Exciting day - rebuild of 78 coupe

[johng]

Had a little play today and it looks like my gauge is under reading. The sensor resistance was 1300 ohms cold (around 5C) and 166 ohms after a good run (which equates to 215F according to JR's chart), my gauge was showing 155F. I couldn't get a good IR reading next to the sensor, as it's tucked up underneath the hot exhaust manifold and I couldn't see what I was pointing at. However, the intake manifold right next to the thermostat was showing 177F which corresponds nicely to the thermostat setting of 180F. I suspect that the sensor resistance of 166 ohms (and hence 215F) is being affected somewhat by the proximity of the exhaust manifold.

 

[teamzr1]

When you took the resistance test for the coolant sensor in the block, did you take the wire off from the dash gauge first ?
If not, there could be some value change as the gauge and its wiring measured into your OHMs reading

But in any case, shows the temp is higher than you thought in first testrun

Can the coolant dash gauge be calibrated, or internals cleaned up ?

 

[johng]

Yes I'd disconnected the gauge when taking measurements. From what I've read, you can replace the resistor on the back of the gauge with a potentiometer and adjust this to calibrate the gauge. It might be something I'll do if I get really bored, but for now I know that the gauge reads low, so I'll just leave it as is and get worried if the gauge ever gets up to 200F

 

[teamzr1]

To make it easy, you could do this from the engine bay of the coolant sensor wire to gauge
The total resistance R of two or more resistors connected in series is the sum of the individual resistances of the resistors,
if that works for what is needed
or do it in parallel to get the corrected resistance value to gauge

 

[johng]

You're right, I could put a resistor in parallel with the sensor to get the gauge reading a bit more accurately, but I'm not too bothered at the moment. I'll think about fixing it next time I've got the centre console apart.

 

[johng]

Now that winter is here and i won't be getting the fun of driving my car so much, I've decided to amuse myself by replacing my exhaust system with side pipes. I recently bought a pair of 69 style fibreglass covers from the very obliging CaptainK and to complete the system I've ordered a set of Hedman side exit headers and mufflers to suit these from High Flo Performance. As these are quite large items, air freight from the states is rather expensive so they will be leaving port later today on this container ship and will hopefully be ready for me to collect in about 4 weeks time

 

[Nassau65]

You can’t beat the look of factory style side exhausts.

 

[Letank]

Now that winter is here and i won't be getting the fun of driving my car so much, I've decided to amuse myself by replacing my exhaust system with side pipes. I recently bought a pair of 69 style fibreglass covers from the very obliging CaptainK and to complete the system I've ordered a set of Hedman side exit headers and mufflers to suit these from High Flo Performance. As these are quite large items, air freight from the states is rather expensive so they will be leaving port later today on this container ship and will hopefully be ready for me to collect in about 4 weeks time
View attachment 25090

You can’t beat the look of factory side pipes on an early C3!

I hadn’t come across High Flow Performance before but I’ve been looking at these ones from them.

C3 Corvette Side Pipe Kit With C2 Muffler & OEM C3 Tip for Stock Covers

I love the sound of the chambered exhausts on the C2 and these look to be similar but with C3 tips.

What were HP like to deal with? Did they sort out your shipping or did you have to do it yourself?

 

[johng]

Those are the ones I've bought Letank. They were really helpful, especially the owner Ryan Westdorp. He offered to give me a price for shipping to the UK, but I'd already got a price to ship both the mufflers and headers, which was cheaper than the cost to just ship the headers.

 

[teamzr1]

Sweet - VaaRoom
Let's make some noise - Boys !

If every looking for performance side exhaust such as chambered mufflers, I have used this vendor in the past

Classic Chambered Exhaust Inc. - Home Page

 

[johng]

I did look at Classic Chambered, the beauty of the High Flo option is that it has both the rectangular outlet and is a direct fit onto the Hedman headers

 

[Letank]

Those are the ones I've bought Letank. They were really helpful, especially the owner Ryan Westdorp. He offered to give me a price for shipping to the UK, but I'd already got a price to ship both the mufflers and headers, which was cheaper than the cost to just ship the headers.

