12.5:1 355 on pump gas, with a little bit of juice safe?

[Chrizar]

So I've been wanting to build a 383 for a while, and decided a 355 is more cost effective and will meet the HP goals I have for now. I spun bearings in my 4 bolt motor and killed the stock crank, my main concern is will a stock crank be up to the job is spinning near 7k on the reg, since I know these motors can handle a 150 shot on a perfect tune stock. I'm not looking to run a big shot, 100 at the most and it's not a track car, just a fun street car that see's a tiny bit of track time and lots of goofing off on the street. I have 93 at the pump, and plan on running that or E85 if I have to.

My current thoughts on the parts combo for my 355 would be:

Compstar comet lightweight crank, stock stroke (or stock crank if I can find a good used one)
Eagle forged I beams with ARP fasteners
Some sort of a forged piston, Mahle, JE, etc -5cc relief
AI 200CC stock castings 52cc chamber
port matched intake
58mm tb
AI matched cam, will probably end up being a custom grind but for the time being I'm looking at a 234 242 .576 .580 with a 110 lsa.
of course proper springs etc etc
ls7 lifters
comp pro mags 1.6's NSA guides, hardened pushrods 7/16th studs etc
not sure on HG yet, I have to figure out what my deck height will be after the block is machined but most likely an .026 or .029 MLS one.


I'm mainly looking for about 430whp through an a4 on motor hoping for 520 give or take on spray, mainly looking for opinions of if this will work for what I want or if i'm way off on my parts list here.

[zooguy]

7K+ on hydro lifters ... you may want to go solid lifters

[Chrizar]

7k max, as I wont have the money for a 24x swap for a while after all this. I'll be picking a cam to stay under 7k hopefully, but the bottom end should be able to spin 8500.

[dawdaw]

like i said man, static compression isn't where you should be looking, dynamics where it's at.... the bigger the cam you run, the lobe seperation, and where you put it in at is gonna have a big determination on how much cylinder pressure you make... Along with having your cooling system up to par and having the tuning spot on will determine whether you can run safely on 93 and run spray... on motor i don't see it an issue, but if you want to spray it would be in your interest to throw some 110 in the tank just for the safety factor... I'm sure with a small shot you could get away with it but a big shot i wouldn't try it... over fueling can bust a ring land and that's never pretty lol

[Chrizar]

This is all in the works still, just mainly getting the ideas down that my parts list is not shit or my goals are not realistic type thing. I'd rather only build this once and have it run great than have to swap stuff around. The cam is by no means set and I know dynamic will play the ultimate role as what cam goes in etc. I have to talk with AI for that when the short block is setup. Spray wise again is only going to be a 100 shot so I'm not overly worried it would hurt anything on 93 pump gas. If all else fails I'll run E85.

[1sickta]

I run 12.2:1 and a 200 shot on 93. It's all in the cam & tune.

[Jayz28]

I run 12.2:1 and a 200 shot on 93. It's all in the cam & tune.

Ah your secret is the wizard tuning your car lol.

What kinda cam are you running? I can't remember.

[OVA1]

Well I'm stroked to a 396, 12.5:1 on 93… I have a nano-nitrous setup, but haven't sprayed this build yet. Tune's a bloody mess… but even with this mail-tune, the engine runs like a raped ape on 93.

Getting a dyno tune in a couple of weeks, so we'll see what they say about the juice.

[96lt1m6]

Anxious to see the numbers;)

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[popo8]

Anxious to see the numbers;)

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+1

Co-Owner/Admin @ LTXtech.com

[Chrizar]

Well as I'm most likely selling my 4 bolt main motor this is going on hold for a little bit, I'm picking up a stock crank for free so that is solved, next would be rods/pistons etc. I'll probably pick rods up before winter, and aim to get my heads around tax time.

