Roller Conversion: Heads off necessary? - Team Camaro Tech
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post #1 of 21 (permalink) Old Dec 14th, 19, 09:17 AM Thread Starter
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Roller Conversion: Heads off necessary?

Hi Guys,
iīm planning a little ahead, and my goal is a full roller conversion. Its gonna be a Straub custom cam..

I want to minimize the steps to the necessary minimum, just to minimize risk of operation.



The engine can stay in car as many videos state, but what about the heads?

There is lots of videos out there for a hydraulic roller conversion, but in all of them at some point the cylinder heads are off the engine all of a sudden. And i wonder why?

Is this necessary?

If so, why?

And if so, is it necessary to resurface the heads once they were off, assuming they probably ran just a few thousand miles since full engine rebuild and there are no visible defects to see across the surfance?

Wouldnīt just a nice composite gasket cope with the surface roughness?



The things you change are cam, lifters, pushrods, rockers, springs/locks/retainers.. and all these parts are accessable just by taking off either chain cover, intake or head cover, right?

Or am i overseeing something? (probably)..

Piston to valve clearance checking procedure is taking place with heads installed, too.. so thats not it.

Thank you in advance for your help guys

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post #2 of 21 (permalink) Old Dec 14th, 19, 09:51 AM
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Re: Roller Conversion: Heads off necessary?

No reason to remove the heads. You should check out Straubís semi-custom cams. Chris is great to deal with.

I highly recommend getting everything from Chris. Springs, retainers, locks, push rods, lifters, etc. Everything worked great. You should also consider using a cam retainer instead of a button. (Gen V)
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post #3 of 21 (permalink) Old Dec 14th, 19, 09:56 AM
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Re: Roller Conversion: Heads off necessary?

You should not have to remove heads, but the valve springs may need changed (do you currently know the specs of what is currently installed), which is somewhat harder in the car than on the bench.

If you have a recent rebuild, removing the heads is not necessary.

Also resurfacing heads is not necessary unless they are warped of have an incorrect surface finish.
Composite gaskets are rather forgiving & seal well..
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post #4 of 21 (permalink) Old Dec 14th, 19, 10:09 AM
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Re: Roller Conversion: Heads off necessary?

You will probably change the rocker arm ratio which changes the push rod location which then requires requires some grinding on the heads. This can be done leaving the heads on but it would be safer to remove the heads to avoid metal grindings in your engine.
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post #5 of 21 (permalink) Old Dec 14th, 19, 10:13 AM Thread Starter
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Re: Roller Conversion: Heads off necessary?

Quote:
Originally Posted by rp930 View Post
No reason to remove the heads. You should check out Straubís semi-custom cams. Chris is great to deal with.
Alright, i see... Yeah the semi-cams are probably the best non-custom-aftermarket cams you can get, but when i go for a conversion, i will go for the very best (full custom grind to my setup)

Quote:
Originally Posted by Lonnie P View Post
You should not have to remove heads, but the valve springs may need changed (do you currently know the specs of what is currently installed), which is somewhat harder in the car than on the bench.

If you have a recent rebuild, removing the heads is not necessary.

Also resurfacing heads is not necessary unless they are warped of have an incorrect surface finish.
Composite gaskets are rather forgiving & seal well..
Thanks, the springs will definitely have to be replaced! There are some springs that stay wihtin certain dimension-limits, resulting in no work neccessary on the heads (i got 1977 781s btw) , i already checked that.

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post #6 of 21 (permalink) Old Dec 14th, 19, 10:18 AM
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Only reason you’d have to remove the heads is possible interference installing a .300 taller lifter.
May not be an issue for you though.

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post #7 of 21 (permalink) Old Dec 14th, 19, 10:32 AM
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Re: Roller Conversion: Heads off necessary?

IMO you need to remove heads to check piston to valve clearance. I'm not current on the method used today but old school was to put clay on top of piston. No way that I can figure out how to do that without removing the head twice. If there is a new method to check I'm all ears.

Jeff
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post #8 of 21 (permalink) Old Dec 14th, 19, 11:14 AM
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Re: Roller Conversion: Heads off necessary?

for a normal cam swap, heads generally can stay on. Since you are upgrading form flat tappet to roller, you will almost certainly need to change out the valve springs. This can be don on the car (couple tricks to it--air pressue in the cylinder, rope int he cylinder, etc to keep the valves from dropping), but it is probably actually easier for this swap to pull the heads to install the new springs and make sure spring pressures are appropriate for the new cam.