Oh nice! You’ll have to let me know how you get on with them then

I thought they went straight onto the standard factory headers. Do you need the Hedman side exit headers too then, or have you gone for a custom set up to reduce a bit of back pressure?

Who did you go with on the shipping? Did they collect directly from HP or does HP send them out to the shipper? I’ve never bought anything this big from the US before, so I was also expecting massive costs and issues.

 

[Roscobbc]

If it helps comparing/evaluating total costs - I had a provisional quote from Hayward and Scott for my big block to fabricate from scratch a set of stainless steel 2 1/8" od individual runner headers (as per Hooker/Dougs) and 4" OD stainless side pipes with internal muffling at £1700 each side plus vat.

 

[johng]

Oh nice! You’ll have to let me know how you get on with them then

I thought they went straight onto the standard factory headers. Do you need the Hedman side exit headers too then, or have you gone for a custom set up to reduce a bit of back pressure?

Who did you go with on the shipping? Did they collect directly from HP or does HP send them out to the shipper? I’ve never bought anything this big from the US before, so I was also expecting massive costs and issues.

You can choose to have the mufflers connect straight to the factory manifold, or they have the option to connect directly to the Hedman headers (the cost is the same either way).
I'll send you a PM with details of the shipping, as I'm not sure if I'm allowed to promote vendors who are not supporters of the club.

 

[johng]

If it helps comparing/evaluating total costs - I had a provisional quote from Hayward and Scott for my big block to fabricate from scratch a set of stainless steel 2 1/8" od individual runner headers (as per Hooker/Dougs) and 4" OD stainless side pipes with internal muffling at £1700 each side plus vat.

That's a fair bit more than my bits have cost Ross, but then they are very big header tubes and stainless always costs more as well.

 

[Roscobbc]

That's a fair bit more than my bits have cost Ross, but then they are very big header tubes and stainless always costs more as well.

TBH John - if I was really considering side-pipes it would probably be Doug's - they do 2 1/8" diameter header pipes - they do the 4" diameter side tube (all as per Hookers) and more importantly you can have polished stainless steel all for less than $2.3K (without inserts - plus shipping) from Corvette Central.......I think that a few words with guy specialising in chambered systems you suggested might be in order to get the best flow rate - he does a 'slip'-'in' chambered insert with a 3" inner tube (most only seem to offer 2", 2.25" or 2.50").

 

[johng]

Luckily I don't need such big tubes as you Ross! A 4" tube wouldn't fit under the 69 style covers and I reckon a 3" inner would be absolutely deafening

 

[CaptainK]

I've ordered a set of Hedman side exit headers

Coincidentally, I have Hedman side exit Headers on my C3 too. Things to note if they are exactly the same as my Hedmans:
1) They don't have a bracket mount area for you to attach the alternator bracket to. So you'll have to fabricate your own bracket mount to accommodate this, else the alternator belt runs loose.
2) Mine weren't stainless steel, so whilst they look good when they are installed - they soon look a bit naff under the bonnet. Hey hum.
3) Heat. As they have no coating or anything, it gets hot around the headers. I installed a insulating gasket between my carb and manifold so that my fuel didn't percolate when I turned off the engine. I don't seem to have issues with heat soak on the starter though, so that's good.

 

[johng]

My alternator bracket must be different to yours, as it doesn't attach to the exhaust manifold, but I will have to make up a spacer for the A/C compressor bracket.
I've ordered the ceramic coated headers, so hopefully they will stay looking lovely . Have you got the original large starter motor, or one of the newer miniature ones? I am a bit worried about heat getting to my old style large starter.

 

[Roscobbc]

John - the ceramic coating does go a bit 'dull' and discoloured after time, oil spills and road spray also make their surfaces dirty.
TBH I have an annual regime, (usually during the winter) of removing the aftermarket wheels and using a proprietary polish specifically for billet alluminium finishes (Mothers or similar) - never, ever Sovol it's too coarse) and thoroughly clean and polish the wheels inside and out and waxing them. At the same time and while the car is 'up in air' on axle stands I use the Sovol on the ceramic header coating and visible parts of the stainless exhaust system - the Sovol does effectively remove the stains and gives a nice clean as-new finish back to the headers.