edusmc1

427Hotrod

Need to look at ALL the flow numbers to at least get an idea. The valve is only at .500 for an instant...but it's at 200,300, 400 twice and all points in between.

Those 041's are doing pretty darn well..must be some good work on them.

How high do you actually rev it? Gears? Trans? Induction? What are duration numbers on cam?



JIM

76strokervette

I would go with the 195 because it will not hurt the performance anywhere and it can support more power
if you decide you to upgrade later.

naramlee

Engine masters on youtube did a bit on this from 160, 180, and 210 heads myth... basically there was almost no loss on the bigger heads

go bigger

The Money Pit

I think you need to do some soul searching to figure out what you are really trying to accomplish. The cam you have is tiny, and so a head swap really isn't going to amp up the power much...I'd guess 20 horsepower, which you probably will not even feel. For the money spent on heads...that's not much gain.

Depending on your ultimate goal, and the existing combination...gears, stall,...a cam swap might be a cheaper, and far more productive course of action. Once the cam is in, you may then realize the engine can use more head flow. and a head swap will really be worth the expense.

jb78L-82

I went through this issue in 2014 with my L-82 355 during the rebuild with my expert builder (undergraduate engineering major plus 16 years as a GM field Tech teaching GM mechanics around the country.).He really knows his stuff and builds real high performance GM motors and tests them......I go by what HE SAYS and everyone else is commentary/opinion, for the most part.

My engine is a 355 with AFR 180's, compression 10.2:1 with howards roller cam (.525/,525 lift, duration 219/225, LSA 110 operating range-1,500-5,600 RPM) and my research indicated that the AFR 180 would be best and supported by my builder for my motor. Bigger heads are NOT going to offer more flow without some penalty depending on the motor. Peak flow is not the whole story since flow at every cam lift point matters. Since my cam operates in the range sub 6,000 RPM and I was looking to maximize mid range torque, the AFR 180's had the best combo of peak flow, mid lift flow and port velocity which effects throttle response. The AFR 195 would provide slightly better peak power on my motor with my cam BUT would hurt low to mid range TQ. I would not slap on bigger heads and think there is no downside, without the right combo of parts...there is!

For your 383 with a cam that has the same operating range as mine, I think you would want to go AFR 180 but being a 383 which is marginally bigger than a 355, AFR 195's would be better suited for the right cam for that motor, as a very broad comment, if you intend to rev beyond 6,000 RPM.

MajD

Check this link out:

http://www.wallaceracing.com/flow-rpm.php

Using that calculator, a 383 running at 5500 rpm requires a head capable of flowing 202 CFM. That's assuming 100% volumetric efficiency.

MajD

edusmc1

Jebbysan

This is a difficult decision......but I think here I would do the 180 and get the small chamber to get the compression as high as possible......the small heads and the fast burn chamber with high compression would be a wonderful street brawler that would light throttle cruise like no other.......
This is if you do not plan to upgrade later......in that case, the 195 is a better choice in the long run.
The 180 would have brutal torque with that cam....it would feel like it has power everywhere......less shifting.

Jebby

427Hotrod

jb78L-82

This description is my motor with decent compression, AFR 180's, and the howards Roller cam described above...AND it is a 355, not a 383!!!!!!! Those AFR 180's with the right combo of parts on the right engine are magical..........

HeadsU.P.

Just cruising, going to the store, going to car shows, traffic-light to traffic-light burst, I wouldn't worry about 15 cube difference. Its not Super Stock racing.
The 180s will be fine.
Just like carb CFMs, bigger is not always better.

Buccaneer

I have both the 180 Dart heads and 195 AFR heads. Which do I like...both. They both did and do the job on my 383, but I happen to like the 195s that are on it now with the higher CR and much bigger cam. I breaths like crazy mid range and up top of course. I should be going to the track in the near future and see how it runs compared to the old 383 motor. 12.95 ET with the old motor running CFI.

