Tuned LT4 DOD cam to Non DOD/AGM cam swap. Necessary changes?

[ZLRob]

I'm going to be doing a Katech oil pump swap in my 2017 A10 Camaro ZL1 soon. While I'm in there I'm going to do myself the favor of swapping over everything to the more reliable non DOD/ AFM delete setup. This requires I swap out the cam and am going to be installing a stock style LT1/LT5 cam with a larger 32% fuel lobe. It's a cam sold by BTR which is called "stock cam big fuel" on their website. The cam is not much larger than current, but it's duration is a little larger than LT4 version.

Specs for new cam are as follows:
200/206, .544"/.522", 117 LSA 32% fuel lobe -31 overlap

Old LT4 cam specs:
189/223, 492"/.551" 120 LSA -34 overlap

The car is currently fully tuned and dialed in to run E50/E60 and is running 27* timing at WOT running a JMS voltage booster for the low side fuel pump

Mods are: Flex fuel, Lid, Soler 87mm ported TB (91mm effective), 5% lower 8.4" ATI pulley, HR7 Ruthenium plugs, Granatelli SS spark plug wires, catless secondaries and full exhaust post primaries, water wetter for both coolant loops, Cordes external LTR reservoir, and JMS BAP

My main concern here is runnability and start ability. I know the car is pretty low as far as mods go which is not too much a concern. It's more so making sure it stays within proper AFR at all times, especially WOT. Given the cam I'm swapping out to is pretty close to stock, what parameters should I be looking at modifying here in order to play friendly with this thing? I'm going to imagine the leading edge parameter in the fuel section needs to get bumped up 32% which is something I've already done. Outside of that, what else will be needed, MAF scaling, VTT, VE, and idle adjustments perhaps? Any idle adjustments? I'm happy to provide my current tune file if necessary. Thanks in advance guys.

[GHuggins]

You might want to talk to Brian before doing that. Just looking at the specs and what you're theoretically going to be losing in exhaust flow will hurt you.

[easttxss]

You might want to talk to Brian before doing that. Just looking at the specs and what you're theoretically going to be losing in exhaust flow will hurt you.

+1
You don't need the added lift and duration of the LT1 cam, that is what the blower is for. But you do need the added lift, duration, and LSA of the LT4 cam to help get the exhaust out of the way. Doesn't sound like a good idea to me. If you're going to go to all that trouble, might as well do a stage 1 supercharged cam.

[ZLRob]

Trouble is I live in that gold state that makes it very difficult to even mod to make the car more reliable. I checked around. ALOT. What I found is that my cam choices were extremely limited when it comes to doing a DOD delete. It was either run a GM LT5 cam which has no extra fuel lobe, the 6.6L GM cam which again has no extra fuel lobe or the BTR "stock cam big fuel" LT1/LT5 cam which gives my pump the overdrive I need for extra fueling..

It puts me between a rock and a hard place because of how invasive a cam job is on these LT motors and the fact that if you ever fail inspections due to being cammed, you would have to rip everything apart again which would require doing the job twice, which is not something I'm wanting to do.

Given what I got I'm sure it would give me the ability to dial up the timing which would demand more fueling, but it would also give me a better power return due to the fact that the high side wouldn't tank like a hot rock while running E.

Is my logic flawed here or am I actually onto something? You guys' thoughts are always welcome as I always value what you guys have to say on these boards.

[easttxss]

Are you a member over on Camaro6? Lots of boosted LT1/LT4 guys over there that may be able to address your fuel needs without a cam. Maybe TooHighPsi port injection would be a better fueling option for you, leave the stock cam in it and just turn off DOD in the ECM like it is with the manual trans cars. Also the JUMP from, "going to replace the oil pump, while I'm there might as well do a cam.." is not a small one. Changing the oil pump is minor compared to pulling the heads to swap the cam.

