:laugh:I was just out for my 5 mile morning run and I was thinking about this thread while I was running. Thought about my 4-7 swap cam, and was going to post that suggestion.:laugh:
Just checked all the wires with a inline plug tester light and I'm good for juice everywhere. The plugs are a little hidden by the headers so it's hard to get at some wires and the headers heat up quick. I'll email the builder about the 4 7 swap, when I pulled the number 1 wire with it running ( easiest to get too ) nothing really changed .
:laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: Funny. Anyway if you are absolutely sure ALL wires are firing and sure they are on correct, then it could be a vacuum leak(seems like you should have more than 15 in. of vacuum anyway)? Could be from the bottom side of intake, a laser thermometer on each header tube will tell if that cylinder is firing, the 2 center cylinders will typically be hotter because of the heat build up from 2 exhaust ports so close together. Had this happen to me before on a fresh build more than once! Was a bitch to track down too because it was leaking from the bottom side!!! The other time the intake wouldn't bolt flush and was visibly obvious before starting. The second time there was no visible misalignment and I was 99.99% sure a new build shouldn't be burning oil and have like 3 cold cylinders.
Found a small Crack on the rear facing side of the cap, seems small and wouldn't be an issue but here's a pic of it Looks like more of a stress Crack, could this be doing anything? Would be nice if it's just been the cap shorting to the firewall the who time. I didn't hear the tell tale Crack or snaps but would be tough over open headers if it's minor
You should just swap 4 and 7 on the distributor cap. You'll know right away if it's that as soon as you start it.
I will tomorrow when I put things back together, I'd be surprised as they're companion cylinders but I'll try anything. What did you think of the minor Crack in the Cap Larry?
The 4-7 swap is pretty popular so I wouldn't be surprised. That cap crack doesn't look like much to me. Connect a screwdriver to ground and probe that area with the engine running.
I doubt it is a 4/7 swap cam, unless Blueprint got a quantity discount on a pile of cams that someone couldn't move and needed to? BP seems like they would be a bean counter place like most production type places like that and usually a 4/7 swap cams costs more. I'm sure they would use that as a gimmick to sell engines with one of them as well if they installed a 4/7 swap cam in his 383? Is this your engine?; http://blueprintengines.com/index.p...g/gm-383-main/item/gm-383-dressed-bp38313ctc1 Looks like the same cam, it doesn't say 4/7 swap anywhere in the ad but that doesn't necessarily mean it isn't just more likely it isn't. It does say 400 external balancer required though, with a late model weighted flex plate. Derek
The builder may have made a mistake, or been unaware it was a 4-7 swap, or some other mistake. That is why they put erasers on pencils. I have inadvertently swapped #5 and #7 by mistake. The engine runs rough and has a shake as you open the throttle. Sure sounds like your problem. 4 and 7 are companion cylinders in the regular firing order as well as the 4-7 swap. One is on the exhaust stroke and one is on the compression stroke. If that is your problem, you are firing 2 cylinders on the exhaust stroke.
I followed that link for the motor, and I am very surprised that they are selling an external balanced engine, without the flexplate and balancer. As a guy who has been building external balanced engines for a long time now, I would not leave that to chance. That's neutral balance thinking.... Although this is not your issue, it shakes because it's running poorly. It's either got plug wires on wrong, a huge vacuum leak, or possibly the rockers have too much preload.. Funny thing on aluminum head motors, if they had borderline too much, but still workable when it was hot, and the heads were all swelled up, it very well might be hanging the valves open just enough to kill compression in a couple cylinders, when it's cold. Run a compression test on it.. cold. JW
That's essentially the motor, I got mine from Speedway motors and they have a setup that comes almost the same just minus the carb. It came with Balancer installed as well as the distributer locked in from the dyno pulls. It came with the weighted flywheel that I installed my self. http://www.speedwaymotors.com/BluePrint-383-Small-Block-Chevy-Roller-Crate-Engine,60536.html
The cam specs on that engine are bigger, Hydraulic roller camshaft .528" Intake lift .536" Exhaust lift 230 Intake duration @ .050" 240 Exhaust duration @ .050" 112 lobe separation That's much like my cam. I have a bit of a rough idle and mine makes about 15" of vacuum at 900 RPM in Park.
the idle will be rougher on a smaller cubic inch engine. whats fairly smooth on a 455 will be a bit more lopey on a 350 or 383
I had checked for vacuum leaks but if it's somewhere sneaky I guess I'd miss it. The bull**** part is I went this route to avoid problems. 4500$ might not be a big deal for some people but it was for me, I'm on the Canadian side so multiply that by 1.3. Figured production builder with dyno sheet was a safe bet. Been a REALLY tough 2 years for me and I really was looking forward to having a fun car again with some reliable power to look forward too. The thought of wasting this summer troubleshooting a brand new F'n motor instead of it being my "happy place" sucks I'll check the cap for a short tomorrow with a screwdriver , I sent the video to Blueprint and they said it looked fine to them which I don't understand. The thought of pulling this motor and crossing the border in NY to send it back is something I don't even want to think about
Can you borrow an infrared thermometer and check the temperature of all eight cylinders? If you have ignition wires crossed or a valve that is preloaded too tightly, it should be quite apparent.
