Aha, two messages that I felt were spam from 2022, I thought I'd opened them, but maybe not. Both were "I have a friend who has the parts your looking for".
So my little envelope icon for private messages is continuously blinking for new private messages, but when I click on it my private message window does not show anything new? Whats up with that?
I gave it a thorough going over this morning. bad news is that cylinders #3 and #4 only have 55 lb compression. So I think I'm looking at a rebuild, at least the top end. I can check the rod bearings once the head is off, but this will have to wait until after hunting season as it seems likely to be more than a weekend job.
Timing is set to 4 deg BTDC, where it's been for the last four years. It definitely advances mechanically when I rev it a bit. Could a lack of fuel under load lead to the knock? Carb is a Weber 32/36 which is always a little limited on the accelerator pump as it only has a pump on one bore. But this is different. I'll try putting some vacuum on the distributor to see if it advances
What Larry said. Rods tend to knock as the load is coming off. That little slack time when it is not under heavy compression or power as you back off. It could be a wrist pin. I once had a knock that turned out to be an exhaust leak. As Larry said the stumble could be the carb maybe the acceleration pump or just some dirt in a jet. No more traffic than is on this site I doubt if it matters where you post your question.
Glad to know the plug fixed your first issue. as to a bad bearing making it stumble more than likely NOT the stumble could a carb or timing issue Or a combo of both.
So I changed the plug in #1 and that cured the timing light not firing. I put in new plugs, rotor and dizzy cap, and reset the timing. It started more easily and idled well, but it still stumbles on acceleration and I am hearing what sounds like a rod bearing knock under load. I swapped out the pertronix with points and reset the dwell, The engine ran the same, still stumbles and knocks under a load. I cannot hear the knock at idle anywhere using a stethoscope. I would have thought that I'd hear a bad rod bearing even if it wasn't under load. Could a bearing going bad explain the stumble on acceleration? Maybe I need to move this question to the engine forum.
Did you check the compression in that hole? Yes, try another plug. Time on the side of the road has helped form my feelings about aftermarket HEI. When I ran it in my '53 pickup there was always a spare module in the glove box and a complete points distributer under the seat. Is the height on the other engine aftermarket or GM? I think there were two GM HEI distributers a small one & a big one. The big one is best but ugly.
So I'm having a strange ignition issue with the 153 in my CJ2a. It has a miss, and in checking the timing I noticed the timing light does not fire consistently on the #1 cylinder. I put the light on the other cylinders and they all seem to fire the light consistently. The #1 plug is black and sooty, the other three look normal. I swapped the plug wires between #1 and #2, same result, (#1 is still inconsistent, #2 is normal). I'm a little baffled by this as the cap and rotor look fine. I ordered a new cap and rotor anyway. I put a pertronix in this distributor about 4 years ago, could it be failing? Question: My spare motor has an HEI distributor on it. Can I just swap that in? The only connections I see on it are for "BATT" and "TACH". Can I just give it 12V from the battery and run it? Doesn't it need a ground like the older coil has?
Thanks Tom! It was in primer for a decade and I got most of the bodywork done in college but never got a chance to paint it. Last September, I finally got it disassembled after getting it running, driving, and tuned, and committed myself to finally painting it. Had some tiger stripes in it from poor paint technique so I wet sanded it and painted it again it came out more orange-peel-ey but the color was consistent this time. I was happy enough with it being the first time painting a car and wanted to get it running and driving for the spring. Now it's time to tear the interior apart and finish sewing up the seat covers and making the headliner and interior panels.
Will do Beater! I wanted to get this car to the GS nationals in more-or-less this current state in the early spring with it running and driving to show it off a bit before anything possibly goes terribly wrong. Then I plan to turn up the boost a bit more and turn up the max RPM a bit more past 5000.
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I was a bit curious on y'alls thoughts on the timing map which you can kinda see in this video When running 93 octane, my total timings at WOT are - no boost is 24-26* - 7psi is 18* - 14psi is 9* Tom, in your turbo 250 video when you had it in the dyno cell, is this timing anywhere close to the ballpark you were in? Did you have a something close to 9.3:1 compression or was it like 8:1 or 8.5:1?
I have a knock sensor linked to my computer so I can visualize any knocking which is what you see on the right half of the screen in that video. I'm super paranoid about detonation given my previous experiences and never paid super close attention to what total timing was on the stock motor or what I was running as total timing beforehand.
I tuned the timing table a ton and have taken the plugs out a million times to check for peppering (detonation) and put a boroscope into the cylinders to check the pistons. I have only ever seen very light detonation evidence on the pistons and very light peppering on spark plugs during tuning but the tune seems quite stable for the moment. Increasing the timing past this point didn't seem to result in much power gain but I figure these are already super conservative timings anyway. The timing amounts just seem super low given I thought total timing was like 32* stock and you're supposed to take like 1*/1psi to be on the safe side which would put me at wanting 18* @ 14psi instead of the 9* I am running. Idk maybe I'm just rambling. It runs well, and maybe 9.3:1 being on the higher end of compression ratios means I need to pull more timing than 1*/1psi. Curious for y'alls thoughts.
Thanks for the full update. Please let us know what happens when you start pushing it further. Thanks for your commitment to your project. Ithaca been fun and informative to follow. Congratulations on all of your other accomplishments along the way too!
They aren't rare and seem to be relatively common on other inline forums. On the Stovebolt forum for instance, they have been offered for free in running condition and sometimes an astronomical price is asked for one that has been sitting out in the elements with the head and oil pan removed for decades. So there is really no normal pricing baseline for them unfortunately....
Yes, I had forgotten that those are machined as a pair. I'm sure many were mismatched.
