403 build - Advice and Opinions

[Decadence75]

Hey everyone. I recently picked up an LQ4 that I plan to rebuild and put in the bird and would like some opinions/advice on what I have planned for it. I am hoping to make 500rwhp N/A and it will be a mostly daily driven car.

I plan to have a cleanup hone to 4.005 and pick up a rotating assembly from TSP that contains the following:
TSP forged crank
TSP 6.125 H-beam rods with ARP 2000 bolts
Wiseco 4.005 -3cc flat top pistons
King main & rod bearings
24x reluctor
Balance everything
I didn't think the upgraded wrist pins would be necessary, although someone can chime in if I am wrong there.

For heads I was looking at the PRC 225 as cast. Although I am undecided if I should opt for the 62cc small bore chambers or the 68cc large bore. They will likely be outfitted with BTR .660 springs.

For a cam I was thinking something in the neighborhood of 24x/25x .62x/.61x 112LSA

BTR SLR lifters

Unsure if an ARP main stud kit is really needed or if I could just re-use the stock bolts.

Melling 10296 pump

LS2 single roller chain

I will probably have to stick with my LS6 intake for the time being unless I come across a great deal for a 92 or 102 combo.

Any advice and opinions are welcome. Thanks!

[98TransAmWs-6]

Personally I would get it bored out to 4.030. Also stock main cap bolts are not reusable. I would go with ARPs just for the fact they are stronger and reusable and the torque sequence is simplified, no torque angle required to get proper bolt stretch. You just torque them down to the ft lb specification. BTR SLR Lifters are no longer available so unless you have some already you are going to need to rethink your lifters. I would also think about upgrading the rockers with either a trunion upgrade or aftermarket rockers. I would replace the cam bearings as well just to be sure since I am assuming you picked this up used and not new?

For a cam that is similar what I have 242/252 I would recommend getting a custom cam from Geoff at EPS. He is fantastic at what he does. For heads if getting ported stock heads I would do no one else other than AI imo. The PRC heads you mentioned are 243 castings right? I have sent AI my 243s to get ported out to 232 cc which should be back in the next week or so. If you aren't planning on doing stock head castings then I would go the TFS or AFR route.

[Decadence75]

Personally I would get it bored out to 4.030. Also stock main cap bolts are not reusable. I would go with ARPs just for the fact they are stronger and reusable and the torque sequence is simplified, no torque angle required to get proper bolt stretch. You just torque them down to the ft lb specification. BTR SLR Lifters are no longer available so unless you have some already you are going to need to rethink your lifters.

Thanks for the input! By boring it out to 4.030 right off the bat it pushes the cylinders to the outer limits of their capacity and 5 more ci isn't going to give any more noticeable power. I was thinking that 4.005 would give me room to salvage the block later down the road if something did happen that would require a bore to fix. The mains bolts are TTA not TTY so it is possible to re-use them. But I could just pick up another set of stockers just to be on the safe side, I just didn't know if they were ideally strong enough for this application or not. The ARP studs are a bit on the pricey side if not needed. The BTR SLR lifters are still available. His page shows 23 currently in stock. BTR SLR Hydraulic Roller Lifters - Brian Tooley Racing

[98TransAmWs-6]

Ah yeah I mixed up TTA and TTY but all the engine builders I have spoke with won't reuse the stock main bolts so I would think there is something to be said for that. I wouldn't say ARP main cap studs are necessary but it is nice added insurance. Interesting the BTRs weren't available for a while and he said they weren't going to be available something must have changed. You can actually go bigger than 4.030, like up to 4.060 but you must still have enough clearance between the cylinders and sonic tested(plenty of people go up to 4.03 to 4.06 all the time) Going to 4.030 is really no big deal but obviously it is your build so do what you want and what you are comfortable with. Regardless this seems like a nice build. I am buying a new iron 4.030 block from Summit and putting a 4.125 stroke in it for my build, no longer a 396 build I switched to doing a 421.

