engine size???

[415ss69]

well the engine in my daily driven chevelle has defiantly seen better days im getting some
Substantial blow-by my question is with keeping my current top end:ebrock rpm 64cc heads rpm air gap intake mighty demon 650 and sn93 with h.o.impeller what engine size would you guys recommend..

335ci....355ci...383ci..or 415ci i guess these are my choices let me know what you think and maybe some feedback thanks

by the way im currently seeing 5.5lbs if boost with a 355

[JPJP]

The SN's are designed for up to about 360 CU-IN. Anything above that they are acting as a restriction.

[Michael]

I'm with JPJP on this. Anything beyond the 355 and the SN won't show much gain; on a 383 the boost will be very low.

But I think the SN is only one part of the puzzle. A 650CFM carb may prove to be a bit small for anything below 355. The Edelbrock RPM heads aren't bad but they're a bit dated in their design. A set of AFR 195 or 220 heads will prove far better; take a look at some of the new Brodix heads, they're really good if you're looking to go with big cubes.

However, getting back to your original question, if you're looking to stay with all the top-end components you already have, then my vote would go to the 355. It'll allow you to continue to use the SN93 as is, and it'll give you a nice bump in power.

If, however you can get your hands on a VR-4 kit, then I'd be looking at bigger cubes for sure. A 383 would be nice, as would a 415 or even a 421. Personally, I'd go with a 396, but that's largely because it has a nostalgic sound to it and I like the way the numbers roll off the tongue. Besides, everyone and their grandmother has a 383.

Regardless of which engine you decide on, I'd spend the money in the right places: splayed 4-bolt main caps, good quality rods and pistons, and a solid 4340 forged crank. All these would be for if (and when) you decide to get even more power from the engine later.

[Buck-Strickland]

Daily driven, then go with a 350. Keep your heads, but step up to a hydraulic roller cam, new valve springs. Forged pistons, good rod bolts, and you should be fine for the 5-7psi. Good usable combination.

If you go to a 406-421 you'll see a large loss in MPG. Plus there would be no reason to use the SN, unless, like previously stated you go to a VR-4.

Weekend only: 421cu in, AFR 205's, Hydraulic roller 230+ @0.050, no blower. It'd run 11's all motor.

Any more power than the two above, and the chassis would really need to be sorted out. (= More $$$$)

I'm considering stepping down in Cu. in. and up on boost for my next build. More MPG, same power. 406 to a 355 or LS 5.3

Just my 2 cents, everyone has an opinion.

[415ss69]

well im on a budget the 355 is definitely my cheapest option 4bolt caps with decent rods and forged pistons for like 1100$ the 335ci is about 400 dollars more im pretty much trying to work with what i got would the shorter 3.25 stroke run better with my combo

[Michael]

I think Buck hit on something that might be worth considering as an option: an LS engine.

If you're willing to go with an iron block LS engine, instead of an all aluminum version, they can be had for almost nothing right now yet they will accept all the same go-fast parts as their aluminum brethren. And the performance numbers they are capable of are UNREAL!

It certainly doesn't help with your "I'm pretty much trying to work with what I've got" requirement, other than maybe reusing your SN93 (which would still require custom mounting brackets), but it's worth considering all the same.

As for the shorter stroke crank, if it will cost you more to go with less cubes, I'd say stick with your plan to build a 355. The shorter stroke would definitely make for a real screamer, but let's not forget you're pulling around a Chevelle... that's not exactly a light-weight. I'd opt for the bigger cubes (more torque) for that reason alone. The lower cost is a nice bonus.

[Buck-Strickland]

I agree with Michael.

[Michael]

I agree with Michael.

:laugh: Which part? The LS engine part, or the "less cubes for more money" part?

[Buck-Strickland]

Build the 355.

[69fury]

I'm gonna have to throw in a different opinion. Big cars need torque to get going. My Fury was 4100lb race weight, my 360 mopar has a 4 inch crank for 415 inches and the extra torque of the line is what got her going.

It's pretty had to build cheaper than a 383 chevy buildup- search around a bit. The 383 would give you more grunt down low.

Remember- the SN is still moving the same air/rpm. True the gauge will read less boost-but that's only a measure of restriction, anyway.

Now it's gonna be a cooler charger since there will be less restriction.

Maybe it will only be a gain of 30% instead of your previous 40% but remember- that 30% is now based on the meatier 383inch mill.

Granted the percentages i'm using are just thrown out there, but keep in mind- my 415 made 460hp and 520 lb/ft and maxed out at only 618 cfm going into the carb using the turbine hat to measure it.

