I have a completely stock 455 in a 70 GS. It seems to run decent for the most part. Cranks well, good temp, oil pressure etc., but I think it seems a bit lethargic. It seems to rev up ok to a certain point, but then kinda falls flat and acts like it won't rev any higher than about mid range. I'm running 93 octane pump gas. I would like to check and make sure everything is set where it should be so I can be certain it is running as good as it can for what it is. What all do I need to check and what numbers or parameters am I shooting for?
Focusing on the ignition curve can be really worthwhile: http://www.v8buick.com/showthread.php?63475 Devon
Start with the simple things first, one or two at a time and see how each one helps. -Check compression and see if all cylinders are even, pull all plugs and open up your carb when checking. -Replace plugs, check gap if necessary. -Check timing - running 93 should enable you to run plenty of advance timing, read the power timing thread on the board, it is excellent! Then read it again. -Check all fuel filters and fuel pickup sock in the tank, make sure they are not impeding fuel on the higher rpm range - pull the fuel line and crank it over and check your flow volume. disconnect your coil-safety first. -Make sure nobody has pulled a banana in the tail pipe trick. -Make sure your choke is pulling all the way off and that you a truly getting wide open throttle. Those are a few easy ones to look at. When I put my 340 in the car, the choke gave me a hard time, wouldn't let the carb open all the way so I had a 2 barrel instead of 4 barrel. A few minor adjustments and I was in business.
Timing is the first thing you should check. Unless the distributor in the engine is the exact same one it left the factory with, forget the stock initial timing specs. What you need to do is check the TOTAL timing. The linked thread explains that. Also make sure your vacuum advance is working. Just because it is connected doesn't mean it is working. Check it with a timing light.
classic Distributor and timing issue- Check distributor for wear, slop, blown vac adv diaphragm, dwell setting, advance weights and spring wear- Forget points and Get an HEI and re time it. for more giggles get a mr gasket performance advance kit. a 455 comes alive with HEI!:eek2:
I plan to check it first of next week. It's the original distributor. How do I check the vacuum advance with the light and can it be done with a standard timing light?
Read and re-read the thread that Devon referenced above. Larry has created an excellent write-up that will get you set.
Yes, it can be done with a standard timing light. All you have to do is apply vacuum to the hose to the canister and watch the timing mark. You will see the mark move upwards as the timing advances. You can use a hand held vacuum tester, or a manifold vacuum source on the carburetor or intake. Read the linked thread to check your total timing.
I'm all new to this old technology. I would like to keep everything looking stock but improve where I can. What about something like a Pertronix ignition setup or what would be my best option in keeping the original distributor but updating the internals to something better?
Proper ignition timing is very important. If you read the Power Timing thread that was linked, it will explain how to check your timing. Read it, and if you don't understand, then ask questions. Yes, electronic ignition can be more precise and dependable, but cars ran for many years using points. You are ready to change parts, but you haven't checked the basics. Check the point dwell, and make sure the dwell is constant and not varying. Make sure the resistance wire and bypass is funtioning correctly. Check the total timing including the mechanical and vacuum advance. Simply changing over to a Petronix or equivalent will get you no where if you have other basic problems. See the linked threads below. http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8 http://www.v8buick.com/showthread.p...nd-HEI-System-function-tests-and-modification
Thanks for the links and info. I'll read up. I'm not ready to replace anything just yet. I've read the link mentioned above and I will continue to read and re-read as I tackle this. I'm at a discovery and learning stage right now. I think it may be assumed that I already know how to do a lot of these procedures when in fact I may not have a clue because I've never done it before or if I have it's been a long time. For example checking the dwell. I've never done that in my life so I have little if any understanding of that, but I'm eager and willing to learn about it and apply what I learn. I'm mainly used to dealing with newer vehicles where these things are controlled by computers. So as I try to get it all together please bare with me and excuse as many of my not so intelligent sounding questions or statements as possible.
