1989 Corvette C4 6 Speed Manual

1989 Corvette C4 6 Speed Manual

Author
Discussion

SturdyHSV

10,097 posts

167 months

Wednesday 10th March 2021
quotequote all
Ooof that's a tasty update smile

Just to throw some ideas into the pot, by which I mean man maths...

You'll want to get the bores honed for the new rings, and will be buying pistons, so possibly wrist pins / locks, maybe reuse the rods etc. but probably buying main / rod bearings as well etc., maybe get the crank polished up? Any sort of balancing done with the new pistons? Maybe new rod bolts as you might want to give it some rpm to take advantage of the cam...So some expense anyway right?

You can get a complete 383 forged and balanced rotating assembly (so crank, rods, pistons, rings, bearings, wrist pins, bolts etc. etc. everything you need) for $788...

https://www.cnc-motorsports.com/1-92000-scat-sb-ch...

That's 11.1:1 compression, there are 10.9 options and lower if you want to keep cheap fuel as an option etc.

As you'd be getting it honed anyway, might as well get it bored 0.030 over right... hehe Plus with the £8k quote you've had, you're well in to 'savings' territory already beer

FelixP

Original Poster:

304 posts

155 months

Wednesday 10th March 2021
quotequote all
Haha yes I've spent many hours looking at all of the options. When I take the block and rotating assembly to the machine shop I'll see what the score is. If it's not much more to go 383 of course I will go for it. I just can't justify spending £8k on it. It's £2700 for a 383 short block here in the UK with a similar spec, so I expected it would be less cost considering I'm supplying a good block.

geraintthomas

900 posts

107 months

Wednesday 10th March 2021
quotequote all
Slightly jealous of that workshop of yours...

I'm also completely stunned by the garage you went to that failed you, and feel really bad for recommending them! If it helps, I popped into the same garage you took yours to last and spoke with the owner (seeing as the garage is quite literally a stone's throw away, no joke, I could hit it from my garden). He seemed lovely and talked about your Corvette too. I think I'll be taking the car there from now on.

Let's have a catch up as soon as lockdown has eased, mainly so I can see the workshop...

SturdyHSV

10,097 posts

167 months

Wednesday 10th March 2021
quotequote all
geraintthomas said:
Let's have a catch up as soon as lockdown has eased, mainly so I can see the workshop...
Remember to peer pressure him in to getting a 383 stroker kit...hehe

Use phrases like "low end torque", "while you're in there", "built it right the first time" and "350ci? but what if there's a hill?" getmecoat

Monsterlime

1,206 posts

166 months

Thursday 11th March 2021
quotequote all
This is a superb thread and a lovely car. It has already had me looking at the classifieds, but I don't think I could give up my TVR. I had already toyed with the idea of going with a Ford Small Block engine to replace the Rover V8 (sacrilege I know), and this has not helped with those thoughts!

FelixP

Original Poster:

304 posts

155 months

Friday 12th March 2021
quotequote all
Thanks Geraint! The older owner has retired now I guess.

SturdyHSV - That is true, although I'm not lugging as much weight as around tongue out

Monsterlime - I'm no expert but it seems to me that a small block chevy is cheaper to build and will take more power. When I do build the replacement engine the one in my car will be available wink What about an LS swap? It would keep the weight down? Have a look on Summit Racing to see how affordable they are...

Monsterlime

1,206 posts

166 months

Friday 12th March 2021
quotequote all
An LS swap is common, and also not cheap (although none of this is cheap). It needs a new box, but the reading I've done indicates a Ford 302 will fit the existing T5 gearbox, plus it is smaller than a Rover V8 width wise which gives some other options re exhaust etc.

I'd need to look up the dimensions of the Ford vs Chevy 302, but the other reason for the Ford is that it was used in other, earlier TVR's (Griffith 200).

If a Chevy 302 would fit the Borg Warner T5 with minimal effort and had similar dimensions as the Ford, it would be worth it.

Every time I look at these engines, the cost of getting more power is peanuts compared to what you get from a Rover V8 for a lot, lot more outlay.

SturdyHSV

10,097 posts

167 months

Friday 12th March 2021
quotequote all
Monsterlime said:
An LS swap is common, and also not cheap (although none of this is cheap). It needs a new box, but the reading I've done indicates a Ford 302 will fit the existing T5 gearbox, plus it is smaller than a Rover V8 width wise which gives some other options re exhaust etc.

I'd need to look up the dimensions of the Ford vs Chevy 302, but the other reason for the Ford is that it was used in other, earlier TVR's (Griffith 200).

