any good lt1 383 info, anyone done this

[69camarokid]

before anyone yells at me to research first, dont worry i have been.

As the post states im building a 383 LT1. I was at the track last night with my 69 camaro and have an lt1 with cc305 cam, 1.6rr, LT, CAI, roller timing chain and a few other goodies. Long story short i threw a rod threw the oil pan. Not good....

So ill be tearing apart the engine this next week or so to inspect the damage and as this is my baby im going to rebuild her right this time. Im looking at a 383 kit with forged everything, pistons, connecting rods, nad crank. I know i need to port and polish the heads for the flow of extra air. As well as an LT4 intake manifold and a twin 58mm throttle body. I also know ill need larger injectors.

I just feel that asking you guys, namely people with more knowledge and experience than me is a good idea. Has anyone built one of these.... are there any tricks i should know. things to watch out for? Any and all advice is both welcome and appriciated.

Overall im hoping to build an engine that will be reliable, bulletproof, and some where in the 450 horsepower minimum range.

thanks

[69camarokid]

https://static1.pt-content.com/images/pt/2010/12/PC150155-1.jpg
https://static1.pt-content.com/images/pt/2010/12/PC150158-1.jpg

the damage so far

[GeoffP]

I started a 383 build several years ago but never finished it because I couldn't find a local machine shop that would take on the balancing work. I highly suggest buying a rotating assembly that's already balanced that you can just bolt the OE flywheel and balancer to it.

[WS6]

No sense in using an LT4 intake unless you have LT4 heads as well. The LT4 intake doesn't match up to LT1 style heads.

Your goals are reasonable for an LT1/4 so long as that's 450hp off the engine and not at the wheels. You may find it cheaper and easier to simply buy a stroker engine from a builder. There are a few that still build and sell LT1 engines. Golen is probably the most publicized but I have no dealings or experience to speak of. http://www.golenengineservice.com/

[ArtosDracon]

Buy a pre-balanced rotating assembly with stroker clearanced rods and it should all go together pretty easily.

Triple check your block for cracks, especially around the pan flange where the rod went through the pan!!!

[69camarokid]

so as im looking into various stroker kits im noticing that some of the kits come with 6 inch rods and others 5.7.

Can anyone tell me why this is and what the difference is. Which is superior and why. thanks

[69camarokid]

ive also noticed a bunch of 383 builds ive been reading that say that you have to bore the cylinders at least .030. Is there a specific reason for this? or is this information inaccurate? thanks again

[WS6]

a 383 is a 350 with a 0.030 over bore and a 4in stroke crank. It's a math calculation. For instance a 385 is the same engine with a 0.040 over bore.

displacement= bore x stroke x # of cylinders

I prefer 6in rods but that debate is a huge one. What you need to concentrate on is whether or not your cam choice will interfere with your rod choice. Let that dictate which rod you chose. Sometimes the 6in rods cause cam interference.

[69camarokid]

everything ive looked up pointes to the 6 inch connecting rods being the best, so ill be going with those.

Im debating between the I beam and H beam connecting rods. Most kits seem to come with the H beams and all the research ive done seems to lean towards the H beams, so ill be going with that. Does anyone know anything about these firsthand?

And lastly, the thing thats holding me back is the various + or - ccs u can get on the forged pistons. Im assuming they mess with your compression ratio, but i dont know how much or if they affect it up or down. My stock compression ratio is 10.4 to one. I already have the engine tuned for 91, but i want to run NOTHING higher than that. I definitely dont want to sacrafice power and lower my compression ratio. i want to run pump gas (91 is the highest in california) but if i can bump up the compressin ratio a bit and be fine on pump gas then id like to do that. ANy ideas, or does anyone know what size +/- ccs i should get?

thanks

[ArtosDracon]

6 inch rods will cause less side force on the piston and will generally let you have a lighter rotating assembly without going into really expensive pistons. Whether or not the cost is worth the effect, is very debatable.

H beam will be fine, I've seen decent H beam rods run up to 700hp without issue, and they'll be lighter.

10.4:1 is pretty far up there even with aluminum heads, I wouldn't run much if any higher. Have you tested the chambers for consistant volume? Also we would need to know if the block has been or will be decked and by how much and what size head gasket you're going to use, then we can tell you the piston dish you'll need.

[Lowend]

The LT1 on the bottom really does not differ from a 87-up small block. For the record a 383 is a 3.75" stroke in a 4.030 bore.

The 5.7 vs 6" rod debate could rage for another 50 years. The short answer is that the differences in performance are small. A 6" rod rotating assy costs the same as a 5.7" rod, so buy 6".

There is no reason to go away from I-Beam rods in this application. Some people will say H-beam are stronger, but you are not getting anywhere near a rod failure with this engine's output levels. Lighter weight rods are generally better, but I wouldn't worry about it a ton in this application.

A new Cast Crank will work fine in this application. I like the Scat 9000's

Pistons should be forged; SRP and JE make outstanding versions for a street motor.

I suggest you buy the entire Rotating assy through Scat; make your life easy and have everything come in one box.

Any decent local machine shop should be able to balance the engine without too much hassle

[camrat68]

All I can say is do your homework before you drop your first dime. I've walked built LT1 383's with my cam-only LT1 350. I'm just saying that maybe the 383's I've run up against may not have been the best combination. You say you have the tune set up for the 350 on 91 pump gas, you can throw that out. You'll need a brand new tune to take advantage of the new cubes. I would check out the Impala SS Forum or one of the many F-Body boards to find good LT1 383 combos......

