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wildfelr

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rqb3263 1981 Avanti II....Justa little about what ive learned in the last 2 days....My 81 /305 has 104k miles and exhibited all symptoms of leaky head gasket (rough run for first 1 min. then smooth)...so its time to do a valve job anyway....the heads had never been off so had the original factory stamped steel head gaskets...what apain....well might as well do a cam and lifters at the same time .....and oooohboy am i glad i did....this too had never been apart...so over to Crane Came in Daytona for a cam/lifter set and oh well might as well get all new valve spring set...now the really good news....the timing chain was very sloppy and my 81/ 305 had the plastic/nylon timing gear (prone to failure)...there is no way to tell what kind of gear is in your motor without taking it apart (to the best of my knowledge)...the new timing set are all steel Double roller about $25. Cloys brand......requires removal of fan , radiator, and move the a/c condenser(not remove just move)....and lotsa other stuff....do it all, do it once....lotsa clean up to do.....more later...BILL RQB3263 in Florida

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RQB3263 Another quick update as i prepare to reassemble the 305 in rqb3263....I picked up the heads from the machine shop painted ready to go, and cleaned lotsa parts yesterday....they will be painted today and more cleanup on the block...interesting note..the old cam had at least one severely worn lobe which acountec for my rough running and "tic"....and four pitted lifters...the new Crane torque (rv) cam and lifters ($190) will make a big difference..reassembly may begin later today id like to be on the road by Fri. if it warms up in my shop....its been down in the 50's...I hope this helps some other 305/small block owners. ...BILL

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Using the 'double roller' all steel timing gear setup is great advice. As far as the worn cam lobe, I believe Chevy 305's were known for that problem......Have fun!!!!!

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Agreed that GM had wear issues sometime during that era.

BTW, the RV grind is a good choice. I built a 305 with the larger valve heads, Weiand RV cam and dual plane intake for my 39 Ford Coupe. It was a nice free breathing, fast revving engine that would put a smile on one's face everytime. If I had a 350 block I'd have built it but the 305 worked nicely in that car.

The Avanti is a heavier car but you should still appreciate the upgrade. Bob

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It shows that up to a point, the actual displacement isn't as important as sometimes thought...it's the internals and their specs and how they work together to achieve specific design purposes. Everything else being equal (which it rarely is), you can take a milquetoast SBC from grandma's Chevy II and change the cam, heads, intake, etc., and you suddenly have a real fire breather. Just a simple cam change can move the power and torque band up or down depending on what you want from the engine...but it still takes matching the cam, induction, exhaust, etc., to get it all working at peak efficiency.

When I used to work in an auto center many years ago, it amazed me how guys would buy a lot of quality parts without a plan on what they wanted as a result...and were disappointed...a lot of money spent for little return. You can buy good quality private label parts that are well matched and well installed and get excellent results and get poor results from buying and installing mismatched brand name parts.

My '69 Vette has a L88 camshaft installed by the last owner...I wish he didn't do that as it makes for a cranky engine. Its power band is 4400-7000 rpm's...I don't drive it that fast so its high end capability is lost on me. The low end suffers some...a 427 Tri-Power makes plenty of torque regardless of the cam...especially with a 4.11 rear...but I'd still prefer a bit smoother running engine than that beast. That's one reason why I plan on putting the car up for sale...6 mpg is a bit hard to take plus I simply enjoy the Avantis more. My age and weak knees make getting out of the Vette painful as well.

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You seem to be knowledgeable about your cam and head work. But, if you need some coaching on breaking in that new cam, we are all pleased to help. Too many new flat tappet cam/lifter installs are ruined in the first 10-20 minutes of start-up.

Joe

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Thanks ...Crane sends a detailed break-in schedule and lobe lube and a recommended high zink break-in oil ($6.00 a qt.) so ill follow there rec. a....ive only done about 100 of these in the last 50 yrs of all kinds, aircraft, marine, auto from oldsmobiles to VWs and about everything in between...Ill take my time, follow directions, and do it all, do it once....BILL RQB3263

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RQB3263...Please enlighten me...im going to install an inline fuel filter on the frame rail.....in the fuel line, on the frame rail under the pass. door area is a small rectangular device...could be a drain i dont know ...doesnt look like a shutoff valve but maybe it is i hope ....what is it ??? YOU CAN ALWAYS CALL ME ...352-475-3190H OR 386 466-6434C RQB3263

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RQB3263...Please enlighten me...im going to install an inline fuel filter on the frame rail.....in the fuel line, on the frame rail under the pass. door area is a small rectangular device...could be a drain i dont know ...doesnt look like a shutoff valve but maybe it is i hope ....what is it ??? YOU CAN ALWAYS CALL ME ...352-475-3190H OR 386 466-6434C RQB3263

It's a drain, should be a brass tee with IIRC 3/8" NPT.