If a Chevy 302 would fit the Borg Warner T5 with minimal effort and had similar dimensions as the Ford, it would be worth it.

Every time I look at these engines, the cost of getting more power is peanuts compared to what you get from a Rover V8 for a lot, lot more outlay.
Even if you wanted to go full CNC'd bellhousing to go from SBC to a T5, that's only £300 or so, and I imagine you'd save that much in parts / support having a Chev 350 engine over the Ford. The SBC is absolutely everywhere, and is supported better as a result thumbup

They're both diddy little pushrod engines and far better than the Rover lump and far cheaper for power thumbup

Monsterlime

1,206 posts

166 months

Friday 12th March 2021
quotequote all
Looking at it, it would fit, but would cause the same issue as the Rover, in that the exhaust would likely have to go forwards in the engine bay rather than be able to drop down and go to the rear immediately, which is what I believe someone else has done already.

Rover width - 30 inch
Chevy width - 26 inch
Ford width - 24 inch

The Chevy is also heavier than the Ford, which is itself heavier than the Rover.

Will need more thinking and looking at to see if viable. In any case, I don't want to derail this thread anymore. smile

sortedcossie

559 posts

128 months

Friday 12th March 2021
quotequote all
Read through this today whilst having lunch but didn't submit the reply. Interesting reading, and a great diary of your journey with it. Thanks for sharing.

EggsBenedict

1,770 posts

174 months

Monday 15th March 2021
quotequote all
Monsterlime said:
Looking at it, it would fit, but would cause the same issue as the Rover, in that the exhaust would likely have to go forwards in the engine bay rather than be able to drop down and go to the rear immediately, which is what I believe someone else has done already.

Rover width - 30 inch
Chevy width - 26 inch
Ford width - 24 inch

The Chevy is also heavier than the Ford, which is itself heavier than the Rover.

Will need more thinking and looking at to see if viable. In any case, I don't want to derail this thread anymore. smile
Ford V8 and TVR

I'm not sure I believe that Rover width, although I want to. My same research indicated that the Ford was an inch wider either side than the RV8. Everything else you said rings true though. I'm restarting this project after a break of about 8 years, but it'll be slow progress, I think.

Back to the 'Vette - lovely car!



Edited by EggsBenedict on Monday 15th March 16:57

FelixP

Original Poster:

304 posts

155 months

Saturday 24th July 2021
quotequote all
Time for a little update again.

The adaptors came for the C6 Z06 brakes along with everything to rebuild them. I bolted them up to test fit and sadly they hit the spokes of the wheel before it got anywhere near the hub. I borrowed some spacers from a friend but it needed 1 1/4” to clear the caliper and that was obviously a no go. If I didn't have the Speedlines put together then perhaps I would have gone for a more big brake friendly wheel but I love the deep dish and this time it's form over function. I sold on the brakes and rebuild parts for what they owed me in short time. I still have the adaptors, I could get base C6 brakes which are apparently still a decent improvement over the C4 13” brakes. With a different abutment bracket you can have 13.4” discs. I would retain the stock rear brakes too so there would be no need for an expensive adaptor on the rear.

The C6Z calipers







Always neat to see how dainty the aluminium wishbones are on a C4



The C6 base brakes by comparison, with some nice coilovers in place of the leaf spring too.



The Pirelli P Zero tyres on the rear were already down to the wear bars (oops, that's only about 7 months driving) and I had bought older DOT code ones from eBay. To be honest, they were dire in the wet and I was looking to go to a slightly narrower tyre to see if I could run less rear camber. I found a great deal on some 295/35/18 Michelin Pilot Super Sports and had those fitted. As the car was lowered to the ground there was a bit of an oh well moment, they seemed to be just as wide as the 315/30 pirellis! Driving home however the traction was very impressive. So much so that I thought it was best to get the diff sorted at last, before it went bang!










