Hey folks,

I've recently had the misfortune to pretty much wreck my 300 mile L98 based 355 engine. I noticed a lot more metal in the oil than there should have been, and pulled it last night. Today I did a little tear down, and discovered that my oil pickup screen was shredded, and the bearings were gouged to hell.

It's been a few weeks since I first suspected the damage, so I've been thinking about some things, and I almost have myself convinced that it'll be wiser to assemble a shortblock from scratch.

Here's what I have right now:
'91 Firebird block .030 over. Walls scuffed from debris
Scat 9000 series crank 3.48
Eagle SIR rods
SpeedPro .030 flat top hypers
AFR 195cc heads
LT4 HOTcam
Miniram

Crank is going to need to be turned, rods are fine aside from needing new bearings. Pistons look good, light scuffing on the skirt coating--but I'll need new ones with the overbore.

I'm looking at picking up a NIB package with an Eagle forged 3.75" crank and 5.7" rods, ARP hardware, forged pistons (but lower compression for boost so I'll need to replace) for about $1500.

I originally went with a 355 in my build as I figured a 383 was more than I really needed, and I'd rather have the MPG than the cubes. This time around I'm wondering how much those 30ci are really going to cost me at the pump. Does anyone have any before and after experience? I'm running Megasquirt, so I have full control for lean cruise fuel and timing.

Will I be able to reuse my HOTcam? It's my first stroker, and I hear that some cams have clearance issues, will the hotcam? Should I go with another cam with the extra cubes? I was pretty happy with the hotcam, but if I can retain streetability and eke out as many ponies as possible that'd be great. I've got a T56, if that makes a difference

Are forged components overkill? The main reason I'm looking at them is because I want to make sure I can rev the engine this time around. Last build the HOTcam like the revs a lot more than I was expecting. It really came alive at 4K and I felt like I need to be able to safely rev to 7K to get the most out of it.

If I rebuild my old setup can I safely spin 7k? Will a forged stroker like I spelled out before be able to safely do that? I kept the revs to 6K or below before as I was using the stock AFR springs, but I'm installing 918s while the engines apart, so I think the springs will be able to handle the revs this time around.

I'm not planning on boosting it, and probably will never run it on the juice although I might want a 50 shot some day. Would hypers be better for me? My understanding is they're lighter, which should be better for revs, right? They also seal better due to the expansion of the forged slugs, right? If I'm not running a power adder is there any advantage?


Thanks for any advice or comments on my build, I'd really appreciate any input.

Thanks!

 

You can safety rev your hotcam to 6500 RPMS. If you see no scratches on the bearing surfaces and the journals are not boogered up you can reuse it.

As for forged internals, if you are running only natrually aspirated then forged is not needed whatsoever on your application, however, forced induction it would be a good investment to upgrade. If you plan on just a 50 shot then forged internals are not required. You can safety run 20 hp shots per cylinder in a healthy motor without ill effects.

 

Going the 383 route will probably cost you some MPG, couldn't say how much, depends on your driving style.

Forged isn't really necessary unless you plan a power adder or revving to the moon. On a similar note, The hotcam is going to act very diferently in the 383 versus the 355. It will seem like a smaller cam, not going to rev as high in the 355.

Clearance issues all depend on rods and rod bolts. If you use rods that are set up for cap screws you're going to have a better chance for clearance. Best thing to do is mock it all up and see.

With the AFR heads and the miniram, a custom cam or something more specific to that setup will probably net you better results.

IMO, If you are debating between hypers or forged pistons, go forged, so then later you don't have to tear apart the shortblock if you want to supercharge or nitrous. Side note, make sure the rings are setup to accept a power adder if you plan to do so in the future.

 

Thanks for the response guys. I visited my machine shop today to price the work out and just shoot the breeze with my friend, and I think I'm going to do this:

Dump the Scat 9000 3.48 in favor of a 9000 series 3.75"
Keep the 5.7" Eagle "SIR" rods
Speed Pro dish 4.060 pistons
Upgrade the AFR 195s to Eliminators
Upgrade the ARP bolts to studs on the main bearings

So, just to make sure the consensus is that I'll be OK with a cast bottom end spinning this combination to 6.5-7K rpm?

As it sits right now, I'm thinking I'll have the block zero decked (currently 10 in the hole), and if I go with the 75cc Eliminators, I'll have 9.9:1 CR and .039 quench. Otherwise, I can do 10.39:1 with zero deck (65cc elims, 11cc dish piston), or 10.16 (65cc elims, 11cc dishpistons, .010 deck). Would the 10.39:1 still be pump gas friendly?

Thanks!

 

Sounds like a good first setup. I'd keep the AFR's. With little work they will perform as well as the Eliminators and you won't have to deal with parts compatability issues. With the money you save, have a good shop work the chambers and upgrade the valves. 10.4 is going to be the upper limits of pump gas friendly.

Keep in mind that if you upgrade to main studs there is a good possibility that the block will need to be line honed. Have the machine shop install the studs and check the line hone. If it's upper limits of spec have it corrected. It'll cost you a few bucks but it's worth it on any block.

 

Good point, re: the main studs, I hadn't considered that.

On the Eliminators, the reason I was thinking of switching, is that I thought the combustion chamber on the elims might be a little better for better efficiency/economy. My goal is to get in the 400rwhp range with 24-25mpg, which I think is doable, but I want every advantage I can get. If I used my old heads, I was also planning on going beehive, and since the eliminators already have a beehive spring, I thought the price differential wouldn't be that great all said and done.


Thanks!

 

why would you go to studs over bolts, is it a two bolt block? with speed pro hypers the mains will not be the weak point.

 

Drew should be here any moment now....