I am thinking I'll dive into my build sometime soon, so i'd like to start buying everything and preparing for the build. I dont have unlimited money for this build, and would like to keep it at as low $ as possible.

I am keeping the TPI setup for a few reasons but mostly because i want a "stock-ish" look and i love the low end power it has. I would be very happy with 350hp & 400/450lbs of torque at the flywheel when its all said and done.

Im not sure what heads i will be using, but I have it narrowed down to the aluminum corvette L98 heads or the Vortec heads. Either way I will be getting the heads rebuilt. I believe I read that with Vortec heads you have to buy a different intake, I have done several searches but didnt find a definite answer. Im pretty sure i remember reading that while the Vortecs are better flowing, they are only slightly better and the intake manifold for it is more restrictive than the stock one on an L98, causing a loss of power. Is that true?

Can lt1 heads be used? Are they any good? Of course id have them rebuilt too.

I believe I read that siamesing the plenum-runners-intake manifold is much better for your top-end, but takes away from that insane bottom-end that the tpi has stock. I would like to keep this a low-mid range engine, so if thats true I wont do it.

Im not decided on a cam yet, I have the lt1, lt4, and hotcam(?) floating around in my head, but thats just because they seem to be pretty popular cams.

I will be getting an adjustable FPR. I might be getting edelbrock runners or long tube runners if they wont take away from my bottom end. I have headers already and Ill have them hooked up to a 3in exhaust (y-pipe) with no cat & flowmasters muffler with dual exhaust tips. Ive already upgraded my ign system with msd/accel parts. I will have my 700r4 beefed up and a trans go shift kit installed too. My car is a JG1 optioned car already (aluminum driveshaft). Ive got ZR1/corvette rims that are 17x9 with 245's on the rear.

Hopefully that gives you a good idea of my cars drivetrain and what Id like out of it when im done. Im open to any and all suggestions, thanks for helping and taking the time to read all this

 

Siamesing the runners is overrated. It helps some but not like youd think.
You need to port the living snot out of the whole system one end to the other.
You wont lose any torque.

 

Possible, but you're going to have to spend a bit to get there. The stock 350 TPI made 235 hp, and you want to bump this by over 100 hp. Small tweaks aren't going to get you there, and you're definitely going to be in the realm of either a custom PROM or running an aftermarket programmable ECM such as Megasquirt to adjust to the changes you're going to have to do.

If cost is an issue, I would use the Corvette heads, or go with an aftermarket aluminum head. The only reason I suggest this over the potential gains from the Vortec heads is you would be required to purchase a new lower intake manifold to be able to use the TPI with them, as bolting a stock TPI lower to Vortecs is not generally feasible. Yes, stock Vortec heads can be drilled for the proper bolt holes, but stock Vortecs are already dangerously prone to cracking. Aftermarket Vortecs can be sourced with the proper holes already drilled and are far less prone to crack, but you still have the issue of intake runner misalignment requiring use of conversion gaskets. Everything I have ever read on this issue says it is a stopgap solution at best and will cause a vacuum leak in relatively short time. So the best option with the Vortecs is to bite the bullet and get a Vortec TPI lower. Unfortunately, they sell for around $400, which is a big chunk of your budget I imagine. LT1 heads are possible to use, but you are looking at machine work to reroute the coolant flow as they feature reverse flow cooling, and do not have an intake crossover. it has been documented on Thirdgen as what needs doing, but it's a lot of added expense for what is basically the same flow design as Vortec heads. The latest issue of Car Craft Magazine just did a comparison on various aftermarket SBC heads, including the Vortecs, and compared them to basic L98 heads. It's good reading and might help you decide which way to go.

Siamesing is typically for top end gains, and yes it will cause of loss of bottom end torque as it effectively moves your powerband up. I would recommend if anything doing a complete port matching job on the upper intake, runners, and lower, removing the rough cast in the lower intake, and rounding off all squared protrusions behind the throttle body in the upper.

I'm running the LT4 Hot Cam in my TPI setup, but I have a Megasquirt-I fully programmable ECM to be able to feed it, as well as a an MSD 2225 high volume external fuel pump, and 36 lb/hr injectors (pulsewidth tuned down, oversized for E85 on my application), and had to have the heads worked for .525" lift and cut for LT1 valve springs. If you want to look thru cam selections, the Camquest online dyno on Comp Cams website is pretty good at showing the effects of various cam profiles on your engine setup, as well as if you'll need computer changes to accept them. I've heard the LT1 cam is pretty much a direct swap in and within the ability of the stock MAF sensor to adjust for, as well as the injectors and fuel pump. Again, as you're looking for a budget solution, this might be the way you want to go.

