WTF! Major problems with vaccum

Ok I got my Stage 1 rebuilt. Here is the combo


1972 Stage 1 with original JW carb (checked and good). TA roller TC, TA up graded but stock length push rods. TA Stock Stage 1 cam, TA lifters and springs, Stainless valves, TA rocker shafts and rockers ( stock) Cast pistons NOS Timing cover rebuilt BB trans.

After break in on the cam the engine will not idle. Carb sent to specialist and its fine. all vaccum lines blocked off. Engine has 10 inches at what we can call a very poor idle as it dies constantly. At 1000 the engine has 17 inches vaccum. The engine is cfanking at 140 lbs compression.
This engine is so mild it should suck a golf ball through the lines!
The engine builder found both end rails torn and the rear pin for locating the intake bent. On went a new intake set. Still poor vaccum. Off came the intake. No evidence of a leak. Intake was sealed with copper coat on the ports not the Hi Tack I am used to seeing. Felpro no longer supplies the Hi Tack in the gasket set.
Off came the intake. The builder says the intake must be cracked. checked and no crack. Checked the angles of the intake and heads. This is all the same as when it was disassembled as no cuts were made. The engine was a 70K mile untouched original that ran ok but needed to be freshened.

Ideas are
1) cam installed wrong as it has the TA lower sproket with multi key ways.
2) push rods not seating correctly and holding valves open
3) Cam ground wrong ( I have to check tonight to see if it was degreed yet)
4) cranking compression too low I was told that I should have 165 or higher
5) !@#$%^&*)(*&^$$@##%^%&&**(^^$$#ou: :af: :shock:


Any ideas we can check? I am out of my mind. I am no expert mechanic but I have done my share of engine work. I usually do my own work but since I had the engine built by this guy I wanted to have him start it. Its been a couple weeks and I guess I am really racking up the bill at 85 per hour this is going to break the bank.

 

I would do a leakdown test on it and make sure the valves are sealing. If they are holding ok I would put .030 shimms under the rocker shafts and see what happens. I have had a couple of builds that would hold the valves open because the pushrods ended up long.

Mike

 

OK the carb was run on a test engine by a so called expert here. The test engine was a Buick 350. It ran fine and idled fine.

How if the push rods were the same length as stock and you can turn the rods when the valves are closed could the valves be open. The leak down was done and at about 1%
No cutting on the heads or deck was done.
Any other ideas please

When the builder said that about the push rods I wondered , why cannot a hydrolic lifter not make up a small difference in a stock rebuild? If I were running a solid cam I would be checking these measurements more closely

 

John, pm me your# and I will give you a call.......Chris

 

I think it's very likely that your cam is not degreed correctly. When I was building my 464, I found out that the 9 way adjustable Rollmaster double roller timing set was not at all accurate to what the marks indicated on the crank gear. The cam I installed was ground with a 110* centerline if installed straight up, and was recommended to be installed 4* degrees advanced. So, I first installed the timing set with the crank gear on the 4* advanced slot, lined up the dots on both gears, then double checked by measuring the actual intake centerline. luckily I did, because the centerline came out to be 116*! 12* retarded from what it should have been! After playing around with different positions on the crank gear, I ended up installing it with crank gear on the straight up position (0*), and the cam gear skipped one tooth advanced! So, I would definatley get a cam degree kit and see where the cam is actually installed, because it's very possible the timing set is not accurate.

 

I just had it with a bottom end rebuild of a 3.8 series 2. I didn't touch the heads, reused the lifters and valve train. I just did rings, bearings, and gaskets. I preoiled it on the stand and did a spinning compression test with the starter on it. NOTHING!!!!:af: I did a leak down on it and it had less than 3% with NONE of it going out through the valves. Did another compression test. STILL NOTHING! I finally loosened the rockers up and suddenly I had compression. I ended up on that motor putting .040" shims under the rocker pedestals.

On another of my 455 builds years ago before I went to adjustable rockers, I had to put .030" shims under my shafts to get it to rev over 4500 rpm.

I'm not saying that this is definatly the case but it is an easy thing to throw some shim under the shafts and see if it makes a difference.

Mike

 

Probably will look into that after I see the cam degreed tonight. I have a degree kit and I would assume they do too. But that said I will be taking mine with me tonight.

 

I don't have an adjustable timing gear, but on my last mad thrash swapping cam's under a deadline, I goofed and the teeth were off by two. The car fired right up, and if I gave it 25% throttle it'd idle up, and run like crap. The vacuum was waaaay down though, about 5 inHg from what it should of been. It would die at idle pretty quickly. Sure enough it was the cam timing, got the dot's to line up and BAM, ran just like it did when I ran that cam several months earlier.

 

I agree with BAD65. The TA roller chain set MUST be degreed in. Save yourself some time and do a quick cam timing check.

Here's how I do a quick and dirty check:

Remove driver rocker arms. Remove all spark plugs to allow engine to turn over freely. Set up dial indicator on #1 intake pushrod. Rotate engine around so that lifter is on the lowest part of lobe. Set dial to "0". Rotate engine around with socket on crank bolt. No need to remove anything up front. Now, if your damper mark is correct, and I've rarely seen them off more than a degree, you should be able to see where IO is at .050". Consult your timing card and this will give you a ballpark figure. If you are not more than a few degrees off what it says then you are probably good there. This setup works with a mild cam because they are usually minus a few degrees before TDC at IO and your timing cover should have enough numbers to cover it. Those numbers usually go up to 12 BTDC and 2 ATDC. Just guessing that your cam should be -8 or something like that.

