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Old 08-18-2019, 08:28 PM
65sport 65sport is offline
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Default #66 heads

I've acquired a 455, it has casting #66 heads. They have press-in rocker studs and bolt-on guide-plates.

My question is:

The pad that the guide-plates set on. Is it the same height as a head that came equipped with screw-in studs from the factory? I'm concerned about clearance between the bottom of stock style rocker arms and the hex on the stud.

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Old 08-18-2019, 08:47 PM
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Same height.

Had a set myself that I converted to screw in studs.

The only heads that need the stud bosses milled to use screw in studs with the bottom hex are the early heads that don’t use guide plates.

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Old 08-18-2019, 08:54 PM
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Big Chamber heads. Pump gas friendly

I sold a set recently that had been converted to screw in studs and were date coded for the guy's car.

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Old 08-18-2019, 09:20 PM
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For b-man
Thanks for the answer man I appreciate the info. Did you use the existing guide-plates or did you replace them?

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Old 08-18-2019, 09:22 PM
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[QUOTE=thepontiacman;6052669]Big Chamber heads. Pump gas friendly

If they aren't cracked, I will have them milled around .060" and the intake side as necessary. With .027" gaskets I should get close to 9:1.

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Old 08-18-2019, 09:28 PM
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65,
6X heads are plentiful and much better heads to start with. Before you go and spend $$$ on your 66's you mean gut shop around...

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Old 08-18-2019, 09:48 PM
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Quote:
Originally Posted by 65sport View Post
For b-man
Thanks for the answer man I appreciate the info. Did you use the existing guide-plates or did you replace them?
I used the existing guide plates, they’re the same ones used on heads with screw in studs. The studs will now hold the guide plates down, no need for the center hold down bolt used on press in stud applications.

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Old 08-18-2019, 10:31 PM
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Quote:
Originally Posted by b-man View Post
I used the existing guide plates, they’re the same ones used on heads with screw in studs. The studs will now hold the guide plates down, no need for the center hold down bolt used on press in stud applications.
Thanks again

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Old 08-18-2019, 10:37 PM
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Quote:
Originally Posted by 77 TRASHCAN View Post
65,
6X heads are plentiful and much better heads to start with. Before you go and spend $$$ on your 66's you mean gut shop around...
Well I have these, and just getting a feel for what will need to be done to them. All things considered, whatever gets the job done and is least expensive. The engine was recently rebuilt so I need to get them tore down. If they are in good shape I can get them magged, and milled on block side and intake side.

A guy on Craigslist has a set of 4X for $100 but he don't know what they are off of. If they are from a 400 they would be ideal. Or like you say 6X-8's would do as well.

I have some nicely rebuilt 6X-4's, but don't want that much compression. 91 octane is what is available here, and I will be happy with 9:1ish.

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Old 08-18-2019, 11:43 PM
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When you add up the cost of tapping for screw in studs and the added cost of conversion studs with 1/2-13 threads on the bottom ($100) plus the heavy milling to try to get 9:1 compression and expensive Cometic .027” gaskets ($200) the 6X-8 heads are a better way to go.

No expensive conversion studs and no tapping needed for the 6X-8 heads and no heavy milling requiring a cut on the intake side of the head.

If your engine is apart you may be able to cut a small dish in your pistons to utilize the 6X-4 heads. Food for thought.

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Old 08-19-2019, 02:14 AM
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Quote:
Originally Posted by b-man View Post
When you add up the cost of tapping for screw in studs and the added cost of conversion studs with 1/2-13 threads on the bottom ($100) plus the heavy milling to try to get 9:1 compression and expensive Cometic .027” gaskets ($200) the 6X-8 heads are a better way to go.

No expensive conversion studs and no tapping needed for the 6X-8 heads and no heavy milling requiring a cut on the intake side of the head.

If your engine is apart you may be able to cut a small dish in your pistons to utilize the 6X-4 heads. Food for thought.

It appears to be a recent rebuild, not sure if I'm going to tear down the bottom end. To my surprise, it has .025" deck clearance, .030" Silvolite pistons. It has the piston size markings on the deck from the factory so it has not been decked.

