90 7.4L intake manifold
 

my intake manifold is getting a couple of little rust spots, so i take it that it is cast iron, or steel. Does anyone know of an aluminum intake that would be a direct replacement for the most part that would work with my rochester carb?

Re: 90 7.4L intake manifold
 

You could just glass bead and repaint your intake. I have two intakes and carbs off '89 454 Magnums that are in liike new condition. I believe they are aluminum, but I would have to check. I would sell cheap. Let me know if you are interested in one of them.

Re: 90 7.4L intake manifold
 

well, maybe, i was just trying to figure out if a company like edelbrock or something made a mild upgraded or stock replacement in aluminum. If i was to go through the trouble of pulling that intake off, i wouldn't want to put another steel one back on.

Re: 90 7.4L intake manifold
 

Ive got an Edelbrock performer that Im not using. rogue2800 (at) hotmail.com

Re: 90 7.4L intake manifold
 

would something like that work with my original carb, i'm pretty sure i have a rochester..... how would a mild upgraded intake effect fuel/air mixture, would i have to play with the carb settings or would they be fine as is??

Re: 90 7.4L intake manifold
 

Edelbrock makes a Performer that takes the spread bore carb.
I ran one on my 1989 330HP/7.4.
A K&N filter is also a nice upgrade.
My engine gained about 100rpm on top with these two additions... :drink:

Re: 90 7.4L intake manifold
 

Yes, mine is for the Quad. spreadbore.

Re: 90 7.4L intake manifold
 

how do i know if i have a "spread bore" I'm not sure what that means. I just know that i have a '90 7.4L merc, and i've been told that i have a rochester but i have never verified that

Re: 90 7.4L intake manifold
 

Might try to find a Merc aluminum intake with the brass lined water passages. Regular alum intakes will corrode at the gasket mating surfaces. Even in fresh water use.

Re: 90 7.4L intake manifold
 

There aren't too many intakes that match up well to the peanut port heads. Be careful with your selection or you will go slower!

Re: 90 7.4L intake manifold
 

Your very likely have a Rochester Quadrajet with is a spreadbore (the carb secondary bores are much larger than the primarys). On Holleys (squarebore), the primarys and secondarys are the same size. The mounting hole locatings are different too.

Re: 90 7.4L intake manifold
 

I have an aluminum Edelbrock "Performer" made for peanut port heads and q-jet spreadbore carb I will sell you. It is in excellent shape, with the center divider cut down about 1 inch. It was used one season, and make 426 HP on the dyno with a 1 inch open spacer. I also have the camshaft and lifters that went with that combo.

Re: 90 7.4L intake manifold
 

what do you mean the center is cut down, and u took a 330hp 7.4L to 426 with a cam and intake???? that doesn't sound right

Re: 90 7.4L intake manifold
 

There is a divider inside the plenum of the manifold where the carb sets. That divider was cut down to make the engine think the plenum is larger. Its an old trick.
The engine was a 330 HP. We installed 2.19 and 1.88 inch valves in the peanut port heads, and just did some minor bowl porting. We added a differnent cam, lifters and springs. Also added roller rockers, which really add very little horspower if any. Did some minor work on the q-jet. I also changed the pistons, went .030 over but keep the stock compression ratio. The engine was completey tore down, align bored, balanced, and carefully reassembled. 426 HP, 502 ft lbs with the peanut heads, on shop headers. EMI's were used in the boat. Infact, I still have those heads, cam and lifters, and intake manifold in my garage.

Re: 90 7.4L intake manifold
 

just curious as to why u ended up parting the engine? I'm new but in the questioning state as far as my engine goes. It's my first boat and i'm trying to learn as much as i can and would like to do a couple of things on a limited budget. I like to spread myself thin with seasonal toys since i'm in wisconsin. Also, what are EMI's. thanks bud

Re: 90 7.4L intake manifold
 

The engine had 550 hours on it. It was running great, we simply wanted to kick it up a notch. When we tore it down for inspection is was in fantastic condition. All we did to the crank was polish up the journels. We replaced the rod bolts with ARP's which is a high quality rod bolt. We changed the pushrods also to 3/8 from the stock 5/16. New timing set and oil pump. Normal things on a engine with that many hours.
EMI's are exhaust manifolds made by Eddie Marine Incorporated. They are an upgrade and improvement on stock merc manifolds, but they are an economy type upgrade. They are not a true header. There are many guys on this board that have done what I have done. Look in the archives.

