[Dragncar]

Cool build.
Those rockers are known for putting metal filings in your oil.
I would not risk it with a Eagle cast crank.
Go Scat 4340 , worth every penny.

[77 TRASHCAN]

It looks to me like you on your way towards final assembly?
Do you have intentions of zero decking block (I hope!!!)
I will never build another engine without getting the quench, spot on, it can make a huge difference in octane sensitivity. Iron heads need this more than alum heads.

I agree with other, a forged crank would be my only choice. The next step up in cam selection, seemingly, has been used by man without affecting drive-abilityat all.
I'm on board withCrower or Harland Sharp rockers, both can be bought direct from their factories.

[25stevem]

If you just switched over to main studs without at least getting the main bore checked with a precision ground round checking rod or if not Aline honed then that’s why number 5 could be doing what your seeing.

Main studs pull on the blocks main Webb in a different way then do bolts!

Before you order up different bearings and if you still have the old rear main bolts, then I would install them and torque them up and see what might change with your bearing clearance.

[HWYSTR455]

Originally Posted by 25stevem

If you just switched over to main studs without at least getting the main bore checked with a precision ground round checking rod or if not Aline honed then that’s why number 5 could be doing what your seeing.

Main studs pull on the blocks main Webb in a different way then do bolts!

Before you order up different bearings and if you still have the old rear main bolts, then I would install them and torque them up and see what might change with your bearing clearance.

Totally agree, and I always use at least main studs in all my builds. Cost is very low for the added insurance.

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[HWYSTR455]

Nice work by the way, and love the build!

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[Verdoro 68]

Originally Posted by 25stevem

If you just switched over to main studs without at least getting the main bore checked with a precision ground round checking rod or if not Aline honed then that’s why number 5 could be doing what your seeing.

Main studs pull on the blocks main Webb in a different way then do bolts!

Before you order up different bearings and if you still have the old rear main bolts, then I would install them and torque them up and see what might change with your bearing clearance.

During the last rebuild is when I switched to studs, it was align honed then. I don't think I have the original bolts, but that would be an interesting experiment.

Originally Posted by HWYSTR455

Pretty sure the OE spec for #5 is a higher number than the rest, and believe the last 2 engines I had were at 30/32, and the one Olds engine was 35, none had any issues. But I would again suggest speaking to Butler.

Good to know!

Just ran into a snag with the bearings if I need another set. I sized the clearances using King XP and the standard size are out of stock until late October. Butler sells the HP line. I'll give Butler a call after the holiday.

Sounds like the consensus across the board is to ditch the PRW rockers. That opens up the 1.5 or 1.65 question again. I'll have to see what the heads are clearanced for when I get them back.

Regarding the cam, I'm already two roller cams into this build since I upped the cubes from a 400. I'll use what I have and see how I like it. This isn't a track car, just looking for something good and torquey to cruise around with and put my foot into every now and then.

[25stevem]

The scoops on the 68 to 70 hoods and even the 65 to 67 hoods do not provide a pressure gain above atmospheric that’s worth even talking about if my two cents is worth anything!

Its more informative to look at temperature drop that they can provide by means of wind chill.

Now the hood scoops on the 71 GTO way at the front of the hood are far better at pressurizing the carb!

[TCSGTO]

Originally Posted by 25stevem

The scoops on the 68 to 70 hoods and even the 65 to 67 hoods do not provide a pressure gain above atmospheric that’s worth even talking about if my two cents is worth anything!

Its more informative to look at temperature drop that they can provide by means of wind chill.

Now the hood scoops on the 71 GTO way at the front of the hood are far better at pressurizing the carb!

Yes, they are at the boundary layer and don’t really “ram” anything. I kept the open scoops but ditched the pan when the car started getting well into the 11’s. Up till then it did seem to help a little on the street on hot days but you cool your engine down between passes anyway at the track.The scoops got to be a restriction at higher power levels.
FWIW keeping the fuel cool is probably worth more power than cooling the air. Cool fuel pulls more heat out of the intake tract than air. The old 1% increase in HP per 10 degree temp drop rule of thumb has been disproven many times. There is an improvement but not that much.

[Stan Weiss]

Originally Posted by TCSGTO

Yes, they are at the boundary layer and don’t really “ram” anything. I kept the open scoops but ditched the pan when the car started getting well into the 11’s. Up till then it did seem to help a little on the street on hot days but you cool your engine down between passes anyway at the track.The scoops got to be a restriction at higher power levels.
FWIW keeping the fuel cool is probably worth more power than cooling the air. Cool fuel pulls more heat out of the intake tract than air. The old 1% increase in HP per 10 degree temp drop rule of thumb has been disproven many times. There is an improvement but not that much.

Interesting. If you look at how the dyno correction factor is calculated you will see that SAE 607 (which is used by most engine dynos) works out to just about 1% per 10 degrees,

Stan

[Formulajones]

Originally Posted by 25stevem

The scoops on the 68 to 70 hoods and even the 65 to 67 hoods do not provide a pressure gain above atmospheric that’s worth even talking about if my two cents is worth anything!

Its more informative to look at temperature drop that they can provide by means of wind chill.

Now the hood scoops on the 71 GTO way at the front of the hood are far better at pressurizing the carb!

I never claimed it as a pressure gain or meant that it had any ram air affect, other than that term just being used as a general reference, that's all.

The fact remains that having those scoops functional on dad's car has proven to be worth a bit of ET and has always run it's fastest time, with numerous engine combos in the car, with the scoops open and sealed to the carb.

