Y Block Help Needed

[countrysquire]

Yes, 1,2,3,4 on passenger side. Isn't that true of all Ford V8s?

[darrell]

yes but sometimes people get thrown by the fact that cylinder is not the real front one.the flathead is the same.only old henry could come up with a firing like that.ford firihg orders really make no sense.

[countrysquire]

Cam overlap on all cylinders is the same, and it's about 5 degrees earlier than TDC. Also, it looks like there's about 2 degrees worth of slack in the chain. I wouldn't think that's enough to cause compression and vacuum issues. 6" of vacuum is pretty piss poor for a stock cam. I checked cylinder by cylinder per the firing order, 90 degrees at a time and the overlap followed on the cylinders per firing order. Measurements were taken with a metal ruler across the valve retainers, giving me two contact points on each valve.

When turning the engine by hand, you can hear the air blow into the oil pan pretty easily. Maybe the rings ain't as good as I hoped, but my experience doing that has been with new engines that I've built, so I'm sure they are tighter. I've not done a leakdown test yet, but I guess that will be next.

[countrysquire]

Cam overlap on all cylinders is the same, and it's about 5 degrees earlier than TDC. Also, it looks like there's about 2 degrees worth of slack in the chain. I wouldn't think that's enough to cause compression and vacuum issues. 6" of vacuum is pretty piss poor for a stock cam. I checked cylinder by cylinder per the firing order, 90 degrees at a time and the overlap followed on the cylinders per firing order. Measurements were taken with a metal ruler across the valve retainers, giving me two contact points on each valve.

When turning the engine by hand, you can hear the air blow into the oil pan pretty easily. Maybe the rings ain't as good as I hoped, but my experience doing that has been with new engines that I've built, so I'm sure they are tighter. I've not done a leakdown test yet, but I guess that will be next.

[countrysquire]

Finally had time to do a cam timing check this afternoon, and here's what i came up with:

Intake valve opens at 29° BTDC vs. Ford spec of 12° BTDC
Intake valve closes at 85° ABDC vs. Ford spec of 54°ABDC
Exhaust valve opens at 89° BBDC vs. Ford spec of 58° BBDC
Exhaust valve closes at 41° ATDC vs. Ford spec of 8° ATDC

All opening and closing measurements were taken at .020" to compensate for valve lash, dial indicator inside of pushrod cup.

The intake lobe center angle came out to 112°.

Intake valve lift measured .278" (.298" - .020") vs. Ford spec of .264"

Exhaust lift measured .281" (.301" - .020") vs. Ford spec of .262"

[countrysquire]

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Dang double post...

[Tinker]

Itll be interesting to see what happens with a timing gear and chain change. If your doing that in lieu of a total rebuild.

[darrell]

time to pull the cam and see what you have.

[scicala]

Originally Posted by countrysquire

Finally had time to do a cam timing check this afternoon, and here's what i came up with:

Intake valve opens at 29° BTDC vs. Ford spec of 12° BTDC
Intake valve closes at 85° ABDC vs. Ford spec of 54°ABDC
Exhaust valve opens at 89° BBDC vs. Ford spec of 58° BBDC
Exhaust valve closes at 41° ATDC vs. Ford spec of 8° ATDC

All opening and closing measurements were taken at .020" to compensate for valve lash, dial indicator inside of pushrod cup.

The intake lobe center angle came out to 112°.

Intake valve lift measured .278" (.298" - .020") vs. Ford spec of .264"

Exhaust lift measured .281" (.301" - .020") vs. Ford spec of .262"

Well, if all of you're measurements are correct, your cam has Intake specs of .428" lift at 294 degrees of duration, and the exhaust is .437" lift at 310 degrees of duration. I also assume the .278" and .281 lift measurements were cam lobe lift and not actual valve lift.
To me, this more than explains the low vacuum. Tons of duration and overlap. The lift isn't that radical, but the duration and centerline are for a pretty much all out racing cam for a Y-Block.

[Fordors]

Your specs show the Ford cam has a duration of 246* and the cam in your engine has 294*In. and 310*Ex. duration. Valve events of 29*IO+85*IC+180*= 294*. Next duration divided by two = 147* and subtracting 29* from that gives an intake centerline of 118*, not the 112* you saw. I think the .020 checking clearance you are using is too low a value and you are seeing errors in the timing events, and also, the use of the push rod cup can skew the readings. I think it would be better if you can take a direct reading from the top of the tappet. Initial lifter rise (your .020) is very slight per degree and for that fact it would be better to check valve events at .050. Most performance cam manufacturers will use .050 for the greater accuracy and the lower "effective duration" it will show.
Another thing I see is the dual pattern in your cam, 294* intake and 310* exhaust. True, specs given by Ford show variance in the timing between intake and exhaust but the duration is the same @ 294*, so the factory cam is set 2* advanced with a new chain and gears. You could have a dual pattern cam, I am not ruling that out, it may very well be.
I'm not saying your chain is good or bad, just that I would go back and check the cam at .050 and see what you get. At that point your intake centerline might coincide with the numbers. An IO event at 29*BTDC for a cam with 294* duration will have a c/l of 118*; if the c/l was at 112* for the same cam grind the IO event would have to be 35*BTDC. There is an error in your readings, but regardless, your low compression numbers may be due to the greater duration of a performance cam combined with stock pistons. Ole Don and Y-Blockhead both mentioned lower vacuum readings with aftermarket cams and I think that is also why you are seeing low vacuum.
Check cam specs at .050 before you do anything else and that may give some insight here. Possibly with those readings someone will have info on an aftermarket cam with like numbers.

