• Welcome to the CaliforniaSpecial.com forums! - You are currently viewing the forums as a GUEST. To take advantage of all our site features, please take a moment to join our community! It's fast, simple and absolutely free.

    If you have problems registering or can't log into your account, please contact Admin.

    Please Note: If you are an existing member and your password no longer works, click here to reset it.

Intake Manifolds for 428 CJs

PB GT/CS

Active member
Joined
Dec 22, 2005
Messages
32
Location
Kansas City, Mo
Folks, I was doing some catch up on the site today. I noticed on the "Member of the Month" section a discussion on Intake Manifolds for a 428CJ started by Don and GT asked the questions about performance issues. I am a long way from being an engine builder expert but I went through this decision process when I built the 428CJ for my Cobra S/C. The bottom line in Intake Manifolds seems to be a question of RPM range the engine is expected to do most of its work and a match to other parts of the engine. This is 4 year old info and my memory may be a little off, but here is how I remember it.

Edelbrock makes several performance intake manifolds. The Alum RPM manifold which is made pretty much to mirror the performance of the intake on the Police Interceptor of the early FE engines. They are designed to work well for engines turning 1500 to say 4000 rpm. The next level up in Performance is the RPM Performer. That makes more HP in the 2500 to say 5500 rpm range. The Victors are the big dogs and are made to make HP in the 3500 to north of 6000 rpm range. My buddy who built at the same time used the Victor Jr since he was interested in running Autocross and such. He geared his car so it would run nearly 6000 rpm on the course and hold HP there. He "chipped" his engine at 7000 rpm max. I chipped mine at 6K.

I bought for my 428 the Edlebrock RPM Performer kit minus Carb. That was Cam, Alum heads, and Intake all matched to make HP in the 2500 to 5500 range. I used a Holly 750 DP as a carb as it was "more original". Almost all of my usage on the car is for street driving with a little heavy foot sometimes. The engine showed exactly what Edlebrock advertised when it was on the dyno. Was a dog up until 2500 and really came to life until it got to 5500 and tailed off after that. From the back of the engine, 460 hp, 525 Torque :grin:

My friend made a lot of HP in the upper range (over 500), but it takes a lot of RPMs to get the correct fuel mixture down those long runners on the Victors.

I am sure others on this site have more engine builder experience than I do. However, this was my observation when I had my engine built. So, the bottom line is decide where you want the engine to be strongest. If it is a street machine only, do you really want an intake that does not begin to really come on until it sees 3500 to 4000 rpm?? If so, probably better look at the cam specs to see how that matches that range. If you have the heads ported polished and big valves, you are on the correct path to handle the additional air flow the Intake will move. Do you have enough cam to hold those big valves open long enough to handle the air flow??

Finally, we gained the most HP on the Dyno by adjusting the curve on the Distributor and jetting the carb. We started out at 390 HP and got to over 450 by making those adjustments. As most engine builders will tell you, all of the parts need to work together. These performance parts make engines move a lot of air and can be tricky on the timing. Everything needs to work together.

Hope this helps and if you have any questions, I will relay the information I can remember or perhaps someone with more knowledge can also come to my rescue if they disagree.

Brian
 

68gt390

Well-known member
Joined
Feb 22, 2004
Messages
2,021
Location
Columbus, Ohio
Brian;
Thanks for the info. My engine builder recommended the Victor and the Street Demon 850. The heads have been ported and polished along with bigger valves. He told me the victor should give me good low end touque but, still have plenty of power through the 6000 rpm range. That's were we plan on capping it with the rev limiter. I had thought of using my Edelbrock Performer 390 off my 390 engine but, he told me I'd really be limiting the power range on the car since I'm running a healthy street cam, Crane roller rockers, .30 over pistons and headers. I guess time will tell. If I'm not happy with it I'll swap it out. We plan on doing a dyno with the motor out of the car and then run another once she's in to see what actual rear wheel HP is. Right now he figures we should be somewhere in the 500+ range.

Don
 

gt bandit

Well-known member
Joined
Nov 26, 2005
Messages
460
Location
Perth , Western Australia
Brian

interesting to see the additional HP you made by lining up the variables. Was it trial and error on the Jetting of the carb or is their a science behind this.

Shaun
 
OP
OP
P

PB GT/CS

Active member
Joined
Dec 22, 2005
Messages
32
Location
Kansas City, Mo
Shaun, the engine build strategy was to match all of the items. At the time of my build, we went to the Edlebrock site and looked at the different packages to figure out what made sense for my application. At that time, they had torque and HP curves to look at for the various combinations. The timing and jetting was trial and error on the dyno stand. We spent an entire morning on the Dyno stand and burned over 5 gallons of fuel trying to get the best combo of jetting and timing. I have the results of 7-8 pulls in my file, but we pulled it a lot more times than that. As I said, we burned over 5 gallons of fuel. To get that last few HP is the real trick and fun to watch. By the way, it is a good time to look for leaks in the rear Main Seal as well.