Some LT1 info....
http://www.goldsswagon.com/monster_lt1.htm

[WS6]

ooops. I was confusing stroker LSx cranks with the SBC/LT1 crank. 3.75" is correct. Thanks for catching that Brett.

The limiting factor on an LT1 are the heads. A proper built 350/355 can really put a beating on a non optimal 383. You'll usually find poor head choice as the culprit for the 383 not performing as well as it should. Built right though and the 383 will pound a 350 all things being equal.

In all honesty, most people over build an engine, IMHO. If I was to build a street 355 on a realistic budget, I wouldn't forged anything but the pistons. I'd run 2 bolt mains with steel caps and studs not 4 bolt splay. I'd balance the factory crank and rods and be done with it all. This will work well for a sub 600hp street engine that spins to maybe 6500rpm. If I do indeed turbo my engine, the only thing different I'd do from what I just told you is maybe change the rods. I'm only looking to make upper 400s at the wheels with low boost levels. So it's not pushing the engine that hard honestly.

10.4:1 CR on an LT1 is stock actually. Most performance builds push 11:1 if not a little higher. Factory Impala SS head gaskets are thinner and will bump compression a few tenths of a point without any other changes to an engine.

[ArtosDracon]

If you're running 11:1 on 91 you better blend the bowls, IMHO.

[kryptik]

If you're running 11:1 on 91 you better blend the bowls, IMHO.

Agreed, especially with all of the additives, including ethanol, which are now mandatory in California. I even get some problems with 9.7:1 because of the ethanol.

Though fuel injection will help alleviate this.

[Scott Parkhurst]

I'd certainly call these guys too- www.tpis.com

They're pals of mine, great engine designer/builder/tuners, and they have won a slew of road races with LT1/LT4 powered cars.

[69camarokid]

Thanks for all the info. Im planning on running the compression ratio around 11:1. But to bump up the compression the right amount i have to know what CC piston to choose. Im not sure which way the plus or minus ccs correlates to higher or lower compression. can anyone explain to me how it works? thanks.

With the Eagle rotating kits ove looked at there are three cc piston choices, -7cc,+5cc,+16cc. but i dont how these piston size choices will affect teh compression ratio. does anyone know what size will raise me from 10.4:1 to 11.0-11.2:1.

And yes i will be doing work on airflow to make sure the air can breathe properly with the new cubes. Ill be getting the stock heads port and polished + extrusion, the heads also have comp cams 918 beehive springs, i have 1.6 roller rockers, the intake will also be port and polished + extrusion, okus ill be installing a dual 58mm throttle body, i already have a nice CAI system as well as long tube headers. The cam is upgraded to a comp cams 305 cam. I have liked this cam very much with my engine but am wondering if i need to get a larger cam to optimize on my new 33 cubes.
The bottom end will feature an Eagle forged rotating assembly. Forged pistons, forged H beams (6") and a forged crank. the kit comes internally balanced.
Ill also be getting anew optispark while the engine is out of the car. the current one has 140K miles on it.

How do you think that will all do? any potential issues or ideas you guys have?

[ArtosDracon]

We would need to know your final combustion chamber size, head gasket and final deck height to tell you what size pistons you would need.

[WS6]

x2 you'll need to get with whoever is going to build the engine to get an actual determination of the CR. This will require them to more than likely do some measuring first. At this point you can only get a guesstimate or a recipe for how to obtain your desired compression.

[69camarokid]

I will actually be building this engine myself at home with the help of my uncle. He had his own engine and service shop for the better part of 20 years and also works for the city's auto repair department so he rebuilts the caprice LT1s all the time.

I looked into the various available headgaskets and their compressed thickness.
.051 - Stock
.039 - Felpro
.028 - GM "Impala"
.026 - Mr Gasket

with stock cc chambers. these sizes will have these compression ratios.

Stock 10.418:1
FelPro 10.734:1
Impala 11.043:1
Mr Gasket 11.101:1

So im thinking of going with the Mr. Gasket setup to raise the compression to 11.1:1 which should be a nice little power bump but not to high to cause detonation issues. IM planning on keeping the heads cc chamber stock. So i need to find which piston will keep me stock cc size: -7cc,+5cc,or +16cc. Does anyone know?

[69camarokid]

from what ive read online it looks like the +5cc piston will keep the compression ratio stock at 10.4:1. this coupled with the Mr. Gasket .026" crushed gasket size that should run me right around 11.1:1 CR.

Any input on this?
Also do you guys think a bigger cam is in order for a 383 than the cc305 im running. Its a 220/230 with 114 las and .510/.510 lift. i believe that puts it at .544/.544 with the 1.6 roller rockers.

[WS6]

That cam would work well but would be mild. So if it's in the budget, get a better cam. If not, run with that and enjoy the broad power it'll have but do realize it will die early in the RPMs compared to a more suited cam.

[ArtosDracon]

You would be better off going for a quality thicker head gasket and flat top pistons. The thinner the head gasket, the more likely you are to blow it out with higher compression. IMHO.

[69camarokid]

You would be better off going for a quality thicker head gasket and flat top pistons. The thinner the head gasket, the more likely you are to blow it out with higher compression. IMHO.

so if i went with the stock head gasket size for a camaro LT1 then does anyone know what size piston i would need to get around 11:1. this is assuming stock deck height. I cant seem to find any info on this anywhere.

thanks

[ArtosDracon]

Assuming: .030 overbore, 58cc chambers exactly, 4.03 x .059 head gasket, and .025 deck then 3.5cc dish would get you 10.91.

[WS6]

You don't need to get the CR exact with off the shelf parts. You get it close and then adjust the deck or heads accordingly. Milling heads is what is usually done to achieve an increase in compression.