Tbi Questions...

[freedomfighter_87]

Okay, I have been wondering some things about TBI since I got my first TBI truck, a 1987 G20 Van. I have had 6 TBI trucks since then, and currently own a 1989 R1500 Suburban, which I think I am going to use as my candidate for restoration.............. OH come on suburbans are cool and you know it!

 

But anyway, although I have gained quite a bit of experience over the years working on cars, TBI trucks in particular, I have honestly never rebuilt an engine by myself... ever. And that's what I am going to attempt for the first time, with the 5.7L in this suburban, so bear with me please. I think I have it pretty much figured out, but one thing is driving me nuts. The Cam. I have read so many different articles and forum posts and I cannot quite figure out, does it have a roller cam or flat tappet cam? Edelbrock sells its Performer TBI cam kit for TBI trucks, but it is flat tappet. However, edelbrock also sells hydraulic roller lifters for this same engine, stating that hydraulic rollers are OE. So is it roller or flat? I've heard some people say it came with either (explain please?) but if that's the case then what do I need to switch from one to the other and do I need to do any machining? I have had a bit of trouble also finding a STREET LEGAL Hydraulic roller cam that will work with the stock computer (or a reprogrammed chip) Remember, I need ths rig to remain 100% emissions compatible.

 

Oh yeah, and what is the difference between a rotator and non-rotator valve spring? I've already deducted that one rotates and one doesn't (correct?) Is there advantages or disadvantages between the two and what type is on my 1989 5.7 TBI?

 

Thanks for your help.

[66nova]

Okay, I have been wondering some things about TBI since I got my first TBI truck, a 1987 G20 Van. I have had 6 TBI trucks since then, and currently own a 1989 R1500 Suburban, which I think I am going to use as my candidate for restoration.............. OH come on suburbans are cool and you know it!

 

But anyway, although I have gained quite a bit of experience over the years working on cars, TBI trucks in particular, I have honestly never rebuilt an engine by myself... ever. And that's what I am going to attempt for the first time, with the 5.7L in this suburban, so bear with me please. I think I have it pretty much figured out, but one thing is driving me nuts. The Cam. I have read so many different articles and forum posts and I cannot quite figure out, does it have a roller cam or flat tappet cam? Edelbrock sells its Performer TBI cam kit for TBI trucks, but it is flat tappet. However, edelbrock also sells hydraulic roller lifters for this same engine, stating that hydraulic rollers are OE. So is it roller or flat? I've heard some people say it came with either (explain please?) but if that's the case then what do I need to switch from one to the other and do I need to do any machining? I have had a bit of trouble also finding a STREET LEGAL Hydraulic roller cam that will work with the stock computer (or a reprogrammed chip) Remember, I need ths rig to remain 100% emissions compatible.

 

Oh yeah, and what is the difference between a rotator and non-rotator valve spring? I've already deducted that one rotates and one doesn't (correct?) Is there advantages or disadvantages between the two and what type is on my 1989 5.7 TBI?

 

Thanks for your help.

 

 

Wow! You are wanting to bite off a lot for your first build. Nothing wrong with that. I would highly recommend having some experienced help around, because there are a lot of little things that you just don't get from a book or the internet that can bite you. But as long as you know that going into it, and don't mind potentially having to redo somethings you are going to have fun.

 

Let me see if I can help some.

 

First off, the roller vs flat tappet situation. Your 89 will be a hydraulic flat tappet. Do you want to stay with a flat tappet or change to a roller? The questions you have to ask your self in order to answer the first question is...Horsepower goals, engines life expectancy, and what is my budget?

 

You will free up some extra hp with a Hydraulic roller, but you will also spend a lot more money on the cam and lifters(that's the big expense). If you have doing some research you probably know that with a roller set-up the lifters have a roller that rides on the lobe. This does a few things. It has reduced friction, less friction=more hp. It also allows for much more aggressive cam lobe designs.

 

To change to a roller you will need to change; lifters, cam, springs (and retainers), bronze distributor gear, timing chain (recommend a double roller, but will need a new timing chain either way). I'm sure there are some things I missed, but that's all I can think of right now.

 

Don't try to pick your cam your self. Call a couple cam company's or buy a pre-design kit. I recommend calling, Comp Cams, Lunati, Edelbrock, Bullet, etc. But edelbrock has some nice set ups for a stout towing/street motor.

 

Rotator vs non-rotator. I don't know what came factory, I would guess non-rotator. I have never used ratotors myself. As far as what it is... A rotator is a circular component that turns the valve slightly in each cycle to help keep a symmetrical wear pattern on valves and seats.

 

Good luck and keep us updated.