355 engine rebuild questions

[Craig 94 TA GT]

I'm going to rebuild the motor to be a 355 with Advanced Induction's top end.
My AI heads/cam are ready to ship. Here's the list of the specs:
CNC'ed Intake Port,Exhaust Port,& Chamber
CNC'ed F1 Quality Competition Valve Job (<3 microns TIR)
Machine Intake/Exhaust Flanges & Valve Cover Rails To Ensure Proper Port Alignment & Sealing
Machine Guides For Any Future Spring Upgrades
Deck is PCD Milled For Superior Surface Finish, Flatness, and Desired Chamber Volume (52cc - 57cc)
Completely Hand De-burred To Remove All Sharp Edges
Hydrostatically Pressure Tested & Hardness Checked to Ensure the Casting's Integrity
Custom Manley Pro-Flo Severe Duty Stainless Valves Valves 2.00 Int/1.56Exh w/Hi-Performance Metal Clad
Viton Valve Seals
Pacaloy 1220 Beehive Spring w/Custom Manley Hardened & Machined 10deg Steel Components (Spring
Selection Based on Application)
Custom 8620 Inductioned Hardened Billet Core Hyd Roller Camshaft w/Premium Aftermarket Gear

I've heard, with that emissions cam on a 355, and those heads, you can put down roughly 400 at the wheels, so I'd assume 450-500 FWHP. I don't want to do this with my stock bottom end, so I'm getting a rebuild. AI is including 0.028 GM LT1 gaskets, FP1284 intake gasket set, new guideplates and chromemoly pushrods. So my questions are:

- I know I need at least new pistons, but would I need forged?
- Can I reuse my rods and regrind the crank? I've read that early 94s came with forged rods (mine was build in Oct 1993), but I have 125k. I also heard that the stock crank is good for 450-500 hp, so I'm not quite sure if that's the limit, or if I'll be fine, being N/A.
- Is a 4 bolt main conversion worth it for this project?
- Are 36 lb injectors good for this HP level?
- Is a stock fuel pump sufficient for this HP level?

The car will be a daily driver that occassionally sees the track.

Thanks a lot in advance.

[ConElite]

If you ever plan on maybe shooting Nitrous or Forced induction then I would recommend doing the 4 bolt mains and forged rods and maybe even the crank. Its always good to do it right the first time so it wont go "BOOM" when you strap on a 150# shot or start pushing Boost.

[Dragkid1917]

if your going to bother getting all that new stuff, especially a crank why dont u just get a 3.75" crank rather then the stock '3.48 (i think)

[MunsonGTA]

-I know I need at least new pistons, but would I need forged?
- Can I reuse my rods and regrind the crank? I've read that early 94s came with forged rods (mine was build in Oct 1993), but I have 125k. I also heard that the stock crank is good for 450-500 hp, so I'm not quite sure if that's the limit, or if I'll be fine, being N/A.
- Is a 4 bolt main conversion worth it for this project?
- Are 36 lb injectors good for this HP level?
- Is a stock fuel pump sufficient for this HP level?

The car will be a daily driver that occassionally sees the track.

Thanks a lot in advance.

- i'd go with forged.
- yes you can reuse your rods and crank.
- not really worth the money, it's up to you if you'd want 4 bolt or not.
- 30# would work, 36# would also work.
- stock fuel pump definitely wouldn't be enough.

[Craig 94 TA GT]

Thanks for your help guys.

Since my motor went south prematurely, it's in the shop. Here is what is going to happen:
- Forged pistons
- Reuse rods
- Turn/polish the crank (engine builder said they're good to over 700 hp)
- ARP bolts for shortblock
- AI's 200 CC heads + emissions custom grind cam
- Keeping it at 2 bolt mains - 4 bolt conversion way too expensive for this kind of power.

Since this package has dynoed roughly at 400 at the wheels, that equates to ~475 FWHP, so they recommend 36 lb/hr injectors.
And after speaking with both Ron @ AI and the engine builder:
- It seems that the stock timing set is adequate, and some customers of AI are still using it. Then, I wouldn't have to change my opti or water pump. The timing set is < 1 year old and the opti is an expensive Dynaspark; so I'd really hate to throw it all away. But the LT4 extreme duty timing set is obviously much stronger. I'm still debating, but I think the stock timing set would be ok for this mild power level?
- The stock fuel pump is adequate for this setup. AI said that several customers are running the stock fuel pump. But it would be up to me if I'd want to replace. It's only 3 years old, so maybe it's worth a shot to see if it works....up to the dyno tune?

Is there anything else I'm missing? Thanks again for all the suggestions.

