New heads = zero hp gain
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
New heads = zero hp gain
I sent my stock 242 heads off to a well known shop and had them do there magic, port, polish, valve job, and so on. I also went with thinner head gaskets per there instruction. I also added bigger injectors. I had 430/390 before and did 430/390 after the heads. Per the machine shop I needed .005 shorter push rods, so I swapped them out. I retuned the car but it doesnt seem any faster and gets 5-6mpg less now vs before the heads. The machine shop says thats from the bigger injectors. I can see from the data that the heads are flowing more air. I am going to re-dyno it this week to see the push rods fixed the problem. My car is no faster than before so Im guessing it isnt going to dyno anymore hp again. Any ideas?
Last edited by minytrker; Aug 27, 2006 at 07:55 AM.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
Originally Posted by billiardcue
If you didn't reprogram the computer for the larger injectors that would account for the loss in fuel mileage and the extra rich condition will reduce hp.
Tuning/programming is the most important part.
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
The stock LSx heads do a remarkably good job in a stock configuration. Putting high flowing heads on a other wise stock engine is not going to gain much and can hurt performance in some cases. Reason being is you will loose port velocity, meaning the air speed in the ports will be much lower even though your max flow is higher. The cam is where the performance is! Now if you change the cam you will see the gain from those high flowing heads.
Of course LT headers will help a lot too, specially with a good cam. The push rods .005 shorter will not fix your problem.
Of course LT headers will help a lot too, specially with a good cam. The push rods .005 shorter will not fix your problem.
Advanced
Joined: Jul 2006
Posts: 67
Likes: 0
From: Phoenix AZ
Port-job
Originally Posted by SpeedyZ
The stock LSx heads do a remarkably good job in a stock configuration. Putting high flowing heads on a other wise stock engine is not going to gain much and can hurt performance in some cases. Reason being is you will loose port velocity, meaning the air speed in the ports will be much lower even though your max flow is higher. The cam is where the performance is! Now if you change the cam you will see the gain from those high flowing heads. Of course LT headers will help a lot too, specially with a good cam. The push rods .005 shorter will not fix your problem.
Of course LT headers will help a lot too, specially with a good cam. The push rods .005 shorter will not fix your problem. Right on target You've got to bump up your Lift & Duration to extract the hidden power from that port-job. Long Tubes to top it off.
Injectors will help with future mods, but not necesary so far.
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Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
I already have every bolton and a cam......430rwhp/430rwtq before the heads. I just didnt bolt on a set of heads on a stock car. The car has been retuned for the heads and injectors. It is not running rich, I have a wideband in the car to double check. The stock injectors were maxed out over 100% duty cycle, I also have nitrous on the car so I need bigger than stock injectors.
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
Oops, sorry about that, I looked in your profile before under mods and seen "bolt ons & tuned" but didn't see your sig until now. So I assume the 430rwhp/430rwtq is without nitrous, correct? You shouldn't have needed larger injectors for a wet shot nitrous. Almost sounds like your nitrous system is not supplying enough fuel. Are you watching fuel pressure? Something don't add up because with that cam you should have seen some gain from those heads. Intake and TB still stock? What kind of number are you seeing on the nitrous?
Le Mans Master
Joined: Feb 2002
Posts: 5,970
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From: San Marcos Texas
Per the machine shop I needed .005 shorter push rods, so I swapped them out.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
Originally Posted by SpeedyZ
Oops, sorry about that, I looked in your profile before under mods and seen "bolt ons & tuned" but didn't see your sig until now. So I assume the 430rwhp/430rwtq is without nitrous, correct? You shouldn't have needed larger injectors for a wet shot nitrous. Almost sounds like your nitrous system is not supplying enough fuel. Are you watching fuel pressure? Something don't add up because with that cam you should have seen some gain from those heads. Intake and TB still stock? What kind of number are you seeing on the nitrous?
Melting Slicks
Joined: Aug 2002
Posts: 2,737
Likes: 2
From: California USA
Originally Posted by minytrker
I sent my stock 242 heads off to a well known shop and had them do there magic, port, polish, valve job, and so on. I also went with thinner head gaskets per there instruction. I also added bigger injectors. I had 430/390 before and did 430/390 after the heads. Per the machine shop I needed .005 shorter push rods, so I swapped them out. I retuned the car but it doesnt seem any faster and gets 5-6mpg less now vs before the heads. The machine shop says thats from the bigger injectors. I can see from the data that the heads are flowing more air. I am going to re-dyno it this week to see the push rods fixed the problem. My car is no faster than before so Im guessing it isnt going to dyno anymore hp again. Any ideas?
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
Originally Posted by chriswtx
Did you actually measure the lifter preload or just take their word for it?? You might want to actually measure the preload on the lifters...
