Official (1990-1993) 270/290 DA thread

Man, I have to start writing all this stuff down.:smt024 I'll never find it later.
Good catch Dan. Keen eye and thanks.:thumbsup:

Quint4 here is a little info about the spread bore intakes. I have know a few people that went to Edelbrock with good results and some with not as good results that why I asked you if your intake was a spread bore because if it was an adapter plate would be needed. Now the ones that did switch to Edelbrock carbs went with a different intake. I will be interested in seeing how your performance and fuel burn goes.

Square bore and spread bore are terms used for 4 Barrel caburetors and the matching intake manifolds the carburetors are mounted on. The term(s) mostly describes the carburetor in normal usage but applies to both carb and manifold..
Square bore carburetor's venturi's are of equal size, ie 4 holes of the same diameter. The primaries generally open first , the secondaries open next with vacum or air flow through the carb air horn or sometimes through linkage designed to provid sequencual opening. On some hot rod/very high performance applications all 4 venturi's open together, generally for strictly perfomance motors where fuel mileage is not considered. Square bore carbs generally offer a little more power and a smoother power range.
Spread bore carburetor means unequal in size venturi. These carbs have 2 equal size small venuri's plus 2 equal size large- huge, venturi's. The small venturi's are called primaries and are used for normal low power application, idleing, crusing at highway speeds for just normal easy driving. The primaries generally run a little lean on the jetting. The secondaries are much larger and used when max power is needed. The secondaries begin to open when the throttle is normally somewhere near or past or well past half throttle and open up quite quickly. The secondarie are open by vacum or flow through of air through the air horn, by demand. Rarely are they open by throttle linkage alone except at full pedal. At full throttle both the primaries and secondaries are fully open. The secondaries jetting is normally set richer than the primaries. Spread bore carbs generally deliver better fuel economy. If you drive them hard you soon lose the advantage of the better fuel economy.
The intake manifolds match the bore sizes specifically for each type carb. You can change back and forth between carb types w/an adapter, however there is a small loss in performance potential when the carb and intake maifold are not matched... adapters work but not quite as well as with a matching carb and intake manifold.
Edelbrock and others make after market intake maniflods that have large bores for spread bores that will work quite well with both style caruretors.

The Edelbrock Tech I spoke with advised I should use their squarebore to spreadbore adapter for my set-up (As did Dan here on CSR). The intake on my motor is "rochester" style or spreadbore and the Edelbrock 1410 (like the original Weber carb) are squarebore.

I do not know why my Weber was mounted on a spreadbore manifold without the proper adapter in the first place. It either came from the factory that way or someone did a really good paint job after they installed it (all the engine black paint was still on all the mounting bolts).

I picked up this adapter today and will mount it tomorrow. Thanks to all for your help. My goal is a safe running, fuel efficient (as possible) engine. I have no interest in "high" performance.

Quint4, do you have a fuel flow meter on your boat or do you know what mpg you are getting. I will be installing a Garmin GFS 10 fuel flow meter in the next week or so. I presently have the Quadrajet with the spread bore intake. The quadrajet has lot smaller primarys than the weber or edelbrock which helps with fuel economy. The only bad thing about the quads are the body's tend to warp over the yrs. I am looking for better fuel economy also and will be interested in what you get when your complete with the install. Hell if I wanted to go fast I would take out one of my other boats that will go well over 100 mph. Remember, it is not how fast you get there but how much fun you have getting there. Good luck!!

I do not have a fuel flow meter....wish I did. I estimate I get 13-15 gph. I do not run my boat hard. I plane at 3600 rpm and that is where I keep it unless just trolling along in no wakes etc.

This morning I swapped the squarebore plate with the proper squarebore to spreadbore plate. Here is a few pics:

spreadbore style manifold

Edelbrock 2696 squarebore to spreadbore adapter installed

Edelbrock 1410 on adapter plate

There's a lot of things to adjust on that carb. I believe that's like the old carter's. There cam adjustments, rod height, rod sizes, jets, springs. Not sure what there is for sure, but there's a lot of room to adjust mixture's at different vaccum.


Dan

Finaly got me seat back after 6 weeks. I had to make a new base. Eighty dollars for new cover, old foam.

Nice. If it ever stops raining here I may finally get my boat on the water!

home made stand off bracket

Two Lights added so I can see better with the top on a night. This way I don't have to Put isinglass in the top for the light on the arch. Don't know how well this is going to work. My just be a Light in your eyes will sitting down. I'll find out I guess. How long can we get this thread? I'm putting just about everthing I'm doing to the boat on here, Figure maybe somebody can use it or tell me I"m screwing up.

Wow, shame on me for not keeping up! take a few months off and I'm years behind on the mods!! I saw my boat for the first time since christmas a couple week back on the kids spring break when we drove down to Phoenix. I did a ton of work on the old girl.

