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1985 corvette cam change

Old 09-10-2018, 08:04 PM
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85 CRVET
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Default 1985 corvette cam change

I have been thinking about changing the cam in my 85 sometime and donít know exactly how hard it is to do. I am planning on changing the intake manifold and have heard that if you do that you are halfway toward the cam. I get that you have to get the manifold and all of the radiator and front things off like the water pump. This doesnít seem that hard as I have taken off some water pumps and radiators, but I donít get how the cam comes out and also how do you line it up when you put it in? I am trying to figure out how hard it is so I know if I can do it because I love the sound of the cam and I want the performance too as I am trying to get it modded more and more.
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Old 09-11-2018, 05:27 AM
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Joe C
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Originally Posted by 85 CRVET View Post
I have been thinking about changing the cam in my 85 sometime and don’t know exactly how hard it is to do. I am planning on changing the intake manifold and have heard that if you do that you are halfway toward the cam. I get that you have to get the manifold and all of the radiator and front things off like the water pump. This doesn’t seem that hard as I have taken off some water pumps and radiators, but I don’t get how the cam comes out and also how do you line it up when you put it in? I am trying to figure out how hard it is so I know if I can do it because I love the sound of the cam and I want the performance too as I am trying to get it modded more and more.
not sure where you're at with the mods and from your post, sounds like this is all new to you. IMO, you're opening a can of worms here. not to sound negative, but looking for a "cam sound" on a stock L98 tuned port is not the path you want to take. mild cam - yes - well, maybe, but anything giving you the "sound" is going to affect overall performance across the board on a relatively stock L98. performance wise with a mild cam upgrade on a stocker - I doubt you'll feel anything. a cam with a "sound" - at a minimum, you'll need a retune. then you have the issues of the long runner intake, anemic heads, restrictive exhaust, etc.. don't think you want to go there.

as far as "what's involved" - pulling the intake is not the half-way point. besides the WP and radiator, you need to pull the harmonic balancer, timing chain and cover, which requires dropping the oil pan, and then there's project creep and all the little stuff - you'll want all new parts, then valve adjustment, timing, etc.. not a job for the faint of heart. cam "alignment," it's all covered in the FSM. speaking of FSM's if you don't have one, get one, or don't go anywhere near a cam change. a little "old man" advice, and as boring as this sounds - unless you want to track the thing, give it a good tune, drive it and enjoy the stock cam.

now, if you want to play around, I wouldn't go with any cam upgrade requiring a retune if retaining the stock tuned port intake and runners. go with a mild cam and pocket port and gasket match the intake and runners. if you need valve job and need to run your heads through a shop, for near the same money, you can get a set of "summit racing" iron heads - 202/164's -https://www.summitracing.com/parts/sum-152123/overview/ , and finally, get a set of headers (my choice, TPIS long tubes). this should get you a noticeable performance increase while keeping it street-able and user friendly. all this will set you back around 3 grand. add another grand to upgrade the rest of the exhaust. (just my 2-cents)

Last edited by Joe C; 09-16-2018 at 04:55 AM.
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Old 09-11-2018, 11:12 AM
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Plus the 85's ECM is not the easiest to tune, nor the best. I did some research while contemplating adding a 4+3 85 to the household. Folks that are serious about 85's typically swap in a 86 ECM (or newer or alternative system)

https://www.corvetteforum.com/forums...m-upgrade.html

https://www.eecis.udel.edu/~davis/z28/ecm_swap/

Also, where do you live ? Are you subject to EPA regulations/checking as far as the car is concerned ? There is a lot of planning, research, budgeting required when contemplating a cam change. It is not like the old days when I was your age when a cam swap was easier to accomplish. Nor the newer days where the computer and tuning software make it easier to accomplish (manual labor/hard part considerations aside).