[GHuggins]

Or just call Brian, give him your predicament and ask if he can grind or have ground a cam that has the lobe with the same durations. You can even change things "slightly" to still not have a cam

The problem with the chosen cam is you have more intake flow with a lot less exhaust - essentially killing an already lacking ability to breathe even worse. Cylinder pressures will go up along with boost pressure (around 2psi through own testing on a lsa engine) and you'll lose anything trying to be gained by adding the lobe to run E.

A few options here for you anyway.

[1scls1z]

I think there is a bit of over exaggerating going on here. It's essentially the sam cam a LT5 uses except with a larger fuel lobe. How would it work for a LT5 but not a LT4?

[GHuggins]

Never said it wouldn't work - said it would contradict what he's doing it for The biggest struggle for any blown LS or LT is getting the exhaust out - whole reason when you get a cam the exhaust side usually has the most changes as far as duration and everything that's involved. Talk to Brian some time. I've spent a couple of hours on the phone with him discussing what I've found to work vs what didn't work back when I was designing and building engine setups and he always pretty much agreed with my findings. Even said lift doesn't make a whole lot of difference and can even cause problems on it's own such as lost port velocity on NA setups - it's all in how long you keep the valve open and when it's opened. Of course I don't remember all of the details of what we talked about as it was 5 or so yrs ago.

He can do it, but cylinder pressure and boost will both go up and it won't flow anywhere as good up top, but then again - who knows - maybe it'll respond well to the added boost.

Main differences for the lt5 and lt4 are cam, crank, rods and blower / take crank and rods out as they should be the same dimensions and then account for the lt5 running the 2650 most likely turning a lot slower - the cam could be used to get boost up in this scenario while still keeping things much happier.

Just to confirm that comment -

Displacing 2.65 liters, the LT5 produces 14 psi (0.9 bar) of boost. That's about 4.5 psi more than the LT4 engine, but achieved with a slower, 15,860-rpm maximum rotor speed, which helps keep down the pressurized air charge's temperature.

And then this for the lt4 stock -

Stock
Blower Pulley Diameter	2.505	Inches
Lower Pulley Diameter	7.75	Inches
Pulley Ratio	3.1	Ratio
Blower Speed @ 6500	20110	RPM's

^^^^ After seeing and understanding this, you should be able to understand why the lt5 was given the cam it got - plus it makes "emissions" a whole lot happier along with the bigger blower being happier turning slower while still able to flow more air and make more power. Also doesn't mean the lt4 will like it - just going from experience here, but who knows perhaps he can turn down the blower speed, keep boost the same without cooking things worse and still be somewhat close to what he's got?

[ZLRob]

Never said it wouldn't work - said it would contradict what he's doing it for The biggest struggle for any blown LS or LT is getting the exhaust out - whole reason when you get a cam the exhaust side usually has the most changes as far as duration and everything is involved. Talk to Brian some time. I've spent a couple of hours on the phone with him discussing what I've found to work vs what didn't work back when I was designing and building engine setups and he always pretty much agreed with my findings. Even said lift does make a whole lot of difference - it's all in how long you keep the valve open and when it's opened. Of course I don't remember all of the details of what we talked about as it was 5 or so yrs ago.

He can do it, but cylinder pressure and boost will both go up and it won't flow anywhere as good up top, but then again - who knows - maybe it'll respond well to the added boost.

Main differences for the lt5 and lt4 are cam, crank, rods and blower / take crank and rods out as they should be the same dimensions and then account for the lt5 running the 2650 most likely turning a lot slower - the cam could be used to get boost up in this scenario while still keeping things much happier.

Just to confirm that comment -

Displacing 2.65 liters, the LT5 produces 14 psi (0.9 bar) of boost. That's about 4.5 psi more than the LT4 engine, but achieved with a slower, 15,860-rpm maximum rotor speed, which helps keep down the pressurized air charge's temperature.

And then this for the lt4 stock -

Stock
Blower Pulley Diameter	2.505	Inches
Lower Pulley Diameter	7.75	Inches
Pulley Ratio	3.1	Ratio
Blower Speed @ 6500	20110	RPM's

^^^^ After seeing and understanding this, you should be able to understand why the lt5 was given the cam it got - plus it makes "emissions" a whole lot happier and the bigger blower happier turning slower while still making more power.