Re: 90 7.4L intake manifold
 

i wasn't implying that i didn't believe you, i was just wondering what you did. My local boat guy keeps shooting me down when i ask him about minor upgrades to the engine, says i will make it unreliable and blah blah blah. So i'm trying to learn about the available upgrades to the 7.4L on here. You just have the heads and other stuff laying around? Is that stuff i could basically bolt on and go, or is there more to it. I plan on pulling the motor out this coming winter and would like to get a game plan together.

thanks

Re: 90 7.4L intake manifold
 

Yes, those heads are in excellent shape, but they are bare, Valves and springs were used elsewhere. The same engine now has different heads to accomadate a completely different combination. The cam and lifters are still available as is the intake manifold. Send me a private message if you want to talk about it further.

Re: 90 7.4L intake manifold
 

cloudmaster,
Check for flame arrestor clearance before you buy a new intake manifold because you will need several inches to fit any low-medium rise replacement. Stock cast iron manifolds on 7.4's are as flat as they get. I think Weiand also makes a model for your carb/head combo called the Action Plus.

Re: 90 7.4L intake manifold
 

good call, here is the link, just have to find a holley dealer now to find out how much it costs.....

http://www.holley.com/HiOctn/ProdLin...AMSM/8017.html

Would i see any benefits from just adding this manifold, or do i need to put in a cam and lifters to see anything or keep the engine reliable. It looks like my current Rochester carb will fit right on as well.

Re: 90 7.4L intake manifold
 

An Edelbrock Performer intake and K&N filter charger yielded a 100-150rpm increase on my engine.
Then free flowing exhaust (Stainless Marine) gained another 100-150.
My old boat went from about 60mph at 4500rpm to 63 at 4800rpm with the same 23p prop... :drink:

Re: 90 7.4L intake manifold
 

I would say just the intake manifold change alone would not be worth time time or expense. However it does look better and you shed some weight. I bet most of what Pat saw was from the switch to headers. The manifold I have is specifically made for the q-jet. Yes Weiand also makes one. Infact I used a Weiand on large oval 049 heads with the q-jet. It worked great.

Re: 90 7.4L intake manifold
 

I agree, intake alone will do little. Intake with cam is better, but you may have to change valve train components now and the cam must be compatable with your compression or you may loose (this reads, stay resonable on the cam unless you plan on upping compression). Intake with cam and heads even better. Intake with cam, carb, heads, and exhaust that all match is the best. But now you will be spinning more rpm and the bottom end may be risky. Minor changes end up leaving you wanting more which leads to major changes which gets costly. I do it myself all the time.

I dont think theres much wrong with the stock manifold on a stock engine except the weight.

Re: 90 7.4L intake manifold
 

formula31,
I agree with everything you said. Working on these things tends to develope into a sickness!! :D

Re: 90 7.4L intake manifold
 

Tell Me About IT... :rolleyes:

Re: 90 7.4L intake manifold
 

Could i get away with putting this manifold on and also a K & N flame arrestor? I don't want to lose performance, i just figured i might gain a little something for the summer and maybe compliment the intake and arrestor with a cam and lifters for next year. I've changed an intake before, but not a cam, so i want to read up on that. Also, if i was to buy a cam, what should i get to compliment that intake and original heads. I'm not looking for something real aggressive, i still want to be able to pull a skier out of the water but i want to play with the motor some and get some extra ponies. thanks for the info guys, it's good stuff

Re: 90 7.4L intake manifold
 

Sure, go for it. Don't expect a whole lot, but I can see you are determined to do this. RMBuilider on this web site is an excellent choice to work with in selecting a camshaft. He will help you out and can set you up. Good luck!!

Re: 90 7.4L intake manifold
 

Red please check your pm's