[Decadence75]

For a cam that is similar what I have 242/252 I would recommend getting a custom cam from Geoff at EPS. He is fantastic at what he does. For heads if getting ported stock heads I would do no one else other than AI imo. The PRC heads you mentioned are 243 castings right? I have sent AI my 243s to get ported out to 232 cc which should be back in the next week or so. If you aren't planning on doing stock head castings then I would go the TFS or AFR route.

How is the drivability with that cam? Nope, they are an aftermarket casting by PRC. From what I have read, they should flow just as well as the AI 226cc 243s with room for CNC porting down the road if needed. I had some 243s that I was going to send off to AI and put on my LS1 but found these for right at the same price point as the AI worked ones.

Ah yeah I mixed up TTA and TTY but all the engine builders I have spoke with won't reuse the stock main bolts so I would think there is something to be said for that. I wouldn't say ARP main cap studs are necessary but it is nice added insurance. Interesting the BTRs weren't available for a while and he said they weren't going to be available something must have changed. You can actually go bigger than 4.030, like up to 4.060 but you must still have enough clearance between the cylinders. (plenty of people go up to 4.03 to 4.06 all the time) Going to 4.030 is really no big deal but obviously it is your build so do what you want and what you are comfortable with.

I'll probably at least pick up a fresh set of stock bolts for the final install if I decide not to spring for the studs. I have read of people going out to 4.065 on the bore but from what I have surmised is that 4.030 is the largest you can safely go without having the block sonic checked to make sure that it can take the extra boring. I was originally going to go straight for the 4.030 and a 408 but after thinking about it some I figured by starting out on the lower end it would act as a bit of insurance if there was ever an opps moment with the motor and I have to expand it out just to fix the problem. Nothing is set in stone yet since it will be a little while before I can actually order the roatating assembly, might change my mind between now and then.

[98TransAmWs-6]

No clue on drivability on the cam since it was made for my 396 build which has now become a 421 and it has not been run in an engine yet. But it was designed for max power but to be used with e85 and 14.1+:1 compression and to be spun from 2000 to 7000 rpm. I doubt it is a DD cam since what I told Geoff at EPS I wanted but maybe for a 403 it would be reasonable.

[Firebirdjones]

Streetability depends on who you ask. I run that size camshaft in my chevelle with a carb. Takes tuning and knowhow to setup properly with a carb. It's aggressive and will thump down the road at 30-35 mph and sound like a pretty serious piece, but I find it streetable, drives fine, idles on it's own without monkeying around with the gas pedal, I can run the AC, and drive the car around town all day long. My wife can drive it easily.
With fuel injection it shouldn't be a problem at all for a good tuner to get that thing to idle all day long and have decent manors.

On the rest of the build, since you want to put a RWHP number on it, you'll need that FAST intake setup for something of this caliber. I preach about using the LS6 all the time, and it's perfect for mild street cars, but with a limit of 400 cubic inch and wanting 500 RWHP you're likely going to need a good intake setup to reach those goals. The camshaft you are thinking should get you there, but the other equation would be the cylinder heads. Not familiar with the aftermarket castings from PRC but I assume it's cathedral if you plan to use the LS6 intake. They would need to flow somewhere close to 300-320 CFM to support the power numbers you're looking for which is easily doable with cathedral heads, but what I like better is the velocity the cathedrals offer with the smallish runner size, this thing should have a pretty nice torque curve and that's what you really want on the street. Any flow sheets on the heads?

My opinion when it comes to heads, AFR has some of the best out there. Trick Flow is also very good. I generally don't look anywhere else when I go aftermarket. So if the PRC's fall in this range you'll make some power. It's a better way to go rather than trying to port factory castings at this power level.

[SMWS6TA]

I may be missing it but please explain, you are basically building the same build as me (see my signature). My one issue is you stated you want a 403 build, I'm not seeing how your getting that?

I have 4.005" bore, same style of pistons (different brand), and same length rods 6.125" (different brand) on a stock crank. What crank are you using? Stock won't get you the 403 and even using a stroker crank of 4" I can't see you getting 403ci?


I know if you bore to 4.030", use stock length rods and crank you have a 370ci. If you bore 4.030", use 4" crank and use 6.125" rods you have a 408ci.



