97 5.7 vortec

[best97obs]

and will I need to replace valve springs, lifters, rockers, etc?

 

[Erik the Awful]

Any time you replace your cam, you really want to replace your valvesprings as well, especially with a more aggressive cam. If you break a rocker, you're down a cylinder. If you break a valvespring or retainer, your valve crashes into the top of the piston and ruins your motor.

From your posts, I'd recommend doing your first porting job on a set of used Vortecs - check them carefully for cracks between the valves and the spark plug boss. About half in the junkyard are already cracked. They don't tolerate overheating.

 

[best97obs]

Alright thanks. I'm guessing some sort of beehive spring? What about retainers?

 

[Erik the Awful]

When I built the motor in WCJr I went with GM LS2/LS6 beehive valvesprings, which are roller cam springs, and are about 10% stiffer than the Vortec roller cam springs. If you go with the beehives, Comp Cams 787-16 retainers are readily available. Note: Summit doesn't have the 12499224s any more. I tried to figure out which BTR retainers go with those springs, but it's not obvious by their website. They might have BTR retainers cheaper than the Comps.

BTR BEEHIVE .560" LIFT SPRING - SP015-16 - LIKE 12499224

BTR BEEHIVE .570" LIFT SPRING - SP015-16 - LIKE 12499224 BTR .570" LIFT LS6 BLUE SPRING - SP015-16 - LIKE 12499224 1.29" O.D. 1.085" Coil Bind Height 375 lbs./in. Spring Rate 1.25" @ 295 lbs. pressure 1.8" installed height at 90 lbs

briantooleyracing.com

COMP Cams 787-16 COMP Cams Steel Valve Spring Retainers | Summit Racing

Free Shipping - COMP Cams Steel Valve Spring Retainers with qualifying orders of $109. Shop Valve Spring Retainers at Summit Racing.

www.summitracing.com

 

[best97obs]

okay thanks

 

[best97obs]

so the XM270HR was recommended by L31MaxExpress. He said it was a good cam for stock heads, is this true?

 

[BeXtreme]

It is not hard to get 400 hp with stock Vortecs. A XM270HR will get you there with long tubes and decent exhaust.

So, there are documented dyno results with upgraded aluminum heads, higher compression, and a more aggressive XE274H cam only making 415hp... but you are saying stock vortec heads and a 270h cam will make the same power? Do you have a dyno sheet showing that?

Comps own results show that with 9.25:1 compression and Dart S/R heads, they only made 342hp with that cam.
https://www.compcams.com/xr270hr

Comps dyno sheet for the 274h shows it makes about 20hp more than that cam, although their dyno sheet looks a bit odd... almost like valve float or something weird on the top end with the curve flattening out and jumping around above 5k rpm.
https://www.compcams.com/xe274h

got recommendations on some good heads that aren't over 600 dollars?

You can't buy stock replacement heads for less than $600... I'm not sure what you are looking for here. A set of assembled Dart S/R heads like the ones used on the engine that comp used for their dyno pulls costs $800 EACH. For IRON heads.

The skip white china casting aluminum heads are $860 for the assembled PAIR. Setup with decent valves and Comp springs for a hydraulic roller cam.
https://www.skipwhiteperformance.co...minum-heads-64cc-straight-plug-nkb-274_95131/

The AFR enforcer castings that have been torn down and assembled with the same upgraded valvetrain is $1120 for the PAIR.
https://www.skipwhiteperformance.co...evy-350-383-65cc-straight-plug-274-afr_95253/

Both have smaller chambers than the stock vortec heads, so they should give you a decent bump in compression, which will help with overall power.


What L31 is saying, is that stock vortec heads and the 270h cam will give you plenty of power and be VERY usable in a truck. It WILL NOT get you 400-450hp, because you would need a more aggressive cam and need to rev the engine higher for that. You would be shifting the power band higher up in the RPM range.

 

[best97obs]

I would spend over 1000 on head if I were aiming for higher hp. I'm just saying I don't want to spend over 800 for heads if I'm only looking for around 400 hp.