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Old 09-11-2018, 01:54 PM
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Ok, I already have a good exhaust other than headers right now. It is 2.5Ē duals with an h pipe and chambered muffler eliminators. It doesnít have cats on it now but I plan on getting hi flow ones when I get long tube headers sometime. I was planning on getting the intake manifold kit that comes with all the gaskets and the Edelbrock performer series intake and I am new to modding a car so I donít know anything about what cam is best. I thought they all required tunes, so which one do you think would be best without a tune and how much power would it add once I get the intake and long tube headers with it? Also, about how much would it cost with all of the other new parts you said I should put on with it, because I donít know what other new parts it would need? I want to get the cam, intake, and long tube headers then maybe add nos to it in a while and test my 1/4 mile time then at a track. Thanks for your help

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Old 09-11-2018, 02:02 PM
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Originally Posted by Joe C View Post
not sure where you're at with the mods and from your post, sounds like this is all new to you. IMO, you're opening a can of worms here. not to sound negative, but looking for a "cam sound" on a stock L98 tuned port is not the path you want to take. mild cam - yes - well, maybe, but anything giving you the "sound" is going to affect overall performance across the board on a relatively stock L98. performance wise with a mild cam upgrade on a stocker - I doubt you'll feel anything. a cam with a "sound" - at a minimum, you'll need a retune. then you have the issues of the long runner intake, anemic heads, restrictive exhaust, etc.. don't think you want to go there.

as far as "what's involved" - pulling the intake is not the half-way point. besides the WP and radiator, you need to pull the harmonic balancer, timing chain and cover, which requires dropping the oil pan, and then there's project creep and all the little stuff - you'll want all new parts, then valve adjustment, timing, etc.. not a job for the faint of heart. cam "alignment," it's all covered in the FSM. speaking of FSM's if you don't have one, get one, or don't go anywhere near a cam change. a little "old man" advice, and as boring as this sounds - unless you want to track the thing, give it a good tune, drive it and enjoy the stock cam.

now, if you want to play around, I wouldn't go with any cam upgrade requiring a retune while still retaining the stock tuned port intake and runners. go with a mild cam and pocket port and gasket match the intake and runners. if you need valve job and need to run your heads through a shop, for near the same money, you can get a set of "summit racing" iron heads - 202/164's -https://www.summitracing.com/parts/sum-152123/overview/ , and finally, get a set of headers (my choice, TPIS long tubes). this should get you a noticeable performance increase while keeping it street-able and user friendly. all this will set you back around 3 grand. add another grand to upgrade the rest of the exhaust. (just my 2-cents)
Half way is also relative. On my car it was easier to take off all the front crap then pop the intake out because you had more room to pry at it. At that point it is just balancer, timing cover and chain and the pan. Lifters and rockers are quick. Not saying you're wrong because you really aren't. (I actually may have been the one to suggest it was the halfway point...) I also said, you don't just do it for sound too. Gotta be a whole package.
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Old 09-11-2018, 02:30 PM
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Originally Posted by 84 4+3 View Post
Half way is also relative. On my car it was easier to take off all the front crap then pop the intake out because you had more room to pry at it. At that point it is just balancer, timing cover and chain and the pan. Lifters and rockers are quick. Not saying you're wrong because you really aren't. (I actually may have been the one to suggest it was the halfway point...) I also said, you don't just do it for sound too. Gotta be a whole package.
Here is my -86 year model with mild cam + Bosch 4 EV14 30lb injectors and tuned original ECM.


Next is coming Procharger P600B, Aeromotive fuel pump and Aquamist water/methanol injection

