5.7 vortec rebuild ?? will non vortec heads work ?

[m00n1957]

just picked up a 1996 standard bore 5.7 vortec short block for $80. I didn't get any heads, intake or accessories. I have heads and intake but they are old school heads (882) and intake is high rise aluminum (holley), my question is can I use these heads on this block ? and can I still run the factory roller cam setup ? I know the heads aren't vortecs but they have 202/160, port matched/polished, de-shrouded, screw in studs and guide plates, my pistons have small dome to compensate for the 76 cc chambers. and I'd like to use them if I can and run the factory roller cam. first time to build a roller block. thanks for answering my dumb question.

[tdangle]

I don't know why it would not work, since you can go the other way and intall vortec heads on an earlier block

[garyd1961]

They should work but I would worry about spark knock( detonation). Probably would get some really poor gas mileage also. My cousin has the same set up, using one of his dad's old race engines in a S10. He mixes race fuel 50/50 with pump gas.

[Captainfab]

The '96-'02 L30 & L31 engines are still a GEN I small block, just with some upgrades. Yes you can run your 882's on that '96 block and yes you can run a factory roller cam. You will just need the correct length pushhrods. The factory L31 cam is a bit on the small side

[garyd1961]

Originally Posted by Captainfab

The '96-'02 L30 & L31 engines are still a GEN I small block, just with some upgrades. Yes you can run your 882's on that '96 block and yes you can run a factory roller cam. You will just need the correct length pushhrods. The factory L31 cam is a bit on the small side

The L31 cam is actually quite a bit larger than the most of the cams that came in these trucks. I'll agree though it's not a high performance cam by most standards.

[Tom]

Originally Posted by garyd1961

The L31 cam is actually quite a bit larger than the most of the cams that came in these trucks. I'll agree though it's not a high performance cam by most standards.

Not sure how much smaller then 191/196@.050 you can get and still have a running engine. My moms 1998 3.0L v6 accord had more duration.

Op- you can run any gen I small block head you want on that block. Not sure what garyd1961 is going on about with poor gas mileage and detonation. You said you'll match the pistons to the heads. 9:1 is 9:1 regardless of how you get there [or whatever compression you choose]

[garyd1961]

How many motor builders today use domed pistons? They were the thing back when we had leaded gas but not today. Sure you can make it work but flat top pistons with modern heads like vortecs will work a lot better.
The old 350 cam had like 396/401 lift and the L31 cam has 414/428 lift plus it's a roller which opens the valves faster than the old flat tappet cam.

[Captainfab]

The small domed pistons that the op said he was going to use with those 76cc chambered heads is going to be about 9:1 or maybe 9.5:1 at the most. If you are going to use heads with 64cc chambers as the Vortec heads do, then yes a flat top piston is a good choice for pump gas.

Originally Posted by garyd1961

How many motor builders today use domed pistons? They were the thing back when we had leaded gas but not today. Sure you can make it work but flat top pistons with modern heads like vortecs will work a lot better.
The old 350 cam had like 396/401 lift and the L31 cam has 414/428 lift plus it's a roller which opens the valves faster than the old flat tappet cam.

[garyd1961]

There more to it than just compression ratios.
Personally I would trash the 882s and get a set of vortecs. You can can make them work but in the end you would be better off with the vortecs.

[truckster]

The question for me wouldn't be compression ratio, as that can be manipulated by changing several factors. The question is flow. I know the OP has a lot of work into those heads; how would they flow as compared to Vortec heads?

[Myself]

It will all bolt together and run just fine as-is. Could it be better........yes. Will it run fine with 882 heads and the stock cam.........yes.

[garyd1961]

Originally Posted by Myself

It will all bolt together and run just fine as-is. Could it be better........yes. Will it run fine with 882 heads and the stock cam.........yes.

I agree with this.
To me it's like rebuilding a 307, nothing wrong with it but you are better off to start with a 350.

[m00n1957]

Originally Posted by Captainfab

The '96-'02 L30 & L31 engines are still a GEN I small block, just with some upgrades. Yes you can run your 882's on that '96 block and yes you can run a factory roller cam. You will just need the correct length pushhrods. The factory L31 cam is a bit on the small side

thanks for answering my question, i was worried about push the push rods. this truck will never be raced stop light to stop light, it will be a highway cruiser and pull a light boat, sometime, so high performance isn't the target but good performance is.
86 Silverado (short) 350 (basically a L82 from 74 z/28), turbo 350 (lockup), 273 gears (going 308 or 342 after build).

[garyd1961]

The 882s are prone to cracking right between the two center exhaust valves. I had a set with one cracked in that spot. With flat top pistons you can easily upgrade to better heads later. Just something to think about.

[Tom]

Originally Posted by garyd1961

The old 350 cam had like 396/401 lift and the L31 cam has 414/428 lift plus it's a roller which opens the valves faster than the old flat tappet cam.

Yes the cam has more lift for a given duration, that's a product of the fast ramps you referred to that open the valves so quickly. The ramps can be steeper due to the roller so more lift for a given duration. That aside, lift doesn't really affect the engines operating range, duration does. And in that area the vortec oem cam is still absurdly tiny.

As for the pistons, yes I get domed pistons don't propagate the flame front as efficiantly as a flat top or dished piston, but at a 9:1 ratio or so it won't be too big a deal. Besides, after seeing inside some European engines lately like the 5.0 from jag/land rover or the 3.0 from Audi, Im really starting to wonder how much faith to put into flame fronts and all that jazz.

[garyd1961]

Iui

Originally Posted by Tom

Yes the cam has more lift for a given duration, that's a product of the fast ramps you referred to that open the valves so quickly. The ramps can be steeper due to the roller so more lift for a given duration. That aside, lift doesn't really affect the engines operating range, duration does. And in that area the vortec oem cam is still absurdly tiny.

As for the pistons, yes I get domed pistons don't propagate the flame front as efficiantly as a flat top or dished piston, but at a 9:1 ratio or so it won't be too big a deal. Besides, after seeing inside some European engines lately like the 5.0 from jag/land rover or the 3.0 from Audi, Im really starting to wonder how much faith to put into flame fronts and all that jazz.

The vortec cam may be absurdly tiny but I smoked a 5.3 Silverado with mine saturday.
The L31 cam makes a lot of torque.