Let me just tell you a story I read showing the importance of LSA. A healthy 400 small block with good flowing heads was tested with both a single plane and dual plane intake. Three seperate cams 248/252 @ .050 roller cams were tested all the same exact specs save for LSA. The cams had no ground in advance, the lobes were straight up. The intake lobe was ground on the revised intake centerline for each LSA change. First cam was on a 107 LSA and ICL, 2nd on a 110 LSA and ICL and the last on a 114 LSA and ICL. At 3,500 rpm the 114 LSA cam gave up nearly 50 ft/lbs of torque to the 110 LSA which gave up 15 ft/lbs to the 107 LSA and the 114 LSA cam actually lost a few HP despite peaking 200 rpm higher. The 107 LSA cam peaked about 4 hp less than the 110 LSA cam about 200 rpm earlier. The 110 LSA cam made the highest peak HP at 6,400 rpm. The 107 LSA cam made 65 ft/lbs more at 3,500 and the same HP as the 114 LSA stick 400 rpm earlier. 107 LSA peaked at 6,200 and the 114 LSA at 6,600. The only thing the 114 LSA cam had going for it was 11.5 in/hg idle vacuum at 950 rpm vs 7.5 in/hg for the 107 LSA. The 110 LSA stick was right in the middle with about 10 in/hg. The 107 LSA cam cranked with nearly 20 psi more pressure than the 114 LSA cam due to the fact it closed the intake valve 7° earlier in the compression stroke trapping more cylinder pressure.

 

I will go even one step further to help save you the embarrasement and waste of time grinding a 118-120 LSA cam and putting iron heads on that engine. I ran a comp custom grind based of the Xtreme 4x4 grinds in my L31 for a year. It was a 206/210 @ .050, 108 LSA, 104 ICL with .484/.484 lift with 1.6 rockers. It made stupid amounts of off-idle and midrange torque but died at 5,000 rpm. My city mileage was exactly what it was with the stock cam and my highway mileage increased 1-2 mpg. Cruising down the highway in overdrive at 70 mph and 2,000 rpm it almost never downshifted on any grade pulling a 5,800 brick down the road.

 

I appreciate your input and there is a reason why I am steering clear of the lobe separation angles that produce more torque, the TPI intake I wish to use. I don't want to stray too far away from what I am used to and that I like about my LT1 engine. There are many things to consider with lobe separation angle and since I plan to use factory cast iron exhaust manifolds once again, I lose the ability to scavenge exhaust pulses. A wider lobe separation eliminates this need and since I am not racing the car it is utterly pointless to spend the money to build a custom exhaust to do such a thing when the RPM levels this engine will operate at won't justify it! If I plan to turbocharge this engine later on in life you want a wider lobe cam. I have read enough articles to conclude that sticking to the stock factory recipe is the better way for me to go on this build.

Based on my research for the TPI, if you plan to use higher lift cams you want to balance it out with wider lobe separation! It makes plain sense to either stick with my 117 LSA or go wider to 120, whichever one is deemed better when working with my entire list of current parts including 1.7 RRs and slightly less duration to mimic the torque curve of my stock cam as close as possible. This is stock performance we are talking about here, I am not expecting a genuine stump puller truck engine using the B-body LT1 cam which I was warned against or a ZZ9 cam twin turbo FIRST TPI intake build which I still desire to use my emissions devices so I can't use the FIRST TPI!

I am merely seeing if I can improve upon the factory cam of my LT1 by using 1.7 RRs to bump up the lift to .51 and exploring the possibility of whether having a wider 120 lobe separation angle will be worth it. Once I get the exhaust manifolds back on to restore some of the torque I have lost to my shorty headers and paired with the cast iron cylinder heads, and paired with the 1.7 RRs and custom grind cam, I should net a small increase in torque off idle. Nothing impressive but a gain none-the-less that becomes more pronounced when the engine operates in the TPI torque band.

The gearing is fine for the daily driving experiences I encounter and hopefully it will be suitable after this build is done since TPI cars tended to use lower numerical gearing.