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Old 09-11-2018, 02:31 PM
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Originally Posted by 84 4+3 View Post
Half way is also relative. On my car it was easier to take off all the front crap then pop the intake out because you had more room to pry at it. At that point it is just balancer, timing cover and chain and the pan. Lifters and rockers are quick. Not saying you're wrong because you really aren't. (I actually may have been the one to suggest it was the halfway point...) I also said, you don't just do it for sound too. Gotta be a whole package.
truth of the matter - you're only halfway when you start putting things back together.
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Old 09-11-2018, 02:42 PM
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then maybe add nos to it in a while and test my 1/4 mile time then at a track
is your car a stick or an auto ? if an auto you need to look into D36 -vs- D44 (the rear ends) as you can grenade a D36 (they came with automatic cars) if you get a real good hookup with a lot of power off the line
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Old 09-11-2018, 02:58 PM
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Originally Posted by 85 CRVET View Post
Ok, I already have a good exhaust other than headers right now. It is 2.5Ē duals with an h pipe and chambered muffler eliminators. It doesnít have cats on it now but I plan on getting hi flow ones when I get long tube headers sometime. I was planning on getting the intake manifold kit that comes with all the gaskets and the Edelbrock performer series intake and I am new to modding a car so I donít know anything about what cam is best. I thought they all required tunes, so which one do you think would be best without a tune and how much power would it add once I get the intake and long tube headers with it? Also, about how much would it cost with all of the other new parts you said I should put on with it, because I donít know what other new parts it would need? I want to get the cam, intake, and long tube headers then maybe add nos to it in a while and test my 1/4 mile time then at a track. Thanks for your help
I think headers with stock exhaust is better than an excellent exhaust with lousy boat anchors they call exhaust manifold. I'd get the LT headers and the intake but all that has to match with the cam. Problem is if they are not matched, you might be shooting yourself in the foot. After all that, it has to be modified by turning the ECM which is about $600 and up for a dyno tune. Cheaper if you have someone guess a tune for you which is what I think the "tune by email" without the datalogging is.

First step is to find someone to tune it. When you have that, you can be more radical. Otherwise, you have a POS running car that won't maximize all the money you put into it.
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Old 09-11-2018, 03:36 PM
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Originally Posted by Joe C View Post
truth of the matter - you're only halfway when you start putting things back together.
This is very very true. So really you're about a quarter in the hole.
Originally Posted by MrBigDee View Post
Here is my -86 year model with mild cam + Bosch 4 EV14 30lb injectors and tuned original ECM.

https://www.youtube.com/watch?v=CqmpETUzWxs

Next is coming Procharger P600B, Aeromotive fuel pump and Aquamist water/methanol injection
Also a mild cam. (Your car sounds good btw.)