[OVA1]

+1

Co-Owner/Admin @ LTXtech.com

+2

I laid out a run in the "kill" section from this weekend…

Guy has a bad-ass 5th-Gen… 1st one I've tangled with where there was a discernible contest. We rolled him up despite the old PB Lvl2 going all kind of slushy on us… BUT, there's no denying: 'dat boy wuh fass'…

Now he said he dyno'd 520 to the wheels… which given the stock crank-values for the SS, plus those of the obligatory bolt-ons and the lumpy-ass cam he was sporting, it all seems to add up…

Which surprised me, cause I was just guess-timating that I was somewhere in the 500rwhp dept, given the build and the spooled 5.13s. (Not sure how the HP translates with the force-multiplying effect of the gears, but I can tell ya for a fact that it DO… just can't do the math; so to PROVE IT, ya sorta have to stage up, but it's no problem proving it.)

Rest assured I'll be reporting the numbers and, with the new tranny going in next week, we should see something around a substantial benefit from the long sought dyno-tune… So, be prepared for gushy, obnoxious, can't live with this asshole, over the top, delivered with humility that I can muster, of course… report.

(We now return to the thread topic, with many apologies to the host {Sorry brother…:embarassed:} )

[Stephen Ertel]

I'm guessing you're somewhere in the 400-420rwhp range. What chamber volume are those 195s?

Compression isn't the issue, it's CYLINDER PRESSURE. You're pushing it with a stock motor on a true 200 hit, 12.5 is a no go unless you're making no cylinder pressure. Those AFRs are a VERY fast cylinder head and are too small in CSA for a true 500rwhp with 396ci. My take on it...

[OVA1]

If that's directed at me, I honestly do not recall what the chamber size is… I wanna say 62cc… but that could be wildly wrong. I bought the from a guy who, ironically, had a 396 and was moving up to larger breathers. At the time, I could not have IMAGINED gutting the car again and building another engine.

But they sat for two years, then the build took two years, so it's been a while. The only other thing I do recall is that the exhaust valves were 2.20.

They had been worked by his builder and more or less maxed out. Seems like he said they flowed 300 @ .600 lift and we're at roughly .580.

Bottom line, no idea… But we'll know more in a couple of weeks. Thanks for the input.

Now pardon me, while I go google CSA…

[firebird_1995]

Chamber surface area?

[MEAN LT1]

Chamber surface area?

Cross section Area. :-)

[Paulster2]

... The only other thing I do recall is that the exhaust valves were 2.20 …Exhaust valves at 2.20? You sure you didn't mean intake valves?

[OVA1]

LOL! Noo... I'm not. :embarassed:

[Ninety5PoloZ]

On my motor I have a stock crank and rods with SRP forged pistons with a 11.7:1 compression with 52cc heads. I have OLD LE3 heads that have been milled down a lot (to the point that I had to oval the intake bolt holes) and the block has been decked down to square everything up. My engine builder said the compression was a little over 12:1 with my FelPro head gaskets, I can't remember exactly what it is as my motor was done 4 years ago.

Anyway I run on 91 pump with no ethanol (recreational fuel) and haven't had any problems and I have hit the 7k rpm limiter a time or 2. I need to work some little bugs out of the tune, but I haven't had a chance to do that yet. My car is tore apart more than it is together :(

[Paulster2]

LOL! Noo... I'm not. :embarassed:

What was it running on, a 5" bore? Or did it have 1.6" intake valves? Not sure where you'd find room to fit those in there ... :thinking:

[OVA1]

Paul, I honestly do not know. It's been SO long…

I looked through all of the sites, trying to find the old posts, when I bought them… The Seller had all the specs, the flow stats from the porter, etc… But they're long gone. I do recall the Machinist being both impressed and concerned, similarly to your's… thinking that they might be problematic. But when we bolted them up, they worked out fine.

On a side note… we got the new tranny bolted in over the week end. And MAN whatta difference. I haven't had a ton of seat time to go through her entirely, but coming back from the shop last night, she was everything ya could hope for. Shifts are back to where they were prior to this build. Smooth and quick… Kept the old Yank SS3600, which seems to be working fine.

Calling the tuner this morning, hopefully he can get us in this week.

[Camaro96]

Agree with popo8 can't wait for the dyno numbers. Has there been a build thread.

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