- replaced a cracked rubber tube on the exhaust manifold outlet.
- replaced all the rubber boots and shift cable on the outdrive - $500 labor $300 parts
- brought all the cockpit seats back to denver to be reuphostered.
_ tried install speakers in my arch - ugh

Don
What happened with the arch speaker install?
I'm finally making it down to my boat this next weekend
For a complete stereo install. I am Planning on placing component speakers In the arch

I pulled the blank speaker cover off the arch cutouts and saw everything must be fished from the star board side hull. I stuck my fish tape down the starboard side speaker cutout and found it would not make the turn from the arch to the hull. I had to remove the seat and the trim panel to get at the location where they entered the hull. Turns out the 1/2" pvc pipe where the wires are contained in does not enter the hull. I tried running the tape up from the hull into the arch but the alignment of the arch hole to the cut out in the hull was off about an inch. I had to cut out an inch of hull to see the hole in the arch. Finally the tape would enter the hole but only go up about 6" from the speaker cut out. The problem was with the wires for the arch lights. They enter the PVC pipe on the starboard side but exit the pipe about six inches from the speaker cut out and travel in the foam filling. The fish tape kept getting stuck at the point where the wires exited. Sooo, I removed the arch light wires. Finally I was able to snake the wires up the 1/2 pipe to the speaker cutout and finally to the light fixtures and down to the port cutout. The 1/2" pipe to the first cutout is jammed full of wiring- Lights, VHF antennea; two speaker wires, GPS antennea. I took a bunch of pics but cant find them, ugh. I'll post if they reappear. Total time 3 days. I still need to install the speakers and the amp. FYI, The speakers are the standard Polk db651s. The cutout must be inlarged 1/2" to accomodate 6.5" speakers. Tools needed, drill, saw, 2 size fish tapes, soldered wires to fish tape, Dawn dish soap to lubes wires as the radiuis of the bends in the arch are impossible to pull through.

Wow! Thanks for the heads up! I had no idea this would be that complicated. I have two types of fish tape, metal and plastic coated. I will add saw to list of tools I allready have loaded.

If you do find the pics and don't mind could you email them to me? at: Heath @ stevescarstar dot com

Well my plan WAS to get all the system in this weekend, if I fight the arch speakers too long I will hold off and install those on another weekend. Hopefully I can atleast get the rest up and running

Thanks again for the info

Don Sr said:

I pulled the blank speaker cover off the arch cutouts and saw everything must be fished from the star board side hull. I stuck my fish tape down the starboard side speaker cutout and found it would not make the turn from the arch to the hull. I had to remove the seat and the trim panel to get at the location where they entered the hull. Turns out the 1/2" pvc pipe where the wires are contained in does not enter the hull. I tried running the tape up from the hull into the arch but the alignment of the arch hole to the cut out in the hull was off about an inch. I had to cut out an inch of hull to see the hole in the arch. Finally the tape would enter the hole but only go up about 6" from the speaker cut out. The problem was with the wires for the arch lights. They enter the PVC pipe on the starboard side but exit the pipe about six inches from the speaker cut out and travel in the foam filling. The fish tape kept getting stuck at the point where the wires exited. Sooo, I removed the arch light wires. Finally I was able to snake the wires up the 1/2 pipe to the speaker cutout and finally to the light fixtures and down to the port cutout. The 1/2" pipe to the first cutout is jammed full of wiring- Lights, VHF antennea; two speaker wires, GPS antennea. I took a bunch of pics but cant find them, ugh. I'll post if they reappear. Total time 3 days. I still need to install the speakers and the amp. FYI, The speakers are the standard Polk db651s. The cutout must be inlarged 1/2" to accomodate 6.5" speakers. Tools needed, drill, saw, 2 size fish tapes, soldered wires to fish tape, Dawn dish soap to lubes wires as the radiuis of the bends in the arch are impossible to pull through.

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Is there enough depht to install your speakers? I just had my covers off this weekend and was wondering about the depth. Don't what he back of the speaker's rubbing the back of the arch.

Bigblock,
I dont know on the depth yet because of size issue I ran into. I believe the holes were designed for 5.5" speakers. The Polk Audio db are very shallow. It will be very close. Also on the starboard side the VHF antennea exits in the middle of the cutout so that will take up a bunch of room. I will be back down at the boat in a couple weeks.

Dave (Quint4) don't you have Polk Audio speakers in your arch what size are they and was there a depth issue?

HHarris, I used a thin 6' fiberglass fish tape and a more stand metal tape. The metal tape had a loop on the end that I had to crimped down to make some of the turns. Don't let the audio store sell you the "Monster" wire, 16 gauge max.

All this to listen to the kids music that I can't stand........

Quint4 said:

I made a template and cut and "dry laid" the main floor over the carpet with Allure. It is heavy and does not offer to move. I will secure with a few hidden stainless screws. Here is some pics:

View attachment 18052View attachment 18054View attachment 18053View attachment 18051

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Dave - i've been staring at this and stareing at this picture and I think you need to bite the bullet and get rid of the blue carpet and go with a beige, LOOKS FANTASTIC!

I am too tired to pull any carpet anytime soon! Here is a pic of my Polks with the spacer :

Dave, I see the young lady in the back ground thinking "if of only this boat had beige carpet, I would make Dave's every wish come true" let us know how easily the carpet comes out!
On a more serious note ... your boat is lookin awesome! Did you make the spacers or did they come from Polk?