I plumbed a fuel filter and shutoff valve in-line before the filter so I could shutoff the fuel from the tank to change the filter. The whole assembly is just before the Tee in the line otherwise the tank will drain without the shutoff.

To drain the tank initially, I parked the Avanti outside and drained the tank into several shallow pans. It can hold over 15 gallons. If the tee drain plug is tough to turn you can disconnect/cut the rubber line in the engine compartment.

My pictures are too far away to reference until next week. Bob

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Thanks Bob now i know what im going to do...now to find an appropriate shutoff valve .....thanks .....RQB3263

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The Avanti gas tank holds 21 gallons, so that's a project to do with the tank just about empty.

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Fuel shut off /filter installation complete...purchased filter at "Car Quest" and all fittings at "Cemtral Hydraulics" in Ocala, fl.....Easy installation, one cut, one flair, install, leak test....done

Valve job/cam, lifter, timing set project close to being done....A/C comp, carb, dist and harness all thats left...oh and lets not forget the hood...It should be ready for test run early this next week... RQB3263...BILL

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RQB3263

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RQB3263 I finished the valve job etc on my 305 and first break-in /test drive is great with new Crane cam. Ill do another 50 mile break-in drive this afternoon and change the oil to 10w40 , new filter and reinstall the hood.....NEXT PROJECT: replace the TH350 trans with a 700R4 in April...I would appreciate some enlightenment on this if you have already done it and know the pitfalls .....thanks ....BILL RQB3263 (on the road again in N Florida)

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When you do the transmission swap, you'll also need a new shifter, quadrant and gear indicator...the shifter it self is not mandatory but it won't line up properly with the indicator dial if you don't. The difference isn't great but do it while you have the parts out. It's all available from Nostalgic Motors.

I would suggest looking at a 200R4. It has a better spread of gears than the 700R4...plus it's smaller with less chance of clearance issues which seems to be a car-by-car thing. The 700R4 has a very low first gear with a very abrupt 1-2 up shift. I have the 700 in my '70 and it's all too easy to spin and even smoke the tires with the very low first gear (and second) until you get used to it. The 700 is really for much heavier cars...or at least cars with less of a front weight bias than an Avanti.

The 200R4 isn't as strong a transmission in stock form compared to a 700 but they can be built plenty strong.

In my car there was no problems with clearance that some have experienced, but I did have to have fabricated new neutral safety and backup light switches due to their proximity to the 2 1/2" exhaust pipes installed on the car.

Another thing I did was to in have an aluminum driveshaft installed. It wasn't much more expensive and reduces rotating mass.

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Bruce has done a good job of describing the tranny differences. A couple of added thoughts though.

200R4's are getting harder to find, and as described, will need to be rebuilt. Generally, $1500+. That is also the cost of a 700R4 rebuild but that's not necessary if you can find one in good shape.The 83 Avanti's had 700R4's installed OEM but used a 3:08 or lower # rear gearing. It's the combination of trans type and rear gearing that needs to be considered.

Both are longer that the 350 both in length and mounting pad length so your rear crossmember will either need to be modified or replaced. I built one for for my T56 in the 74 and I'll add the post if necessary.

Both will require a TV cable so your carb needs the correct linkage. No big deal but necessary.

Let's consider a third option. The later electrically controlled 700's are 4L60E's and variations of that. They would be the most available as they are newer and were used in bigger cars and pickup for a number of years. I know the controller costs are higher but, i believe that they can adjust shift points and they also eliminate the TV cable which can be problematic if adjusted incorrectly.

My 2000 Silverado had a 4L??E trans with a 3:77 rearend and shifted just right. That's with the GM computer but my point is for a few hundred more you can get the best of all worlds.

JMHO, Bob

Edited by Avanti83

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The 700R4, being longer, may require the driveshaft to be shortened. I went with a rebuilt 200R4 in my 76 on the advice of the trans shop owner. My 76 has the 400 motor and the 200R4 replaced the Turbo-hydramatic 400 with no issues. You do need as Gunslinger mentioned, a new rear trans mounting plate, shift linkage, tv cable and the plastic shift indicator plate, all available through Nostalgic. The only tricky part is adjusting how you want to control the lock up convertor, whether by a lock out switch or by braking or manual adjustment of the shift lever. The 400 with 200R4 and 3:31 rear end are a good highway mileage friendly combination, dropping my rpm's at 70 mph from 3000 to 2000. If I keep the speed around 65 instead of the 70-75 usual range, I can get 28+ mpg.

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Bill, first I must scold you...you were sand bagging us ! I looked at your profile and saw you do aircraft mechanical work, and we were trying to gingerly advise you...you know more than we do.