Surfer69

I have the 195s with 383 and half an inch lift and 110 LSA on cam. I love them and see no loss at low end either. That's my vote.

condor7

May not be the correct thread but close enough. I currently have a 355 with the Howards (111145-10) retro roller cam, 110 LSA .510 in, 525 ex with 1.5 roller rockers. the operating range is 1500-5600 which I am very happy with. Moving on, heads are Dart 180 SHP 64cc. Intake is a Edelbrock Airgap performer 1500-6500 RPM Range. Have installed a Holley Terminator some time ago and it is great. I recently installed a dual sync distributor for the addition of running CNP with LS7 coils. Everything works great. Have a TKO 5 speed with a BB 308 rear. The combination is perfect for my cruiser and I keep up with C7's all day long without any issues. About 2K RPM at 70 MPH. So my question is; I am wanting to go to MPFI using the Holley Terminator (which is a Holley HP). My problem is I don't understand the relationship between a dry runner intake (MPFI) and a wet intake (TBI). The CFM or RPM range has me confused. I only see MPFI manifolds starting at 2200 RPM. Most start at 3000 RPM and go up. I want the intake manifold to compliment my current cam and heads while using the benefit of MPFI. My dilemma is will a broader RPM intake cause my combination to go out of wack? Will as an example an intake manifold (MPFI) with a power band of 3000-7000 be okay without having to change the cam or cylinder heads? Would i just be loosing a little low end torque? I don't race the car but do some spirited driving when with the big boys. I hope I have provided enough information to get a good answer. I have built engines in the past being careful to match parts to get the best performance from the engine, I don't want to screw up my current setup by having an intake manifold that has runners to large for what I want. Thanks for any help and I do apologize if this is not the right place. Not trying to hyjack the tread, just looking for a little advice.

NewbVetteGuy

195s for a 383 and if you currently have 1.5 ratio rockers, buy a set of 1.6 ratio rockers for the intake side.

You want to size heads based upon the min CSA, not just the advertized port volume. You'll find that AFRs have a slightly smaller min CSA for every volume vs. most other top-shelf heads (Because their port designs are so dang efficient.).

The correct formula for determining how big of cylinder head you need (This formula is focused on flowing the air at max port speed at your RPM peak for your cubic inches):
MIN CSA = (bore x bore x stroke x RPM x .00353) / 613.8 (.55 MACH x 1116 fps)

The AFR 195 COMP head has a min CSA of 2.1 or 2.15", which is EXACTLY what the engine builder calc says you should have for a 383 with a 6,000 RPM peak.

• SBC 383 Version: 6,000 RPM peak
  • Min CSA= (4.03" x 4.03" x 3.75" x 6,000 RPM x 0.00353) / 613.8
  • 1290/613.8
  • 2.1" Min CSA

Adam

condor7

I have virtually the same set up except my heads are Dart SHP 180's with scorpion roller rockers. Plenty of power. Currently running a Holley HP with the Terminator set up, dual sync distributor and CNP using LS 7 coils. Considering moving to the MPFI system using the Holley HP but almost all MPFI manifolds start in the 2000 RPM range and go up. Do you think a MPFI manifold starting at the 2K range will make much of a difference? I mean significantly reduce power from the engine? Some of these EFI intakes start at 3000 RPM. I think they are for larger displacement small blocks. Currently using the Edelbrock Air Gap dual plane with the center cut down (Factory) spread bore. Runs out of steam at 5500 I think but that's not important. Not used for racing.

Jebbysan

Pay little attention to advertised powerband number on intakes for EFI. Run a single plane intake with a medium size runner to keep the velocity up.
Do you know why a dual plane works better down low? Because the 180 degree left/right pulses "signal" the booster better than an open plenum. That's it.
EFI needs no signal...the fuel is introduced.
You will lose no power anywhere given the EFI is tuned correctly.
Why not go to a large runner intake then? Because you want to help speed up and keep sped up the airflow right down through the runner into the cylinder.

Jebby

REELAV8R

condor7

This was really the answer I was looking for. Thanks for the information. meant for Jebbysan