Big difference in an 4.500" bore engine and a 4.310" bore engine. A single plane is better suited for a Big Bore engine due to the amount of cylinder fill area you have initially. The Dart intake is a good piece. It is currently getting "tweaked" by an intake designer and I look for Dart to introduce an next generation in the up coming months.

Chris

I have both victor jr's now. I'm still on the fence as to putting the motors on a dyno simply because of cost. I am very curious as to what horse these motors will make. The set up seems to be a solid one without being overly aggressive.
I have also heard that the larger bore is FAR better suited to airflow as the 454 or 468 even, still crowds the valves. So in the end, maybe the difference will not be all that significant...

Brian,
The following dyno chart will provide some interesting information regarding your decision as to the correct intake manifold for your 468 cid engine. The test was performed on the same engine as yours (468 CID Chevy big block/hyd flat tappet), the only changes from test to test was a swap of the RPM Air Gap manifold for the Victor Jr manifold, both with 1” spacers, for a basis of manifold comparison only. There were no other tuning or component changes. It is “apples to apples” with no other variables to be considered. The test engine is nearly identical to yours, however what differences there are may affect the total HP/Torque figures, it will be a clear indicator of what manifold will operate the best in your particular application and required rpm range. Your cam has slightly more lift and duration and a wider LSA than the test cam (236*/246* .553/. 571 on 114* LSA vs. 230*/236* .552/. 555 on 110* LSA). Keep in mind these will move your engines HP/Torque peaks higher in the rpm range than the test engine.
The results.
The Air Gap produces significantly more torque (nearly 30 lbs/ft @ 3900 rpm) and HP (20 hp @ 4200 rpm) throughout the entire rpm range until 5000 rpm. The Victor Jr does not surpass the Air Gap in either category until above 5400 rpm. The Victor Jr does make 6.3 more hp and 8.8 lbs/ft torque @ 5700 rpm.
This test would indicate that unless you are propped for 6000+ rpm @ WOT, and do the majority of your running @ 4500–5700 rpm, the Air Gap would be the clear choice for the 468 CID. The full test and build sheet are at this link.
http://www.carcraft.com/techarticles/116_0109_big/
Bob

Good read Bob, as I stated in No.8 post on this thread. . .Airgap.

Chris Straub
Stef's Performance

Bob and Chris,

I should have known better...

I'd still like to dyno them because of all the reasons Bob gave me...

Brian,
It depends on what type of running you want to do, RPM range you run, and how much pain you want to put your wallet through. Like they said earlier, dual plane works good under 5000 RPM, but start to lose some power as they climb. The single planes are made to produce power all the way to the uper RPM range around 9 grand. with a bigger motor, especially a 468, I'd go with the dual plane. You might sacrifice a little low end, but whoever wnats to run you will deffinantly get smoked!! Have fun!

Ran stock hi-rise dual plane manifold(Winters)with 1" spacer on a 468 with 9.6:1 compression.
Had Crane 731 cam,800 Holley,Stainless exhaust.
Engines ran out at 5,600rpm with 475HP
Went with port matched Victor Jr. and saw no increase on top.
Actually boat planed out easier with dual plane.
Had better torque on the bottom with dual plane manifold.
Mo money wasted.............:rolleyes:

Brian,
Hey we all have to learn, I over cammed my first hotrod. I am a nobody and a "Who" to most on this board. I work with engine builders only across the nation and the world. We make oil pans. But I get the "low down" from the top engine builders in the country, hell on most sundays 37 out of the 43 have our stuff on them. So when I say top, I mean the professionals. Since I have to live with my customers, I have to have the right answer or they loose trust in you.

Chris
Stef's Performance

I'm running Brodix single planes w/1050 Dominators. Valves are .225/.188. Runs good, idles good:cool: :cool:

Very impressive article on the Air-Gap vs. a race prep single plane. I would like to see an extrude honed AirGap used. Best of both worlds.

Chris,

I DO NOT want to upset or alienate anyone that has been friendly enough to give advice based on their experience.

Having said that gentlemen, Chris knows his stuff. He just won't brag about it.

Chris, I purchased these intakes and because of money I'll put them on until I find Air Gaps. I didn't realize who you were until Bob told me. Thanks for taking the time.
Thanks to everone else, too. I will post results of what we find...

Brian,
Don't listen to Bob, I like to under the radar. I am forturate to love what I do so that makes the job easier.
I am not here to hack anyone off either and I love the input that everyone gives. I am lucky that I have been in situations that are the "what if" sceneros and have thrown 5 different intakes at an engine to see what it would do. I can't stress enough with these marine bullets, don't get hung up on HP numbers, that is a calculated number, the torque is what is measured.
Good luck with the install.

