Intake Manifold
 

I am looking to replace my existing air gap intake manifolds for next boating season. The manifolds are 4 seasons old and with the part saltly waters in my area I'm afraid that they will start leaking soon. I was looking on the internet and came across a BBC intake made by Speed Master. The price for this is almost 100.00 cheaper than Edelbrocks. Has anyone heard of this company? why so cheap.? Also if i switch to a single plane manifold (which they also have Polished for 169.00) will that help my performance or hurt it. Will I have to re-jet my carbs. My dyno sheets show 490 HP @ 5200 rpm. Nickerson 930 holleys.
Thanks

http://store.speedmaster79.com/p-277...old-satin.aspx

http://www.store.speedmaster79.com/p...-polished.aspx

http://www.store.speedmaster79.com/p...-polished.aspx

You get what you pay for. Well, except with Nickerson.

I've heard single plane manifolds are usually for high RPM applications, you could end up screwing up your complete tune

2 words

chinese knockoff.

will it work,maybe,probably never feel the difference in performance,,good or bad.

Never heard of them, so who the H E L L knows.

You could always check locally for a place that does Hard Anodizing for aluminum. That will give you a handful more years on a new intake. price will probably be under $200 per intake. Watch out, since it makes it electrically dead, your temp sensor probably won't work. Don't worry - you can run a small ground wire to it and hose clamp a male spade terminal to the temp sensor's body to ground it. Yup, obviously I've done this. LOL.

In case you didn't know, Edelbrock has been slowly releasing their MArine RPM line of intake manifolds.
The coolant (water) passages are lined. It's not cheap, but.....

Here's the BBC Oval Port Marine RPM intake:
http://www.summitracing.com/parts/edl-2561

http://static.summitracing.com/globa...2561_at_xl.jpg

wow. 519.00 and its not even an air gap..Maybe i'll try the polished dual plane speed master...for the price how bad could it be

http://www.ebay.com/itm/Chevy-BBC-45...f77564&vxp=mtr

I wouldn't buy it from ebay..

52 negative feedbacks in the last 6 month's from this seller,............... good luck

I have a pair of GM marine dual plane intakes with the brass passages from 1992 502 Mag motors. If you are interested I will post pics.

Thanks anyway I like the air gap design better

What makes the Air Gap RPM so much better than the RPM ?

air under the plenum so the oil dont boil the fuel charge..kinda like a mopar intake..

ir path is raised up alittle on the bottom runners and the top runners a touch straighter.

Besides the fuel thing it also makes for a clean install. The wiring for the elec choke, temp and alt can be run under the carb.

Just a FYI, I've had a Edelbrock and Pro Comp airgap intake side by side for a few days on my bench while I was building two motors. Besides the name stamp you couldn't tell the difference between the two. Runners looked the same and the ports were the same size.

Last, I run in brackish water and used a Edelbrock air gap for 8 years. I just replaced it this year due to being taken off and reinstalled to many times but the front water runner (the only place water runs through it) looked fine but I do flush after ever use.

No one has on the dyno or on the water performance and/or driveability differences to report ?

My 1" aluminum carb spacer sweats after a run..The air gap isn't hot like regular manifolds

SB, here you go,
http://www.hotrod.com/how-to/engine/...pm-vs-air-gap/

As has been stated you may see a difference in a hot environment like under a car hood in the summer as the intake charge is separated from the hot lifter valley. Don't know if it's really needed in a boat.

FWIW, I run the air gap on my small block.

I posted the link because they basically found no difference. While we are on the subject, I took a temperature gun and shot my engine after a moderate run, just up against the 4 barrell in degrees:

Ambient temp: high 70s
below thermostat : 140
Oil pan: 190
exhaust manifold: 140
Carb: 55

Double post

That just means the outside of the spacer is hotter and more humid than the inside of the spacer. The air just came the venturis (carb) and is cooler. Big factor is that the fuel just came out of the boosters in the carb and is cooling down the intake charge big time.

Same principle is how Air Conditioning works.

What you are seeing is carb intakes (non heated) run much cooler than fuel injection (mpi) intake manifolds.
Fuel is why.

You'll see the same thing on a non Air Gap RPM with the heat crossover's blocked (if they have them) and running a lifter valley tray.

I'll read it, but i don't need to.

I've run a quazzilion of both type of intakes and studied them, obviously.