If you also plan to upgrade to 1.6 rockers, the heads may need some grinding (may or may not), in which case, you should 100% pull the heads to avoid any potential debris falling into the bottom end.

just my $.02

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post #9 of 21 (permalink) Old Dec 14th, 19, 12:24 PM
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Roller Conversion: Heads off necessary?

Not sure what Iím missing here? 1.7 rocker arms. 781 heads. No grinding should be required. The lifters arenít even close to the head.


69 COPO clone, 461" BBC 11.25:1 Compression
840 Rec Heads (2.25/1.88) AED 850 HO carb
Orig Exhaust Manifolds
Straub (Clay Smith) cam, 288/300 .600/.569 109.
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post #10 of 21 (permalink) Old Dec 14th, 19, 06:07 PM
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Re: Roller Conversion: Heads off necessary?

Are your rocker studs pressed or screwed in ?

You'll need to change springs for the cam. (easier off the car) Checking spring height.
IF you have pressed-in studs, you'll want screw-in studs IMO (really should be off the car)

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post #11 of 21 (permalink) Old Dec 14th, 19, 08:09 PM
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Re: Roller Conversion: Heads off necessary?

Based on the signature for the original post... this is a 396.
1.7 ratio, screw in studs in all big blocks.....

Now what you have to watch for is piston to valve clearance.
You do this with a dial indicator on the retainer, using a checking spring.

When the piston gets close to TDC, you can push down the rocker till the valve touches the piston & note the amount of travel measured with the dial indicator. If you go too big on the cam, you get to remove the heads & cut valve reliefs in the pistons.

I had this problem on my 396 with a 256/260 .666 lift. I got to tear the entire engine down & cut both the intake & exhaust reliefs.
With stock or TRW type pistons... If you stay relatively mild & under .600 lift, you may be ok.
Other aftermarket pistons have better valve reliefs.
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post #12 of 21 (permalink) Old Dec 15th, 19, 03:52 AM
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Re: Roller Conversion: Heads off necessary?

Harris, Like mentioned already, if you remove the valve retainer to remove the spring, gravity will cause the valve to drop into the cylinder. Filling the cylinder with air by screwing a air fitting into the spark plug hole (with both valves closed) or feeding rope through the spark plug hole and filling the cylinder up with the rope up against the valve will prevent the valve from falling.

If it was my engine, I would rather replace the springs with the heads off the car. This will minimize any issues that could occur with the head-on methods. If you drop a valve, it is pretty challenging to try to retrieve it. You will have to try to feed a magnet through the valve guide and pull the valve back up. Another benefit is with the heads off, you can inspect the valves and seats when you remove the valve retainer and spring. Then you can also install new, high quality valve seals.

I would also feel better that I have the springs set into the spring pocket nicely and the retainers seated good and the valve seat inspected and cleaned - just an all around better peace of mind that the spring replacement was done properly. I personally feel like doing this with the heads on is a shortcut that I would not take, but that's just me and my .02. A lot of people do it with no issues. With my luck, something would go wrong on the last valve, haha.

Then, with the heads off, you can measure the quench and get new head bolts/studs that have not been stretched and install correct thickness head gasket.

Brett.....

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post #13 of 21 (permalink) Old Dec 15th, 19, 06:04 AM Thread Starter
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Re: Roller Conversion: Heads off necessary?

Quote:
Originally Posted by ilikeike View Post
Only reason youíd have to remove the heads is possible interference installing a .300 taller lifter.
May not be an issue for you though.
Thanks, the lifters i will use (Morel 4795) have following specs:
Lifter Type: Hydraulic Roller
Plunger Travel: .015" - .030"
Body Type: Billet
Body Diameter: .842"
Body Height: Stock -> so should be ok.
Offset: N/A
Wheel Diameter: .750"
Tie Bar: Vertical
RPM Capability: 7000+ RPM
Seat Pressure (Lbs): 100-200
Open Pressure (Lbs): 285-650
Do Not Use Oil Heavier Than 5W40!

