Re jetting quadrajet carb
 

https://cimg7.ibsrv.net/gimg/www.off...f66986f75b.jpg
I put new heads , cam and intake on my 280 TRS's. Where do I start?

hard to tell, my 377cid made 380hp at dyno. 39 main rods. 73 main jets. CE secondary rods. P hanger.
https://cimg4.ibsrv.net/gimg/www.off...12fa88f9f5.jpg

Thank you, ill pop the tops off and see whats in it. It wont run below 1700 rpms now.

You may want to consider a wideband 02 sensor so you have some idea which way to go.

What size engines, static and dynamic compression, cam card? It should still idle, check your timing and check for air leaks between the intake and carb or intake and heads.

Its a 350cid (1975 L82 short block) changed from 76cc heads to 64 cc (so about 10:1 ) with 190 cc intake runners, Compcams extreme marine Advertised Duration 278/292, Lift .498/.500, dual plane air gap intake with stock 280trs carbs (7044290) I have sprayed BOTH engines intakes with carb cleaner !!!! Both act the same. No change in rpm. If I block the air horn it will speed up a lil.

Sure it's not sucking in water and stalling it ?

Does the samething when dry fired.

What part number is the intake? If it's a square bore intake there may not be enough flange to seal the carb on a spread bore carb. Edelbrock makes an adapter plate that's only an 1/8' thick for just this. Might be sucking air around carb base.

This one ?
https://www.summitracing.com/parts/c...44-4/overview/
Brand:COMP Cams
Manufacturer's Part Number:12-244-4
Product Line:COMP Cams Xtreme Marine Camshafts
Summit Racing Part Number:CCA-12-244-4
Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:2,000-6,200
Duration at 050 inch Lift:234 int./244 exh.
Advertised Duration:278 int./292 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.498 int./0.500 exh.
Lobe Separation (degrees):112

If so, yeh,exhaust sucking water back is a huge possibility
#2, engine will probably ant initial timing somewhere between 16-20* BTDC
#3 the stock carb metering will be out too lunch. don't know what to suggest with your cam/comp....can't help you there as cams that large I have a Holley Carb on it.

yes it is a square intake with this adaptor https://www.speedwaymotors.com/Unive...SABEgLt7vD_BwE

Yup, that's the one. But like I said it does the samething when dry fired.

Same cam, same cam part # . CCA-CL12-244-4
You just linked the cam + lifter kit. # CL12-244-4

my bad, I fixed my reply. :)

Some good Qjet idle/low speed tuning info linked below.

Drilling Qjet Idle Tubes- Fact, or just BS ?? - Performance Years Online Forums

Those cams are going to want a lot more ignition advance at idle too.

Im at 10deg. now

Bump it to 20* initial (idle) ......but DO NOT drive the boat like that since that will likely be overtimed once the centrifugal advance kicks in....this is simply seeing what it wants for idle timing.

You will likely need to reduce the amount of centrifugal advance so you can run more initial and not overtime the engine while running at higher RPM under load.

What is your total timing now?

not sure , should still be what the stock 280TRS had.

It liked that !!!! down to 900rpms now

At 3000 rpm im at 35deg

Is that where it stops advancing?

Also, as suggested previously...you will want a wide band AFR gauge for tuning.

This manifold adapter may work for you.

https://www.cpperformance.com/p-1043...SABEgKdxfD_BwE

widebands almost make me feel like im cheating...lol

Every single IC engine toy I have either has a wideband on it or has a provision for me to hookup one of my handheld widebands.

Since you have changed the configuration of the engines you will need to change the calibration.

I would consider a wideband a requirement since you have modified the engines.

Thank to you all. Now that it runs, I have something to work from so ill be good.

agreed. Will run so much better at idle, fire right up and not foul up. I so the same initial at aroind 20 , 32 at full on my talldecks. Short curve in at 3500 or so

Go to a holley if considering changing carbs. Hate thise quadra jets

Now that you have idle you can keep on figuring it out. See if it will idle with less timing because 35 degrees at full advance is a little on the iffy side. But if you think you will run it that way give it premium fuel to fight off detonation. What ignition is in there? Can it be adjusted for less advance all in?
Also SB alluded to possible reversion. I see you have the low rise exhaust risers. After an idle period remove them and inspect inside the exhaust for water. If you find water you will have to change to a higher riser. And you might want to just do it any way.
And be sure your exhaust has functioning flappers on the ends to reduce the same water incursion. I did not and have been battling reversion with a bigger cam.

If the heads are the newer style vortec they need a lot less timing. You'll need to limit your mechanical advance to 10 degrees.