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I've recently completed a LQ4 408" stroker engine (by a builder, not me) and I'd like to get some feedback from some experienced LS guys. I'll try to keep this as short as I can. I did post an introduction but I don't think it's cleared the moderators yet. I hope this post makes it through, I need some help understanding my results. Essentially, I'm asking - does this look right? I'm not an engine builder which is why I seek the input of professionals. I did a good deal of research and paid for a cam selection. The goal is 550HP NA, carbureted, pump gas, performance street application. Components/specs as follows:
4.030" bore, 4" stroke, Forged crank (eagle I think), Forged H-beam rods, ARP-2000 rod bolts, ARP main studs, I believe zero decked.
-12cc inverted dome pistons, 10.5:1 static CR
TFS GenX 220 cathedral Heads with Ti retainers (assembled), 65cc, 2.055" intake vlv., 1.57" ex. vlv.
Cam guy indicated he thought this combo would be 575HP on engine dyno with 9.5:1 static and an 850 carb. My builder insisted on a 750 carb. I bumped the compression up 1 point at the recommendation of some experienced LS guys on another forum. This was done to increase the calculated dynamic compression above 8.5:1. It made sense to me at the time, I hope it was the right move. Dyno results and vids posted below. Peak HP wound up being 537, peak TQ was at 501 on several pulls, 498 on posted picture. This feels low based on cam manufacturers estimate and others feedback. Am I getting what I paid for or is something off? Thanks.
First thing I see immediately is compression. You could easily bump it up to 12.0: 1 and run pump gas all day.
There’s a lot of work that can be done to a carb to improve brake specifics, if it’s an out of the box unit. I’ve seen a good carb guy pick up 30 hp dozens….repeat….dozens of times. Carb guys are almost gone today with the advent of today’s fuel injection gurus.
Are heads worked or out of the box?
My .02
The combo of Dual Plane Intake, 750 carb, Schmedium Cam, & Schmedium Intake port are limiting your 408"
Above 6000 RPM.
Dual Plane needs the 850 and/ or plenum divider work on the manifold.
If it were mine I would strongly consider the GM Single Plane or Edelbrock Victor Jr. Intake.
They would still provide good low -end with that cam & 220 CC Intake port in a 408" as well
as another 25+ from 6000+
First thing I see immediately is compression. You could easily bump it up to 12.0: 1 and run pump gas all day.
There’s a lot of work that can be done to a carb to improve brake specifics, if it’s an out of the box unit. I’ve seen a good carb guy pick up 30 hp dozens….repeat….dozens of times. Carb guys are almost gone today with the advent of today’s fuel injection gurus.
Are heads worked or out of the box?
I was told they did some minor port blending on the heads. Actually, I was told they were going to do that. I'll confirm through. Thanks for the response. I don't think raising the static compression is on the table anymore. As far as the carb tune goes, I don't know what, if anything, was done. I have to think they did what was necessary to keep the AFR in the safe zone?
My .02
The combo of Dual Plane Intake, 750 carb, Schmedium Cam, & Schmedium Intake port are limiting your 408"
Above 6000 RPM.
Dual Plane needs the 850 and/ or plenum divider work on the manifold.
If it were mine I would strongly consider the GM Single Plane or Edelbrock Victor Jr. Intake.
They would still provide good low -end with that cam & 220 CC Intake port in a 408" as well
as another 25+ from 6000+
I think the builder and cam manufacturer hit the mark based on what I was asking for as far as performance characteristics. You know, street car, pump gas, good low/mid range torque. The cam guy did tell me he thought this combo would make 575HP on the engine dyno and that's where my concern arises from. I see these stroker LS engines approaching, even exceeding 600HP all the time on forums and YouTube. I guess I convinced myself that I'd soon be in that club. I feel like I'm being inconsiderate even questioning the builder but I do want to make sure I'm not leaving anything on the table. I'm not sure I understand the plenum divider suggestion. The Edelbrock manifold and the 1" spacer does have a divider I believe.
An old Holley 750 made over 650hp on our 415" ls3 it isn't the carb.
The biggest thing here is the intake manifold. The dual planes are all terrible for high rpm performance. You can look up some of Richard Holdener's videos. A single plane will dyno better, but what are you putting the engine in?
An old Holley 750 made over 650hp on our 415" ls3 it isn't the carb.
The biggest thing here is the intake manifold. The dual planes are all terrible for high rpm performance. You can look up some of Richard Holdener's videos. A single plane will dyno better, but what are you putting the engine in?
It's going into a 74 Nova with T56 Mag., 4-link & 3:73 gears. 335x35x17 tires.
One thing I just remembered. I sent a GMPP windage tray, but they didn't install it. Also, they are running (and recommending) I run 5w40 diesel engine oil in it. I know the stock windage trays require some trimming/fitting but they didn't seem too concerned with it. They put a Melling standard oil pump in with the high pressure spring installed because I'll be running a remote oil cooler. He commented that the pressure was a little high for his liking but it would be ok. It has the Holley 302-3 pan with the $300 baffle in it. He commented that they had to do some work to the pick-up. I suspect it was the interference issue with one of the main bolts, but don't know for sure. If I decide to put the windage tray on myself, I'm sure I'll figure out what was done with the pick-up. Lastly, I also sent a GMPP LS3 (I think) dip-stick assembly and he indicated it wasn't the right length and the markings were not correct.