[Craig 94 TA GT]

Just as an update:

AI's work is amazing. I got their H/C package today and here is a pic of how clean and well made the heads are. They flow around 285/195 and really put many "full port" stock LT1 castings to shame IMHO. These heads are like brand new, yet the core had 60-70k on them - which is expected, of course, from top notch head porters.

The motor is out and hopefully will be ready sometime in the near future. The cam is somewhat mild, to pass smog, but it is quite a bit better than the LT4 Hot cam or CC305. 38# flow matched Bosch injectors have been ordered, and the 54 mm AS&M should be on it's way sometime soon.

[MunsonGTA]

why did you chose a 54mm TB? why not just go with a 58 from bbk or holley?

[Craig 94 TA GT]

I know that planning on future mods is always expected, but I seriously have no plans for nitrous, a blower, or turbo. Based on Fred's calculations, 500 hp used all the air it needed at 77% of the 58 mm TB fully opening. Based on my expected hp (I'd assume 450, 475 absolute maximum), I did the following calculations:
58 mm area = ((58/2)^2 * pi)*2 = 5284.2
52 mm area = ((52/2)^2 * pi)*2 = 4247.4
54 mm area = ((54/2)^2 * pi)*2 = 4580.4

Since the 52 mm is 80% of the area of the 58 mm, it appears that ~100% of the 52mm would be sufficient for the 500 hp level. And just to pad it, the 54 looks to be slightly better, at 86.6%, giving a bit of comfort room, but not over-kill.

And I don't have to port out the intake holes with the 54.

Does this reasoning sound logical? I've been trying to figure this for a while, and hopefully didn't "overcalculate" anything. Thanks.

[MunsonGTA]

sounds logical to me. i just wondered because the AS&M parts are always much more expensive then other units. i only run a stock 48mm TB on my 400+ hp GTA.

[Injuneer]

The stock intake manifold ports are only 52mm diameter. There is a small chamfer at the leading edge, so the 54->52mm reduction does not involve a sharp edge, but its not a very gradual transition. You might want to have the manifold bores opened up to 58mm "just in case". There is no downside to a 58mm TB in a 500HP engine. I was just pointing out that it isn't absolutely necessary.

What kind of valve guides do the heads have? Hopefully they are bronze.

Rough injector sizing 500 flywheel HP X 0.07 = 35 #/HR minimum. Bigger is better. Many people run 42's without getting into trouble with idle quality.

You might want to look for a set of the PM rods used late-94 and up. They are stronger than the earlier rods, which are basically the SBC "pink" rods. The PM rod failures I have seen documented happened at about the 600 flywheel HP level. Or just get some low cost forged rods.

Forged pistons aren't essential at that HP level. Hypereutectics are dimensionally more stable and weigh less. But they aren't a good idea if you plan to spray.

Stock crank is fine at that HP level, particularly with the refinishing you outlined.

4-bolt mains are not essential at that HP level.

[Craig 94 TA GT]

Thanks Fred, I was hoping you'd chime in. I always thought that 93 and early 94 pistons were forged, then GM put in PM rods to save costs. But I guess that story is just a rumor I'll look at prices for forged rods - I think they're fairly cheap.

About the TB holes - wow I didn't realize that the holes were tapered to 52. And I think I may be overestimating this predicted hp. It'll probably be closer to 450 at the flywheel. Still, 450 hp is adequate for my needs. With that said, would a 58mm TB hurt with this power level? Or would it still be ok? If I can calculate it this way, 69% of the TB opening is maxed out for the motor. I did the math this way: 500 / .77 = 650. 450/650 = 69%. I don't know if it's a linear ratio like this, though.

[Injuneer]

The PM rods are stronger than the forged rods, and cheaper to make. From the "Rebuilding the LT1" article:

RODS

The original LT1 came with regular forged 350 rods, that were shot peened for localized hardness under the head of the bolt and nut. Powdered metal rods were phased in for the Corvette around 1994 and used in all of the LT1 engines by 1995. GM made the change because the powdered metal rods were cheaper to make and were much stronger than the GM high performance "pink" rods. In fact, they are supposed to be good for up to 450 hp. They are machined at the parting line so they can be reconditioned.

[Craig 94 TA GT]

Thanks for the rod info, Fred. Until now, I didn't realize that '93/'94 forged rods were the "pink" rods they are referring to

And the valve guides are K-Line bronze; the core's were bellmouthed so they had put them in.

[Craig 94 TA GT]

I just ordered the Spohn tubular k-member to go along with the motor. Hopefully, it'll arrive in good time - est time is 4-6 weeks. For my application, they said mild steel is fine. It's only about 4 lbs difference, and for 500 hp, there's absolutely no issue...I can do a lot with the $250 difference. The engine builders said it shouldn't be any additional cost in labor (maybe an hour max for fitment issues), so now's the time to do it. I'm sure access will be a lot better.