Newport transporter bridge on the way home



I ordered an SKF complete rebuild kit for the Dana 44HD diff along with poly mounts for the “batwing” diff mount. Also on the list were new UJ's for the half shafts and poly engine mounts to hopefully eliminate the movement in the gear stick. The diff is connected with a C beam a bit like an MX5 so the drivetrain is only mounted by 2 points on the engine and 2 on the diff, there's no gearbox mount. By having both of these poly I hoped I would eliminate any play and really firm things up. The other item I had to fit were some nice ceramic coated long tube headers to replace the cheap ones I bought first time around. My usual guy who does all the big horrible jobs was busy and it was agreed I'd go somewhere else. I tried a different garage which seemed to have a good reputation and plenty of interesting cars in always on their instagram account. Well, it went smooth as a hedgehog. It took them 2 weeks to even start and 8 weeks and 16hrs labour later my car was back. I'd missed a big portion of summer. They couldn't get the headers to fit, the starter interfered with them. I dropped off an aftermarket mini starter which is clockable but that wouldn't fit either apparently so it was back to the original starter and headers. When I eventually got the car back it pulled to the side, well one tyre was on 10psi! It got a bit hot on the way home. They'd removed a coolant sensor from the cylinder head and left the radiator half empty and overflow bone dry. Finally the starter motor struggled, I put a new battery on but no change. I got petrol and the car wouldn't even start. I took a look underneath to see the wiring against the headers. Unbelievable!! I told them I'd drop it off my next day off for them to sort. Well the owner wasn't even there at the time and the mechanic seemed surprised to see me. I explained the issues and he seemed perplexed when I turned the car off and it wouldn't even crank from the heat soak, loose connection, improper shimming etc. Later that day I called by to pick it up, where it obviously hadn't moved and they offered to fit a new starter for free. I just drove off. There was no problem with it before they touched it and after the timescale for such shoddy work I wouldn't leave anything with them again. If it was a back street garage where you paid cash for a day at a time I would be a little more patient but this was a professional outfit with £70ph labour rates. Dire. I'm just hoping the diff rebuild turns out to last but if they can't shim a starter and think wires should go next to hot manifolds I'm not filled with confidence.







I'm going to take it elsewhere to get the starter fitted properly and then call by with the invoice for them to pay. After that I'll post on an honest review on the trusted garages website they put on their paperwork.

In the meantime I got a bargain with some new seats. The seat foam alone is $360 and the covers about $700 before postage and duty. I snapped up a set from Canada for £450 all in. I got red ones as I wanted to change the interior and always wished it was the flame red on black. With the amount I saved on the seats I could get the carpets and other little bits of trim. Only one problem when the seats arrived, I got two different types! One sports seat (fully adjustable) and one standard seat (100% leather whereas I opted for vinyl on the sports seats) Luckily it was ebay and I used Paypal so the seller would have to sort it out. I said I'd be happy to return them for a refund (but he would lose postage costs both ways, pretty much what he sold the seats for) or he could send me the missing sports seat. I said I'd be happy to return the other one at his cost, but again that would be expensive so he just told me to keep it. A pair of leather standard seats is $1300! I promptly put the spare seat on eBay and if it sells I'll recoup the cost of the seats. Since the drivers seat is always first to wear I'm confident someone will buy one for half the price.



I'm going to order up the other items to redo the interior now, I'm going to change the centre console to red, red carpets and dye my door cards black since they're in good condition and I think it might be too much red otherwise. It should flow nicely with the black dash too then and set it apart from the factory colour options.

I met up with my friend Vesa and his LT1 auto C4. His car is a later model with 300bhp factory whereas mine left with 250. With my modifications though I imagine it's an easy 300bhp now. We drove over the Bwlch and Rhigos mountains. My car feels very tight now, really drives the best it ever has.








FelixP

Original Poster:

304 posts

155 months

Tuesday 30th November 2021
quotequote all
Whoops, who wants a well sorted C4?


unpc

2,835 posts

213 months

Tuesday 30th November 2021
quotequote all
I do but I've got no room for it.

mnaylor

268 posts

129 months

Tuesday 3rd May 2022
quotequote all
Don't suppose the C4 is for sale? I am after one.

Anyone know a good importer in the UK? I could try and get a fresh US import. Or if anyone knows of any good UK cars for sale please get in touch. I am not looking for a project car, it needs to be a good one. Looking at years 1985 to 1989 and couple only. Open to Auto or Manual.

Thanks.

FelixP

Original Poster:

304 posts

155 months

Sunday 17th July 2022
quotequote all
Wow can't believe it has been a year since I wrote about this! Just been back through my photos to remind myself of the woes... Actually it's been nice to look back and realise I've actually managed to have a few adventures this year already!

Managed to finally find an “upper fender liner” in the UK so postage was reasonable. It's always had a chunk missing on this side which has irritated me. Nice quick fix.





Also in the depths of covid I thought I'd keep the car forever and so splashed out on the last piece of the puzzle (at the time) and bought a complete new red interior and lots of other trim pieces. Replaced the badges with the black version from 92-96, expansion tank & front splitter. The splitter was a chore, every bolt was rusted and rounded. It took all afternoon.

















Met up with Geraint and his MX5 for a catch-up



And then obviously because I spent thousands on new interior parts everything else started playing up. The heater core went. A horrible job in most cars, the C4 being no exception. One simple DIY guide online said 1. Drive heater core into garage. 2. Remove car. They weren't far off.