I have a 700R4 in my 75 with the 400 engine. It works great and as Gunny says it shifts hard (1->2) and smokes the tires (is that a problem ????). Two comments to all the above good advice:

1.The 'switch' on the lock-up can be simple or complex; some use a speed controller and many use a simple vacuum actuation. I just put a toggle in the circuit and activate when at cruise where it yields benefit.

2.Must do !!! check the plastic gears speedometer on the transmission shaft before you install. You can change the plastic gears on the tip of the speedo cable; however, if the tranny shaft gear and speedo tip gears ratio are not within range, you can not use the appropriate speedo tip gear to get the speedometer to indicate correctly. My speedometer reads 10+ mph high and I can not select a cable tip gear that is the same range as the tranny shaft gear.

To change the plastic gear in the 700R4 must pull and remove the tail housing. So at 75 mph, I read about 90 mph which makes passenger squirm a bit.

Joe

Edited by Devildog

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Good morning Avanti wizzards !!....Sand bagging no not exactly...yes i have been doing this car, aircraft, hot rod thing for 55 years, with many many motors behind me ...but..that experience doesnt keep me from asking for advise. Very little ive done in my entire life hasnt had to be done twice (sometimes more), but i always get it right eventually with the help of others with knowledge and recent experience. mistakes are easy and its been 10 years since ive been into a SBC. So today I will reinstall the intake manifold on my 305 for the 3rd time !! Itsa pain, another hour, another day....

So here is what ive learned in the last 3 days.....NEVER EVER use the silicon manifold end gaskets (rubbery seals) supplied with the gasket set...PERIOD !!. (unless of course you want to do it over because it will leak oil, guaranteed) .. Use gray or black silicon gasket maker instead..degrease the surface and lay a 1/4 inch bead across both ends and wait 15 min.....Smooish the manifold straight down into it and tighten and torque to 25 ft. lbs..A little bit of gasket sealer around the water openings at the 4 corners of the long gaskets is a good idea also ..Ive re torqued mine 3 times and always seem to get a little more each time ...This morning will be the last torque and final reassembly (Im getting good at this)...Its much more difficult (on a 70 yr. old) to do this in the car, easy on an engine stand...I should be back on the road by noon ...As for the 700r4 trans replace ...it will happen...after i recuperate....April at the earliest ....thanks for the info and please keep it coming ....BILL RQB3263

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Devildog, you are on the mark about the plastic speedo gears. The trans shop guy said they had the right gear in my 200R4 trans, but the speedo reads about 8 mph fast. If I'm doing road trips, I usually have the GPS in the car and on so I keep track of the speed that way. Its much better and easier on the wallet to have it reading fast instead of it being off the other way.

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Devildog, you are on the mark about the plastic speedo gears. The trans shop guy said they had the right gear in my 200R4 trans, but the speedo reads about 8 mph fast. If I'm doing road trips, I usually have the GPS in the car and on so I keep track of the speed that way. Its much better and easier on the wallet to have it reading fast instead of it being off the other way.

Just to be clear for others, there are TWO plastic speedo gears. ONE on the tranny shaft in 700R4 tail which can only be replaced with the tranny out of the car. The SECOND is on the tip of the speedo cable which can be easily changed to another gear ratio plastic gear.

However, the cable tip plastic gear choices will only work in a range of 2-3 tip gears for any installed internal shaft gear. There are website that have these gears and the matrix to match to any differential ratio....3:08, 3:36, 3:55 etc.

Joe

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In my '79 with TH400 trans, the drive gear, on the transmission tail-shaft, is brown plastic, 15 tooth,

and the driven gear, on the speedo cable is plastic.

GM uses color coding to help differentiate the number of teeth on gears.

Each additional gear tooth is supposed to change the ratio by 2.5%. accordingly.

For my rear gear ratio, 3.08, and tire size I needed a 33 tooth driven gear. GM only goes down to a 34 tooth so

the speedo will be slightly off but much closer to correct. My '79 had a 36 tooth .

I used several of the calculators available on-line to check for gear tooth required. They all gave the same answer.

Needing a 33 and having to use a 34, anybody know if the speedo will read fast or slow?

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Needing a 33 and having to use a 34, anybody know if the speedo will read fast or slow?

Considering that the DRIVEN gear is 34 teeth instead of 33, that means the driven gear will make slightly fewer revolutions (than a 33-tooth driven gear) as compared to the number of revolutions of the driving gear in the transmission, so the speedometer will read slightly slower than actual.

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Thanks Wayne. Somehow the logic escaped me. Reading slightly slower is in my favor then.

Not that it matters but the newly raised speed limits here locally to 70 mph on some stretches of highway

are mere suggestions for most drivers anyway. As long as I let them go I'm good.

Most days traffic resembles a NASCAR track with all the drafting going on!

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