What would you think about opening up the combustion chambers a little? I have a couple good books by Jim Hand and Pete McCarthy one of them illustrates where to and not to take material out.

I like the ideas. If I replaced the rods I could mod the pistons, because I would have to balance it anyway. I wish I could replace the rod bolts without taking them out but I've heard the ARP's will distort the rods so they have to be honed.

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Old 08-19-2019, 12:25 PM
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You should not need to mill anything to get 9 to 1 compression with 6X heads. 6x-8-100cc's, deck clearance-6cc, gasket-10cc's. 116cc's with a 455 is 9.0 compression.

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Old 08-19-2019, 01:30 PM
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Quote:
Originally Posted by tc View Post
You should not need to mill anything to get 9 to 1 compression with 6X heads. 6x-8-100cc's, deck clearance-6cc, gasket-10cc's. 116cc's with a 455 is 9.0 compression.
116's with 455 is around 8:1.

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Old 08-19-2019, 02:23 PM
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My 455 also has the 66's. Unfortunately for me, mine came with the cheap cast pistons that have the bevel around the edge of the piston, lowering the CR even more. My final CR is less than 8.0:1.

But with a set of Tri-Y headers, a really good exhaust system, and a custom low-lift HFT cam, it runs pretty decent. With a stock torque converter and a 3.08 posi, it will smoke the tires off-idle, even at just part -throttle. The motor is DONE by 4800rpm, but it has killer torque and runs great on the cheapest gas I can find.

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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'.

'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust

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Old 08-19-2019, 02:45 PM
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One cylinder volume is 932 cc's. 455 cu in is 7456 cc's
116 + 932 = 1048
1048 ÷ 116 = 9.03

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Old 08-19-2019, 03:00 PM
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Quote:
Originally Posted by tc View Post
One cylinder volume is 932 cc's. 455 cu in is 7456 cc's
116 + 932 = 1048
1048 ÷ 116 = 9.03
+ deck height + gasket thickness (or volume) + valve relief (and bevel, if any) volume.

Actual CR ends up right around 8.0:1

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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'.

'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust

My webpage http://lnlpd.com/home
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Old 08-19-2019, 04:34 PM
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Quote:
Originally Posted by Lee View Post
My 455 also has the 66's. Unfortunately for me, mine came with the cheap cast pistons that have the bevel around the edge of the piston, lowering the CR even more. My final CR is less than 8.0:1.

But with a set of Tri-Y headers, a really good exhaust system, and a custom low-lift HFT cam, it runs pretty decent. With a stock torque converter and a 3.08 posi, it will smoke the tires off-idle, even at just part -throttle. The motor is DONE by 4800rpm, but it has killer torque and runs great on the cheapest gas I can find.
That's good to know because I'm torn between 3.0 and 3.25 gears on my 9 inch. My pistons are Silvolite and only a very small bevel. I won't have Tri-Y, just the RA cast "headers" and X pypes 2.5". Regardless what heads I use I plan on 9:1 ish CR and 91 octane fuel.

I'm worried about the stock rods though. Might get them honed with ARP bolts. Cost would be $180 for that.

I'm curious the specs of your custom cam.

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Old 08-19-2019, 04:36 PM
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Quote:
Originally Posted by tc View Post
One cylinder volume is 932 cc's. 455 cu in is 7456 cc's
116 + 932 = 1048
1048 ÷ 116 = 9.03
You are missing a part of your equation. You have to add for piston dish (valve reliefs in this case), head gasket and deck clearance.

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Old 08-19-2019, 05:13 PM
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Quote:
Originally Posted by 65sport View Post
I'm curious the specs of your custom cam.
222/242 @ .050", .443"/.435" valve lift, 116 LSA, ICL target was 111 but it ended up at 112.

The motor had a .454" lift cam in it, when I got it. There was no wear on the cam or lifters, so I knew that whatever the springs were, they were fine for up to .454" lift.

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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'.

'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust

My webpage http://lnlpd.com/home
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Old 08-19-2019, 05:39 PM
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Thanks Lee !

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