Different Kind of Head Swap question re: unknown cam
05-27-2016, 02:31 PM
#1
Racer
Thread Starter
Different Kind of Head Swap question re: unknown cam
Last year I lost an '04 c5z in the Memorial day floods, and unfortunately due to the short timeframe that I had with my insurance-supplied rental car I was forced to buy its replacement in a very small window of time. Thus, I could not do the amount of researching that I normally like to do when I buy cars, and ended up picking up something that has been a headache for the last year or so.
In that time, I've sorted out a bunch of electrical issues and ended up rebuilding/beefing up the transmission, and now my attention is on the heads of the car.
I bought the car (another '04 c5z, this time a z16) from a guy who was very clearly curbstoning it, and while he had a list of modifications, he didn't have any service records at all, just a bunch of signage/plaques/etc. that the PO would bring with the car to car shows, as it has an impressive stereo system in it, as well as just about every bolt-on that you can do to it. The guy claimed that it had heads/cam done by Corvettes of Dallas (no longer in business/bought by corvette world, who doesn't have the old shop's records) and the claim was that it put down 464 rwhp. At the time of purchase, I honestly didn't know a whole lot about heads, so I didn't know what to look for; during the test drive/inspection I was only looking for the problem areas of C5's that I learned of from my 2 years of ownership of the one that drowned. If only I knew what I know now!
When I started looking for replacement vehicles, I wanted to find a car that had already had the work done to it that I would have done, so I wouldn't have to sink that money into it myself. This was a mistake...
So, the mods that I know the car has on it for sure:
Callaway Honker Intake
FAST 90/90 intake manifold/TB
LG Long Tubes
Random Tech HF Cats
Random Tech X-Pipe
Callaway Double-D Exhaust
Callaway Sways
As for the Unknown:
There is a cam in it, but have no idea on the specs, though based on smell it has some amount of overlap to it
The heads are 317s, and they weren't milled/etc. My thinking is that the PO had some AFRs or other $$$ head on it, and when he sold the car he pulled them off to recoup some money, and then slapped on the first thing he came across that would fit.
Over the past few months, I've spent a lot of time straightening out this car and its issues, doing things such as:
Rebuilding the transmission to stage IV specs
Replacing the valve springs (since I had no idea the mileage on the ones that were on it, which I knew was a ticking time bomb on a car with a cam) with .650 Patriot Performance Gold Springs with titanium retainers
Swapping in a new MAF as the old one was producing readings 2-4x higher than it should have, resulting in the computers adding ~20% fuel thinking it was lean, which fouled the o2s, which were reading super rich
Changed the O2s after changing the MAF, which brought the fuel trims to where they were supposed to be
Adding a big 3 kit as I thought i had ground issues, but it ended up being a chafed BCM 5V reference wire off of the main harness under the battery, which I then repaired.
After getting everything straight, I then figured it would be a good idea to get it tuned, and it put down 395hp/375tq, and the tuner made sure to point out that the compression ratio is WAY low due to the heads and that if I got the car back stock at the very least it would pick up ~50hp given the supporting mods already on the car.
I'm very comfortable with my ability to work on the car/fix things, and from the writeups that I've found on here/etc. I do believe that I can swap the heads myself, but I was concerned about what I *don't* know about the cam/etc., so I called the shop that I use to get work done and got a quote of ~3200 to have a set of factory 243s installed (he'd supply them, and would send them off first to get them checked out, so he said that on its own would be ~900 or so) and that price obviously includes new LS7 lifters, pushrods/etc.
Keeping in mind that this is my daily-driver/only car, if I were to do the work myself I would need to do it over the weekend, so I could get to work on Monday (and would obviously schedule a date very soon thereafter to get it re-tuned with the new heads). So, with that novella of background, it brings us to my main concern: the pushrods and their length.
If I don't know the specs of the cam, it appears it's difficult to know which pushrods I would need with new heads (just thinking factory 243s that I'd find on here or ls1tech/etc., but if it makes $$$ sense to get something else that I might be overlooking, I'm all ears), and it would be in my best interest to get a pushrod measuring tool to figure out what length pushrods that I need. However, it seems that I'd need to measure for pushrods with the new heads on the car, right? If so, this would bring us back to the issue of this being my only car, so I can't easily swap heads and then wait for the proper pushrods to come in (i'd much rather use money that I'd spend on a rental car on this project), so is there a method that I'm not thinking of that would work, or is there a "safe" pushrod length that I could run? Alternatively, could I just swap the pushrods from the 317s to the 243s? (I already plan on swapping the springs over as they have less than 5k miles on them)
All of that being said, is there something else that I didn't mention that I should be looking at/for?