Cobra,
The extrude hone is neat stuff but it works better on a fuel injected application. Intake surface texture needs to be rough to promote laminer flow. . .simple terms this is an undercurrent that is created right above the surface of the intake. This "air highway" helps to carry the atomized fuel/air into the bowl area of the head and to the intake valve. With a smooth surface the fuel molecules will drop from suspension at lower velocity and hamper good combustion events.

Chris
Stef's Performance

I used the air gap on my 468 also. As I wanted to spin my engine a little higher than the standard RPM

Thanks Chris. Many people would charge for all of the advice you gave. I owe you a beer...

Bryan

Re: Big Block Chevy Intake decision
 

Diggin up bones here.... Any update on performance with the Victor Jrs Brianspeedracer?

BT

Re: Big Block Chevy Intake decision
 

bt,

I have not run these motors. I ran short on time before winter came so I put them in the boat (No indoor shop). I did put Victor Jr's on with a 2" HVH spacer as my carbs are a little large (850). It's a comprimise for sure. Before I started this I wanted the boat to go like hell. Now I just want it to be reliable. I'll update in the spring when I get it out on the water.

Re: Big Block Chevy Intake decision
 

I'm going to try a set of victor jr in the spring too brianspeedracer. Right now I run edelbrock rpm performer dual planes. I think victor jr will be an improvement. I really don't care about torque under 4500rpm. I want the power coming on at 4500, not tapering off like a dual plane. Should be a good test. If I don't like them I will sell them next winter....

BT :cool:

Re: Big Block Chevy Intake decision
 

bt,

What is your engine set up? I'm running 468's with GM 990 heads at 9.5 to 1 comp. Valves are 1.88/2.25. cam is an isky 114 centerline marine cam (I've forgotten the duration/lift (I'll post later). My machinist used Isky springs as well. Crane Roller Rockers. Comp Cams pushrods. Nothing exotic, probably more of a compromise between opinion, experience, and finally money.
If I had to give advice from my experience, it would to be more conservative than experimental in a build-up. I found many, many opinions on the correct set-up. I now understand why the top marine builders command themoney that they do. Lots of destructed parts. I enjoy building these things and I value the experience that comes with it (although trial and error at times...). Ultimately, I'm too short in the pockets to just write checks without learning anything other than theory...

Re: Big Block Chevy Intake decision
 

My engines are 469cid (.070 over) and running ~9.5:1 compression. Edelbrock rect port heads, as of a few minutes ago (found bad lifter) I am going to run .564/.570 278/288 111cl flat tappet cams. I was running .544/.564 .270/.278 111cl with good luck. Changing to the single plane moves the torque band up considerably on my dd2000. That is why I am thinking Victor Jr. That and the hp500s ran single plane w/ 800dp. I have better exhaust than the hp500 so I think even though I have less cid, I will be able to utilize the flow better. That is one thing about this whole thread never mentioned, exhaust. That has a significant bearing on induction selection. Dual planes constrict the free flow to 1/2 of what the single planes offer. Hopefully I don't push my torque too high. Looking to run at about 5400rpm max. With this setup my torque will peak at 4000 rpm, my hp at 5500. Peak VE between 4500rpm and 5000 rpm at 93.5% Just the way I think it should be for WOT max pumping efficiency.

BT :cool:

Re: Big Block Chevy Intake decision
 

My cam specs are as follows...

Advertised. Int. Exh.
Degree 280 292
valve lift .565 .590
@ .050 232 244

Re: Big Block Chevy Intake decision
 

Is that a flat tappet speedracer? If so what is the part number and mfgr? I have been looking at a comp cam 11-240-4, 564/567 278/292 with a 112LS. Wouldn't mind checking yours out if you have the info handy.

BT

Re: Big Block Chevy Intake decision
 

bt,

It is flat tappet. The cam is an Isky 280/292 Mega Hyd. (marine grind)

Re: Big Block Chevy Intake decision
 

Do you have the Intake centerline and lobe seperation angle specs?

BT

Re: Big Block Chevy Intake decision
 

At the risk of hijacking the thread, how much can be safely bored on a 454 block? Is it any different for a marine application?

Great info on the intakes everyone!!

Re: Big Block Chevy Intake decision
 

I believe mark IV 454s can go to .120 over, depending on how much hp you are pushing. The wall starts getting weaker and moves more the further you go. Problem with most marine engines (unless closed cooled), is corrosion is working on the other side of the cylinder wall to make it even thinner. There are things that can be done to counter the flexing wall issue, like putting cement in the water jackets to stiffen things up. I run closed cooling, so the .070 doesn't bother me a bit but without it I think I would start getting nervous over .060 over.

BT :cool:

Re: Big Block Chevy Intake decision
 

Does anyone have an opinion on the Isky cam mentioned above? Good, Bad?

Re: Big Block Chevy Intake decision
 

bt,

I do not have those specs, sorry. I remember looking up the cam on Isky's site. I don't believe that they had it there either.