Now regarding ARP bolts - it is worth the upgrade. All of my critical bolts have been swapped over to ARP. Only non ARP are the cover bolts, oil pan, valve covers. Only reason my intake has ARP is because it came with the LS6 purchase when I bought it 4 yrs ago.

[98TransAmWs-6]

I may be missing it but please explain, you are basically building the same build as me (see my signature). My one issue is you stated you want a 403 build, I'm not seeing how your getting that?

I have 4.005" bore, same style of pistons (different brand), and same length rods 6.125" (different brand) on a stock crank. What crank are you using? Stock won't get you the 403 and even using a stroker crank of 4" I can't see you getting 403ci?


I know if you bore to 4.030", use stock length rods and crank you have a 370ci. If you bore 4.030", use 4" crank and use 6.125" rods you have a 408ci.



Now regarding ARP bolts - it is worth the upgrade. All of my critical bolts have been swapped over to ARP. Only non ARP are the cover bolts, oil pan, valve covers. Only reason my intake has ARP is because it came with the LS6 purchase when I bought it 4 yrs ago.

He's using 4.005 bore with a 4" stroke. If you do the math that comes out to 403.

[SMWS6TA]

In that case just go to a 408 build. Cost the same and better HP/TQ numbers.

[kingls1]

My only suggestion is on the bolts, I have replaced every bolt I can with ARP so far and the day my motor gets cracked open ARP will be the only bolt used...cost of new bolts are far cheaper than rods or new block! Jmo

[Decadence75]

Streetability depends on who you ask. I run that size camshaft in my chevelle with a carb. Takes tuning and knowhow to setup properly with a carb. It's aggressive and will thump down the road at 30-35 mph and sound like a pretty serious piece, but I find it streetable, drives fine, idles on it's own without monkeying around with the gas pedal, I can run the AC, and drive the car around town all day long. My wife can drive it easily. With fuel injection it shouldn't be a problem at all for a good tuner to get that thing to idle all day long and have decent manors.

Great info, thanks!

On the rest of the build, since you want to put a RWHP number on it, you'll need that FAST intake setup for something of this caliber. I preach about using the LS6 all the time, and it's perfect for mild street cars, but with a limit of 400 cubic inch and wanting 500 RWHP you're likely going to need a good intake setup to reach those goals. The camshaft you are thinking should get you there, but the other equation would be the cylinder heads. Not familiar with the aftermarket castings from PRC but I assume it's cathedral if you plan to use the LS6 intake. They would need to flow somewhere close to 300-320 CFM to support the power numbers you're looking for which is easily doable with cathedral heads, but what I like better is the velocity the cathedrals offer with the smallish runner size, this thing should have a pretty nice torque curve and that's what you really want on the street. Any flow sheets on the heads?

My opinion when it comes to heads, AFR has some of the best out there. Trick Flow is also very good. I generally don't look anywhere else when I go aftermarket. So if the PRC's fall in this range you'll make some power. It's a better way to go rather than trying to port factory castings at this power level.

I really would like a FAST setup but I don't know that I have it in the budget for the initial build, it might have to be added in later down the road.

The heads are an aftermarket as cast set from PRC with 225cc intake runners and 2.06/1.600 valves. This is the flow info from the TSP page:

4.00" Flow Plate - No Exhaust Pipe

LIFT INTAKE FLOW EXHAUST FLOW
.100" 68 CFM 56 CFM
.200" 145 CFM 113 CFM
.300" 210 CFM 164 CFM
.400" 257 CFM 200 CFM
.500" 300 CFM 214 CFM
.600" 318 CFM 229 CFM
.650" 321 CFM 230 CFM

Another factor about the heads I need to decide on is that they come in 2 forms. A 62cc chamber small bore they say is for 3.9"-4" and a 68cc chamber for large bore. Any opinions on that?

[Decadence75]

Did a little work on the tear down tonight and got it from the complete dropout down to the shortbock.

[Firebirdjones]

Another factor about the heads I need to decide on is that they come in 2 forms. A 62cc chamber small bore they say is for 3.9"-4" and a 68cc chamber for large bore. Any opinions on that?