The part that I found most interesting was the question that Bruce brought up, since now those 2 little scoops are the only thing feeding the 571 that makes 724hp, and it hasn't seemed to kill any performance. So how much CFM actually gets through those openings?

I did however mention how those scoops are poorly positioned right in the boundary layer. My 70 Formula works the best out of the bunch from what I've experimented with, and the Z and Chevelle both grabbing at the base of the windshield work exceptionally well.

I'm still of the mindset that the OP's setup would look killer with the 68 system intact and functional. He likes period correct making the car appear as if he would have built it in 69-70 using over the counter OEM performance parts, as he mentioned in an earlier post, and to me the 68 RA pan setup is at the top of that list.

[HWYSTR455]

FormulaJones - Thank you for a detailed response, much appreciated! Would be interested in more details on the mods required for the Chevelle pan, probably more than this thread should have. (Maybe PM me)

Cold air, that too is a very good point, and guess with EFI, it would have less effect/improvement, but cold air is still an improvement. IAT readings fatten it up with colder air, hence, more power. (theoretically)

I agree, functional on the 68 in discussion would be a cool/wow factor, and at a lower power build makes much more sense. Well, if you consider 525-600 a 'lower power' that is!

On the #5 clearance, wasn't the factory spec bigger for #5 too? I thought for some reason it was like .0003-.0005 more than the rest, but I honestly can't recall specifically. (Wish I wasn't living out of boxes right now)


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[Formulajones]

Originally Posted by HWYSTR455

FormulaJones - Thank you for a detailed response, much appreciated! Would be interested in more details on the mods required for the Chevelle pan, probably more than this thread should have. (Maybe PM me)

Cold air, that too is a very good point, and guess with EFI, it would have less effect/improvement, but cold air is still an improvement. IAT readings fatten it up with colder air, hence, more power. (theoretically)

I agree, functional on the 68 in discussion would be a cool/wow factor, and at a lower power build makes much more sense. Well, if you consider 525-600 a 'lower power' that is!

On the #5 clearance, wasn't the factory spec bigger for #5 too? I thought for some reason it was like .0003-.0005 more than the rest, but I honestly can't recall specifically. (Wish I wasn't living out of boxes right now)


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You are correct, at least the one old book I grabbed does have the #5 main with slightly larger "range" for oil clearance. I don't know if all books or more recent books are like that.

I'll send you a pm.

[Verdoro 68]

Originally Posted by Formulajones

I'm still of the mindset that the OP's setup would look killer with the 68 system intact and functional. He likes period correct making the car appear as if he would have built it in 69-70 using over the counter OEM performance parts, as he mentioned in an earlier post, and to me the 68 RA pan setup is at the top of that list.

Twist my arm The main thing holding me up from adding the ram air gear is that I don't want to cut the hood. That said, I did punch a 4" hole in it for a hood tach and my scoops are already open so...

Originally Posted by HWYSTR455

On the #5 clearance, wasn't the factory spec bigger for #5 too? I thought for some reason it was like .0003-.0005 more than the rest, but I honestly can't recall specifically. (Wish I wasn't living out of boxes right now).

Originally Posted by Formulajones

You are correct, at least the one old book I grabbed does have the #5 main with slightly larger "range" for oil clearance. I don't know if all books or more recent books are like that.

Interesting - which book are you looking at? The '68 service manual only shows .0002-.0020 for all main bearings. (.0002!!??)I looked in an old Chilton's in addition to Rocky Rotella's books and they all listed a uniform range for all mains. I tried calling Butler today for advice, but they're closed for the holiday.



While I figure out the bearing clearance situation, I picked up on a few other things. First, I primed and painted the block, new valley pan, new Canton pan and repro front cover. A while back I found a snafu on Amazon's site and got a 6 pack of Pontiac Duplicolor 1616 for $15. Came in handy today.



Next, I checked the crank endplay. I rigged up a dial indicator from my cam degree kit, I hope that's kosher. I couldn't get it on the crank snout, so I set it up against the first counterweight. Looks like I'm at .007 which is in the acceptable range. I also test fit the factory windage tray with spacers to make sure it's going to clear the crank (it will, no problem).



Finally, I got familiar with the Total Seal ring pack and set up the ring filer. The instructions say to go for .012-.022 for my bore size. I looked through some old threads and it seems like the consensus is .016-.018 on the first ring and .020-.022 on the second, although Cliff mentioned he does .018 on both. I have the first one at .017 right now. Taking this first one slow and being very careful to ensure I'm filing square and not taking too much off.

[Skip Fix]

For 3" mains King does have a 0.001 tighter set also.

[android 211]

Jim Hand found the cast iron intake was worth 10hp over the RA/HO aluminum intake. The repros aren't as good as the originals either. And the '68 RA II had an iron intake. Very cool setup overall. Will the air conditioning be revived?

[grandam1979]

That would be cool ram air II with a/c then that cam you got will be perfect. Actually I would use it if you already have it either way. If your not chasing e.t.’s at the track and you drive it a lot you will like the cam you have. My 2¢

[25stevem]

How much hp are you looking to add with the NOS shot?

[HWYSTR455]

Originally Posted by 25stevem

How much hp are you looking to add with the NOS shot?

I believe he is not using any N2O, but what I was suggesting is to go to the 1st level to be safe, in the even of things like det, overheating, etc, which can make the ends butt.

As I commented, there is no downside going to the next step bigger, and is a good safety padding.

.

[25stevem]

Yes, I always go .001” more just to be totally safe with a NA motor, I also check the ring gap on two bores in each back at the bottom of the bore just to check for taper.

[HWYSTR455]

Taper is another good reason to go bigger than just the standard gap recommendations.


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