I am still trying to figure out my low vacuum problem. Idles poorly at 10-12 vacuum, steady 20 at 2000 rpm, less than 800 miles since rebuild.

engine - 350/300, 041 heads 194 intakes, 1.60 exhaust with hardened seats, 929 cam, 184 intake, Qjet. Crane .530 positive valve seals. Roller rockers. Everything was professionally restored.

I have had the intake off twice looking for vacuum leaks. None found, gasket surface is sealing properly, no evidence of oil stains on bottom of runners.

Compression test -

1- 175 2- 162
3- 180 4- 158
5- 175 6- 168
7- 170 8- 170

Spark plug check -

1- oily 2- clean
3- clean 4- clean
5- clean 6- oily
7- clean 8- oily

Intake valves have an oily/carbon residue on them when looked at from intake runners. Intake runners themselves are clean.

Used compressed air to take valve springs off #1. Valve seals look fine.

I noticed that there was compressed air coming out of the intake port while taking the springs out. Is this normal? Shouldn't the valve's seal enough to stop the compressed air from escaping?

If the valves are not sealing properly, would that cause my vacuum leak?

This has been driving me nuts since the engine was rebuilt.

Thanks!

[ 09-19-2004, 03:35 PM: Message edited by: KevinW ]

I just checked #4 and #8, no leaks past intake valve, but it is leaking around rings. I hear the air leaking into the crankcase.

Just pulled my reciepts. Engine had new valve guides (VG5002), new seals (VS1611), new pistions (trw .30 Hyper H631P) and new rings (Sealed Power Moly Ring Set (E251K))

Do I need to put it back together and just put some more miles on it? and it will magically seal itself?

The vales may leak some while using the compressed air. Sounds like you may have an intake manifold leak. Hvae you put a vacuum gauge on it or spray some carb cleaner at the suspect gasket while the engine is running; if it leaks, the engine will speed up. The leak may be on the underside; does it use oil?

Kevin,
All engines will have some leakdown. The valves really should be sealed up pretty good as long as the springs are on them, but you will always get a little past the rings. Only way to know for sure if it is too much is by using a leakdown tester.

BillK, Thanks for the reply. Would you know how many miles new rings (Sealed Power Moly Ring Set (E251K)) would take to seal. Is 700-800 mile long enough?

I think I am going to take the heads off and have them checked by a different machine shop.

Bill,

What do you think about him getting a small $1.00 tube of lapping compound and a $3.00/$4.00 rubber suction tip wooden spinner and lap them himself.

I'm going to do my -601's this way b/c their seats all look fine and I will be running new valves on them..

I was supprised at how tight the guides are as well as the condition of the seats for the usual crudded up/rusty old heads sorta deal....

I've been so used to seeing soft-seated old leaded gas heads that I am supprised at how they look..

pdq67

I have resigned myself to pull the heads and have them checked by a different machine shop. I need the valves to seal. The low vacuum is causing shifting problems with my trans. :(

I just checked all the valve with compressed air. valves were good in 2,4,6,8 and 3 and 7. they just had blow by the rings. 1 had air leaking past the intake valve and 5 had air leaking past exhaust.

Heads are going out today for a valve job and new seals. There was quite a bit of carbon deposits on the pistons.

Here are the pics of the pistons. I had cleaned the number 1 piston with a razor blade and laquer thinner. The deposits are some kinda oily wet mixture. Heads have them too, but machine shop will clean them.

Does anyone have any clues on why I have this gunk after only 800 miles? Thanks

http://www.fototime.com/A49006AA1809EF2/standard.jpg
http://www.fototime.com/4A421AE0623606E/standard.jpg

pdq,
There really should be no need to lap the valves in if the valve job was done properly. If you insist on trying to get some wear started prematurely, do not use valve "grinding" compound .... make sure you use "lapping" compound which is veerrryy fine grit. Just barely marks the valve at all. The only time I use it is when I am doing a valve job, especially with the 3 angle carbide cutters, I will cut the first seat, then lap the valve in to make sure it is hitting where I want it. After that, I reface the valve and cut the rest of the seats.
Kevin ... if the cylinder walls were finished properly, any good modern ring will basically be sealed up on the engine stand or within a couple of minutes of starting the engine.
By the way, the tops of your pistons look like the engine is "drinking" a lot of oil for some reason.

Kevin,
Who built the motor? Was it a Crate motor, or did a shop build it.

I know you mentioned that you had the heads done by another shop previously, but i'm wondering who did the short block.

The rings should seat one the stand from turning it over.