No problem at all, that's why I come here, to help. If I may make another suggestion, get yourself a 1970 Buick Chassis manual. That will be your best resource, not only because it has all the service procedures for your car, but because it can educate you on the basics. Just reading the ignition section will explain to you what dwell is. Dwell is the amount of distributor degrees that the points are closed. It can be measured with a dwell meter. http://www.amazon.com/s/?ie=UTF8&ke...=aps&hvadid=3485829185&ref=pd_sl_l76rzftwq_pp The dwell angle for our engines is 30* If you look on the distributor cap, you will see a small aluminum door that can be raised up. Under that door is the point adjustment screw. I believe it takes a 3/16 allen wrench. When replacing points, you adjust the gap (again covered in the manual), then finish the adjustment with the engine running, using the meter. Dwell affects timing, but not visa-versa, so as the points wear, your timing changes. So first order of business is to give the engine a tune up, replacing among other things, the points. You can find the Buick Chassis manuals, used on E Bay, http://www.ebay.com/itm/1970-BUICK-...192?pt=LH_DefaultDomain_0&hash=item4d18735c18 In reprint, http://www.taperformance.com/proddetail.asp?prod=TA_3070 Or even on CD ROM, http://www.gearheadcafe.com/servlet/the-512/1970-Buick-shop-manual,repair/Detail
I've seen numerous Q-Jet carbs that have stuck secondary throttles. They seem to hang-up on distorted intermediate gaskets. The gasket pushes out-of-position over time, and the secondary throttle blades can't move past them. Verify that the primary and secondary throttles fully open. Have someone press the gas pedal to the floor, verify that throttle lever moves to the fully-open position, then look down the primary venturis, and rotate the secondary air door so you can view the secondary throttle blades.
While you can learn quite a bit fooling with points, gap and dwell, it really isn't worth the hassle unless you fear an EM pulse will wipe out all the electronics. I would suggest buying a point replacement module and get beyond that. They are ultra reliable and you'll never have to worry about anything under the cap for quite a while. It will eliminate several headaches and let you concentrate on the power timing. JEGS and Summit both have a Crane kit with a built in rev limiter for $70 http://www.jegs.com/i/Crane+Cams/271/750-1710/10002/-1 http://www.summitracing.com/parts/crn-750-1710
I'll check the carb. I think there's issues there too. The timing was right, but the initial dwell was 25. I reset to 30 then re-timed it to 6. Seems to idle a little fast now doesn't seem to take fuel exactly right. A little of a splutter if you blip the throttle. Also kind of feels like a low idle miss or shudder, but maybe that's the cam? Going up in the revs it smoothes out with no shudder or missing. Definitely running on all 8 cyl though. Maybe it partially fouled a plug cause once I reset the dwell before I re-timed it would barely idle and was running real rich. I hope it's not a wiped cam lobe or anything like that. I still need to check vacuum advance and total timing. I'm trying to get my tach working right first.
I too was used to newer cars. But there isnt a better group of guys on any other forum than these guys. Definitely invest in a chassis manual for your car. It has plenty of diagrams and step by step instructions to follow and then you have the guys here to simplify anything else you dont understand...
Ready to check vacuum advance and total timing. I have timing at idle hose off set to 6 dwell at 30. I plan to check the diaphragm first to see if it will hold vacuum. To check the vacuum advance with the timing light would I simply hook the vacuum hose back up, leave at idle and see if the mark moves up or ? How can I verify exactly how much vacuum advance there is with a conventional light?
Your approach to testing the vacuum advance will work if you're on the right vacuum port. Some ports go directly to the intake manifold and some are positioned above the butterflies to sense vacuum under throttle. Check to see if the port that you're using is sucking air in at idle - if it is it will work the way that you thought. The main effect you'll get with an operating vacuum advance is smooth cruise and better mileage. If you're sorting out an acceleration issue, bear in mind that the vacuum advance drops off when you open the throttle. Too much vacuum advance will lead to surging at cruise. That's not likely to be a problem with your stocker. Cars with big cams end up needing more initial advance and less vacuum and centrifugal - that's explained in Larry's sticky on timing. You can make a timing tape and stick it on your harmonic balancer. This lets you read timing at the indicator without needing a dial-back light. I don't remember the dimensions, but I am sure there have been posts on the board about doing this. Make sure that you use indicators large enough to be read at a distance - keep your face out of the belts.