Former Vendor
Joined: Mar 2004
Posts: 1,518
Likes: 7
From: Valencia CA
You should have about a turn and a half to two full turns from zero lash to fully torqued....if you do, pushrod length is not the culprit.
If the heads were opened up a bunch with minimal gains in airflow you will experience similar results to what you described (minimal power gains, sluggish/lazy part throttle, and poor fuel economy). I have seen some 240+ cc ports that could parctically swallow a golf ball barely muster 300 CFM. Airspeed in that situation and subsequently the ramming effect from inertia are both compromised, hurting performance. Also, the bigger lazier ports are more prone to reversion once again due to the fact a slower traveling column of air doesn't have as much energy/momentum and is more likely to change direction.
Whether any of what I just mentioned applies (to your scenario) is anybody's guess but trust me that the situation I just descibed is not that uncommon.
If the heads were opened up a bunch with minimal gains in airflow you will experience similar results to what you described (minimal power gains, sluggish/lazy part throttle, and poor fuel economy). I have seen some 240+ cc ports that could parctically swallow a golf ball barely muster 300 CFM. Airspeed in that situation and subsequently the ramming effect from inertia are both compromised, hurting performance. Also, the bigger lazier ports are more prone to reversion once again due to the fact a slower traveling column of air doesn't have as much energy/momentum and is more likely to change direction.
Whether any of what I just mentioned applies (to your scenario) is anybody's guess but trust me that the situation I just descibed is not that uncommon.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
I have 1-1.5 turns now, with the old push rods I had 2.5 turns. Yeah Im lost, the shop that did the work is saying they have never seen less that 20rwhp gain on any car. It really sucks going from 430/390 at the wheels & getting 30-31mpg to 430/390 and getting 23-24mpg.
Originally Posted by Tony Mamo
You should have about a turn and a half to two full turns from zero lash to fully torqued....if you do, pushrod length is not the culprit.
If the heads were opened up a bunch with minimal gains in airflow you will experience similar results to what you described (minimal power gains, sluggish/lazy part throttle, and poor fuel economy). I have seen some 240+ cc ports that could parctically swallow a golf ball barely muster 300 CFM. Airspeed in that situation and subsequently the ramming effect from inertia are both compromised, hurting performance. Also, the bigger lazier ports are more prone to reversion once again due to the fact a slower traveling column of air doesn't have as much energy/momentum and is more likely to change direction.
Whether any of what I just mentioned applies (to your scenario) is anybody's guess but trust me that the situation I just descibed is not that uncommon.
If the heads were opened up a bunch with minimal gains in airflow you will experience similar results to what you described (minimal power gains, sluggish/lazy part throttle, and poor fuel economy). I have seen some 240+ cc ports that could parctically swallow a golf ball barely muster 300 CFM. Airspeed in that situation and subsequently the ramming effect from inertia are both compromised, hurting performance. Also, the bigger lazier ports are more prone to reversion once again due to the fact a slower traveling column of air doesn't have as much energy/momentum and is more likely to change direction.
Whether any of what I just mentioned applies (to your scenario) is anybody's guess but trust me that the situation I just descibed is not that uncommon.
Advanced
Joined: Nov 2001
Posts: 63
Likes: 0
From: Lawrenceville GA
????????????
Originally Posted by minytrker
I have 1-1.5 turns now, with the old push rods I had 2.5 turns. Yeah Im lost, the shop that did the work is saying they have never seen less that 20rwhp gain on any car. It really sucks going from 430/390 at the wheels & getting 30-31mpg to 430/390 and getting 23-24mpg.
I'm confused. The .005" reduction in p rod length equates to 1 less turn of the adjuster???
Are you sure they didn't say .050" shorter?
.005" is a mighty small differece to get for a choice in p rod lengths.. .050", yes. .005", I doubt it, unless someone is really splitting hairs.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
Originally Posted by Old geezer
You said:"Per the machine shop I needed .005 shorter push rods, so I swapped them out."
I'm confused. The .005" reduction in p rod length equates to 1 less turn of the adjuster???
Are you sure they didn't say .050" shorter?
.005" is a mighty small differece to get for a choice in p rod lengths.. .050", yes. .005", I doubt it, unless someone is really splitting hairs.
I'm confused. The .005" reduction in p rod length equates to 1 less turn of the adjuster???
Are you sure they didn't say .050" shorter?
.005" is a mighty small differece to get for a choice in p rod lengths.. .050", yes. .005", I doubt it, unless someone is really splitting hairs.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 910
Likes: 0
From: Burton TX
Originally Posted by vettenuts
You aren't by any chance running the Comp R lifters, are you?
Who did the porting?
Who did the porting?
I would rather not say until all this is resolved, they are a supporting vendor.