Quote:
Originally Posted by yellow69RS View Post
IMO you need to remove heads to check piston to valve clearance. I'm not current on the method used today but old school was to put clay on top of piston. No way that I can figure out how to do that without removing the head twice. If there is a new method to check I'm all ears.

Jeff
Thanks, the method i know is the one where you install a extreme light "checking spring", heads installed. Lonnie P is referring to it down below

Quote:
Originally Posted by keithl1967 View Post
for a normal cam swap, heads generally can stay on. Since you are upgrading form flat tappet to roller, you will almost certainly need to change out the valve springs. This can be don on the car (couple tricks to it--air pressue in the cylinder, rope int he cylinder, etc to keep the valves from dropping), but it is probably actually easier for this swap to pull the heads to install the new springs and make sure spring pressures are appropriate for the new cam.

If you also plan to upgrade to 1.6 rockers, the heads may need some grinding (may or may not), in which case, you should 100% pull the heads to avoid any potential debris falling into the bottom end.

just my $.02
Thanks. Stock rocker ratio is actually 1.7, and i am gonna stay with that

Quote:
Originally Posted by rp930 View Post
Not sure what Iím missing here? 1.7 rocker arms. 781 heads. No grinding should be required. The lifters arenít even close to the head.

yeah correct, 1.7 is stock which i will use, so should be ok.

Quote:
Originally Posted by DOUG G View Post
Are your rocker studs pressed or screwed in ?

You'll need to change springs for the cam. (easier off the car) Checking spring height.
IF you have pressed-in studs, you'll want screw-in studs IMO (really should be off the car)
I also think all MARK IV BBCs have 7/16-14 Screw in studs with adjuster nuts. But i will change to better ARP ones with Polylocks (with internal setscews).

Quote:
Originally Posted by Lonnie P View Post
Based on the signature for the original post... this is a 396.
1.7 ratio, screw in studs in all big blocks.....

Now what you have to watch for is piston to valve clearance.
You do this with a dial indicator on the retainer, using a checking spring.

When the piston gets close to TDC, you can push down the rocker till the valve touches the piston & note the amount of travel measured with the dial indicator. If you go too big on the cam, you get to remove the heads & cut valve reliefs in the pistons.

I had this problem on my 396 with a 256/260 .666 lift. I got to tear the entire engine down & cut both the intake & exhaust reliefs.
With stock or TRW type pistons... If you stay relatively mild & under .600 lift, you may be ok.
Other aftermarket pistons have better valve reliefs.
Very good info, thanks.

Of course thats the absolute worst case for me, trying to minimize steps needed for conversion by letting heads on, then resulting in having to cut the pistons... thats something i have to make sure doesnt happen.

Thats why your info is of high value to me.

Is there a way to calculate PTV-clearance? if so, please enlighten me. Or what else can i do to avoid clearance issues in the first place?

I will go with a full custom cam, but i estimate the timing will be in the 240+ @0.050 and Lift probably 0.600(+).

Chris Straub told me its gonna exceed the semi-custom timing, but doenst know how much till he ran my setup through the simulation.

But i guess it should not exceed the 250s timing-wise, since the cam only hast to provide mixture for a demand of 402 cui. not 454 or even 496.

I have a L78-Block with these pistons: -> do you happen to know/see what kind of valve reliefes they have? is the dome shape .335 an indicator maybe?

Pistons @ 6223 Crankshaft 1053 Steel
L2242NF + .030 = 402 CUI
FORGED .030 OVER**4.124 Bore
TRW / Sealed Power / Federal Mogul**
PISTONS FOR A CHEVY**L-78***396 1st Design Closed Chamber Head
The***skirts**are COATED AND COME WITH PINS.
THEY ARE SET UP FOR PRESSED PINS...
RING LANDS ARE** 5/64"** 5/64"* 3/16" .
Compression figured with .020 deck clearance and .028 gasket.
*102CC HEAD = 11.58 : 1
*109CC HEAD*= 11.00*:1
*117CC HEAD*=*10.00 : 1
*119CC HEAD*=*9.80 : 1
*124 CC HEAD =*9.25 : 1 ....
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Chevrolet Eng. Family Big Block
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Compression Distance 1.765
Weight (Grams)*657 approx.
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2nd Ring 5/64
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Quote:
Originally Posted by Brettallen59 View Post
Harris, Like mentioned already, if you remove the valve retainer to remove the spring, gravity will cause the valve to drop into the cylinder. Filling the cylinder with air by screwing a air fitting into the spark plug hole (with both valves closed) or feeding rope through the spark plug hole and filling the cylinder up with the rope up against the valve will prevent the valve from falling.

