Rod length for 383?

[NorCal_z71]

Which rod length should I go with for my 383 build? I know 6.0"s provide a better rod ratio than 5.7"s, but have also heard that the 6"s are not as suitable to an every day, street driven application. IIRC, they have a tendency to clatter on colder start ups and can set off the knock sensor?

[Bryan TTM]

there will be no noticable performance gain on a street engine by using 5.7's or 6.0"s...there's barely any noticeable difference in an all out drag motor...the longer rods will have more piston noise at startup...you wont have any adverse effects tho...pin height & deck height and valve clearance bc of cam lift will dictate pistons whether off the shelf or custom cut...its been a big debate for years and i have run the snot out of both...i'd run the 5.7's and do off the shelf stuff in a street motor cause its cheap & readily available with hardly any performance loss

[Stroker 1500]

there will be no noticable performance gain on a street engine by using 5.7's or 6.0"s...there's barely any noticeable difference in an all out drag motor...the longer rods will have more piston noise at startup...you wont have any adverse effects tho...pin height & deck height and valve clearance bc of cam lift will dictate pistons whether off the shelf or custom cut...its been a big debate for years and i have run the snot out of both...i'd run the 5.7's and do off the shelf stuff in a street motor cause its cheap & readily available with hardly any performance loss
Everything i have read is that the 5.7 rod will have more noise because of how the shorter rod throws over compared to the 6, they say the 6 will have a smother transission. But using the 6 rods can make the engine a little weaker because of where the wrist pin is located with a 6 rod making it to where the ring lands have to be moved up a little

[NorCal_z71]

exactly what i was trying to say, thanks rc, still trying to learn this stuff a bit. So is your motor running 5.7"s or 6.0's? Im curious, what are the specs and number (hp,tq, mpg) for your engine, is it a vortec?

[SBCStang]

If you run 6" rods, you'll need special pistons that have the pin higher in the pistion also you'll need to have the block clearanced.
A friend of mine used to run long rod 400's (5.7 rod instead of 5.65) and said that it holds the pistion just a hair longer at TDC which builds up a bigger charge in the combustion chamber. Not sure he's right, but his motors ran strong!

[jshouse]

i run 6" rods in mine because every builder and engine guy i talked to said if you have the money, it is worth the improvement in wear and tear on the motor.

[Old88]

On a street engine the gains are small

Bottom line is....
If you need new stuff, get the longer rods...
A comlete stroker kit costs about the same whether it consists of 5.7 or 6.0 rods


Here's a good read.

http://64.233.187.104/search?q=cache:jT2uUB8YsP0J:www.grapeaperacing.com/GrapeApeRacing/tech/connectingrods.pdf+rod+length+comparison+5.7&hl=en#4

[NorCal_z71]

Old88 you seem to know quite a bit about build ups, I was wondering what is overkill and what is just being safe? I am hoping to have a 383, vortec heads, running around 400hp and 475 ft lbs+ if possible. At what point would certain grade rods and crank become overkill and not worth the extra $$? I also hope to eventually slap a turbo on this thing, perhaps a remote mount design like STS running minor amounts (5-10 tops) boost. Thanks

[badburban]

Old88 is right on. A 6" rod will produce a bit more power especially with a cam meant for it. A 6" rod will dwell around TDC a bit longer but a 6" rod engine generally will want 1-2* more LSA then a shorter rodded engine. The power differences for a DD are small but on an all out race engine these are real differences. As for overkill. The power levels you are talking about a good cast crank is just fine. Now stick 10 psi boost on top and you're pushing it. The thing is that its not really hp that kills rods etc its inertial loading that kills them. Build an engine focusing on the biggest fatest torque curve you can get and not high rpm and you should be fine. Besides in two similiar cars with similiar drivers the car with the most avg tq will always win.

Also what injection system are you running. Your going to run TBI as I recall. Just wait for all the naysayers to jump on the bandwagon here and start mocking you for doing a 383 TBI let alone wanting to do a turbo'd 383 TBI. Though Im a stubborn person and Ive got a custom ground camshaft of my own specs on the way with some other parts which supposedly are a bad idea for my combo. But I think Ill be able to prove a few people wrong. Hopefully soon Ill be able to report back with some good info.

Josh

[NorCal_z71]

Josh, I need to start talking to you again. I strayed from TBI for awhile and toyed with the idea of a 6.0 swap, a 383 vortec, an ls1, and LT1 etc etc. I agree with you, there is more too the TBI than people will give credit and I am looking to find it. One of my dads friends has started to already, kind of my motivation. How much do you suppose I am looking at as far as costs of whipping my stock 350 from my truck in a 383 around 400/475? I found a set of vortec heads for $125, less than 20k miles which i think is a good start........

[Old88]

In most cases a cast crank, PM rods/w good bolts and Hypereutectic pistons will get you to 400hp....Unless you wanna stay on the throttle all day long............

If you wanna go higher, dig deeper in the pocket....

Turbo/blower/nitrous engines like shorter rods
NA motors benefit from longer rods.

If you are "definitely" gonna go boosted/squeezed in the future, you gotta set the clearances a little differently than a NA motor. Ring package and gaps, piston pin/wall clearances, and bearing clearances need to be addressed, not to mention cam specs. If you don't boost it, you will be stuck with a motor that may not perform/last as well as it could. (excessive ring gaps/piston clearance meant for pressurized conditions are not condusive to longevity/performance in an NA motor).

