Nassau65
CCCUK Member
My dads done that a couple of times in recent years as he’s not that good at getting out of convertible Corvettes.
Exciting day - rebuild of 78 coupe
- Thread starter johng
- Start date
johng
CCCUK Member
Here's where the crack started. You can see it's just in from the top left hand corner. The top most screw for the side trim is where my wiggly arrow is. Can't see how that can be the problem. I am wondering though if one of the clips that holds the top windscreen trim in place could have touched the glass. Could be fun trying to remove the top trim, as I put it on straight after fitting the windscreen, because I was worried glue would get into the clips and prevent me fitting the trim. If it has then the trim is now glued in place!
johng
CCCUK Member
When I got the car, the front trims were black and the rear ones were polished. I re-painted both ends black.
Where did you buy your screen from? I'm pretty sure mine came from American Glass, they originally sent me one from an earlier year Corvette, perhaps that's the one you've got now.
Where did you buy your screen from? I'm pretty sure mine came from American Glass, they originally sent me one from an earlier year Corvette, perhaps that's the one you've got now.
Oneball
CCCUK Member
It wasn’t them, (not going to say who it was) didn’t use them for my first screen either, but thanks for mentioning them. Can’t believe I didn’t know about them as they’re almost local, will speak to them in the week.
Forrest Gump
CCCUK regional rep
It seems odd that the crack has started right in the corner. It looks like it’s getting longer too?
Stingray
CCCUK Member
Stress fracture. They start at the edge of the screen and grow inwards.
A typical impact fracture starts at the point of impact and grows outwards.
johng
CCCUK Member
Not sure if it's getting longer, originally I'd seen it from inside the car and there are several inches you can't see from there.
Sounds like a stress fracture then, the question is what caused the stress and how do I stop it happening again. Maybe things will be a bit clearer once I've removed the windscreen trim.
Sounds like a stress fracture then, the question is what caused the stress and how do I stop it happening again. Maybe things will be a bit clearer once I've removed the windscreen trim.
Forrest Gump
CCCUK regional rep
Oh. The installer should have checked there was sufficient clearance though. I still think that there might be grounds for FOC replacement.
johng
CCCUK Member
Couple of small bits of good news today. The rear camber bolts still haven't moved 
and I've re-done my timing as per the method from Lars on the US forum. Timing at tickover without the vacuum advance is now 15 degrees and it's all in at 3200rpm at 36 degrees. Originally the mechanical advance wasn't all in until 4200rpm, but fitting 1 soft spring in the distributor bought this down 1000rpm. I've also made up a limiter for the vacuum advance, so it now only gives 11 degrees rather than 20. Tickover is still stable at 600rpm and it definitely pulls better ( it's not another 50bhp, but a worthwhile improvement for very little cost or effort).
and I've re-done my timing as per the method from Lars on the US forum. Timing at tickover without the vacuum advance is now 15 degrees and it's all in at 3200rpm at 36 degrees. Originally the mechanical advance wasn't all in until 4200rpm, but fitting 1 soft spring in the distributor bought this down 1000rpm. I've also made up a limiter for the vacuum advance, so it now only gives 11 degrees rather than 20. Tickover is still stable at 600rpm and it definitely pulls better ( it's not another 50bhp, but a worthwhile improvement for very little cost or effort).
Chuffer
CCCUK Member
Good to hear you got have it running better and can feel the benefits . With a new Edelbrock 650 cfm fitted I have mine set up at 34 degrees all in . Pulls much more strongly now and a steady tick over at a smidge over 500 rpm .Couple of small bits of good news today. The rear camber bolts still haven't moved
Chuffer
CCCUK Member
This will probably provoke a lot of debate on the Forum but my vacuum advance is not connected since I had the new Edelbrock 650cfm with mechanical secondaries installed in place of the previous oversized and warn out Holley 750 cfm with vacuum secondaries that came on the car . Williams Brothers Racing in Northamptonshire did the install and reset the timing to 34 degrees all in . For the record my engine is a 1985 Camaro IROC -Z 305 cu. in . with 10.9 :1 compression ratio and an Edelbrock Torker 2 flat plane inlet manifold and a Hypertech HEI Street / Strip dizzie . I queeried the no vaccum connection with Williams Bros who are well established and highly regarded drag racers and engine builders and they specialise in Chevy small and big block engine builds . They said the vacuum was not necessary with the car set up as it was .I figured that they were the experts so went with that . Certainly after a bit of minor tuning by them it runs great , pulls like a train as revs build and ticks over fine . It has transformed the car from how sluggish it was before .