Don, I just looked in the Summit Catalogue. The Performer manifolds are made to work from start to 5500 RPM. The Performer RPM is from 1500 to 6500, the Victor and Victor Jrs are from 3500 to 8000 RPM. I dont know the Cam matches for the Victor, but you may check the Edlebrock site. The add for the Victor says its application is "You'll find these single plane manifolds on oval track, mild drag, and NASCAR engines. That's because the Victors boost power where these engines use it most- the 3500 to 8000 rpm range". Don, if you are on the dyno stand, I would be very interested to see both Manifolds on the engine to see the HP and Torque curves. That is where the proof is in the Pudd'n.

One last interesting note (to me at least). The engine I have makes about 5 HP more at 150 degrees of heat rather than 180 degrees. She likes to run cool. So for a drag race, get heat into the engine, shut it down so it will cool a little, then come off the line as close to 150 on the heat guage as is possible. Don, your single plane may solve this issue as it is taller and allows more air around the intake runners. Anyway, that morning on the Dyno was well worth the price just in the entertainment value.

Sorry to be so long winded. If you have other questions, please let me know. I have the total timing and jet sizes for my Holly 750 pulls if you are interested. I would just have to dig them out.

Brian
 
OP
OP
P

PB GT/CS

Active member
Joined
Dec 22, 2005
Messages
32
Location
Kansas City, Mo
Shaun and Don, you may also be aware of this, but here is another fact we found made a big difference; "Port Matching". What that means is to match the intake ports on the heads with the openings of the runners on the intake manifold. As well, match the exhaust ports with the header pipes. This sounds simple, but takes time and Patience. We used some sort of carbon paper on the manifold runners to match then to the heads and same on the exhaust side. Then be real careful when you put in the gaskets on both sides so you don't block the Ports.

A buddy of mine had a really strong small block Stoker that was just not making HP. He bought AFR heads to replace his GT-40 Ford Racing heads. When he pulled the intake manifold he found the intake gasket had slipped closing off some percentage of the intake ports on the manifold. It made a huge diff when they matched the ports. The guy who built my engine told me that port matching is nearly as important as Porting and Polishing. He port matched both the 428 and our 302 in the GT/CS. He would only begin the process when he had the intake Manifold and the headers. That way he knew where to take off the material to get the ports matched. He had to take some material off of the intake gaskets to get the ports to match on the 428. Then he uses a little silicone to hold the gaskets in place while he installs the intake manifold.

This is why we pay the engine builders the bucks to do it right. Good luck.

Brian
 

68gt390

Well-known member
Joined
Feb 22, 2004
Messages
2,021
Location
Columbus, Ohio
Brian;
That's what I did with my 91 LX and plan on doing the same thing with the 428CJ. It just takes a little more time but, is well worth it. I have found that almost everytime I have put on new exhaust gaskets, Intake gaskets they always in some way block part of the openings.

Don
 

gt bandit

Well-known member
Joined
Nov 26, 2005
Messages
460
Location
Perth , Western Australia
Brian ,
can you post the details on the jetting and timing , I think this information should go in the Tech section for easy reference later. Not sure about the rules their but.

Brian be prepared for more harassment soon - i have every intent to wring the last ounce of HP out of my 428.
 
OP
OP
P

PB GT/CS

Active member
Joined
Dec 22, 2005
Messages
32
Location
Kansas City, Mo
Shaun, any question you have, please let me know. Frankly, when we get down to the last few HP (the 5 we discovered by temp) these engines are nearly living things, all are different. However, there are some things that are common and will give us good ideas how to get those first "easy" HP and Tqe. Those are the ones we don't want to miss. The tuner of my engine called them "Free HP" just laying there for us to harvest. As any competition drag racer will tell you, the last 10 Hp are 10 times harder and 100 times more expensive than the first 50 hp in an engine. Please let me know what you want and anything I have I will be glad to post.

Brian
 
OP
OP
P

PB GT/CS

Active member
Joined
Dec 22, 2005
Messages
32
Location
Kansas City, Mo
Don, the strategy the engine builder used here was two fold. He used some bolts that had the heads cut off as studs to hold the gaskets in place. then he used some silicone to really hold them down. One has to be careful to not make the studs too long as the Manifold will not go down on the heads. But this works well as it is difficult to drop an intake manifold exactly straight down on the heads. The studs guide them down. The silicone dabs work to hold that last quarter inch in the middle of the gasket. Good luck.

By the way, are you running top loader or C6?

Brian
 

gt bandit

Well-known member
Joined
Nov 26, 2005
Messages
460
Location
Perth , Western Australia
PB GT/CS said:
Oh Shaun,

I forgot to say, Good Morning. I hope your Saturday is going well so far.

Brian

good evening Brian

Saturday is going great so far, thanks for asking. I used to own a 429 and with my recent purchase of a CS i have acquired a 428.

Plenty of guys in OZ with 429 knowledge , but FE info and experience is a little harder to find.
 
Top