Oh yeah, I forgot to mention. I'm running a 5% lower pulley and making 11 psi currently.

[GHuggins]

Oh yeah, I forgot to mention. I'm running a 5% lower pulley and making 11 psi currently.

I finished editing my last post about when you were posting this one

You'll cook things worse in this case - maybe you can go back to a stock pulley and boost will stay the same or go ahead and turn it up with the cam, but things will get hotter - don't know if you'll notice the power loss with the additional boost, but I know you would notice a lot more power increase with the same boost increase with your current cam - if that makes any sense...

[ZLRob]

I finished editing my last post about when you were posting this one

You'll cook things worse in this case - maybe you can go back to a stock pulley and boost will stay the same or go ahead and turn it up with the cam, but things will get hotter - don't know if you'll notice the power loss with the additional boost, but I know you would notice a lot more power increase with the same boost increase with your current cam - if that makes any sense...

No it makes sense. When I bought the car I actually had a 12%er already installed on it and I had to step it down but the smallest pulley available for it was this 5%er from ATI. As of right now the stock fueling system handles it wonderful with a JMS all the way up to E60 so I left it be. I'm just wanting to do this since I'm gonna be in there doing the Katech pump. It was either go with a cam outside of stock stuff or stick with stock spec stuff. Regardless I wanted a 32% fuel lobe non negotiable so it limited me single handedly to the BTR can that I got. I would have waited for a custom grind but my guy doing this is going to be free without other commitments,so it was sort of a now or never thing and a custom ground one was three weeks out.

[GHuggins]

OK, I get it - just make sure to pull a couple degrees of timing (3 or 4 probably best) until you can get it dialed in.

[1scls1z]

LT1 runs the same cam as a LT5 and guys put LT4 blowers on those with the boost turned down and make the same power as LT4. Granted some of that is the compression increase. Either way you are looking at this like it's some wild build where cam selection is going to significantly have an impact. I don't see it being a issue on low to mid boost. If we are talking 18-20+ psi build yeah we want different valve events to help flow the boost out the exhaust. Under 800whp I doubt it makes much difference. Pretty much any LT engine with any LT stock cam can do that efficiently with enough fuel support. The fuel lobe to support E is more important.

Not trying to discredit your methodology here because it does make sense on somebody shooting for big power.

This is going against the grain from what many do, but I also think many over cam their engines. I have also considered the same for my car but it's hard to go through the effort to tear one of these engines apart and not at least go a little bigger on cam. Something 21x 22x 115 and under .600 lift so a beehive can be used. I like mild lobe stuff for street cars. Jm2c

[GHuggins]

The 117 lsa will be it's saving grace. That alone will help it over the stock lt4. I would really like to see some dyno numbers on the swap. Like I said who knows - may be a good improvement. Just googling shows people who have discussed it, but not a single one ever posted a follow up so don't know how it did or if they were happy with it. The right cam can make a 70 or so hp difference even below 800hp and running 14 to 16 psi of boost. Like I said from the getgo - don't recommend it as there are better, but in his case it might do all he wants.

[ZLRob]

The 117 lsa will be it's saving grace. That alone will help it over the stock lt4. I would really like to see some dyno numbers on the swap. Like I said who knows - may be a good improvement. Just googling shows people who have discussed it, but not a single one ever posted a follow up so don't know how it did or if they were happy with it. The right cam can make a 70 or so hp difference even below 800hp and running 14 to 16 psi of boost. Like I said from the getgo - don't recommend it as there are better, but in his case it might do all he wants.

Unfortunately, my hands are tied from a legal standpoint, with that being said, I'm not looking for an all out racecar either so it's not a big thing to me to chase wild numbers, and I'm definitely looking to stay within the LT4's boost numbers without overheating things, with which from what I observed needs to stay under 12 psi in order to stay happy as far as MAT's are concerned. A Kong X port is not something that interests me either as that will only make boost #'s climb as well.