There is much discussion about about no vacuum advance at low revs being an issue for starting , low speed running , shorter plug life and poorer fuel economy . As fuel economy on a Vette is a tenuous point anyway , any loss of a couple of MPG at town speeds doesn`t bother me and as the Flat Plane Inlet is better suited to higher revs anyway I tend to drop the 3 speed auto down to 2nd gear for in town low speed driving and the engine is much happier at the slightly higher revs .
Roscobbc
Moderator
People make a big thing about vacuum 'or' mechanical secondaries - they'll quote the Holley 'double' pumper as a example and how 'experts' say that a double pumper (Holley mechanical secondary carb) shouldn't be used on an automatic car and then only ever on a lightweight high numerical gear ratio vehicle.......and they are 100% correct.
The reason why is...... a Holley double pumper doesn't have an over-ride device to prevent the driver 'planting' his right foot heavily on the gas pedal from a slow speed, opening-up all 4 barrels and overfueling the engine at lower rpm. Its not just fuel economy that's at issue - its also the longer term effects of potential bore wash from an overly rich mixture.
Edelbrock's carb is what was originally a Carter AFB. Designed in the '60s it was seen as an OEM fitment on many muscle cars of the period and gave a great combination of performance and economy (as compared to the Holley of the 'day'). Seemingly Carter were never able to resolve some of the operational issues that were seemingly ocurring out in the field with older AFB's. Edlebrock bought the rights from Carter and seemingly re-engineered and re-marketed it as thier own carb.
The Edelbrock carb is a mechanical secondary carb. It is not a 'double pumper'. Only a Holley or generic equivalent can be a 'double pumper' with its 4 no. accelerator pumps.
Carter's AFB, Rochester's Quadralet and Edelbrock's carb all have mechnical actuation of the secondaries AND importantly an 'interlock' system built-in to the carb that prevents the secondaries opening before the engine has developed sufficient vacuum.
The reason why is...... a Holley double pumper doesn't have an over-ride device to prevent the driver 'planting' his right foot heavily on the gas pedal from a slow speed, opening-up all 4 barrels and overfueling the engine at lower rpm. Its not just fuel economy that's at issue - its also the longer term effects of potential bore wash from an overly rich mixture.
Edelbrock's carb is what was originally a Carter AFB. Designed in the '60s it was seen as an OEM fitment on many muscle cars of the period and gave a great combination of performance and economy (as compared to the Holley of the 'day'). Seemingly Carter were never able to resolve some of the operational issues that were seemingly ocurring out in the field with older AFB's. Edlebrock bought the rights from Carter and seemingly re-engineered and re-marketed it as thier own carb.
The Edelbrock carb is a mechanical secondary carb. It is not a 'double pumper'. Only a Holley or generic equivalent can be a 'double pumper' with its 4 no. accelerator pumps.
Carter's AFB, Rochester's Quadralet and Edelbrock's carb all have mechnical actuation of the secondaries AND importantly an 'interlock' system built-in to the carb that prevents the secondaries opening before the engine has developed sufficient vacuum.
Roscobbc
Moderator
Missing nothing Chuffer - thread has gone a bit 'off topic' anyway. Too many misconceptions our there about carb types and mech/vac systems. The merits or otherwise of advance/regard on a street engine are another rather large and often misunderstood 'can of worms'.Ross , am I missing something ? I tought we discussing vacuum advance and settings on timing not the ins and outs of vacuum secondaries versus mechanical secondaries on carbs .
Chuffer
CCCUK Member
Thank goodness for that Ross ! Having reached a significant birthday yesterday that features a 7 in it I thought I had lost the plot already .
I know just what you mean about misconceptions on carb types , and as for the advance / retard `can of worms` , I have stopped reading up on it as hit made my brain hurt !
johng
CCCUK Member
I've read that vacuum advance is only of secondary importance, but I find it interesting that Chuffer has 0 degrees, I have 11 degrees and Andy (aka Forrest Gump) told me the other night that hasn't limited his, so he presumably has 20 degrees and yet all of us have cars that tickover and drive well. Mind you we all also have different size engines, compression ratios, inlet manifold, cams, etc. Just goes to show that one size doesn't suit all I suppose.
Oneball
CCCUK Member
The way vac advance works in most SBC means you’ll notice it in mpg but you probably won’t tell in the way it drives. It just advanced the spark at a cruise on low throttle openings and is only helpful in allowing a lean mixture in this instance. If you’ve not got the carb setup like that it won’t be doing anything.