I do apologize if it feels like a big waste of time to all members of this community. However, I have been researching your suggestions and from my research, based upon what I feel I really need and want out of my daily driver, I am convinced that this is the best route to take and totally to the contrary of what LS1 tech is all about. After all, a second-generation LT1 is a small block Chevy, so why the hell not take another perspective and build the thing like an L98?!

 

So I have to ask. Do you have dyno propf of losing torque with shorties? I have had them on several engines and never lost any torque at all. In fact gained torque and power over the manifolds in every setup. I have used BBK shorties on a L31 in an Escalade as well as on my Hemi Ram. The Hemi Ram ran within 1/10th of a second the same ET with shorties, stock cats and a 2.5 to 3.5 single exhaust as it did with long tubes and catless dual 2.5" exhaust with a X-pipe. I also pulled the factpry log manifolds and Y-pipe for JBA shorties on my 4.7 Dakota with dual 2.25" exhaust to a 2.25" dual in/ single 3" cat and single 3" exhaust with a magnaflow and it was a noticeable torque difference especially towing. Got better mileage and was alot more responsive across the whole RPM range. The 305 in my brothers 1980 C10 also had mid length headers for a 1988-1998 C1500 on it and it ran alot better with the headers and a 2.5" dual exhaust system with a H-pipe than it did with the logs and factory Y-pipe.

 

Do you have proof of your claims? Furthermore, are the exhaust set-ups from these different vehicles with different engines, stock? I take it no with the big red flag "catless". Again, I am not racing my car and I don't determine improvement by track time! If you remove all restrictions in an exhaust system from the factory set-up which includes emissions devices, and tailor the long tube headers and the rest of your exhaust system to your engine, YES, you will pick up more power on high! The problem I noticed not long after getting my engine back with shorty headers was that the car seemed to lack some of it's lower end torque. This is where I started complaining about the expressway with inclines and needing to downshift when before I could stay in gear. The shorties had to have removed exhaust back pressure which is great for power on up but hurts low end torque! I read it last night!

I have to avoid suggestions for focusing on horsepower building when anything associated with the TPI intake must focus on torque building! These are contrary goals and the torque building goal, in my case, depends on keeping the engine set-up mostly stock with stock exhaust! If some C4 L98 owners swapped over to my factory LT1 exhaust manifold and exhaust system and enjoyed improvements to their TPI set-up then this is clearly a telling aspect that my factory exhaust flows enough for the set-up I am trying to go for, ESPECIALLY to use a cam that may go as high as 120 on lobe separation angle!

I have to sift through everything I read from hot rod magazine to various forums in order to determine what is most likely going to work for this build and how to keep it on a good budget which, I am well on my way!

 

Vettes even LT1 Vettes do not use the same exhaust manifolds your car runs. The Vettes use a center dump under the plug manifold.

Back pressure has nothing to do with torque. Less back pressure equals increased scavenging and more power. Exhaust velocity and scavenging do. I suspect the shorties leaned out your engine and you need some fuel added to the tune to get your torque back. Datalogging and tuning are an important part of any engine modification.

I also confirmed something yesterday I was going to say before about the iron LT1 heads. The iron heads have a different chamber design and are 64cc. The factory used a thinner head gasket on the iron head engines. Something around 0.026" rather than the 0.051" of the aluminum head engine. If you use a .028" compressed head gasket with 54cc aluminum heads you will get to about 10.8:1 like the LT4s came factory. Using the same gasket with iron heads you will be about 9.8:1.

Also like cast iron Vortec heads the iron LT1 heads have thinner decks and are prone to cracking.

 

