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NOT A CAM QUESTION, Valve spring question

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NOT A CAM QUESTION, Valve spring question

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Old 11-06-2019, 12:44 PM
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Default NOT A CAM QUESTION, Valve spring question

I am looking to put a Comp Cam 01-775-8 ( Comps 731 clone) cam into a Merc Performance Gen VI 502 415 HP version. The rocker studs have been swapped out for adjustable and Comp Extreme rollers installed.
Here is the question I get varying answers to.
I am looking at these springs both Comp 924-16 and/or 26120-16. Can these be installed in the stock heads without removing the heads, or more simply put without machining?
I am open to other brand springs also.
I know there is brain trust on this site that has a definitive answer. Please provide solid experience responses.
Thank you in advance.

Last edited by GLENAMY 242SS; 11-06-2019 at 12:49 PM.
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Old 11-06-2019, 01:28 PM
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IMO, the springs you listed are too light on pressures.
The 731 is comparable to a 500efi cam and one of the main replacements springs used is the Comp 929's.
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Old 11-06-2019, 01:32 PM
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Originally Posted by Griff View Post
IMO, the springs you listed are too light on pressures.
The 731 is comparable to a 500efi cam and one of the main replacements springs used is the Comp 929's.
Thanks Griff. The springs I listed are the ones that Comp recommended.
Do you have any knowledge if the 929's work without any machine work to the heads?
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Old 11-06-2019, 01:52 PM
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you're going to change the springs and not set the installed height ? What is the recommend closed and open pressure for the new cam,
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Old 11-06-2019, 02:02 PM
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If its anything you care about Id pull the heads and set the spring height. My machinist showed me the difference of spring pressure from the lowest to the highest and it may as well have been two different cams.
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Old 11-07-2019, 01:40 AM
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Originally Posted by GLENAMY 242SS View Post
Thanks Griff. The springs I listed are the ones that Comp recommended.
Do you have any knowledge if the 929's work without any machine work to the heads?
Not 100% but I don't think any machining is needed.

How many hours on the engine? What is your goal?? Doing just the cam and ECM tune will probably only gain about 25hp/2mph.
Are you going to do the cam swap in the boat? I did a complete top end in my old Baja.......Never again.
Way easier to pull the engine and if the engine is out, just pull the heads, have them checked and springs installed and then new head gaskets.
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Old 11-07-2019, 05:49 AM
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I would pull heads, check seats, do a valve job, check guide wear, and make sure installed height is right, installed height can be done in boat also as thats what sets pressure, but i would pull heads..
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Old 11-07-2019, 08:20 AM
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OK some additional info.
This is a carb 502 with just over 200 hours on the meter, it has been treated very nice, not abused and flogged.
My goal is 5,400 rpm and primary usage is just cruising around with infrequent visits to the 5200-5400 area. Some occasional sustained 4000-4200 runs. Boat is Formula 242 SS (1987).
Additional oil cooling has been added and I am running Stainless Gen II exhaust w/air gap intake. Motor is out of the boat but out of town, I will be traveling to put my accessories on, tune and haul home for install in boat. Not building an all out ball buster motor.
I am aware this is not the most ideal way to do the cam but it is all I can afford with the motor. Hence my question.
Griff, You say you don't think any machining is required, but, with which springs. I am also curious that Comp recommends the 924 springs or the Beehive equivalent and some think that is insufficient, not doubting your experiences but just confused.
I want to replace the springs and the cam would be great at the same time if it is financially feasible. A complete valve job is not in the plan.
Thanks for the replies and advice.
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Old 11-07-2019, 08:29 AM
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are these heads 088 ?
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Old 11-07-2019, 08:42 AM
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Strange, I have attached a picture of the head and serial number. I cannot see any casting number on the head.
The motor was purchased new from perfproplus and is a GM performance Marine crate motor.
Here are the pics of the motor and S/N.

Last edited by GLENAMY 242SS; 11-07-2019 at 08:47 AM.
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