-rick

[Buck-Strickland]

I think it depends on "Street Car" or "Track Car". He said it was for a "Daily Driver", so I'm thinking "Street Car".

I run a 406 in my “Track car”, 72 Olds Cutlass, and yes getting it out of the hole requires low end grunt. But, I run Drag Radials and have a suspension setup to take the hit, 1.57 60ft. Most "Daily drivers" would never be able to use the power I make down low. A normal suspension and radial street tire would just go up in smoke with the torque.

I could be wrong, but most "Daily Drivers" smash the gas when they are already rolling. A 350 with instant boost available from these SN units would feel mighty strong. Also, it would get decent mileage while driving normally.

In my opinion it's best to be realistic about how the vehicle is going to be used, and what can be afforded (read, broken parts replaced). It's easy to make power these days, but it's still expensive to up-grade an entire car to handle the power you can make. If you can afford a 500hp motor then make sure you can afford the parts to go along with it, axles, transmissions, suspension upgrades, larger fuel lines, etc. If you can't afford the other parts, then build a car you can enjoy without worrying about breaking it.

Yes, 383 kits are dirt cheap, and the added 30 cubic inches would be worth 40-50 ft/lbs of torque down low. But, gas isn't getting any cheaper. If it was a naturally aspirated engine then I agree go big, but with the blower there is no reason too. Look how fast all the 302-347 SBF's with blowers are. My buddy gets 20mpg on the way to the track and runs high 10's with 332 cu in SBF with mild tune and single digit boost.

Nice thing about a supercharger/nitrous is that you have the power when you want it, but don't have to feed it all the time.

Different strokes for different folks. Not saying I'm right or your wrong, just my opinion.

[69fury]

I think it depends on "Street Car" or "Track Car". He said it was for a "Daily Driver", so I'm thinking "Street Car".

I run a 406 in my “Track car”, 72 Olds Cutlass, and yes getting it out of the hole requires low end grunt. But, I run Drag Radials and have a suspension setup to take the hit, 1.57 60ft. Most "Daily drivers" would never be able to use the power I make down low. A normal suspension and radial street tire would just go up in smoke with the torque.

I could be wrong, but most "Daily Drivers" smash the gas when they are already rolling. A 350 with instant boost available from these SN units would feel mighty strong. Also, it would get decent mileage while driving normally.

In my opinion it's best to be realistic about how the vehicle is going to be used, and what can be afforded (read, broken parts replaced). It's easy to make power these days, but it's still expensive to up-grade an entire car to handle the power you can make. If you can afford a 500hp motor then make sure you can afford the parts to go along with it, axles, transmissions, suspension upgrades, larger fuel lines, etc. If you can't afford the other parts, then build a car you can enjoy without worrying about breaking it.

Yes, 383 kits are dirt cheap, and the added 30 cubic inches would be worth 40-50 ft/lbs of torque down low. But, gas isn't getting any cheaper. If it was a naturally aspirated engine then I agree go big, but with the blower there is no reason too. Look how fast all the 302-347 SBF's with blowers are. My buddy gets 20mpg on the way to the track and runs high 10's with 332 cu in SBF with mild tune and single digit boost.

Nice thing about a supercharger/nitrous is that you have the power when you want it, but don't have to feed it all the time.

Different strokes for different folks. Not saying I'm right or your wrong, just my opinion.

I agree with what you're saying about street vs. Strip- but i wanted to let you know that my 415 was grandma docile- daily drive it any time you wanted-

Remember- the bigger the engine, the more mild and drivable any cam becomes- the only "Strip" part was the sticky rubber that let me put it all down without any hesitation.

You're also right about the rest of the build being able to handle the power- I have no idea about the Ford stick shift power ratings but the old school 3 speed automatics T350, Mopar 904 can easily take 500 hp in good stock condition with a shift kit-the T400- Mopar 727 are good for maybe 650hp before having to spend a nickel.

Any healthy Chevelle powertrain should be fine with 700hp at the wheels- Remember they were built before computer finite analysis design/engineering- they were built with overkill for strength.

As for fuel mileage- you're probably right that a 383 will eat more.-cant argue with that one.-but we're talking about hopping up a Chevelle so 30 cubes might be worth it.

You've got a lot of valid points-there are alot of things for a guy to consider. The hardest thing for people to do is to be realistic as to what they want and how it's gonna be used. I've blown that one a few times-now i tend to do more planning regarding the end product.

rick

[415ss69]

thanks for all the feedback i still have a few more weeks before i can start laying some bucks down I imagine im going with a 355 it all depends on how much spare change i can dig up