If it was my engine, I would rather replace the springs with the heads off the car. This will minimize any issues that could occur with the head-on methods. If you drop a valve, it is pretty challenging to try to retrieve it. You will have to try to feed a magnet through the valve guide and pull the valve back up. Another benefit is with the heads off, you can inspect the valves and seats when you remove the valve retainer and spring. Then you can also install new, high quality valve seals.

I would also feel better that I have the springs set into the spring pocket nicely and the retainers seated good and the valve seat inspected and cleaned - just an all around better peace of mind that the spring replacement was done properly. I personally feel like doing this with the heads on is a shortcut that I would not take, but that's just me and my .02. A lot of people do it with no issues. With my luck, something would go wrong on the last valve, haha.

Then, with the heads off, you can measure the quench and get new head bolts/studs that have not been stretched and install correct thickness head gasket.

Brett.....
Thanks so much for the info.

haha last valve fail.. classic.

I would let an experienced (US-car) workshop do the conversion for me. They probably are equipped with tools (magnets) for these kind of operations.

But since the full rebuild is only 1300 miles ago, i guess everything should be ok inside the head.

Thats why i think to let them on in the first place..

If i have to take them off, i will go for a compression raising gasket, too.




@everyone: guys you are suys a great help, its really a pleasure being a member of this forum.

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Last edited by Harris Roc Malouda; Dec 15th, 19 at 11:18 AM.
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post #14 of 21 (permalink) Old Dec 15th, 19, 09:33 PM
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Re: Roller Conversion: Heads off necessary?

I'm worried as your pistons are the same as mine.

I barely cleared a 256/266 .600 solid flat tappet cam.
The roller was worse even though less duration due to the more aggressive opening/closing ramps

The tighter the LSA, the worse the valve to piston clearance typically gets. Mines on a 112.
I think I had to take off .100 for proper clearance.

Also are your heads cut at all?
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post #15 of 21 (permalink) Old Dec 16th, 19, 06:33 AM Thread Starter
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Re: Roller Conversion: Heads off necessary?

Quote:
Originally Posted by Lonnie P View Post
I'm worried as your pistons are the same as mine.

I barely cleared a 256/266 .600 solid flat tappet cam.
The roller was worse even though less duration due to the more aggressive opening/closing ramps

The tighter the LSA, the worse the valve to piston clearance typically gets. Mines on a 112.
I think I had to take off .100 for proper clearance.

Also are your heads cut at all?
Hey Lonnie,

did you really cut valve reliefs into your pistons? Of course i want to avoid that and am trying to precalculate the possible outcome..

i estimate the cam to be max 240/250 dur. and 0.620 lift with 109LSA. But thats still a guess.

What i read mostly about main criteria for P2V issues:
- Intake is more critical than exhaust side
- duration is more critical than lift

So my focus is on intake duration.

So lets take a look at those Stock L78/L37 cams:

L78 (solid) 1965-1966 /// 1967-1970
Adv. Dur 336/336 /// 316/302
@0.050: n.a./n.a. /// 242/242
LSA: 114į /// 114į
Lift: 0.520/0.520 /// 0.520/0.520

L37 (Hydr.) 1965
Adv. Dur 342/356 --> look at this intake duration !! I think there is some room left for me in my case.. but maybe not that much.
@0.050: n.a./n.a.
LSA: n.a.
Lift: 0.461/0.500

Since Chris Straub does Semi-Customs especially for 781/049 heads i think he knows their limits.

But of course he doesnt know the pistons those heads are bolted on top.

And our pistons do have quite some dome (0.335).

I found a calculator, which, if feeded with correct data, appears to be extremely correct, at least according to others who used it, as i researched in other forums:

Piston to Valve Clearance Calculator ? PCM of NC, Inc.

I am still figuring out how to use this one.. e.g. i donkt know the "valve drop" of 7781 heads.. do you know how to use that calculator?

and i think they are just resurfaced in a minimal way, because the preowner said they have 118cc.

Thanks for your help though

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Last edited by Harris Roc Malouda; Dec 16th, 19 at 10:10 AM.
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