Hot Rod Forum banner
1 - 19 of 19 Posts

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #1 · (Edited)
Hello guys I am making another post so as to not take away from my other post and I was wondering on some opinions here on things. Here is my build 350 Dart shp, Edelbrock performer rpm air gap intake, Dart pro 1 platinum 200cc aluminum heads ported and bowl blended and combustion chambers cleaned up and exhaust as well. 268/272 220/[email protected] 510/510 lift 114 lsa hydraulic roller cam. Scat rotating assembly with forged flat top pistons and 9:1 compression.

As to some who knows I may or may not have an issue with my air gap intake with the current camshaft I have and its a long story and on another post. I am posting this as I know the basics about intakes and flow and rpm rating range etc but I would like to get some more advanced knowledge from guys on here who knows better things about them. Ok I have been looking around and I want to stick with Edelbrock if I can and nothing against Weiand as I have used them in the past with great results but there corner flanges seem awfully thin and Edelbrock seems to have thicker flanges which I like. I won't use other knockoff brands like the procomp aka speedmaster stuff.

Ok onto my question I saw an article on a dual plane intake manifold done in a hot rod magazine and the engine was a 406 small block chevy with trick flow 215cc aluminum heads with a hydraulic roller cam with 232/[email protected] 525/543 lift 112 lsa. Don't know the compression. They ran a Holley 750 Hp double pumper.

That engine made 506 torque and 461 horsepower peak. On the Edelbrock rpm air gap and performer there was not much difference at 4 on power and torque at 504 torque and 470 hp on rpm and air gap 508 tq and 474 hp. So there is only a difference of only 9 horsepower between the non air gap eps and performer rpm. I know the EPS sits higher versus the old Edelbrock performer and I have used an EPS intake in the past with 200cc heads and it worked well but the cam was slightly smaller at 211/[email protected] 500/500 ish lift with a 112 lsa.

My question is what the results be similar in my 350 build if I were to use the performer eps vs the performer rpm intake? I don't race my truck nor do I take it past 5500 rpm anyways as its a cruiser and I always use a one inch spacer on it anyways for clearance for certain things and it always gives me good results. I figure going by the article results I would not loose any torque on what my engine makes and I might loose less then ten ponies on the top end which would not bother me any. My few questions though would the EPS intake give better fuel distribution and better fuel mileage vs the rpm intake and better overall fuel atomization?

The reason is everyone is out of stock and the dates for parts for many intakes keeps getting pushed up and I was able to get an EPS intake on order and hopefully should have it here soon but I am second guessing that it might cost me a lot but anyone with more knowledge on the subject could help me with more info about the more scientific part of things could shed some light and it would sure help. I don't like buying used intakes because I don't know there history and I have gotten used parts off ebay before and have been given lemons and ended up being stuck with a dud.

Like I said I don't race it and am not worried about every last bit of power. Just want this to finally get this problem fixed and if its the cam not liking the air gap and I have no problem swapping out intakes. I won't be changing things out till about March or April but who knows how parts will be by then so I am scooping things up now so I have what I need by the time it comes. I feel if I were to use the EPS intake and loose less then ten horsepower and still have the same amount of torque and yet gain more efficiency overall in mileage and things still be well enough matched then I would feel fine with those results as that outweighs just a few ponies.

Sorry for all the questions and hope to hear some advanced info.
Thanks guys
Eric
 

·
Hates: Liver. Loves: Diesel
Joined
·
6,303 Posts
I know you mentioned not racing... how much do you drive it? Is this a "take it to three car shows a year" thing, or a "drive it every other day thing?" The reason I ask is that you can put up with a lot of mismatch for a vehicle that only drives from the trailer to the grass at the show, but you're kind of asking about how to mismatch parts to mask some things. You have a bottom end, air flow, and cam that will shine from 3500-6000 rpm, but you want an intake that shines from idle to 5000. I look at that combo and I see great airflow, cam matches airflow, but compression and intake are not a match to flow and cam. If you really drive this thing, I would think you can get a much better SOTP by dropping down one cam (and narrowing the LSA) and then everything will match a Performer RPM.

Having said that, I would personally put a non-air gap Performer RPM on it. You'll give up a bit of top end, but you might be able to reclaim a bit of the midrange torque you're giving up with a cam that really needs 10:1.
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #4 · (Edited)
I only got the RPM air gap as I had good luck with one on a previous build in another truck but I don't know its just not going very well on this build since day one and I want to just ditch the air gap. Unfortunately everybody is out of the performer rpm intake and the date keeps getting pushing ahead and the price keeps going up. I don't want to end up having to pay $300 plus by the time somebody gets one. I checked Summit and it says December 20 but Jegs is like in January right now.

