383 vs 355

[skinny z]

I honestly think if the cam was on say a 108 or 106 the full exhaust wouldnt like it.

The would say the exhaust is key.

[RevTheory]

I honestly think if the cam was on say a 108 or 106 the full exhaust wouldnt like it.

The would say the exhaust is key.

Fix the exhaust so you can give the engine the cam it wants. If you can't fix the exhaust, I guess it is what it is. Bandaid the cam. Again, just my opinion.

[skinny z]

I honestly think if the cam was on say a 108 or 106 the full exhaust wouldnt like it.

Fix the exhaust so you can give the engine the cam it wants. If you can't fix the exhaust, I guess it is what it is. Bandaid the cam. Again, just my opinion.

The OP may get some benefit from this.
This has come up more than a couple of times in reference to a tighter LSA and pursuit of the next new engine. Many bits of advice relate to the effectiveness of the exhaust. So much so, I'm tending to list my spec as "open headers with suitably sized collector/secondaries". If nothing else it tends to level the field when it comes to a discussion.

[RevTheory]

I really don't see a pair of 2.5 inch pipes being an issue at this hp level as long as you've got a crossover to split muffler flow when 8/4 and 5/7 hit each of their sides (not all four, you know what I mean) basically at the same time. Anti-reversion at the right length would be a good idea if you're over say 218* at .050 on a 108.

I know for sure that a full-length pipe without any attention paid to tuning lengths, a/r or any of that stuff is a torque-killer.

[mt-engines]

I honestly think if the cam was on say a 108 or 106 the full exhaust wouldnt like it.

The would say the exhaust is key.

Fix the exhaust so you can give the engine the cam it wants. If you can't fix the exhaust, I guess it is what it is. Bandaid the cam. Again, just my opinion.

It made 265hp and 435lbft at 3200rpm.. thats way more than stock. Just because a book salesman tells everyone to run a 106 lobe sep doesnt make it right. Saying a 112 degree lobe sep wont run is just more BS.

I guess the cam was way off, ill call the customer and let him know.

[BOOT]

I try to follow some cam guidelines and from what I can tell nothing is concrete with cams combo to combo BUT I've also herd a higher LSA with full exhaust works better and lower lsa with short exh.

Now for my project truck, I plan to just use a cam I already have summit 1103 .444/.466 lift, 214/224 dur and 112 lsa AND prob 1.6 stamped rockers I also already have. Exhaust will be 1.5 shorty's Y into a 3" single perforated tube muffler dumped at the pass side before the axle. LT headers would be more ideal but I got bout $150 into headers & Y pipe and just looking for something with a bit of zip.

350, Vortec heads with mild blend, 6000rpm dual plane cleaned up, 650 dp, nv3500, several tricks/odds&ends for a bit of extra.

[KnightEngines]

port the pro max heads. do a cam swap on the 355. a basic mild roller and some port work should be an easy 430hp 440lb ft

Winner!

There is plenty left on the table without touching the short motor.
Port the existing heads, around 260-270cfm intake, 190-200 exhaust is plenty, 2-2.1" mcsa.

252/256 on 107 centres solid flat tappet, put 1.6 rockers on the intake.

Get compression up to 10.5-11:1

Switch the intake to a vic jnr with a match port.

Job done, that'll make 460-470hp & leave a smile on your face.

[mag2555]

On your current 355 what is the hot cranking compression you have, I hope you will say 175.

If not then that’s the root cause of your motor not putting a smile on your face!

Even if your heads only flow 240 cfm@28” and your running a tad more valve lift then needed to access that flow then with the needed cylinder pressure you should have a 450 hp motor without question !

[BOOT]

How much does the truck weight?

[RevTheory]

port the pro max heads. do a cam swap on the 355. a basic mild roller and some port work should be an easy 430hp 440lb ft

Winner!

There is plenty left on the table without touching the short motor.
Port the existing heads, around 260-270cfm intake, 190-200 exhaust is plenty, 2-2.1" mcsa.

252/256 on 107 centres solid flat tappet, put 1.6 rockers on the intake.

Get compression up to 10.5-11:1

Switch the intake to a vic jnr with a match port.

Job done, that'll make 460-470hp & leave a smile on your face.

Holy smokes, man, he just wants to light up the tires and have some fun. 252*?

[dfarr67]

port the pro max heads. do a cam swap on the 355. a basic mild roller and some port work should be an easy 430hp 440lb ft

Winner!

There is plenty left on the table without touching the short motor.
Port the existing heads, around 260-270cfm intake, 190-200 exhaust is plenty, 2-2.1" mcsa.

252/256 on 107 centres solid flat tappet, put 1.6 rockers on the intake.

Get compression up to 10.5-11:1

Switch the intake to a vic jnr with a match port.

Job done, that'll make 460-470hp & leave a smile on your face.

If the heads are done right- no reason not to use them on a later 383. So it is money well spent.

[dfarr67]

I didn't see anything about usage. If you want to make the brick faster, add more cubes. If you want more towing capacity, add more cubes. If fuel economy matters and you spend a lot of time on the highway, tune the 355. I work my C20, so a 400 with Vortec heads was the best and cheapest answer.

I would argue my 4x4 with a 383 TPI returns at least as good mileage as the 355 ever did, never shifts out of OD up the hills. I had a choice at one point to go with either displacement- I made the mistake of staying with the 355 and kicked myself until I had a chance to change up. Its not night and day, just some more torque.

[Rick!]

Nice! Yea mines a 95 short bed single cab 2wd. I'm running a 28" tire so its fairly small as far as truck tires go. The current 355 has a compression ratio of about 10.5:1 running 93 premium gas only and I put down a little over 300 to the tire. Maybe the engine is making close to 400 and i'm loosing 100 through the drivetrain, but i'm more inclined to think that it's making closer to 350 and im loosing about 50 through the drivetrain. Either way, i'd love to pick up 50-75 rwhp.

Drivetrain losses are typically 15%. Divide your chassis dyno number by .85 and all you have is around 350hp, give or take a couple.

To make a 1/2 ton happy, you'll want around 400hp, maybe more if the rear tires are sticky as they shorten the burnout.

Not quite sure about the LSA argument, even 5.7 Hemi after market cams are in the 112-113 LSA with good torque with HP pushing 450 easily.

Carry on.

[skinny z]

Not quite sure about the LSA argument, even 5.7 Hemi after market cams are in the 112-113 LSA with good torque with HP pushing 450 easily.

It comes down to the efficiency of the cylinder heads and as it pertains to a SBC with a 2.02" intake valve and average valve seat. That tight LSA for the given CID pertains to the Gen 1 SBC architecture. Outside of that and all LSA bets are off in that regard.

[BOOT]

Not quite sure about the LSA argument, even 5.7 Hemi after market cams are in the 112-113 LSA with good torque with HP pushing 450 easily.

It comes down to the efficiency of the cylinder heads and as it pertains to a SBC with a 2.02" intake valve and average valve seat. That tight LSA for the given CID pertains to the Gen 1 SBC architecture. Outside of that and all LSA bets are off in that regard.

Yup I rem that from comparing LS stuff the better the heads