dyno 380hp/355tq @ 6k thoughts
12-29-2008, 07:42 PM
#1
dyno 380hp/355tq @ 6k thoughts I've done 95% of the upgades needed. Seems like my original fuel pump started to die around 6k. I watched the fuel pressure gauge on my rail and saw the needle jump around from 40-50 psi around 6k before that it was 50 solid all the way up. Don't get me wrong I love the power band just think she has more in her up top. There was no valve float. Its a real nice car to drive (not my DD) power is smooth all the way up...I like that I don't need to go 6500 to get those numbers.
12-29-2008, 08:07 PM
#2
Who ported your heads? And what is your compression ratio? Also what makes you think you are not getting valve float? The power is taking a dive over 6k which doesn't happen on its own. It looks like there are some severely mismatched parts in that combo since it is severely lacking torque.. especially low end torque. Do you happen to have the SAE #s so we can more accuratly compare the #s?
12-29-2008, 08:54 PM
#3
I ported the heads a few years ago, they flowed 255/190 @ .550. At the time the the machine shop said I had ported the exh a little too much and that my TQ would suffer. Comp 10.5:1
I read on here a bit more since posting and from what I can tell the #s are a bit low for all I have. Good thing is I have a set of stock heads with the good cast #. I guess that bonus $ is going to a set of LT1 heads.
I wanted to use it for my LS1 rebuild since I missing just a few parts.
I can see with the head swap over 400/400. agree?
SAE? Refresh my memory...you mean the Air Fuel for all the runs? On the last Run just after this one is where the TQ came up to 355 and 378hp AF was 12.9
I read on here a bit more since posting and from what I can tell the #s are a bit low for all I have. Good thing is I have a set of stock heads with the good cast #. I guess that bonus $ is going to a set of LT1 heads.
I wanted to use it for my LS1 rebuild since I missing just a few parts. I can see with the head swap over 400/400. agree?
SAE? Refresh my memory...you mean the Air Fuel for all the runs? On the last Run just after this one is where the TQ came up to 355 and 378hp AF was 12.9
12-29-2008, 09:30 PM
#6
Umm needed to make power. Haven't done adj fuel pres reg or fuel pump. All else has been bolted on or modded...
After all this I think I may just leave it the way it is and focus on my 383 with heads and all the goods from this block... I built this in 04 and for what it is, its ok. Its not the fastest LT1 locally by far but the fun factor is there and the pride I did it all good or bad. I know to get to the next level I'll need help.
Only thing is now is which engine do I start with, LT1383 or the LS1. I may just try to see which is the least expensive to build. My formula is my DD.
After all this I think I may just leave it the way it is and focus on my 383 with heads and all the goods from this block... I built this in 04 and for what it is, its ok. Its not the fastest LT1 locally by far but the fun factor is there and the pride I did it all good or bad. I know to get to the next level I'll need help.
Only thing is now is which engine do I start with, LT1383 or the LS1. I may just try to see which is the least expensive to build. My formula is my DD.
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12-29-2008, 11:05 PM
#10
I ported the heads a few years ago, they flowed 255/190 @ .550. At the time the the machine shop said I had ported the exh a little too much and that my TQ would suffer. Comp 10.5:1
I read on here a bit more since posting and from what I can tell the #s are a bit low for all I have. Good thing is I have a set of stock heads with the good cast #. I guess that bonus $ is going to a set of LT1 heads. I wanted to use it for my LS1 rebuild since I missing just a few parts.
I can see with the head swap over 400/400. agree?
SAE? Refresh my memory...you mean the Air Fuel for all the runs? On the last Run just after this one is where the TQ came up to 355 and 378hp AF was 12.9
I read on here a bit more since posting and from what I can tell the #s are a bit low for all I have. Good thing is I have a set of stock heads with the good cast #. I guess that bonus $ is going to a set of LT1 heads.
I wanted to use it for my LS1 rebuild since I missing just a few parts. I can see with the head swap over 400/400. agree?
SAE? Refresh my memory...you mean the Air Fuel for all the runs? On the last Run just after this one is where the TQ came up to 355 and 378hp AF was 12.9
SAE is the correction factor for American cars. STD reports a higher or inflated #. The a/f ratio doesn't go lean up top so it appears that the nose dive in power is valve train related. What springs are you running and what is the installed height? With a set of properly ported heads and a matched camshaft you would have no problem going well beyond 400rwhp in a 350/355 engine. Even with that camshaft 400rwhp shouldn't be a problem, but it will want to be pushed to the limits of the stock pcm.
12-30-2008, 10:16 AM
#13
In 04 when I did everything I got the valves and springs from the same guy. I don't remember the specs only that they were good to .625 and the installed hight was higher than stock. I do have a set of 918s. They work for LT1s if I recall.
Speed, After thinking a bit, your right if the pump was failing the dyno would show lean, it might be valve float. Still it points to making a set of heads and see what happens.
Speed, After thinking a bit, your right if the pump was failing the dyno would show lean, it might be valve float. Still it points to making a set of heads and see what happens.
12-30-2008, 11:04 AM
#14
Yes 918's or beehives in general will fit the LT1, but there is a big difference in running them on a LT1 compared to a LS1. The LS1 has 9mm stems which makes the valve a good bit lighter whereas the LT1 has the bigger and heavier 11/32" stems. The LT4 uses the same 11/32" stems but they are hollow to reduce weight.
Running less pressure makes sense assuming that the components being controlled are lightened as well. I have never had good luck with beehives for my setup mostly do to the more agressive cam. I floated my valves like crazy with Comp and PAC beehives.
I prefer dual coils Patriot springs.
Running less pressure makes sense assuming that the components being controlled are lightened as well. I have never had good luck with beehives for my setup mostly do to the more agressive cam. I floated my valves like crazy with Comp and PAC beehives.
I prefer dual coils Patriot springs.
12-30-2008, 03:49 PM
#16
Speed, stock PCM? I was also getting a tune along with the Dyno. The set up started with 361/335 with AF 11.3. The PC kept pulling timing and by leaning it out I got to the 380 mark. My last run was 377 but 355tq. I know it has more. I'm thinking about those heads...AI or LE with the same valves and new springs...
12-30-2008, 04:32 PM
#17
Speed, stock PCM? I was also getting a tune along with the Dyno. The set up started with 361/335 with AF 11.3. The PC kept pulling timing and by leaning it out I got to the 380 mark. My last run was 377 but 355tq. I know it has more. I'm thinking about those heads...AI or LE with the same valves and new springs...
You can see though, where the torque is suffering... in the lower portion of the powerband... not necessarily the peak #'s.
12-30-2008, 09:30 PM
#20
I might try to look for some springs. I do know that I don't want to go to 6500 to make that power. I'll look for some springs and go from there.
I thought my porting wasn't that bad. I've done it before I just opened the exh ports a little too much.
I thought my porting wasn't that bad. I've done it before I just opened the exh ports a little too much.