Then a couple of weeks later the car cut out and would flood the engine. Strange. Doing some investigation I found that one bank of injectors were shorted out so would stay open. Just had to find the wire. Dash back apart...



I lost the wire somewhere from the fuse panel to the engine bay and a friend recommended an auto electrician to help out. We ended up running a new wire from the injectors to the fuse panel and cutting the old one after finding it out of the firewall.

Then a few weeks of just using it all the time just because. It's a riot in grotty winter weather.



Went to the Bristol Queens Square meet in January







Bought a pressure washer from a mate in work for £20





Met up with another local friend who got his ridiculous G40 supercharged MK1 Polo back on the road







Then of course the clutch release bearing went again. I had it changed 5 years ago but they're all made in China and rubbish now. Could last 5 minutes, could last 5 years. So whilst I pondered a solution I cracked on with stripping out the interior. I did test fit the red seats first to boost my mood













The lovely thing about a plastic car is it's actually quite easy to rip everything out from inside and I was pleased to see the floors were all in good condition, no cracks or stray jacking incidents. I put some modern insulation down before replacing the OEM jute padding.





I did some of the rear carpets



And the front larger pieces but left the door cards and sills due to the complexity.





The carpet had a preformed plastic backing so it was roughly the proper shape but still needed to settle after being in the box for ages. Lots of trimming too.

Then I took the C6 too see a mate who bought a farm in Llandovery and didn't believe him when he said the lanes to his house wouldn't suit the car. I think I cut the grass in the centre of the road all the way up there.



Lovely drive back though through Brecon



Next up a little group trip to Spa



Yours truly at my regular place









We had parking right inside Eau Rouge! Everyone else bought slow sensible cars apart from the TVR



Saw a couple of ZR1s, infact mine was the only peasant model C6 there!



Had a great French lunch on the picnic table



Back in Vianden. Luxembourg is great, well worth a visit if you're nearby.



Last night we stayed in a chateau, less than £100 a night!



Another shift cycle in the summer. 5Am commutes are great this time of year, hardly any traffic and decent A roads to myself



Made a new friend in Cardiff by the Museum. Awesome widebody SWB 300ZX



Went to some more American meet ups with my friend Mark & his big block 4 speed Camaro, mega car this!







Then more procrastination with the C4. Went to visit a friend staying in Earls Court before they went home to Paraguay. C6 in central London was a bit interesting, wide with awful visibility at junctions because of the huge B pillar from the cloth roof. Sounded awesome though!



From there I went to visit a friend who moved to France. Gorgeous house for the price of a nice flat in Cardiff!



Peaceful toll roads in France!





Went to a great museum near Rennes, Manoir de l'Automobile. Highly recommended and not far from Le Mans









Coming back on the ferry with Le Mans classic traffic!



Then when I got home I still had a week off so felt all motivated to finish the C4. Came out brilliantly I think! I opted to paint the door cards as new ones are about £1k to the door and mine were in good condition, just the wrong colour! A £10 can of Halfords flexible vinyl spray worked really well and I wish I'd repainted other plastics with it rather than buying black versions.
















I replaced lots of other little bits of trim and all the screws etc as well.

As for the clutch, an OEM one is £300 or an aftermarket hydraulic kit was £1100. Since the interior came out so well I raided the piggybank for the hydraulic one. It'll future proof the car and save having the job done again. It also means getting rid of the original dual mass flywheel that's no longer available, the clutch slave, fork and troublesome throw out bearing. Hopefully that'll arrive and be sorted by the start of August, then I'm planning to go to Radwood UK again!

SturdyHSV

10,097 posts

167 months

Sunday 17th July 2022
quotequote all
The C4 looks so good, it's also one of very few interiors whereby banging in an aftermarket touch screen actually looks factory! It's the perfect sort of retro-futuristic look for an 80s vette!

Remember this interior touch screen from the old Buick Riviera, it was spaceship grade when I was a kid!


TopTrump

3,226 posts

174 months

Monday 18th July 2022
quotequote all
I am very envious of the time you have on your hands. Is the C6 yours then too? Love the C4

FelixP

Original Poster:

304 posts

155 months

Monday 18th July 2022
quotequote all
Thanks! Yeah I added the C6 in November as I wanted to try an LS powered car. work continental shifts so get blocks of time off and my usual week is 6-2, 2-10, 10-6 so I have free time when most people are working

Edited by FelixP on Monday 18th July 14:48

ZedLeg

12,278 posts

108 months

Monday 18th July 2022
quotequote all
That's very cool, the C4 has aged well.