Sounds good here, but I wouldn't go with the larger runners, as they have the tendency to move your powerband up and take away from your bottom end torque. It's also unnecessary expense that can go to other parts of your build.

 

Ok, that was very helpful! Thanks!

I had never thought of the cam affecting the maf to be honest, i didnt even think it could. How does it?

If i buy an lt4 hotcam (read about this, seems very popular) what do I need to do to install? Just different pushrods/lifters/springs?

If i buy vette heads and have them shaved, ported & polished ect, and an lt1 cam, is that a good combo? Would i get decent torque out of this? How much of a gain would i see from an lt1 cam over the l98's? My hp id like to be at LEAST 300 and i dont think thats too hard to hit, but my torque is what i want to be as high as possible.

Would I most likely get better results out of the vette heads & lt4 hotcam?

I do plan on upgrading injectors, i think i forgot to mention that. Ill probably bump it to 24lb tho. (daily driver, need to be reasonable on gas lol)

 

porting those stock valved vetted heads should gain you an easy 30+-
LT1 cam is awful similar to the L98...little better but too close to stock for me.
You should be able to squeeze 300 out of it with heads/cam/intake/headers without issue. I disagree with loss of torque but everyone has their opinions.
port that intake with those changes and it will run strong.

Lunati 256 is a real strong TPI cam with great manners no real lope. Sounds healthy but not rumpity.

 

It's not that the cam effects the MAF, it's that the MAF allows a certain degree of leeway when it comes to tunability. It's able to adjust to changes in the engine setup, such as a larger cam, to a greater degree than a speed density MAP system is. However, the LT4 Hot Cam is a bit outside of this window, and would require ECM tuning to be able to run correctly, as well as larger injectors, if you wanted to run the 1.6 ratio rockers the lift is spec'ed at you must have the heads worked and different springs (LT1 or equivalent) installed, hardened pushrods are suggested, etc. The LT1 cam however IS within the ability of the MAF and stock ECM tune to adjust for, which will give you some gains over the stock L98 cam without having to invest in an aftermarket programmable ECM or a custom tune / EPROM on your stock ECM.

 

I'm not sure about LT1 heads on a Gen1 small block. The LT1 has reverse flow cooling and I don't think the heads will work with the Gen1 cooling system. LT1s aren't really so special as far as performance potential goes. They flow about like the vette aluminum L98 heads. For your power goals, you could use the stock iron L98 heads and have them ported and machined to accept .500 lift. Port the crud out of the stock base and open up and smooth out the plenum. A 52mm TB wouldn't hurt. Leave the runners alone and, in my opinion, don't siamese anything on the OE setup. Install a cam with about .500 lift and 220-230 degrees @.050(most cams will have slightly higher lift and duration on the exhaust side to compensate for the lesser exhaust flow), 112 degrees LSA for the long runners. SLP at least used to make a cam for highly modified TPI engines with 223/230 .050 duration and something like 501/513 lift, 112 LSA. I've used this cam in a few builds and it will work well for you with the other mods.

Add some 1 5/8" short tube headers and 3" cat back. You'll need to have the ECM tuned for this motor. This should put you real close to your goals.

BTW, With these mods, you will gain torque. Not lose it. By increasing flow and cylinder filling in a slightly higher RPM range, you will move your peak torque northward about 1,000 rpm and can gain as much as 80-100ft lbs over stock. The TPI responds very well to these mods. Of course good after market heads will always be better than stock.

 

LT1 heads have been made to work on a standard SBC, but it requires machine work. There are threads on Thirdgen detailing this. Usually it's not worth the expense over simply using aftermarket heads, or in a budget build doing a decent port / polish. My best suggestion would be to sit down, look thru the various heads available, play with the Comp Cams Camquest dyno, and figure out what cam / head package you like that stays within your budget. Talk to an engine builder about your combo and get their thoughts, I use Kendrick Performance in San Antonio...decades of racing engine experience, and extremely helpful and friendly about providing it. Tommy never minds being asked questions, and is very knowledgeable about what combos work and which ones don't. This will also help you properly balance your build, so you don't make the mistake a lot of people do in trying to throw a lot of parts together that don't necessary combine well. On a budget build that's the LAST thing you want to do. Plan your build, look at your budget, and only then start buying parts.