Can you feel a ridge at the top of the cylinder?

Are the walls shiney, or can you see a semi-smooth cross hatch pattern.

Brian, I saw you drive in with your 67 at tonight Outlets Cruise. We were on our way out when you went past. You were past before I could wave. Very nice 67 you have, sounded nice.

A shop in Jamesburg did the entire engine. It was a std bore E-town swap meet special, but it is a numbers and date correct engine for my SS350. The block had to be glass beaded before they could work on it, but was sound under the surface rust. All the rest of the parts (except .30 pistons and roller tip rockers) are numbers and date correct 1969 parts. No Crate stuff here. smile.gif

It had the full nine yards, new mains, line bored, fully balanced, etc. It was not decked, but is very close to flat. The shop also assembled the engine too.

All the cyl walls still have the cross hatch and look really good. After I cleaned up the gunk off the ridge area, there is no ridge at all.

http://www.fototime.com/6B28FE1CC28F094/standard.jpg

Hope you and your Dad can fix what ever problem my heads have. graemlins/beers.gif

BillK, the gunk is also coating the insides of the intake valves, so I still think the problems are in the heads somewhere.

Thanks!

Kevin,
We'll fix the heads, no problem.

However i would suspect that you had an intake gasket leak which was pulling in oil, or another problem.

The way that we do valve seat grinding is very accurate, and in my opinion superior to the Serdi, although more time consuming.
You'll be happy with them!


thanks for the compliment, i was having a heck of time finding a parking spot, couldnt get into one until about 8:00


BTW, the guy you spoke to, the owner is Paul, he's not my dad though.

Oops, sorry. My mistake.

When my car is running, I normally take the day off, so I can get there by 5:00 to get a good space. Then bring dinner and eat while watching the cars drive in.

I first thought it was the intake seal too. I replaced the intake once already, without any change. I did not see any oil on the runners when I took it off and I checked very closely the wear pattern of the gasket and it was sealing perfectly.

I have another (better dated) intake to go on this time.

what is your procedure for installing the intake?

You might have fault in installing it, or their could be a problem with the intake sealing surfaces.

Brian, I just the lean over the fender with all that weight smile.gif and lay it on. Second time I used a thin coat of non hardening sealer around the intakes. RTV on the ends.

I will bring in both intakes for you to check out when I pick up the heads.

Thx.

Alright,
We usually use High Tack around the ports, and Black Lawson RTV around the water inlets, and RTV on the ends.

Wait until it beads up then put the intake on.

OK, NOW we are cooking!

Got the heads back from shop. All valves were miscut by previous shop. graemlins/clonk.gif

Seals and guides were fine. one bad spring and the springs had to be shimmed (1st shop must not have checked spring height! :mad: )

Installed the heads and intake with Brian's suggestions. Worked great, thanks!

Put the engine all back together again (took me a while with the family and work committments. Replaced the plug wires, most were cooked cause I did not install the plug shields the first time. graemlins/clonk.gif they are there now!

No leaks smile.gif Used the base circle valve adj method #2, 3/4 turn. Started right up!

But it is back together and I have been redoing the tuning mods I used the first time trying to fix the engine.

Put stock mech advance springs back in, before that the 36 degrees were in by 2000!

replaced the R-43S plugs with R-45S.

readjusted trans modulator out 5 1/2 turns.

readjusted Crane vaccuum advance back out, cause I was getting part throttle pinging. Adjusted vaccuum stop plate to give it more advance at idle.

But engine is running smooth at idle 17 in. vaccum at 950 rpm (650 in drive). 12 deg initial, 27 deg with vaccuum advance at idle, 36 degrees all in around 2600. It does not diesel when you shut it off.

graemlins/beers.gif I got to drive it today :D (many times!)

I still need to adjust the vaccuum can to give the most advance without part throttle pinging and adjust the shift points for the trans, but it is 1000% times better than what it was.

Thanks for everyones advice!

[ 09-19-2004, 03:37 PM: Message edited by: KevinW ]

Thats what i like to hear!

Actually the valves and seats were out, typically production line machines that are used by many rebuilders will cut the valve seat with a run-out.

We use stones, and the valve seats are dead on accurate when me or Paul grind the seats.

I ground the valves and they were out of concentricity as well.

your advance curve looks good!

See you on friday probably.

One thing that is a "maybe" here is if the rings didn't stay put and walked around so that just maybe the ends lined up???

I really doubt it b/c if they had, you would have a bunch of blow-by big time!!

Just trying to help.......

pdq67