When I was a kid my dad was a mechanic. He was also a machinist and was allowed to use the machine shop at a couple of the bigger parts houses in Amarillo. I often went with him. Those guys knew their stuff. When I was a counterman for several years I got to work with one of those old time lifelong parts guys. He taught me so much but there was more in his head than there was in the books.
Never realized that O'Reilly bought up those other stores. They have still been my best bet for finding folks who know what they're doing around here these days. I seldom have a simple "look up the make and model" part that I'm after but no mater what I'm looking for the ones here seem to have the folks that can at least look up part numbers and find it in the back no sweat.
Side note. Cleaned some grime off the transmission to get some pictures to be ready to sell it and noticed a part of the casting on the "bellhousing" indicating that both halves need to stay together and be installed together (the upper and lower parts that I was initially confused over before you pointed out that the 30 bolts on the converter needed to come out). Thought that was interesting, I suppose that makes sense if they were machined as a set but I wonder if that was the same for all or something unique to the military applications like the motor / trans I just removed...
Anyway, last parts store quip I'll share since I feel like I've taken this very simple thread way off topic... My first trip to a "proper" parts store, the kind with big and little boxes stacked to the roof and a guy behind the counter who know what every single one was for was with my grand father. We were getting a 66 Nova, car I still have, back on the road and needed wheel cylinder rebuild kits for all 4 corners. I still cannot express how amazed I was that we could bring the old one it, tell the gentleman a few words about what it was for, and that he could grab a couple boxes and be right. I was astounded... Things I never thought I'd miss.
Hi all, very similar post to one I just made in the engines forum about a GMC straight 6. Going to be some overlap of wording here because I'm not sure what the overlap between the two forums is and could use the assistance on both.
I have a working GMC Hydramatic, I believe this came out of a deuce and a half army truck and it was paired behind a 302. We just pulled this from my family's motor home as part of the process of getting it modernized and back on the road.
I'm struggling to figure out what a fair price to sell it would be. I've done a little looking and can't find any listings for these for sale, or even vehicles with them in them for sale or sold. GM didn't do me any favors by keeping the "Hydramatic" name running strong all these years later with their more modern stuff so the search results get really muddy.
Any insight into the value of something like this would be greatly appreciated.
To be clear, just so this doesn't get flagged as being in the wrong forum, once we have some more info about the market for these, I'll post a for sale in the swap meet here with pictures and more specifics. Just trying to continue educating myself before we sell it.
PS. I understand this is possibly an odd post, so by all means, feel free to PM me, or reply with any relevant info that might help.
Hi all, I'm not a particularly active member here but sort of invited myself into this world when we decided to resurrect my family's old 60's motor home that was, at some point probably in the 70's, swapped with a 302 GMC from a deuce and a half Army truck. (So that's the sealed engine, no cam driven fuel pump.)
We're in the process of getting this coach back on the road and for all the 302 is a cool retro piece, it needs to go. Parts are hard to find, so is knowledge about them, and we need to go a different direction with the powertrain for it to be a viable RV.
Here's my dilemma, I'm struggling to figure out what a fair price to sell the current 302 for is... There aren't many online that I find for sale or sold. It feels like the sort of thing that is pretty niche today but I was originally directed here when I was asking for help about getting it back on the road for our resurrection trip back home here in NC. Y'all seemed like a good group to ask now that the motor is out and able to be sold.
So here's the deal:
It's a running 302 GMC, out of an Army truck. Stock oil pan, no mechanical fuel pump. I'm looking to get an idea of what fair market value would be, or a range, or first hand experience from folks who have sold or bought a big GMC straight 6.
To be clear, just so this doesn't get flagged as being in the wrong forum, once we have some more info about the market for these, I'll post a for sale in the swap meet here with pictures and more specifics. Just trying to continue educating myself before we sell it.
PS. I understand this is possibly an odd post, so by all means, feel free to PM me, or reply with any relevant info that might help.
I totally get it! Sometimes projects just get shelved for a bit. I kinda felt like that with the 250 turbo project and always felt horrible whenever I thought about it, but I started making cardboard lists of little things to get done and would spend weekends here and over the past couple of years and it just took putting one foot in front of the other to get it over the finish line.
Alright everyone. After 14 years, I wanted to bring this thread to a soft close with an overview and driving video I just posted here
Since starting this thread, I've been to college, gotten married, bought a house, and switched jobs and over the past couple of years, I finally had the time and money to finish this build up.
Below is a list of the details that I go over most of in the video Original Chevy 250 block inline 6 bored .040" over .040" over Ross racing forged pistons 1.94" intake/1.7" exhaust head with lump ports and 7/16"? studs done by @tlowe Compression ratio calculated to be 9.27:1. Comp cam roller rockers Stock Rods with ARP rod bolts Stock crank and crank bolts Offenhauser 4BBL manifold SPA Turbo Manifold GTX 3582R Gen II ball bearing turbo running at 13psi (water cooled) Holly Super Sniper 650 Go EFI replacement fuel tank with 340lph in-tank fuel pump Generic eBay intercooler hydraulic flat tappet turbo Cam (cam card in video) high flow water pump Tial MVS 44mm waste gate 3" exhaust to straight through borla muffler Standard HEI distributor modified for timing control by Holley super sniper (shown in video)
I can't thank y'all enough for all your help along the way. I'll probably be pushing the limits here and there hoping everything stays together. I have a complete spare 230 and spare 250 just in case anything goes wrong because this car will never see a V8. I'll post here if there are any major developments but as of now, I'm happy with the power levels (I'm guessing low to mid 400HP?) and it'll spin the tires in first and sometimes second gear on my 255/70R15 tires which are quite tall. 0-60 I'm guessing in the mid to low 5 seconds but a column shifted manual doesn't help much in that regard.
