebuild shouldn't cause problems. The computer and the chip are programmed for the stock engine, and in 1981 both the computer and chip were relatively crude and cannot tolerate much variation at all. Depending upon what you do, the practical effect of changing things would likely be a very unhappy engine which runs badly, no matter what the "experts" tell you. Of course, you could always go to an earlier, non electronic carb and disconnect the computer, but then you will have to go to a different, non-computer controlled distributor. Also, 81s used, I believe, a computer controlled diverter air valve, which means if you disconnect the computer......you get my drift. All this can be done, of course, but just be aware of it.

If you are making serious changes to the engine, or are putting in a crate motor with higher power and other performance characteristics, you will probably have to disable the entire computer-controlled components and figure out the emissions issues. Again, this can certainly be done, but just be aware of it. If you do not change the stock engine or do not put in a crate motor with different characteristics, you will have enough problems getting everything hooked back up and working as it should, but things will ultimately work out.

Engine rebuilding or swapping is, generally, a much more complex and frustrating procedure than you might think. Getting everything functioning properly will take longer and be more frustrating than you think.

--Chris Kennedy
Houston, Texas

 

[mikejpss]

gedmeyer- my crate slipped right in- EVERY bolt hole , etc. was the same. I had already chose to by-pass the computer and take the smog pump off- however, had I chose to reinstall the smog pump the necessary bolt holes are there already. The crate was a genuine exact replacement for a 1970 to 1985 "general replacement" 350 c.i. replacement motor. By the way, it carries a GM factory warranty for 36 months, or 50k miles...
Rebuilding guarantees everything will match back-up, just has some of the same old parts (crank, etc) ....The crate has everything NEW.....
Just a different perspective, each choice is a good one..
Ya'll have a good weekend. Mike J.

 

[81 Corvette]

thats my favorite 81 of all time.

 

[gedmeyer]

hey guys, I just was talking to someone about my rebuild and I'm really leaning towards giving it a "go". We discussed possibly going up to a 350 gm cam as well as maybe some 2.02 heads that he had. Anyways, if I decide to do this, I plan on staying with the stock carb (in the process of rebuilding) and computer controlled setup.

now my question: what computer control issues do you think I will face? I will be keeping all of the smog equipment in place as well. Can I adjust or do anything so that if I proceed with the engine rebuild, I do not run into these gremlins?