Some things are not a perfect match but still close and nothing to far off to make anything a bad match. I have had many builds similar to this and always has run very well and made good power from off idle all the way to the top and get me 19 mpg on mileage. I know the compression is about half a point low but its nothing to effect things to the point of it being horribly bad. I gave all my specs and such when I got this cam and mentioned about going back to a 350 in the future and it was custom grounded for me. All I do is drive it as a daily driver even though I don't drive it everyday and mostly just during the spring and summer months into fall time. Just highway cruising and I would get laughed out at a car show lol as its nothing fancy. Just a plane jane looking truck. Not for looks but just for driving.

Johnsongrass1 I have checked my ignition and everything so far has checked out and nothing is showing out of the ordinary with this thing. The distributor and plug wires are the same that was used on my 377 and everything was excellent and only after the intake swap and the slightly smaller cam was installed on the previous 377 did I start to have problems and I have had my ignition module checked and even tried another one and also a different coil and no change in anything.

Something with either the cam not wanting to work with the air gap intake. So far every carb which has been three on this thing has just not worked and I have enough years of experience with tuning things to know something is just off. From research and I even posted a link on the subject in my other post. You know a heck of a lot more then me so I won't argue there and I am trying a different carb which will be the fourth one and if it does the same thing then I don't know what the heck else it could be.

All other things have checked out and the plug wires are all reading good on the ohms readings and the spark is good on all eight cylinders as I have checked that in the past and just again recently. With the 4 hole spacer it does worse, with the open spacer it works better but still a problem fuel distribution here. Goes from super fat rich in the front two cylinders then backs off some in the four middle cylinders and then way leaner in the back two.

To me that is more a fuel distribution problem when all things in my distributor have been changed already and no difference in how its doing with the same problem. If plug wires are good and cap and rotor and coil and pickup coil and control module are all well then it has to be elsewhere.

Won't post anymore here as that is for the other post. If you have any ideas by all means shoot me with it as I am getting out of ideas here. I am going to try this one last carb later on this week and maybe I am jumping the gun here and I have a history of this but after three different carbs before from the 377 to this 350 it was lesser on the 377 but worse on the 350.

Can I ask though Johnsongrass1. I used an open gasket on top of the four hole spacer and could that have caused problems between the carb and the four hole spacer? Open gasket on the bottom would have not mattered because of the cut plenum. Just a thought as I am trying to think of everything I can think off for troubleshooting.
 

·
Hates: Liver. Loves: Diesel
Joined
·
6,303 Posts
China has dozens of options for RPM copies if you want to go that route. We'll just agree to disagree on the compression. With iron heads I would do a minimum of 9.5:1 with that cam. Aluminum I would shoot for 10.25:1. I think you're giving up a ton of mid-range at 9:1, but your truck and I applaud making it what YOU want. I'm not the nut behind the steering wheel :)

The only real difference between the RPM and the RPM air gap is how long it takes for the runners to get up to temperature. Great if you tune it rich to match the cool runners and run it 12 seconds at a time, but pointless on the street. They are very similar in performance and airflow with a slight nod to a bit more gravity/higher rise on the air gap. I'm saying that to mean... if you're not happy with the RPM air gap, not sure if an RPM is much different.... which also begs the question - with so many RPM intakes being the go-to choice on the street, is it possible that it's not the intake giving you fits?
 

·
Race it, Don't rice it!
Joined
·
8,812 Posts
Can I ask though Johnsongrass1. I used an open gasket on top of the four hole spacer and could that have caused problems between the carb and the four hole spacer? Open gasket on the bottom would have not mattered because of the cut plenum. Just a thought as I am trying to think of everything I can think off for troubleshooting.
As long as the gasket is sealing the hole I don't see a problem with it. As far as spacers go, I've seen adapter type spacers create problems on my own rides. The tapers edge in the throat, cause a fuel shearing action that pulled the fuel out of the air.

Post a pic of what your messing with, Intake, carb and spacer
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #8 ·
I have only used a one inch aluminum 4 hole spacer and a one inch open spacer on this thing which is aluminum as well. I had in my previous 350 which was very similar to this except it had 1800 dart shp heads and a weiand 8150 high rise dual plane intake and a lunati 270/278 219/[email protected] 5??/5?? lift 112 lsa and 9:1 compression with a four hole one inch spacer and ran excellent. Even ran that same motor with a set of RHS 200cc iron heads before I had to take it apart but that is another story and it ran just fine with the said camshaft up above and same intake without any problems running a Holley street avenger. Only thing I had to do was richen up the idle circuit from the primary .028 ifr to .031 and it had .078/.048 idle air bleeds and jetted 67/73 on the jets and the plugs were all within pretty close on both builds and I am running the same gear ratio and everything else with this one that I did with those.

I sold that motor to make room and cash for my SHP build. This should not be happening regardless of what spacer I am using. Just going to a slightly smaller camshaft and then the dual plane intake from the victor jr on the 377 produced the problems since day one. I tried three carbs on it and tuned one direction and the other from richer to leaner and just one thing after another of nothing working right. It took longer for the plugs to foul and with the 350 it just happens so much quicker and I am assuming because the lesser cubic inch.
 