Unless I am mistaken and confusing the third-gen guys who swapped in L98s and used LT1 factory exhaust systems or the C4 owners converted their exhaust over to the LT1 as well. I am sure this information was on one of the many forums I have come across but suffice it to say, I realize I did make a serious mistake in swapping my exhaust manifolds over to shorty headers. The individual tubes are definitely on the larger side which, from what I read and what you state, exhaust velocity has now been altered. There is plenty of contradictory sentiments about back pressure, if exhaust velocity is somehow tied into this. From what I got out of it, more flowing exhaust with regards to shorties will shift torque up the RPM band which seems to be the definite case with what happened to my performance. Yes, proper diameter long tube headers would address this problem but since I want to use my catalytic converters and oxygen sensors, the cost to build this custom exhaust will be high and then to run into the possible problems of my long tube headers scraping the ground. This is where I am best to stick with cast iron exhaust manifolds and accept the performance trade-offs. The cast iron does help to retain heat which helps in the emissions department, which is why California won't allow aftermarkets. I tried to contact Brzezinski about their LT1 cast iron racing exhaust manifolds and whether they could be modified to work as emissions compliant stock replacements with the caveat of using header heat wrap to act as the factory heat shields, but I see they don't seem interested [Post Edit: They did respond to my inquiry and YES, I can use their exhaust manifolds and have them set-up to use the emissions equipment! Their exhaust manifolds are ported too so this is another perk!] although this would be another market for them to promote their exhaust manifolds. So, I will have to source used exhaust manifolds and fortunately there are plenty of places that held on to them.

With regards to the Cast-Iron LT1 heads, I believe I started a silly thread with the idea to explore converting the vortec heads over to reverse flow and using them on my LT1. I later found a forum thread by someone inquiring about the same thing and being shown how the LT1 heads will flow more than the vortec heads at every lift range. So, I am glad I got away from that idea. Yes, I am aware my compression will drop if I have those cast-iron LT1 heads put on my block with the appropriate thin gasket. Power wise it should still make about the same power as my aluminum heads with increased compression. Just like how cast iron exhaust manifolds are great for emissions, so too will these heads and I should get a more complete burn out of them which makes them attractive in addition to their ruggedness compared to my aluminum heads. I am sure timing is going to be different granted how hot the cast-irons will be but for my performance goals it shouldn't be much to worry about and I am sure an upgraded ignition over to the torque head using an LS1 computer will help me give me more flexibility than my optispark ignition system.

I am not too worried about cracking, the entire coolant system is going to have to be checked and the radiator will be upgraded to full aluminum, no more of that half plastic garbage that bit me when it did crack back in 2015 and put me on my journey to the reman engine I now have.

 

 

^^^
!!!!!!!!!!!!!!!!!!

 

 

I am glad to see you guys are taking this seriously.

 

Have you heard of the saying, paralysis by analysis?

 

I can only take you so serious and I am sure many of the people watching this thread feel the same.

You want to add weight to your car, criple your static compression ratio, and then add a further blow to your dynamic compression ratio by using a 118-120 LSA cam all in the quest for low speed torque and fuel mileage. ALL of which are directly opposite of your end goal! If you were to someday add a turbo a wider LSA would be appropriate but even then 118-120 is too wide for a 23* small block. If it worked so well why do you think GM started narrowing LSA on the Gen1 engines when the computers and injection systems became better. Thats right to increase throttle response and power.

 

This is why I am asking, although, I shouldn't treat the members here as though they are veteran cam grinders. These are proposals I am considering for this engine. With regards to the cam going possibly as far as 120 LSA, this would also be in combination with 1.7 rockers while trying to get it to behave like my factory cam at 117. Furthermore, this is in combination with the TPI intake. I am on the wall as to whether it is worth my while to have the bottom manifold mild ported and to maintain port velocity while also using large runners like the AS&M or if using the stock runners is what I really want. Most say the performance will be negligible and I am not stroking the engine so it further adds no benefit. If going 120 LSA on a custom grind is not worth it, then I will have to stick with stock 117 and maybe even forget the custom cam. I am still on the wall with the ZZ4 cam but again, trying to have a custom grind tailored to this build is money well invested for the long term. Then lastly, I got this information from grumpyvette's site, the 1.7 RRs will help improve my low end and mid-range torque on the factory cam but they do increase duration which shifts the torque slightly up the band which is why I want duration reduced to match my stock cam. However, I have a guy in mind for this engine build who also grinds cams for racing or daily driving or both. Hopefully he can talk me into what is the better set-up for my seemingly conflicting goals on this build.

