Camshaft Replacement Question

[Andrew]

I've been considering adding performance camshafts to 5052. However, after researching camshaft upgrades on this forum and other resources going back to DMCNews, I still have a few unanswered questions:

1. Do the reground cams on the market retain the mechanical fuel pump cam lobe?

2. What is the HP increase from cams alone? I read a post from 2009 which confirmed that Don's Crazy Cams when matched with SpecialTAuto headers resulted in an increase of 62HP at the rear wheels. I already have headers installed on 5052; thus I'm wondering what I would really gain from adding cams.

2a. What are the HP differences between the cams currently available on the market? DMCEU, DPI, Dbilas, etc?

3. Do the heads need to come off to install the new cams? (I've never taken PRV heads off / apart)

Any insight / advice would be welcomed.

Thanks,

Andrew
4194
5052

[FABombjoy]

Some real world examples here:
http://dmctalk.org/showthread.php?19...d-Details-Here!!

If you want +62RWHP without a motor swap yer gonna need forced induction or nitrous

[David T]

Some real world examples here:
http://dmctalk.org/showthread.php?19...d-Details-Here!!

If you want +62RWHP without a motor swap yer gonna need forced induction or nitrous

Be skeptical of all of the alleged claims about HP and performance. It is difficult to compare all of the different options and combinations. You WILL notice a difference but it isn't going to turn the car into a race car. Then there is the Law of Diminishing Returns. Every time you modify you will spend more and get smaller and smaller results. More radical cams and headers will give you a notifiable performance gain. Basically what DMCH calls their Stage II. You never get something for nothing. For the added performance you can expect lower gas mileage and a noisier car besides spending a bunch of money. In some States you may not be able to pass emissions (if you actually have to).

[Andrew]

In light of those dyno results (141hp at the wheels with cams and headers), I will defer doing cams for the time being. I'm already running headers, HEI and a cold air intake, which based upon my research adds roughly 20hp at the rear wheels over stock. Frankly, I'm happy with 5052's performance as it moves a lot quicker than my V8 powered daily driver, but it would always be nice to move a little quicker. It seems kinda silly to take the a nicely working engine apart simply for an additional 20hp. However, if I have the engine out and apart for other reasons I might make the investment. :-)

There's no emissions testing here in Michigan for any vehicles. At this point I wouldn't even consider moving to a state with emissions unless there is an exemption for antique vehicles. I'm too set in my ways to deal with that ever again.

Andrew
4194
5052

[FABombjoy]

Your other consideration, and I only ask because I know very little about carbs, is how flexible would the Solex system be with different cams?

I had to Borg my K-Jet to get the kind of control that I wanted. I wouldn't know where to start with carbs

I say we make an adapter plate and hook you up with a 50 shot of N2O. That would have to be a first!

[dmruschell]

The performance increase between stock and an engine with performance cams and exhaust is about 25%. The 62HP number is probably not accurate, or they're talking about gross horsepower and not comparing apples to apples when comparing numbers. Performance cams really come into their own around 3500RPMs. The car just starts to take off.

The cam specifications for most of the advertised cams are not listed. Someone did list the cam specs for a cam they bought from DMC-CA that is supposedly a bigger cam than the normal performance cam that they used to offer. It was ground by Isky cams, and the duration/lift ratio was smaller than the Dbilas cams, which is a good thing. When you increase lift, you have to increase duration because there is a slope that has to start somewhere that leads from the base circle (0 lift) to the maximum valve lift. A more aggressive slope allows for a more streetable cam that has a smoother idle and wider power band when compared to a cam with similar lift and greater duration. So, I'd investigate the Isky option since that's apparently where Don had his cams made. I'd also see if you can get any numbers form any of the vendors since none of them are published.

Or, get a package that is made to work together. DPI had cams that you can still order that are matched to their exhaust. I also just installed cams and reqorked heads from DPI on a friend's DeLorean with DMC's Stage 1. Josh had us take some measurements of the exhaust so that he could grind the cam to match the exhaust, and the results worked out pretty well.

If you have to pull the engine or if you need to replace the head gaskets, that would be the best time to install cams.

[Andrew]

Your other consideration, and I only ask because I know very little about carbs, is how flexible would the Solex system be with different cams?

I had to Borg my K-Jet to get the kind of control that I wanted. I wouldn't know where to start with carbs

I say we make an adapter plate and hook you up with a 50 shot of N2O. That would have to be a first!

N20 on a D...that would be quite the sight!

Or perhaps a carbed turbo...like the late 70's Turbo Trans Ams or the first generation 79-83 Riviera T-Type / S-Types :-)

[Andrew]

The performance increase between stock and an engine with performance cams and exhaust is about 25%. The 62HP number is probably not accurate, or they're talking about gross horsepower and not comparing apples to apples when comparing numbers. Performance cams really come into their own around 3500RPMs. The car just starts to take off.

The cam specifications for most of the advertised cams are not listed. Someone did list the cam specs for a cam they bought from DMC-CA that is supposedly a bigger cam than the normal performance cam that they used to offer. It was ground by Isky cams, and the duration/lift ratio was smaller than the Dbilas cams, which is a good thing. When you increase lift, you have to increase duration because there is a slope that has to start somewhere that leads from the base circle (0 lift) to the maximum valve lift. A more aggressive slope allows for a more streetable cam that has a smoother idle and wider power band when compared to a cam with similar lift and greater duration. So, I'd investigate the Isky option since that's apparently where Don had his cams made. I'd also see if you can get any numbers form any of the vendors since none of them are published.

Or, get a package that is made to work together. DPI had cams that you can still order that are matched to their exhaust. I also just installed cams and reqorked heads from DPI on a friend's DeLorean with DMC's Stage 1. Josh had us take some measurements of the exhaust so that he could grind the cam to match the exhaust, and the results worked out pretty well.

If you have to pull the engine or if you need to replace the head gaskets, that would be the best time to install cams.

I'm tempted to get 5052 dynoed to confirm my baseline HP with the current setup of headers with stock cams. Thanks for the information regarding Isky cams! I'll get in contact with them and see what information they can provide. Either way, I agree that I won't do this mod until I have the engine out / heads off.

[David T]

I'm tempted to get 5052 dynoed to confirm my baseline HP with the current setup of headers with stock cams. Thanks for the information regarding Isky cams! I'll get in contact with them and see what information they can provide. Either way, I agree that I won't do this mod until I have the engine out / heads off.

It is better to do the cams with the heads off. That way you can port and polish the heads. Also clean up the valves and seats. Although the castings are very clean compared to an American head of similar vintage, a little polishing can't hurt. Do a compression test before and after. You may have to alter the base timing and vacuum and mechanical advance to take full advantage of the cams. Discuss with the cam supplier for recommendations.

[DMCVegas]

Frankly, I'm happy with 5052's performance as it moves a lot quicker than my V8 powered daily driver, but it would always be nice to move a little quicker.

There is another way to move a bit quicker without touching the engine. It's the same reason your V8 isn't as fast.

Sounds like it's time to swap over to a new gear ratio on your final drive.