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Old 09-11-2018, 10:40 PM
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My car is an auto and has the better gear ratio of 3.07 now. I like the sound of the cam in those videos even if they are mild, I live in Ohio and donít need inspections. Do you think a mild cam would work without a tune then? And then I could get the long tube headers after that and maybe cylinder heads a while after that and tune it after everything? I should get a factory service manual sometime, I have been being told that. It doesnít seem hard with getting the radiator and water pump and things out of the way but I would need help being told how to do the timing chain and harmonic balancer because I donít even know what the harmonic balancer is.
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Old 09-11-2018, 10:43 PM
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Originally Posted by 85 CRVET View Post
My car is an auto and has the better gear ratio of 3.07 now. I like the sound of the cam in those videos even if they are mild, I live in Ohio and donít need inspections. Do you think a mild cam would work without a tune then? And then I could get the long tube headers after that and maybe cylinder heads a while after that and tune it after everything? I should get a factory service manual sometime, I have been being told that. It doesnít seem hard with getting the radiator and water pump and things out of the way but I would need help being told how to do the timing chain and harmonic balancer because I donít even know what the harmonic balancer is.
What are your intakes like? Get that and the headers squared away. You won't notice as much benefit but you can live with that for a while. After which, get the heads and cam done after you are sure the lower end is good. Ask me how I know to do that.
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Old 09-11-2018, 10:46 PM
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I didnít mean I wanted it just for sound, I am trying to get it more power. I have a new open exhaust and need to get the long tube headers though. I cut the air lid box too . I have heard that the intake manifold is restrictive so thatís why I plan on changing it and am trying to figure if I can change the cam with it because I would like to a lot if I can for more power and the sound.
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Old 09-11-2018, 10:49 PM
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Originally Posted by aklim View Post
What are your intakes like? Get that and the headers squared away. You won't notice as much benefit but you can live with that for a while. After which, get the heads and cam done after you are sure the lower end is good. Ask me how I know to do that.
I think the car is all stock from what I can tell and no mods were listed done to it so I take it the intake manifold is stock then. What, so you think I should get the long tube headers and intake manifold and then do the cam and maybe heads after that? I just thought it might be easy to change the cam while the intake manifold is off.
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Old 09-11-2018, 10:51 PM
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Originally Posted by 85 CRVET View Post
I didnít mean I wanted it just for sound, I am trying to get it more power. I have a new open exhaust and need to get the long tube headers though. I cut the air lid box too . I have heard that the intake manifold is restrictive so thatís why I plan on changing it and am trying to figure if I can change the cam with it because I would like to a lot if I can for more power and the sound.
Good ceramic LT headers aren't cheap but they last for a while and perform well. Kinda like the clothes might be oversized for the baby they they can grow into it as opposed to a perfect fit today. The intake is restrictive but you need to have it complement the system you are going to build. Get the tune with the headers and intake since that will be about $3000 in parts, give or take. There are always the "while I am here" stuff like injectors, gaskets and who knows what else you broke going in. After that, save up for the heads and cam and another dyno tune. That is more pricey.
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Old 09-11-2018, 10:54 PM
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Originally Posted by 85 CRVET View Post
I think the car is all stock from what I can tell and no mods were listed done to it so I take it the intake manifold is stock then. What, so you think I should get the long tube headers and intake manifold and then do the cam and maybe heads after that? I just thought it might be easy to change the cam while the intake manifold is off.
Intake and headers followed by dyno tune. After that, figure out how much heads and cam cost plus another dyno tune. If you don't have a dyno tuner nearby, figure the cost of getting it there, motel bills, etc. See if you are still motivated to go further at that point. Nothing is worse than a half fawked project because you have a circumstance change and can't afford to go further (marriage or baby or new house, etc) for example. Ask the tuner what he likes for heads and cam and what he recommends for a good intake that will complement them when you do it in the future.
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Old 09-11-2018, 11:08 PM
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Where in Ohio ?
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Old 09-11-2018, 11:18 PM
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Joe gave some good advice. Make the most of whats there (porting stock stuff, small cam/headers/100shot and go for it). So it isnt "the best", so what. Youll have a solid 13 sec car or better on your hands. Lots of 12 sec cars with 14 second drivers out there.
Post in your regional section to see if there are any C4 owners in your area, you could use a hand thats good with a wrench. First attempt wiht the intake can be a pain.
At the end of the day its a basic 350 nothing complex so if it pops toss it out and get another, you didnt have any real money into it.

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Old 09-11-2018, 11:52 PM
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So it will need a tune after just the intake and headers? I thought it would be fine without a tune for that but would need a tune later just for something big like the heads and cam. Thanks for all of your help by the way. Do you think dyno tuning is the only way or is getting a chip through email almost as good or will work fine?
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Old 09-12-2018, 12:03 AM
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Originally Posted by 85 CRVET View Post
So it will need a tune after just the intake and headers? I thought it would be fine without a tune for that but would need a tune later just for something big like the heads and cam. Thanks for all of your help by the way.

Do you think dyno tuning is the only way or is getting a chip through email almost as good or will work fine?
It might work ok since you are MAF to drive it without an optimized tune. I suppose it depends on what you can live with. I had a SD car that drove without a tune after a Superram intake and headers. It was much better without the hesitation after Lingenfelter tuned it although he said the system was designed to work with the stock system. It wasn't as good and the question is what can you live with? If you think you are going further, why not source out the tuner first instead of attaching the other stuff and then "where do I find someone who can....."?

If I am confident that the guy will datalog and use the info honestly to improve the car, sure. OTOH, I have no faith in "Guess a Tune" where you tell me what you have done and I guess what you need adjusted. If I were the tuner, I doubt I will be as aggressive since I don't want to increase the risk of adding a window in your block and having you pissed. IOW, I will leave something on the table. I have seen the dyno tuning process where they do a base tune, make a run, and try again. Repeat the process till the power level drops off, going to the last known good tune, all the while checking the datalogs. Depends on how sloppy you can stand it as to whether a "Guess a Tune" via mail order will work. For me, it works till I get it to a dyno facility but I tend to be more nitpicky about these things. If you are willing to accept guess work, you can mail order.
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