Yeah, I am going to add weight to the front end of my car, around 50 more pounds, who cares! The purpose of this engine is street driving and it may see autocross in it's future. I do give a damn about emissions and I miss the way the car used to behave with it's cast-iron exhaust manifolds. At least now I have an opportunity to buy upgrades to those factory exhaust manifolds which are also ported! As far as the cast iron heads, why cry about it? They should make the same power as the aluminum heads only they do it in a different way, better thermal efficiency in the combustion chamber while being at less compression. It's no different than me swapping a Caprice engine into my Trans Am only the camshaft is for the F-body and then considering the rocker ratio.

I am sure I do come off as a troll to everyone else and not buying into swapping out my gear ratio for a higher numerical value. I just don't think that is what I really want and making my car "slower", well, even when I do enjoy the rare launch from a green traffic signal there is always another car up ahead that can make a quick lane change as I am zipping up to them. I just don't want to stray too far from the factory camshaft when I am somewhat content with it. It seems to me that more lift up to .51, which 1.7 rockers will grant me, is as far as I should go with it, and slightly less duration. However, I could be wrong or the real life mechanics of it won't work the way I think it will.

As far as GM engineers not doing the 120 LSA cams for these blocks, honestly we would need to ask them, I personally would like to know what one would think of this build and why such a cam on the larger cube LS7 works when it won't for my application using the TPI intake.

 

LSA discussion
https://www.speedtalk.com/forum/view...hp?f=1&t=52272

 

LSA without any other spec is pointless.

Relatively short duration with a tighter LSA and advanced ICL builds cylinder pressure which builds torque. Lift and Cylinder head flow build power. That cam is not far off from what I am running with Assault Racing 205cc heads. I just had a set ported by Lloyd​​​​​​. I am using a 1.7 rocker arm in my setup. I have a ported L31 Marine intake. Also have Doug Thorley Tri-Y headers. I am expecting somewhere in the 460-470 hp range out of a 9.6:1 350. Also should see around 440-450 ft/lbs of torque across a broad RPM range. The Marine intake runners are about 1.5X the length of a LT1 runner. My only requirement was this cam have good manners from 1,500 rpm and have a decent idle at no more than 850 rpm. It idles in drive with the a/c on at 750 rpm with 15 in/hg vacuum. From 2,500 rpm this cam and out of the box Assault heads made more grunt than the 2.02/1.60 valved 906 Vortecs and the GM 395' marine cam with 1.7 rockers did. The converter was stalling about 2,500 rpm with the Vortec/Marine cam setup and about 2,700 with the larger 215/224 cam and 205cc head ports. When I am in the throttle it is never under 2,700 rpm. At WOT shifting at 6,200 1-2 and 6,100 rpm for 2-3 the shift recover is right at 4,000-4,200 rpm.

Cam Specs
271/284 @ .006
215/224 @ .050
.578/.578 lift
110 LSA, 106 CL

Head Flow
Assault Racing Heads
Ported by Lloyd with 2.02/1.60 valves
LIFT------INTAKE-----EXHAUST
.200----------138-------107
.300----------192-------138
.400----------241-------164
.500----------274-------183
.600----------291-------193
.700----------295-------199

This engine pulled like a freight train from 1,500-6,200 rpm with out of the box Assaults only flowing
LIFT------INTAKE-----EXHAUST
.200----------135-------103
.300----------183-------131
.400----------225-------150
.500----------244-------164
.600----------241-------175
.700----------241-------177

 

At this point we are comparing apples to oranges. I will need to seek the counsel of a cam grinder, one who knows TPI L98s as well as the 5.7L LT1 to craft what I am expecting for this build. Also, at bare minimum, I want 20 in/hg vacuum at idle, just like I get now. The cam idea I have proposed with 1.7 rockers may not be well suited for this build or perhaps I can have the same effect with a custom grind using 1.5 rockers. I need to see what my options are and what they suggest I do. There is no point debating on this thread anymore and using information I have been reading about. Your application is entirely different from mine! I appreciate your input.

 

Testing with some wacky TPI stuff IRL!

 

He made some good numbers with the SuperRam. Much better than I expected. I wished he had snapped some pics of the SuperRam setup. If it's a direct bolt on and clears the cowl, that could be the answer to '97's torque quest.