 

[best97obs]

gotta remember I want around 400 hp because it's my daily driver not a race truck.

 

[L31MaxExpress]

So, there are documented dyno results with upgraded aluminum heads, higher compression, and a more aggressive XE274H cam only making 415hp... but you are saying stock vortec heads and a 270h cam will make the same power? Do you have a dyno sheet showing that?

Comps own results show that with 9.25:1 compression and Dart S/R heads, they only made 342hp with that cam.
https://www.compcams.com/xr270hr

Comps dyno sheet for the 274h shows it makes about 20hp more than that cam, although their dyno sheet looks a bit odd... almost like valve float or something weird on the top end with the curve flattening out and jumping around above 5k rpm.
https://www.compcams.com/xe274h


You can't buy stock replacement heads for less than $600... I'm not sure what you are looking for here. A set of assembled Dart S/R heads like the ones used on the engine that comp used for their dyno pulls costs $800 EACH. For IRON heads.

The skip white china casting aluminum heads are $860 for the assembled PAIR. Setup with decent valves and Comp springs for a hydraulic roller cam.
https://www.skipwhiteperformance.co...minum-heads-64cc-straight-plug-nkb-274_95131/

The AFR enforcer castings that have been torn down and assembled with the same upgraded valvetrain is $1120 for the PAIR.
https://www.skipwhiteperformance.co...evy-350-383-65cc-straight-plug-274-afr_95253/

Both have smaller chambers than the stock vortec heads, so they should give you a decent bump in compression, which will help with overall power.


What L31 is saying, is that stock vortec heads and the 270h cam will give you plenty of power and be VERY usable in a truck. It WILL NOT get you 400-450hp, because you would need a more aggressive cam and need to rev the engine higher for that. You would be shifting the power band higher up in the RPM range.

There is documented data of a 330 HP 350 HO engine upgraded to a GM Hotcam and 1.6 rockers making 401 hp and 428 tq with the crappy flowing Mexican 062 heads that came on that engine. The comp cam I mentioned is slightly more aggressive for the same 0.050" duration as the hotcam.

Back in the day when the L31 head swaps were just getting popular Hotrod Magazine took a mid 70s 350, put a Comp XE268 cam and vortecs on it. They managed 394 hp out of that. Vortecs do not need huge cams to make 380-400 hp.

Vortec Blazer put a marine intake and XR270HR in his L31 swapped ~1987 S10 Blazer and went from 210 whp to 311 whp. He gained 100 hp at the wheels and from what I have learned swapping a ported stock manifold to a ported Marine manifold, I gained nearly nothing with the Marine manifold on my 383 making ~500 hp. There was another guy that went by VortecStroker or something like that back in the day. When his truck had the stock L31 bottom end and heads he put a GM LT4 Hotcam in the truck. It made 305 RWHP with the stock heads, intake manifold and injection. That was around 380 hp at the crank on his truck and possibly a touch more.

The EFI connection owner, Mike Noonan put together a L31 with a Hotcam and a Ramjet intake in his S10. It made 311 whp.

Edit- Mike Noonans S10 was 311 whp. I was remembering his torque number when I said 330. What Mike Noonan got from Hecho en Mexico 062s and a LT4 Hotcam. So 218/228 @ 0.050 will make over 300 whp in a L31.

I had a stock long runner TPI setup on a 10:1 355 I setup in a 1987 Firebird that made 290 whp through a TH400 with a 2,800 rpm converter. It had the older design Dart Iron Eagle 180 heads which are arguably worse flowing than Vortecs and a LT4 Hotcam. for reference a stock 113 aluminum head L98 makes about 240 whp through a 700r4 with free flowing exhaust. Flow numbers show the 113s are about the same flow as the 180 iron eagles used on that engine. So a little compression, shorty headers and a LT4 hotcam added 50whp through a slippy, loose converter and TH400.

This was Mike's result with his S10.

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