That blower cam with 114* LSA ain't gonna perform as well as it could without boost

That rumpity cam with 110* LSA will run fine till it sees 10 PSI.

That 9.5:1 comp ratio for your 400hp 383 will be prone to detonate under 10 PSI, so you back it down to 8:1.....Bye Bye 400HP till (if/when) she sees 10 PSI

If I were to boost/squeeze anything with the intent of obtaining over 150 additional HP with it I would definitly get to know what 4340 is (crank/rods)

Stay away from forged 4130 stuff, 4340 is better.

Decide what you want.

[NorCal_z71]

old88: i know on the NBS trucks, the guys running the STS turbos pretty much just slap them on, tune and go. Are the Gen III's just designed better for this situation, or is this actually somewhat of a bad idea. I am thinking about adding an STS style setup down the road, maybe 5 psi, on top of my 383 that was built to be N/A. Would this work effectively the same as the STS for the gen III's, assuming i use strong enough parts initially to take the boost later?

[badburban]

Once again Old88 nailed it right on the head.

NA and FI engines and especially Turboed engines require radically different cam timing requirements and different build requirements (ie ring gaps etc). This is something you have to keep in mind from day one during the parts selection even before the build up. Once you want to make boosted power on top of that set up Id look heavy into 4340 stuff if you want any kind of longevity. Can you say ouch. As for gen III stuff metallurgy has come a long long way. There are guys pushing 1k+ rwhp on stock cranks. It can be done but they only rack up mileage 1/4 mile at a time. So longevity or outright power. You cant have both.

Now if you build with turbo in mind and look at 8:1 or 8.5:1 and take your time in careful crank and rod preparation (assuming you start with good stuff. Scats cranks are 80-60-06 which isnt bad. Actually stronger then a 1053 forging I beleive) and you dont want much more then 5-6 psi you'd probably be ok.

Josh

[Old88]

The stock cams have a wide LSA
That's why it's a plug/play deal

Josh cam set you up with a cam, if you are going to inject it you need a wide LSA anyway.

I can guarantee you that if you can adjust the boost, if 5psi is good 10psi is better.

It's better to build for 10psi and run 5psi
Than build for 5psi and run 10psi

[NorCal_z71]

I see, so basically if it will be turbo'd eventually, then I will need to drastically change certain items to prepare for the boost as opposed to the gen III's which can go basically stock other than tuning with 5psi+? If so build 1 might need to be N/A, then begin again down the road with boost in mind.

[badburban]

Even then a gen 3 would benefit from a proper camshaft. The factory stuff has wide enough gaps you probably dont have to worry about anything but for a performance oriented engine an NA motor can run a tighter ring gap to lower blow by without worrying about touching ring ends together. But add in the extra head of forced induction and normal hypers like to pop the top of the piston off. What kind of budget you working on here. Im guessing a semi tight one. You have enough money for decent parts but nothing spectacular. Id say build a good NA engine now and then later on when money is available build a maximum effort turbo oriented engine then.

Josh

[NorCal_z71]

i think that might have to be how it goes. Perhaps i can find the middle ground, but still a 383 is going to be an insane improvement over the current dog of a 383. How much am i looking at in rods, pistons, crank, cam, etc? Also, the heads i found are bare so they will need to be re-assembled with new parts.

[NorCal_z71]

what the ffawk? is there a reason youre spamming my posting/PM?

[jshouse]

stick with what you want. i too had a lot of people saying i was picking the wrong parts for my combo, and although i am trying to scale it down a bit for more streetability, when i built it i wanted to race it. dont let people talk you out of using what you want. the only reason i went with my own parts is because i did the research and knew they would work.

use the tbi, not many people do and it will be a little unique.

[papa_smurf49319]

6 inch rods here

[Scharged Caddy]

i run a 5.7 inch rod, supercharged everyday, run great :sniper:

wiesco pistons and eagle rods.

[vortec stroker]

5.7's here also.

[Stroker 1500]

5.7 here. 4340 crower rods, keith black pistons, and 4340 callies crank :)

[NorCal_z71]

rc.....how much did you pay for that stuff if you dont mind me askin'

white90....what injection are you running? carb, tbi, tpi vortec?

[Scharged Caddy]

rc.....how much did you pay for that stuff if you dont mind me askin'

white90....what injection are you running? carb, tbi, tpi vortec?

ah the crank was the eagle 4340 forged in summit, i think 750.00 and then the rods were 350.00 there full floating pin with spiral locks and the pistons were 600.00, there wiesco pistons. i also have some total seal plasma moly rings. they were 220.00 a set. im running a 750 holley mechanical secondary carb. i had a 600 holley it was restricting boost. carb was 350.00, the blower was 1800.00, my heads are just pocket ported and have bigger valves. valves 2.02/1.6 were 100 bucks and 250 to cut the heads with a fresh rebuild and 5 angle valve job. theres some odds and end stuff, but it all adds up kinda fast. i also run an msd distrib, and 6AL box with msd boost retard and msd knock sensor. im still messing with the tuning.

[NorCal_z71]

right on man, sounds like a sweet setup