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Posted By Discussion Topic: Engine has low vacuum -- page: 1 2     LTim1947 02-14-2012 @ 12:10 PM reply profile send p.m. Member Posts: 11 Joined: Feb 2012 This is a restored engine with less than 500 miles on it, has equal compression on all 8 cylinders. The distributor has been rebuilt with new points, rotor and cap, new wires. The engine starts and idles fine but will not accelerate. I have detected low vacuum. Any suggestions? alanwoodieman 02-14-2012 @ 2:12 PM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 try adjusting the timing to optomize vacuum reading, will help if you will tell us what year engine and what has been done to it. radical cam? stock? aluminum heads, etc LTim1947 02-15-2012 @ 12:22 PM reply profile send p.m. Member Posts: 11 Joined: Feb 2012 I dont know about the cam as I bought the car wrecked from Haggarty. The engine idles very quietly, so probably it has no special cam. We have slid the timing up and down the range without any change. The heads are finned aluminum by Eddlebrock. The intake manifold is polished eddlebrock also. I am measuring the low vac at the base of carb 1, with the line to the distributor disconnected and also with the gauge plugged in line (T) both read the same. Your help is greatly appreciated. I am really stumped as I believe that I have explored everfy thing I can think of. This motor has the crab type dist. and the cap was cracked,rhe rotor was damaged and one set of points had the spring broken. Everything has been removed cleaned and inspected of any subsiquent damage. then reassembled points gapped vacuum brake set properly. I however did not go behind the points plate to check the counter weights as they seemed to be ok. I plan to go and check this out,alrhough it should not relate to the low vac at carb one or so I think. The intake manifold was checked for flat and its flat and checked to see if it sustained any wreck damage.A new gasket was installed and the bolts are torqed to 35 lbs. It would have to have a serious crack to destroy the vacuum so much,again so I think. Any other help would be appreciated. LJT Stroker 02-15-2012 @ 1:20 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Just curious...you say the manifold is an Edelbrock 2-carb. Edelbrock made 3 totally different 2-carb flathead designs. One had the carbs close together, and featured a plenum, like the stock manifold. The other, called "The Super" had the carbs spread apart with no plenum. The 3rd, was called the "Slingshot", and has the two carbs mounted on a sort of "Y" above the plenum. If yours' is the "Super", it is very hard to get a good vacuum reading as each carb barrel only feeds 2 cylinders, and those are isolated from the remaining 6 because there is no plenum (are no plenae?) The Super while cool-looking, and the most efficient at full throttle due to the short-direct runners, was never intended to be run on the street. If your manifold is an Edelbrock "Super", and you block off one carb, it will only run on four cylinders. I just went back to your other post, and saw that you mentioned the fan bracket. Forget my comments regarding Edelbrock "Supers", as they didn't have a fan/generator bracket. In any case, a crack in that area shouldn't affect vacuum. It's a little tricky trying to troubleshoot two posts on the same subject with different portions of the problem distributed on each, but we're trying! This message was edited by Stroker on 2-15-12 @ 1:44 PM deuce_roadster 02-15-2012 @ 2:01 PM reply profile send p.m. Member Posts: 284 Joined: Oct 2009 Stroker, the older Edelbrock Supers did have a generator/fan mount. Look closeley at the front of mine, I have an alt mounted there. I have notices that the new ones do not have any mount. I have plenty of vacuum and it idles fine after it gets above 150 degrees. I am using the stock vacuum w/s wiper motor. Stroker 02-15-2012 @ 2:27 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 What a pretty sight! I stand corrected. I think I was mentally imaging the V8-60 version, which is a lot like the current offering. Appreciate the input, and I hope LTim finds the source of his problem. Maybe O'l Bill could swap his late issue Super on an early one like yours, and eliminate his electric fan. I had an Edelbrock 3 pot on my 32, and while it had the bracket, there would have been no room for an alternator, had there been such an animal back in 57. I made a fan mount using the front of a 3-brush generator w/stock bearing, a 1-inch aluminum spacer, and a Fafner flange bearing on the shortened armature shaft. I ran my generator off of a head bracket, and the set-up worked for years. It finally bought the farm when I lost a blade off the fan, which punched an additional louver on the left side of the hood, and the un-balanced remains damaged the guide rails on the manifold generator mounting surface. This message was edited by Stroker on 2-15-12 @ 2:44 PM deuce_roadster 02-15-2012 @ 5:05 PM reply profile send p.m. Member Posts: 284 Joined: Oct 2009 Stroker, I can tell from your many posts you have a vast knowledge and experience. I wasn't correcting you but adding to your knowledge base. I machined an offset bracket for my alt, not much room with the carb so far forward. I am very curious to find where this low vacuum reading is coming from. Has the location of where the reading is being taken been stated? My flathead has 6k miles on it, runs and idles fine even at 6600 feet up on Mt Rainier (see picture). Stroker 02-15-2012 @ 5:47 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 deuce_roadster: I'm just "old"*. When you have been around for as long as I have, you tend to accumulate a lot of mostly useless mental detritus. However, I will say that my "mutterings" were not in vain, since they elicited the beautiful photo of your roadster, which is definitely a "keeper". I also appreciate your comments regarding the tractability of multiple carbs. For some reason, I don't recall that 3 Strombergs on a flattie created great drive-ability issues. Perhaps our current generation of operators are so used to drive-by-wire-injected throttle response that any micro-second hesitation is unacceptable. *but not quit as "old" as Supereal. Pauls39 02-15-2012 @ 8:30 PM reply profile send p.m. Member Posts: 81 Joined: Oct 2009 You really need to remove the distributor and give it a good looking over. Taking a hard hit is bound to do some damage. Check for cracks particularly around the vacuum brake area. Check to be sure the shaft is straight and that the bushing line up. The advance weights should be free. Also give that front cover a good look for cracks. Internal engine damage is a posibility. The engine came to a sudden stop with presure on the distributor shaft and thus on the cam. Be sure the cam gear is still lined up on the cam where it is suposed to be. 60 lbs of compression is not great, the cam maybe off time. Old timers used to spray carb cleaner around suspect cracks listening for an increase in rpm they would get when the spray hit the affected part. Do so with extreme care! supereal 02-16-2012 @ 11:19 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 That very low compression, which should be at least in the 75-85 range, should be checked with a dry/wet test to see if it is due to leaky valves or poor ring sealing, or both. With only 60 lbs reported, I would hazard a guess that the engine was junk before the collision. The condition of, or damage to, the distributor would not affect compression, nor would timing, unless the cam was out of sync with the combustion cycle. I wouldn't expect much vacuum with that low compression, anyway. The last time I saw that problem, a local guy brought in a very nice '57 T-Bird that would hardly run. It, too, had low compression, and we found that some idiot had tried to "relieve" the block, and ground it down until the top compression ring was exposed! We suppose the former owner gave it a good selling when it wouldn't run well. That may be the case here, too.

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