2 questions from a new owner

[Tbruz]

All,
Two questions/issues i'm trying to resolve on my new to me 1972 4 speed Blazer
1) Speedometer reads 20 MPH higher than actual speed. 32" tires on the vehicle. Speedo gear at the transfer case??

2) Slow in cranking when warm. almost a no start condition, wait two to five minutes and it cranks over perfectly.

Thanks for any help.
Tbruz

[thepenguin99]

You might be surprised to learn that pics of trucks new to the forum help facilitate the answering of questions. I don't mean pics of the problems just pics of the blazer in general =).

1) Sounds like your tires are the issue here. Stock diameter is like 29" I think. Speedo gear change can help with the issue but you need to know your axle gear ratio as well to pick the correct one.

2) Look for the same causes you would look at if it wasn't turning over cold, Connnections/Battery/Starter. Had this issue on my rollback and it was simply a weak battery that was good enough to spin the motor when cold but had issues when hot.

[Tbruz]

With photos as suggested
Tbruz

[thepenguin99]

Wow, very nice blazer. Love the color.

[lks dcvn]

Delayed start when warm - could be a sign of heat soak in the starter...

Here are a few posts to review when you have time:

http://67-72chevytrucks.com/vboard/s....php?p=3388179

http://67-72chevytrucks.com/vboard/s....php?p=2852218

Nice blazer!

[1949gmc]

NICE Blazer!!!

[jaros44sr]

Originally Posted by lks dcvn

Delayed start when warm - could be a sign of heat soak in the starter...

Here are a few posts to review when you have time:

http://67-72chevytrucks.com/vboard/s....php?p=3388179

http://67-72chevytrucks.com/vboard/s....php?p=2852218

Nice blazer!

Dammit Tom, you read my mind! I had a '67 442 that used to do the exact same thing

Very,very nice Blazer, welcome to the boards from Philly. Pa. I wouldn't be hanging any bikes around that close to such a sweet blazer

[dan76]

Good looking rig. Nice score

Along with the above suggestions, I'd check condition of the grounds, battery cables/connections and get the battery checked. It's tough to check a starter (for heat soaked condition) but when it's cranking slow, try pouring water over the starter housing, wait a couple of minutes and try cranking.

[bigdon-70blazer]

Very nice and love the color! Ditto on the bikes!

[Dusty71blazer]

Beautiful truck!

problems starting when warm could be ignition timing too.

[old man jimmy]

I agree. Very nice truck. When you say 20 mph over. At what speed? Speedo error will be a %. With your bigger tires, sounds like someone dropped a lower gear in the rear end. bigger tires should make your speedo read slower. Find a highway with mile markers, and check to see how many tenths on your odometer you gain in a mile. Like if you gain 1 tenth in a mile. Your speedo is 10% fast. So 70 mph on your speedo would be 63 mph. If you still have that little gear box on the tranny end of your speedo cable, you might try removing it, and just hook up your cable direct. See what that does to your speedo error. By the way, your don't need it anyway. Speedo gears are machined steel and rather expensive. Good luck. Also agree with the started heat soak.

[thepenguin99]

Doh, for some reason I read 20mph under which is why I said tires.

[old man jimmy]

Originally Posted by thepenguin99

Doh, for some reason I read 20mph under which is why I said tires.

Speedo running slow would probably be larger tires(same as taller gears) But TBRUZ said his was showing fast, and his pictures didn't show small tires, so It's probably gears. By the way does your speedo read 20 mph slow at 5 mph? That's what I mean by percentages.

[bigdon-70blazer]

Does that fine blazer have a jacking instructions decal lurking on the back of the drivers side rear wheel well under the carpet?

[Tbruz]

Wow thanks for all the replies.
I just bought this truck as it stands fully restored from a guy in TN. Unfortunately he was not the one who restored it so getting issues answered from the original source isn't possible; unlsess someone on here recognises the vehicle and can add input.

As for the speed being off by 20MPH, that offset was at 55MPH per my GPS, speedo reads 75 to 78. I will re-check at lower speeds to see if 20 MPH error is a constant or not.I will also recheck the odometer with the GPS and see if a mile traveled equals a mile on the odometer.

As for jacking instructions, I do not have any under the carpet on the drivers side wheelwell, but I do have instructions inside the console. see attached photo.

Again, thanks for all the comments and replies/suggestions.
Tbruz

[msgross]

my guess was that they replaced the speedo adapter on the TC with the wrong ratio... easy fix....

http://www.transmissioncenter.net/sp...n_______va.htm

Look for this box where the speedo cable goes into the TC, it might have a ratio stamped on it..

[Tbruz]

Speedo update,
Msgross is right; easy fix.
I went to my local tranny shop and they gave me a replacement speedo adapater as Msgross had pictured. 30 MPH swing from 20 mph higher to 10 mph lower. I just have to keep looking for one that gets me closer to correct speed.
Thanks for the inputs.
Tbruz

[Longblock]

slow start when warm....... sounds like timing may be a little to fast......

[BLUE THUNDER]

Welcome from San Antonio. That is a nice Blazer. It is dialed in. Congrats.

[bigdon-70blazer]

Originally Posted by Tbruz

Wow thanks for all the replies.
I just bought this truck as it stands fully restored from a guy in TN. Unfortunately he was not the one who restored it so getting issues answered from the original source isn't possible; unlsess someone on here recognises the vehicle and can add input.

As for the speed being off by 20MPH, that offset was at 55MPH per my GPS, speedo reads 75 to 78. I will re-check at lower speeds to see if 20 MPH error is a constant or not.I will also recheck the odometer with the GPS and see if a mile traveled equals a mile on the odometer.

As for jacking instructions, I do not have any under the carpet on the drivers side wheelwell, but I do have instructions inside the console. see attached photo.

Again, thanks for all the comments and replies/suggestions.
Tbruz

Wow, when I first pulled up your post, I thought that it had the original jacking instructions but that decal is a truck jacking instructions. Swing and a miss! Thanks for the pic and great Blazer, have fun!

[msgross]

Originally Posted by Tbruz

Speedo update,
Msgross is right; easy fix.
I went to my local tranny shop and they gave me a replacement speedo adapater as Msgross had pictured. 30 MPH swing from 20 mph higher to 10 mph lower. I just have to keep looking for one that gets me closer to correct speed.
Thanks for the inputs.
Tbruz

try hooking it up with no adapter.... can't hurt to see where it's at, then do the calculation and find a better ratio...

[Tbruz]

Update on starting issue and speedo.

Timing was way advanced at 40 degrees primary.
Set to 25 degrees and problem resolved.

Tried speedo cable directly into tranfer case and speed offset is 15 mph slower than GPS indicated.

Back to tranny shop for other options.
Thanks to all for their inputs.
Tbruz

[Longblock]

Glad you got the starting issue figured out....... The Blazer looks great......congrats.....