Depends on where you want your compression to come in at.

[98TransAmWs-6]

If you want under 11.5 compression I would go with the 68cc chambers since with your setup that would put you at 11.1:1. With 62cc that would put you at 11.9:1.

[Firebirdjones]

And even that would really be pushing the limits of pump gas. Depending on the final camshaft you choose will play some roll as well, but you might end up running a slightly dished piston to get that down to 10.5 or so to keep it a little more friendly while sipping off the pump. I personally wouldn't push more than 11:1 if you plan on running pump gas. In the long run you'll be happier, and there is no telling how much worse the pump gas may get in coming years.

[98TransAmWs-6]

And even that would really be pushing the limits of pump gas. Depending on the final camshaft you choose will play some roll as well, but you might end up running a slightly dished piston to get that down to 10.5 or so to keep it a little more friendly while sipping off the pump. I personally wouldn't push more than 11:1 if you plan on running pump gas. In the long run you'll be happier, and there is no telling how much worse the pump gas may get in coming years.

I guess I should have said he also needs to make sure he gets a cam spec'd to match to make sure it does not put his drc too high for pump gas (93 or 91 octane). You might consider some heads in the 72 cc department if you want to play it really safe.

[Decadence75]

And even that would really be pushing the limits of pump gas. Depending on the final camshaft you choose will play some roll as well, but you might end up running a slightly dished piston to get that down to 10.5 or so to keep it a little more friendly while sipping off the pump. I personally wouldn't push more than 11:1 if you plan on running pump gas. In the long run you'll be happier, and there is no telling how much worse the pump gas may get in coming years.

I haven't decided on final cam specs yet, the 24x/25x listed above was just a rough guess and may be too large for a road warrior/daily car. I plan on talking to either Martin @Tick or PatG for some recommended grinds. When I did some of the tear down on the engine this past weekend I found that 2 of the cylinders had rust and what felt like maybe some scoring. So I might need to bore out larger than my original 4.005 and go with the 4.030 that most folks have been suggesting.

I guess I should have said he also needs to make sure he gets a cam spec'd to match to make sure it does not put his drc too high for pump gas (93 or 91 octane). You might consider some heads in the 72 cc department if you want to play it really safe.

I have the 317 heads that came on the motor which have 71cc chambers and could be ported out to 232cc by AI to flow the same as the 243/799 heads. I was thinking that the 225 as cast might have been a better choice in case I wanted to get them opened up more in the future. What other head choices in that price range would you suggest that I look at?

[Firebirdjones]

I haven't decided on final cam specs yet, the 24x/25x listed above was just a rough guess and may be too large for a road warrior/daily car.

With a goal of making 500 rwhp with 400 cubes naturally aspirated, you'll be looking at camshafts right in that range that you roughly guessed
Now if you run an excellent set of heads, say from AFR for example, you might be able to tame the camshaft down a tad for a little more streetability and still realize your goal. Heads are going to make the difference.

[Decadence75]

With a goal of making 500 rwhp with 400 cubes naturally aspirated, you'll be looking at camshafts right in that range that you roughly guessed
Now if you run an excellent set of heads, say from AFR for example, you might be able to tame the camshaft down a tad for a little more streetability and still realize your goal. Heads are going to make the difference.

I set that goal just so I would have one. When I first got the car I didn't set any goals and ended up going off in so many directions I ended up changing stuff too often and wasting time and money, haha. I wouldn't be heartbroken if I didn't reach it. TSP claims that the 225 As Cast flows a bit better than their Stage 2.5 243s and similar to the Trick Flow 220s. I've seen some folks with stock bottom ends making claims of up to around 460 with them as well so I was thinking that they might be able to get me somewhere near that mark with more cubes. One thing that I would like out of the heads is that they be factory rocker friendly. The way I understand it is that AFR and Trick Flow have bronze guides that wear much faster unless you go with a roller rocker setup.

I also realize that I probably won't make that goal using the LS6 intake I have and will at some point need to upgrade to a FAST setup. I'll have to keep an eye out on classified to see if someone is getting rid of a 92/92 or 102 setup.