Thanks for reading that book, and I appreciate any help that anyone can provide!
Pat
In that time, I've sorted out a bunch of electrical issues and ended up rebuilding/beefing up the transmission, and now my attention is on the heads of the car.
I bought the car (another '04 c5z, this time a z16) from a guy who was very clearly curbstoning it, and while he had a list of modifications, he didn't have any service records at all, just a bunch of signage/plaques/etc. that the PO would bring with the car to car shows, as it has an impressive stereo system in it, as well as just about every bolt-on that you can do to it. The guy claimed that it had heads/cam done by Corvettes of Dallas (no longer in business/bought by corvette world, who doesn't have the old shop's records) and the claim was that it put down 464 rwhp. At the time of purchase, I honestly didn't know a whole lot about heads, so I didn't know what to look for; during the test drive/inspection I was only looking for the problem areas of C5's that I learned of from my 2 years of ownership of the one that drowned. If only I knew what I know now!
When I started looking for replacement vehicles, I wanted to find a car that had already had the work done to it that I would have done, so I wouldn't have to sink that money into it myself. This was a mistake...
So, the mods that I know the car has on it for sure:
Callaway Honker Intake
FAST 90/90 intake manifold/TB
LG Long Tubes
Random Tech HF Cats
Random Tech X-Pipe
Callaway Double-D Exhaust
Callaway Sways
As for the Unknown:
There is a cam in it, but have no idea on the specs, though based on smell it has some amount of overlap to it
The heads are 317s, and they weren't milled/etc. My thinking is that the PO had some AFRs or other $$$ head on it, and when he sold the car he pulled them off to recoup some money, and then slapped on the first thing he came across that would fit.
Over the past few months, I've spent a lot of time straightening out this car and its issues, doing things such as:
Rebuilding the transmission to stage IV specs
Replacing the valve springs (since I had no idea the mileage on the ones that were on it, which I knew was a ticking time bomb on a car with a cam) with .650 Patriot Performance Gold Springs with titanium retainers
Swapping in a new MAF as the old one was producing readings 2-4x higher than it should have, resulting in the computers adding ~20% fuel thinking it was lean, which fouled the o2s, which were reading super rich
Changed the O2s after changing the MAF, which brought the fuel trims to where they were supposed to be
Adding a big 3 kit as I thought i had ground issues, but it ended up being a chafed BCM 5V reference wire off of the main harness under the battery, which I then repaired.
After getting everything straight, I then figured it would be a good idea to get it tuned, and it put down 395hp/375tq, and the tuner made sure to point out that the compression ratio is WAY low due to the heads and that if I got the car back stock at the very least it would pick up ~50hp given the supporting mods already on the car.
I'm very comfortable with my ability to work on the car/fix things, and from the writeups that I've found on here/etc. I do believe that I can swap the heads myself, but I was concerned about what I *don't* know about the cam/etc., so I called the shop that I use to get work done and got a quote of ~3200 to have a set of factory 243s installed (he'd supply them, and would send them off first to get them checked out, so he said that on its own would be ~900 or so) and that price obviously includes new LS7 lifters, pushrods/etc.
Keeping in mind that this is my daily-driver/only car, if I were to do the work myself I would need to do it over the weekend, so I could get to work on Monday (and would obviously schedule a date very soon thereafter to get it re-tuned with the new heads). So, with that novella of background, it brings us to my main concern: the pushrods and their length.
If I don't know the specs of the cam, it appears it's difficult to know which pushrods I would need with new heads (just thinking factory 243s that I'd find on here or ls1tech/etc., but if it makes $$$ sense to get something else that I might be overlooking, I'm all ears), and it would be in my best interest to get a pushrod measuring tool to figure out what length pushrods that I need. However, it seems that I'd need to measure for pushrods with the new heads on the car, right? If so, this would bring us back to the issue of this being my only car, so I can't easily swap heads and then wait for the proper pushrods to come in (i'd much rather use money that I'd spend on a rental car on this project), so is there a method that I'm not thinking of that would work, or is there a "safe" pushrod length that I could run? Alternatively, could I just swap the pushrods from the 317s to the 243s? (I already plan on swapping the springs over as they have less than 5k miles on them)
All of that being said, is there something else that I didn't mention that I should be looking at/for?
Thanks for reading that book, and I appreciate any help that anyone can provide!
Pat
😐
05-28-2016, 09:43 AM
#4
Le Mans Master
Damn that sucks man! Two cars, two years in a row...
Maybe time to get into 4x4 trucks...LOL
Weather has been terrible here for sure.
If it got water in it, hopefully they total it... You only thought you had electrical problems before.
Good luck for the hunt for a new one... Do your research.