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GT40P Head Replacement

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Post Options Post Options   Thanks (0) Thanks(0)   Quote FFImarine Quote  Post ReplyReply Direct Link To This Post Posted: March-07-2020 at 1:15am
keno..... ARP does state you can reuse there head bolts if you use there moly lube and torque them to there spec but they can only do that one time after initial use. Your more then welcome to reuse head bolts as many times as you like (it’s not my engine) but is $80 really worth it??? I think not
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: March-07-2020 at 5:24am
I called on engine rebuilders that built a combined 8-10,000 engines per month.
On engines that did not use TTY bolts they always re used the head bolts, main bolts, connecting rod bolts.   These engines all went out the door with warranty.
I do know my performance accounts always recommended new rod bolts on the small block GM 350 engines. Again, these were for performance builds because they have seen so many fail on high RPM engines if not replaced.   Other engines they re use every part that has proved to be reliable.   

One final note for discussion.   Many head bolts are built in the far EAST today, not New York but overseas.   Do you trust the made in America bolts your engine had from the factory or the copies made in China.   Other than ARP you will be searching hard to find made in America today.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: March-07-2020 at 8:17pm
Originally posted by phatsat67 phatsat67 wrote:

Better change the wheel lugs with every tire rotation.


Good thinking Zach

I'm gonna change my studs too, 'cause I don't want to worry about my nuts falling off
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: March-08-2020 at 12:27pm
Brian:

What will you be using for rockers on the new heads?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 3:21pm
I was hoping that I could reuse the existing ones, but am open to any ideas! I went with the GT40P's based on Keno's recommendation and am ready to listen to all advice on this project.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mille1sj Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 5:08pm
I used 1.6 Roller rockers for the GT40P heads I put on our 302. I believe they are the Ford Performance rockers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 6:51pm
You can reuse your rockers and pushrods but you should check your lifter preload. Later on if you wish you could go for roller rockers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 8:55pm
Originally posted by BRKOUT1K BRKOUT1K wrote:

I was hoping that I could reuse the existing ones, but am open to any ideas! I went with the GT40P's based on Keno's recommendation and am ready to listen to all advice on this project.


Make sure you get a recommendation from someone who's done it (The 1.6 roller rockers) on a GT40 with it's "pretty finicky" ECM.   

Numerous people have swapped from GT40 to 40P heads without a problem, some have put a new cam in that wasn't much different without a problem, but once you're very far from original you seem to come up with the loping idle issue that's hard to solve.

The 1.6 rockers are pretty much like putting a new cam in and might just be too much for the ECM    Edit............this should say using 1.7 roller rockers not 1.6 since the stock ratio is 1.6 (thanks TRB)

For that reason, I'd use the original pushrods and rockers and not throw anything else into the equation that might make the ECM have trouble controlling the engine as smoothly as it did before.

I've done the head swap only with no running issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 9:48pm
Although some of you claim to be 'backyard hacks' , I can't thank you enough for all your inputs....I might have learned more on this forum than i did after 6 years of 'struggling ' to get through school...Admittedly, I had flashbacks after the 'simple stress-strain' comment Appreciate everyone's help. I know 'swapping' out these heads is probably a simple task for many of you (and I"m no pro) so it is a little more of a challenge to this ol' bus driver. Looking to make sure i've got all the i's dotted and t's crossed! Thanks again....

A little more background....I'm told this boat had some 'issues' before I bought it with the ECM and it was replaced...seems to be running well with the new or used replacement with the exception of the water leaks .and a few 'noises' that i wouldn't have honed in on.   Without all of the time I've spent trying to work out all the gremlins I probably wouldn't have heard most of 'em with the music cranked up!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 9:50pm
OBTW- I work with a guy that is selling an 'older' Malibu if you know anyone in the market...I'll get the flyer and post if there is an interest.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: March-09-2020 at 11:14pm
There’s nothing that stock ratio (1.6) roller rockers would impact... theyre just a little lighter weight and less friction. Increased ratio on the other hand, would be a change similar to cam that may cause tuning issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: March-10-2020 at 5:56am
Originally posted by TRBenj TRBenj wrote:

There’s nothing that stock ratio (1.6) roller rockers would impact... theyre just a little lighter weight and less friction. Increased ratio on the other hand, would be a change similar to cam that may cause tuning issues.


For some reason I had 1.7 roller rockers on the brain when I wrote the earlier post about staying with the stock rockers      Edited the previous post

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: March-10-2020 at 10:53pm
Originally posted by KENO KENO wrote:

Originally posted by GottaSki GottaSki wrote:

huh, bolt holes look small, don't look opened up yet.
are they?


Originally posted by BRKOUT1K BRKOUT1K wrote:

Found a pair of GT40P heads for $535 (includes shipping from Chicago)...1/2 holes w/ Brass plugs. Anything else I need to be on the lookout as far as compatibility is concerned?


Hopefully just an eyeball calibration issue Gotta Ski. The above was from a post in his transmission thread


Gents,
I was able to pull one of the head bolts and confirm that it fits!   Glad you pointed it out so it will be one less thing that could potentially hold me up once we start pulling it apart...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hollywood Quote  Post ReplyReply Direct Link To This Post Posted: March-11-2020 at 12:42am
Potentially undersized bolt holes on the new heads won’t hold you up pulling it apart
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: March-12-2020 at 9:53am
Originally posted by BRKOUT1K BRKOUT1K wrote:

OBTW- I work with a guy that is selling an 'older' Malibu if you know anyone in the market...I'll get the flyer and post if there is an interest.


Here's a pic of the flyer that was posted @ work! Hope it's not a forum party foul to 'advertise' for him since it is not a Nautique:)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote BRKOUT1K Quote  Post ReplyReply Direct Link To This Post Posted: April-03-2020 at 6:16pm
Originally posted by Hollywood Hollywood wrote:

Potentially undersized bolt holes on the new heads won’t hold you up pulling it apart


Well I finally was able to get the heads installed. So far we ran the motor on the hose yesterday and at the ramp this morning. The motor sounds good to my untrained ear...We are almost ready to hit the lake with the kids after some good weather and a couple of maintenance runs

Hollywood, you were correct and your eyeball calibration was spot on!. Despite 2 of the holes not being drilled out for the 1/2 bolts, it didn’t hold us up from pulling it apart. Unfortunately we discovered the issue during the installation and obviously held us up for a few days.

Just wanted to drop a quick note to thank everyone for their inputs & assistance on the project.

Thx
Brian
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aupatking Quote  Post ReplyReply Direct Link To This Post Posted: May-20-2020 at 1:40am
I’m sure one of you guys knows: what’s the spec torque lbs and sequence for the GT40 heads on the 351W?
My current project is ready to have it's engine put back together. It had a rebuild with 10-12 hours on it. Not sure if the head bolts weren’t torqued or were just stretched enough to not hold torque, but those cylinders were slam full of antifreeze when I pulled it apart and the impact didn’t even stutter pulling the head bolts.
On the bright side, rebuilding a 12 hour engine is the cleanest rebuild I’ve done.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: May-20-2020 at 3:54pm
For 351W 1973-1998 Fel-Pro says to torque in 3 steps.
1. torque all Head bolts to 85 ft pounds
2. 95 ft pounds
3. final torque to 105-112 foot pounds for 1/2" bolts

I will look for a picture of the torque sequence for this head.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: May-20-2020 at 4:11pm
351W Torque Sequence

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