You bump the compression up you definitely will need a different carb and intake. You might want to leave it alone and run it. Prolly a nice fast reacting street combo that is nasty through the whole rpm band, and should run on regular. Don't take too much into dyno results. You go to ten different ones and you will have ten different results. They are just a tuning aid, and not real world results. For example our motor wanted 4 jet sizes larger from the dyno room to the track. Picked up over a half a second by the time we got done tuning on motor only. You obviously went to your builder because you either knew for a fact, or went on others recommendations. If he has a good reputation, and others are happy with their results. Why not give him a chance? Engine builders like to keep a lot of little things that they do, that get the results they are looking for, on the combo the are producing a secret. I say give it a chance and see what you think. The way it is it will be very simple to tune and you could get away with a 150 maybe a 200 shot and that thing will last forever. Just my .02.
I would ask him why he left the windage tray out. There may be a reason.
If he wants you to run that oil there is nothing wrong with that ,many do. I'm sure the bearing clearances he uses are the reason. Stay with his recommendations. As for the carb. Don't worry about it either. You ever see the power those circle track guys can get out of a 2 barrel? Pretty impressive to say the least.
I would ask him why he left the windage tray out. There may be a reason.
If he wants you to run that oil there is nothing wrong with that ,many do. I'm sure the bearing clearances he uses are the reason. Stay with his recommendations. As for the carb. Don't worry about it either. You ever see the power those circle track guys can get out of a 2 barrel? Pretty impressive to say the least.
I did ask him about the windage tray. He said there are 2 schools of thought. Some swear by them and some don't use them. They subscribe to the latter. He added that the tall skirts on the LS block keep the parasitic losses down. Also, he said it didn't fit. I sort of inferred that the labor to trim it wasn't in the budget and they didn't feel it was worth the effort.
I have nothing but respect for the shop and the builder. As far as I know, their reputation is rock solid in the racing industry. I'm slightly conflicted when I know I probably shouldn't be. There were some other things that annoyed me, generally, with the final stages of the build. I had asked for them to use my ignition box to tune the engine and to tune it on pump gas. Initially, this wasn't going to be a problem but when the time came, they tuned on 110. This poses some obvious concerns on the output. They assured me it was tuned for 93 during the pulls, but it was running on 110. I assume an experienced builder can pull this off. Also, I didn't see my ignition box in the room when I was there. That doesn't mean they didn't use it the day before and then transfer the timing table(s) to their system, but why would you do that? I didn't see any AFR values and they were not mentioned. Again...is this because they were tuning for 93 on 110 and the AFM values were going to be skewed? I guess what I'm trying to say is, I'm a little disappointed in the attention to detail on the tune and turnover of this mill. I've got about $13k into it, $6k to them. That's probably chump change in their world but a-lot of money to me. Lastly, I believe the tune and turnover was rushed. They were working on an important project with a deadline and were behind on it. It was all hands on deck and that much was obvious. Everything mentioned above was probably the result of this.
Just judging by the rock solid EGT's on that computer screen i would say its dam close. All your info is on that screen. Looks like that intake has pretty dam good distribution. I would run it. If it was going to blow up, it would have done it on the dyno. Don't bail on your builder till there is a reason to doubt him. You don't know his procedures and i can tell you every one of them is different. You going to run the 6014 MSD box? Thats the one we run. Very happy with it. Very easy to navigate. 500+HP is nothing to sneeze at especially with a stick. That car will be a blast on the street.
Kim, does this sound like what I told you last night on SNS? Lol. Save up for extra rear tires. I don't know why everyone is afraid of compression on LS engines. This isn't your dad's iron headed small block. Again with everything said I think you have a very solid combo and you can what if yourself to death. Go enjoy that thing.
Just judging by the rock solid EGT's on that computer screen i would say its dam close. All your info is on that screen. Looks like that intake has pretty dam good distribution. I would run it. If it was going to blow up, it would have done it on the dyno. Don't bail on your builder till there is a reason to doubt him. You don't know his procedures and i can tell you every one of them is different. You going to run the 6014 MSD box? Thats the one we run. Very happy with it. Very easy to navigate. 500+HP is nothing to sneeze at especially with a stick. That car will be a blast on the street.
Not bailing on him at all. Just pointing out some things I noticed. Cam manufacturer got back to me today and pretty much said there’s nothing to worry about with the power output.
There were no EGT sensors in the headers or exhaust pipe that I noticed. No AFR sensors either. Appreciate the words of encouragement and agree, engine is stout for a dual plane, NA, street mill.
I’ll be picking it up tomorrow and bringing it home.
Kim, does this sound like what I told you last night on SNS? Lol. Save up for extra rear tires. I don't know why everyone is afraid of compression on LS engines. This isn't your dad's iron headed small block. Again with everything said I think you have a very solid combo and you can what if yourself to death. Go enjoy that thing.
yes sir. I’m eating plenty of crow for it, as I should be I suppose.
08-01-2021, 12:15 PM
Iron 408 build/dyno results 