I'm doing this 'questioning' as more of a mental excersise for people. Just like to see what people assume vs actually know. And not on a matter of who's smarter than who...I don't get into that...more more of a matter to see thoughts, theories, and more importantly assumptions vs data from real world use.

That's all.

It was 26*F here this morning (prob same for you) and thus physical boating is done...but mental continues. LOL.

So lets change the subject and talk about a single plane manifold. 2nd part of my post. Why does the HP 500 come with a single plane verse a dual plane. Top rpm on an hp 500 is 5200- 5400 These single plane manifolds just start working at 4500 rpms and are good to 8000 rpms. My dual plane is good from 1500- 6800 rpm. Can someone explain?

#1: Cubic inches changes things.
#1.5: Manufacturer states an rpm range as help, however thry don't know if you are installing it on a 396, 454, 502, 540, 572, 598, 632 or ??? and add to those the countless different possibilities of cam heads, compression, torque converter (or direct drive), trans gear ratios, rear end (outdrive) , exhaust, and etc,etc. Not trying to make this more difficult than it is...but it all plays a part - some more important than others. cid, cam, and heads together make a massive influence on what to get.

#2: Not all single plane intake manifolds are created equal.
- Runner cross sectional area
- Runner Length
- Plenum size

#3 Who wants to see a car intake on a blue motor ?
A single plane says 'Race' and blue motors are 'mercury racing.'

Again, 500cid's with high lift cam and heads with big valves requires a bunch of air. The dart single plane 4150 intake has conservative plenum and runner sizing, so it works quite well in this application.

Put on a Super Victor or Super Victor II and things won't work out so well.

http://i.ebayimg.com/00/s/MjIzWDMwMA...s0!~~60_35.JPG

BTW: great info Mr Maine.

PSst: always great to see another involved sbc guy around here.

ok so my 509 490 hp engine with a crane cam 547 lift 224-234 duration, oval port 781 heads with large econel valves and a nickerson custom built 930 cfm carb will have to stay with a air gap dual plane intake.

really,,you know this as fact,,because I have a few engines that say otherwise.and a couple were 454's.and the jr's were ported for the 454's too.
I've heard this argument since 2001 when I built my 502 for my truck.w/ the boat in tow I could blow the tires off that thing,,my only regret,,putting in a whimpy azz cam 218,222 less than 600 lift.

oops,,II's turned into jr,,damn narcotics shot in my back yesterday.<lol>

damn this site is messing up posts.

SB must be editing cause I keep posting above his original.

LOL S30.

I did not mention Vic Jr's.

I wrote Super Victor and Super Vic II's.

Way different manifolds - other than being single planes.

Has any body tried the new super victor II on a 500 inch or larger engine? I looked a one at Summit last week and the runners are huge!

Nah, i didn't edit that one other than adding the #1.5 .

Past week or two, if you quote someone, your post will go over the post you quoted.

A lot of us are feeling like we have some special form of ESP. No one's won the lottery yet, so it must be the site is F*ked up.

Yah, it's a pain the azz.

We dyno tested a Dart 4150 single plane against a Performer RPM on a 516 inch big block motor. The single plane only beat the RPM by 5 horsepower, 604 vs. 599.

I'll throw in my .02.

I've run both the RPM Air Gap and a Victor Jr on a .030 over 454, 9.3:1 CR, Isky cam (221/232 @/.050, 114 LSA) ported 781 heads with 2.19/1.88 valves, HP500 800 cfm carb. So, a pretty mild build. No dyno results, only in the boat.

The RPM air gap did perform well, but fuel distribution at high rpm sucked. Spacers only made it worse. Tune for good AFR on both banks at 3500 and at 5000 rpm they were 1 full point apart (12's vs 11's for example). Distribution was not only a problem with AFR, tune for 12.6 @ 5000 rpm and # 2 and #5 were showing lean on the plugs. Jet to get all the plugs looking good, and I was in the high 11's on AFR again. Costing me power and money.

Changed to a Victor Jr this August. Of course, had to re-tune, started with HP500 jetting and leaned out from here. Tuned for 12.8 at WOT and all plugs looked good; both banks were close on AFR (no more than .2 apart). Tuned for mid-range, AFR and plugs still looked good. Picked up a couple of mph on the top end (due to the more consistent cylinder to cylinder mixture IMO). Noticed no issues on the low end - idle, planing time and throttle response all great.