Attachments

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #10 ·
I know the intake says Trick flow but its exactly the Edelbrock RPM air gap intake as I have had one before and everything is identical except the name being branded into the intake. Summit on there stage two intake that is a dual plane is a Weiand 8150 as I had owned both before and compared them and everything is identical down to the casting underneath and the only difference was the name inscribed on the intake.

Summits even had the 8150 number on the bottom of it like the Weiand did. I would go with a Weiand speed warrior but the flanges on those are a lot thinner then the Edelbrock and have seen some warp after awhile. Maybe I should just bight the bullet for the Weiand if after the carb number four does not work out and it still does the same thing. I would rather change the intake versus the camshaft. Lot less work etc. I just like Edelbrock versus Weiand which is made in China versus Edelbrock being American which nowadays does not always mean a lot.
 

·
Registered
1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
Joined
·
237 Posts
If you've already covered this, I apologize for being redundant. If not, have you checked to see what the timing curve (initial vs overall and when it comes in) looks like on this set up? I was looking through some of the discussion on this problem and didn't see anything about it.

The reason I ask is because of an often overlooked problem with the mechanical advance in the distributor. Sometimes the springs get weak or even break and it makes the mechanical advance act like too light springs/too heavy weights or both. In doing so, you can have the mechanical advance coming on at idle and if the timing is set (without knowing you have too much mechanical advance there) it causes trouble with the timing at rpm. If you have too much mechanical advance at idle, it doesn't have room to advance properly at rpm. Add to the fact that you lose vacuum advance under load when the manifold vacuum drops. You end up with the retarded timing at rpm....plug fouling, poor performance.

Just a thought. If you already know you have a proper timing curve, disregard my ramblings.
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #12 · (Edited)
My distributor and timing have been checked and my advance is working just fine. I checked all that already when I set my timing and to rule anything out. I have all my mechanical advance in by 3000 rpm or a hair over and my mechanical advance moves freely. Heck its even still shiny as the day I put it in a few years ago. Mechanical advance starts about 1200 rpm give or take a few and is all in around 3000 plus rpm.

I run about 15 initial give or take a few degrees and with vacuum advance I have around 27 degrees at idle give or take a few degrees. Timing has always worked excellent this way for almost all of my builds over the years.
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #14 ·
I checked the carb base plate and it was spot on and I have not checked the spacer or the intake yet but will do so. What is an acceptable amount of using a feeler gauge? I am guessing it won't be like .001 perfect at the most but never had to check anything like this before so I don't know what the proper amount of acceptance is.
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #16 · (Edited)
I already got an intake coming so this thread can be done but I posted my info and findings to who ever has followed my post about my Holley carb issue and it just running weird. I am ditching the Air Gap and going with regular Edelbrock performer rpm as I was able to get one by chance.

On this intake on my engine It has grade 8 bolts with washers and lock washers and I am wondering if the lock washer is interfering with a proper amount of clamping force? If I were to take each bolt out and remove the lock washer and put new silicone on the bolts if it will seal up? Its probably to late at this point and having silicone gasket maker to cure on those bolts in cold weather I don't think has a chance of doing so.

What a nightmare this has been ever since the cam and intake swap last year to just be passed over to my 350 build :( I am sick of all this bad luck. Never got to even enjoy one day to cruise this year.
 

·
Registered
Joined
·
2,797 Posts
The center intake manifold bolts on an SBC are the only ones that are exposed to oil, so they need ARP thread sealant or something similar. I also use thread sealer on the four corner bolts, but its not absolutely needed because they don't go into the oil gallery. Keep the thread sealer warm until you use it, and it should set up fine in colder weather. You also need a flat washer under each bolt head to keep it from cutting into the intake, and many folks also add a lock washer. I've never had a problem with any interference from the lock washer if the flat washer is the proper size for the bolt.

The Edelbrock Performer RPM Air Gap should have worked fine, but can be a PIA during cold weather warm-up, so most folks use the regular Performer RPM. The base Edelbrock Performer intake you have coming is a good match for stock heads and cam, but you won't get the most out of the high performance parts you have added.
 

·
Registered
Joined
·
4,707 Posts
Discussion Starter · #19 ·
I got an Edelbrock performer rpm intake coming and as far as sealant goes it was used on all my bolts and everything was sealed up well. As far as using a spacer I use one to help with clearance or the rear fuel bowl won't clear the vacuum hookup connector on the intake and its a downfall with Edelbrock intakes as they are all like that. I have used the low profile fitting and you still have to use at least a half inch spacer and I also have to use it to clear my Holley fuel rail from hitting my heater hose that goes into my intake as it goes right across it and I have always got better results in tune with using a spacer anyways and its helped with giving more throttle response. The divider is installed intact on the performer rpm intake. Getting rid of the air gap style anyways. The gaskets are weeping on the front coolant and slowly dripping down the front of the engine even after re torquing the thing several times after several heat cycles.
 
1 - 19 of 19 Posts
Top