[countrysquire]

Thanks, I'll check it at .050" and see what that shows.

[Oldmics]

Ford never used .050 for cam specifications in those early years.

To try and duplicate the factory specs your .020 measurements are probably pretty close

Unfortunatly I don't know where they checked for the 1955 cams.

I do have all the 56 and 57 cam check points (but that's no help)

I will say that based strictly on your lift measurements - its not a stock Y Block Ford camshaft from any era.

It is worth it to recheck at .050. Perhaps by posting up those measurements and IF its an Isky cam the pedigree can be disclosed.

Oldmics

[countrysquire]

Per the 1955 Ford shop manual:

Intake opens tappet lift @ degrees BTC - 12°@0.016
Intake closes tappet lift @ degrees ABC - 54°@0.019

Recommended valve lash is 0.018" hot.

I'm a little under the weather, so I didn't get a chance to check it at .050" yet, but will post the data once I do it and maybe we can figure out what's in there. I'm thinking that it's a case of mixing a big cam with stock compression ratio.

[Ole Don]

If you remove the cam, you can mail it to Comp Cams in TN. and for a very small fee, they put it on the cam doctor and get accurate measurements and make up a new cam card. Your measurements seem to be very good. Some companies give measurements at .050, and some at .020. You are in the ball park. The numbers you came up with is a wild - wild cam for so few cubic inches. With the correct valve springs, it should run to 7500 RPM's and make its best power between 4800 and 7000. The numbers are similar to the Iskenderian 505T I ran for two years. It didnt want to pull the car below about 2200 to 2500, but it 3500 it felt like it had a turbo. That was the engine I shifted at 7000. 287 HP in street trim on the chassis dyno on 91 octane with corn in it.

[jim galli]

You know that '56 - '57 rocker arms have a different lift ratio. Who knows what's in there. iirc those were the only 2 years with the better ratio, (also bigger ports,) as the 352 was the hot rod in '58 and the 292's were de-tuned to '55 numbers or less. Some of the Merc Y blocks kept the better heads and rockers for a couple more years? Maybe? It's all in a 1970's Hot Rod magazine article that I've kept somewhere in the rafters all these years.

Just googled it. September 1968 issue of Hot Rod mag. John Thawley wrote an article called "one more Y block" It has all the ECZ numbers and years of the stuff that flowed the best. Most of it 1956,57 If you can find that issue, it's excellent information. If not, let me know and I'll look for mine and maybe scan the stuff. Should be public by now.

[countrysquire]

Thanks Jim. Who knows what parts are on it? Once I have it out, I'll have a look at the casting numbers and at least figure out what the big pieces are.

I found an old link to the article that you mentioned:
http://www.oocities.org/yblockhead/OneMoreY_block.html

[jim galli]

Originally Posted by countrysquire

Thanks Jim. Who knows what parts are on it? Once I have it out, I'll have a look at the casting numbers and at least figure out what the big pieces are.

I found an old link to the article that you mentioned:
http://www.oocities.org/yblockhead/OneMoreY_block.html

That's the text, but the original article had a bunch of good sidebars with numbers and casting codes and duration of production. Dating myself. In 1968 I was only 16. Honest.

[countrysquire]

OK, leak tester built and it appears to work, based on a lot of correlation with the compression test. All the cylinders but two had between 25 & 35% leakdown. One cylinder only had 6%(!), and one had 75%. That one might have a problem. I went back and checked it again and got the same reading. Moving the crank back and forth made no difference, nor did tapping the valves. I followed that with a couple squirts of oil and retested. The pressure came out about 5 psi, but you could hear the air blowing through the oil. I guess this tells me that I better go ahead and open it up while it's out of the car.

[wellcraft17]

Well it looks as tho you have narrowed it down to camshaft and probably rings and I am assuming you will rering it and get a new stock cam providing the cyl. bores and crankshaft are good to go. You indicated the heads had recently had a valve job and I would put them back on but I would also check the valves seats for leakage prior to. Don't know if anyone still does this but we use to pour a little gas down the ports of the heads and look up in the cumbustion chambers and see if there was any seeping of gas around the head of the valve and seat after a valve job. Easy and quick way to check.

[countrysquire]

Yeah, I plan on doing a close inspection on everything while it's apart. Ordered a reground cam for Oregon Camshaft with a reground set of lifters. The cam is a stock '57 312 grind. Hopefully I will have the engine on the stand by this weekend.