Do I think the air gap is a bad manifold? No, I've used them on the street several times. However, based on my experience I'll stick to a good single plane on BB marine engines - the 15 or so foot pounds you lose at 2500 won't be noticed.

Think I have posted this before. I had a base 454 315/330 HP with a Performer RPM otherwise stock peanut port heads. Purchased a set of Performer RPM roval heads.
Had to pocket port them a bit to acheave Edelbrocks advertized air flow. Installed them and topped it off with the Performer RPM and took the boat out couldnt feel any real differance compaired to the original engine. At the same time tried 3 different marine carbs,an 830,750 and an 850 marine holleys. The carbs showed no differance in performance.
Then swapped out the RPM for a Air Gap. Had to modify a 80.00 upper coolant hose due the the hight of the water crossover. The intake cost 100.00 over the RPM. Took the boat out again and along with testing the three carbs again couldnt feel any differance between the AIR Gap and the RPM other than it cost me 180.00 over the RPM including modifying the hose. Ouch in the wallet
Next installed a Torker II didnt need the modified hose. The bow rise encountered with the above configurations was gone the boat jumped out of the water no noticable bow rise, jumped out of the water like a frog and up on plane (before had to stand up to see over the bow most of the time) and hit 75 (redline). It was like I added 70HP or better. Tested with the 3 carbs also which made no differance on the Torker. Wish I HAD GOTTEN THE CHANCE TO reprop to see just how much speed I WOULD HAVE PICKED UP. The way the boat reacted with the torker and RPM heads guessing at least 5MPH

Worried about heating of the under side of the intake THIS YEAR ON MY TOW VIHICLE COATED THE UNDER SIDE OF THE INTAKE with a ceramic coating

Did you stay with the HP500-style staggered jetting? Your results kind of make me wonder if I should be going with staggered jetting on my 489 - running 265 AFR's, Dart oval port intake and Holley 800 (HP500) carb with Lightning headers. Very similar cam specs - was that flat tappet or hyd roller?

Yes, I still have staggered jetting, but not just like the HP500. Cam is a flat tappet grind, 221/232 @.050, 114 LSA, 114 ICL, .542/.565 lift. I have the 496 exhaust modified per comments here by Raylar, which is working well for me.

Here is where I am now on jetting (note that I changed the air bleed and idle feed restriction sizes to flatten out the mixture and eliminate rich conditions down low). P is primary, S is secondary


Secondary Constant Idle Feed 0.031
Idle Air Bleed 0.07P 0.032S
Main Air Bleed 0.020P 0.018S
Idle Feed Restriction 0.033P 0.04S
Pwr Valve Channel Restr 0.069
Main Jet (P) 79
Main Jet (S) 89 Port/ 88 Stbd
Pwr Valve 8.5

It required some major changes over the HP500 stock - for example the primary idle feed restriction started at .058, I took it down to .033 to get idle transition mixture into the high 11's / low 12's

I have the Eddy Oval RPM heads (ported) with the Q-Jet dual plane performer intake on 9.6:1 CR, and didn't really think that manifold was doing it justice. Thanks for the info.

i HAVE DONE SOME FLOW TESTING OF INTAKES BOLTED TO HEADS mostly small block Fords AND cHEVYS. What I found is the performer style intakes flow about the same as factory stuff. RPM style intakes a bit more. The torker II and VrJR about the same but a bigger jump than between the Performer and RPM. aLSO FOUND BETTER FLOWING HEADS DONT INCREASE air flow of an intake.

Are you saying a stock 330/454 gained lowend with a torker manifold oval heads and no Cam?

I love reading these posts debating what type of intake to use on a BBC marine performance motor. Most have never had their motor on a dyno, let alone had their manifold on a flow bench (fixtured to the head that they are using on the motor). Here is a big taste of reality. Mercury engineering has forgotten more that most posters here (me included) on this thread when it comes to marine performance motors. The most widely acclaimed, most reliable, solid performing marine racing and performance built motor---------The Mercury HP500. After all of their testing, the Dart single plane manifold was the manifold of choice. Possible that Mercury had Dart make a special (beyond the nice blue paint) manifold with alterations to the Dart specs for the Mercury part, but it's DNA is still Dart. Still don't believe me. Ask a professional. Wilson Manifolds has possibly the most experience in cast aluminum manifolds then most. For a performance marine BBC motor, it is certainly not a dual plane anything!