Should a carb swap from one engine to another?

I have the 540 fired up using the same Dominator carb that was on the 499. the 499 was about 15-1 (or more), big heads and cam, 3.85 stroke. The 540 is 14-1, pretty big heads and cam (440-1 CNC Indy R2 cam), but with a 4.25 stroke. Same C-16 fuel.

The 540 won't idle where the 499 was set and I have had to crank in a bunch of idle stop. Why would a different engine not run the same carb? Is the signal strength difference with the stroker that much of an influence? Other factors? I have the timing at about 34* fixed.

With the open collectors it sounds pretty stout.

Have you checked for vacuum leaks?

Lots of reasons. Signal strength, venture and booster size will change how the fuel is pulled, engine manifold vacuum, jetting and bleed package etc etc. If it was a simple as bolting it on and it working great there would not be so many choices out there.

I have a boost/vac gauge that I can hook up and see how much "idle" vac it is pulling. I do not think there any leaks but who knows?

A good carb will swap from engine to engine and work pretty well. (carbs are self adjusting - more airflow generates more fuel flow)

We use a Braswell 750 high flow on almost all of the dirt track motors that go on the engine dyno. That carb works on most anything between 600 to 800 hp and 90% of the time it works better than the customer's carb.

So if your carb was working fine and now it isn't, I'd suspect something happened to the carb or maybe the motor has an issue. Did you leave the carb sitting with Q-16 in it? That stuff is nasty.

That's what I thought. No, I got all the gas outta the carb and it has sat for over a year. Very well could be the motor, or plug wires, or a bad plug. All of the header tubes are hot so I think they are all firing. This is the first time this pile of parts has ever ran.

I have a gen 3 1150? Dom I will try tonight. I got it new from Holley on fleabay way too cheap so it is probably not calibrated properly.

Yeah, on a new motor I'd check everything over twice. Check the plug routing, it is easy to swap wires. Pull the plugs and see what they look like, maybe one plug wire isn't seated all the way. Lots of little things go wrong with new builds. I think I've made every mistake in the book at least once, some more than once.

It ain't the carb cause I slapped another on and it did the same thing. I think the problem is too much drag in the engine. As I was triple checking the timing and advancing it a couple degrees I noticed how hard the engine is to turn over. I have been thinking this was due to the rings seating in... the engine cranked over slower with more timing so I am thinking it was too advanced. Backed it off to a couple degrees less than the baseline and the engine still turns over hard with the starter. Same by hand. It is now just downright hard to get to spin.

My hope is this is an interference with the cast Indy front cover and the Powerbond balancer. We had to machine the cover a tad to get it to clear when the motor was built. So either the pulley bolts or the balancer is my hope. May need a spacer behind the balancer if what I suspect is the case and that would be the easiest thing to fix. Otherwise something else along the crank centerline is not happy. .100 clearance with the converter to flex plate. Better not be internal to the motor but if so we'll fix that and drop the CR down to 13-1 and ditch the C-16.

The last roller cam motor I built had 325 lbs on the seats and 830 lbs opened, it turred over really hard by hand with a breaker bar, it made the oil temps get real hot really quick on the dyno also. I ended up removing some of the valve spring shims to allow .030 more to coil bind and that dropped the open pressures to 800 lbs It runs fine in the car so far Let us know what you find, lots of Murphy gremlins out there

My heads and valve covers seem to get kinda warm also compared to the water coming out of the block. This better be a simple fix like getting clnc between the balancer and the front cover. I'm anxious to get the thing where I can drive it on the trailer, get mufflers put on, and do a big fat burnout and seating in the rings.

Got's the need for speed.

It was the Power Bond balancer rubbing on the Indy cast front cover causing drag so it would not idle. Couldn't see any witness marks on the cover but putting masking tape on the cover and turning it over with everything bolted in place revealed the culprit. The guy who assembled the motor had clearanced the cover but didn't go wide enough.

Take away is use a long snout ATI balancer (regular snout also interferes) in the first place. In this case I will get a 0.093 thick spacer from ATI (#916370) to put behind the PB balancer and re-do the belts / crank pickup alignments. Hope the thrust surfaces on the crank / bearing face are still OK and the clearance hasn't gotten too big. But hey, at least the rings had some load on the first runs.

Glad you found the problem. I'd change timing covers instead of having to use a balancer spacer and then having to realign the belt and pickup.

That damn cover is glued in pretty well as is. I have a plethora of spacers now so it won't be a big deal. I want this thing running before it gets too hot to drive.