Another note: Kendrick also has a large consignment selection, and may have aftermarket heads you like for far cheaper than brand new. I've gotten quite a bit from him, and his pricing has always been excellent, such as my LT4 Hot Cam for $40, and a used TPI lower for the same price. Also, if you're planning on a larger lift cam, look into buying bare heads and re-using valves from another set since you're going to have to get different valve springs anyway. This is another way to keep within your budget.

 

Ok, I get it.

I am sold on the vette heads. I have the l98 as you know but im fairly sure they are cast iron (IIRC, no l98 F-body got alum. heads?) Is there a way to double check?

I plan on upgrading to 24# inj's anyways, so i plan on getting a custom tune. So that doesnt scare me away from other cams lol.

What I like about the lt1 cam is its cheap, and essencially a bolt-on add, it sounds like very little if anything is needed to be done for it. But, if its really that similar to the l98's I dont think id go that route, kinda seems like a waste. If im going to be much better off with another cam and its not too much more expensive i'll definetly do that. Since im having the heads completely redone, IDC what I have to do to them to get them to work. I also plan on roller rockers if I can. I want as much bang for my buck as possible, but dont want to skrimp on the most important things.

Ill look into the Lunati 256, maybe see if i can find any vids to hear it as well. Is that a good low-mid range power cam?

If lt1 springs are a good match for what parts i have and what i want power-wise that'd be nice, I can get them for cheap and they're abundant. Would they be a good spring for what I want?

ASE Doc: do you know the name of that cam?

 

I looked up lt4 hotcam and almost all of the results were of vortec headed engines or lt1s. I found 2 vids that werent, first one sounded real lame and weak, then there is this one:


I love this sound. Its exactly how I want mine to sound, i want it to lope but not much more than that. I really do like that. I think the first vid had a stock exhaust, it sounded very restrictive, almost stock-like. Is this how most cars with the lt4 hotcam sound?

Can anybody else with the lt4 hotcam post vids of how it sounds please? Also list what other mods you have.

cuisinartvette, do you have a vid of yours running? What other mods does yours have? I looked up vids of the Lunati 256 and didnt find any.

 

Other than that being a deeper tone (don't know what exhaust system he is running) than mine, the loping is pretty much what my LT4 Hot Cam 327 sounds like...same rough idle.

As far as the valve spring question, again I recommend talking to an engine builder about what your goal is, and what you want to use and getting their input. To check the heads, the easiest way is to check with a magnet. If it sticks to them, they're iron. If you want to check casting numbers, look on the Kendrick Performance website. He has casting numbers for all the GM factory heads.

 

You're right about the heads. F bods were Iron. And with the vette heads, you'll want to port them to wake 'em up. Out of the box, they're just barely better, but with some work, they'll shine! ...only issue is that may drive up costs to where another head can actually be a better value.

Yeah, the LT1 cam isn't worth the swap. I have a zz4 cam (.478/.510 - 208*/212*) and it's great, but I have stock heads. You'll want at least a little more cam, and as it stands, the zz4 is a lot bigger than the LT1 cam. I like the Hotcam too, although it's probably about as big as you wanna go with a TPI. I've heard several cars with this cam and it sounds awesome on a 350! Final sound/volume depends on exhaust system, but the lope is really nice! I don't have speakers here at work so I can't listen to the clip.

You should come up to Greensboro some time and check out the Triad F Body Club- www.triadfbody.com

 

Ok, ill do that. Thanks for all the help.

I found out he has a 4in exhaust, and IMO its too much for the car. Its a built 350, but IMO a 3in is good enough for most 350's, if you think 3in isnt good enough id go duals before a 4in y-pipe. Sounded much better in the video i posted above than the other one i saw. If i get my car to sound like his does in that first video and get the power out of it I want ill be very happy lol.

 

The Cam I'm refering to I found in the Summit catalog back when TPI was mainstream(pre-LS1). It is an SLP part. You might find it on their website. TPIS also offers several cam options for TPI and Comp Cams of course has many EFI cams to choose from. From my experience, hyd rollers are all in about the same price range so cost won't change much according to what you choose. Roller rockers are certainly a good investment for any motor that will see 6,000 rpm very often. You do need to stay with narrow body rockers for the center bolt heads. Comp Cams Magnum or Crane Gold Race are two options.

 

The only problem I've run into looking for roller rockers for my centerbolt heads are the excessive cost, as well as the added expense of tall centerbolt valve covers. Between the two expect to spend around $300-$500.

And generally speaking, unless it's a turbo setup, 4" exhaust is WAY too much for a 350, even a built one. You want to maintain a certain amount of backpressure or the valves won't seat properly, leading to carbon buildup on the seats and performance losses. The idiots that try to run open headers on street cars find this out the hard way.