That Stage 1 cam shouldn't be a problem unless it is really retarded. That's what I'm betting on. For most builds I like the Cloyes 4 chain sets or a good stock set for mild setups. Less fuss.

If you have any compression then the valves are not being held off their seat. It only takes a fraction of an inch of valve lift to kill cylinder compression.

Did you try looking at the rockers while the engine is being cranked to make sure all the rockers are moving about the same amount? You never know about lobes wiping out.

If nothing on the cam then it is back to looking for vacuum leaks.

 

It definately doesn't take much. I had zip for compression when my head gasket blew into the lifter valley. I didn't think that would be enough to register zero on the compression gauge, but it was.

 

cranking compression is 140 to 145. timing is my main concern tonight. I am taking my degree set in and will do it myself if I have to. I know that the builder did not degree the cam because he mentioned that he could do it if needed. No leaks detected so it is now a must do. I expected this to be done when assembling the engine. Since we have no idea where we are at I will be insisting on the checking of the cam first.

 

Take it from a guy who has put in about 60 cams recently.. and degreed every one of them.

This has nothing to do with the Rollmaster timing chain. The only problem folks run into there, is not putting it on correctly. It can be confusing, especially if it's your first time with it.

As far as advanced/retarded cam timing, it's all about the cam, and how it's phased into the grinder.

Check every one, every time.

JW

 

As per ouir conversation I wanted the cam to be degreed. The builder said he thought my cast iron intake might be crackedou: He checked it and its not cracked. Then he checked the angles on the heads and intake. The parts were not cut so... No problem there. I expected the cam top be degreed but on a "simple" rebuild I guess they thought it wasn't neededou: ou:
We'll know tonight

 

Cranking compression will come up if cam has to be advanced from where it is.

Confusing yes, on the Rollmaster Jim. That's why I don't recommend them to "tinkerers" who are just swapping out cams. That set can get you in a world of hurt if you don't degree your cam or make a mistake aligning it. That's why the stock type is nice. Only one chance of screwing it up and if your cam is ground reasonably close it should work ok. Maybe not optimum, but ok.

 

Yea, I geuss I shouldn't have been so quick to blame the timing set, as i had no way to verify there was actually something wrong with it, it could very well have been that the cam was ground incorrectly. But, regardless of which part is at fault, the point is that you should always degree your cam.

 

Yes Mike, I will agree that for the Novice, less choices might be better.. if and I mean if, they can get the cam to degree it in properly.

But there is also value in getting even the home installers to really dial in a cam, and to be sure of it's position in the engine.

That's because cam position accuracy is really hit and miss these days. I have seen it be an issue from at least 4 different cam grinders.

I will say that from what I have seen, approximately 1 in 3 cams needs adjustment, beyond what you can do with a 4*chain, for optimum cam timing. 1 in 6 need that much adjustment, just to run correctly.

I have had three that, like the previous poster, were off so far that they had to have a tooth skipped on the chain, to get them to come in correctly.

On a small cam, you going to get away with more error in position, but when the cams get larger, it's critical to be in the right spot. Not only for power, but for the dreaded "idle quality" issue.

Witness the number of guys on the board that have that TA 290-08H cam.. and swear it won't idle with enough vacuum to run the brakes. Yet I have put at least 7 of those in, with the appropriate advance curves and amounts, with the right torque converter, and the brakes work adequately, in all but maybe that first couple of minutes after a cold start, when the motor is a bit groggy.

100% of them that I have actually built the motor, and put the car together, work just fine.. I think I have used that cam, and it's straight pattern brother (290H) in about 5 cars built at the shop here, and brakes were never an issue. But they certainly can be, without everything being "just so", and that starts with cam timing.

If you put that cam in at 108-109 degrees, it will not run the brakes worth crap.. I actually put one in that way on purpose, on one of these motors for a car build here, just to see, and it was as horrible working the vacuum brakes as I have read about on the board. Advance the cam another 2-3 degrees, and it makes a world of difference at low engine speeds.

I encourage folks to use that rollmaster, because I want them to understand what they are doing, when they assemble an engine, and/or install a cam. And that chain, with all it's keyways, will make you really think about it.. and question if you have it in correctly. And if that prompts you to actually degree the cam, and you correct the position of the cam in the engine, that's a win-win situation for you. Your motor runs good, and you learned something along the way.


If they take the time to really dial that cam in, and to be sure of where it's at, then typically the end result turns out better, and they are happy they took the time to learn the very simple procedure. It does take some tooling, but that should be considered as part of the cost of building an engine, or changing a cam.

One of these day, I am going to make a cam degreeing video, and put it on the internet..

When folks actually see how simple it really is, it will take the mystery out of cam degreeing.

I can fully degree a cam, on a new motor, in about 15 minutes, start to finish. And that's not just ILC position, but also .006 and .050 valve events, lobe lift, base circle runnout, and doing the math to check the Lobe Center Separation that it was ground at.

I will admit, my first degree job probably took 2 hours, but that's how we learn. Learning and understanding what's going on in your engine, is good for every hot rodder.

JW

 

I've got the 290-08h. you talk about groggy. I'm messing with efi tuning still (haven't been able to get to it enough) Groggy really describes this in the first minute of running. But at 106 plenty of vacuum for brakes after that first minute or 30 seconds. After that it's great and very responsive.

about the timing. I remember changing the timing chain on my old 350 and found it was already changed. however at TDC it was approximately a tooth off. I already had ordered and had the timing chain and replaced it again putting it straight up and it had nothing. I don't know if the cam was ever replaced (felt and sounded stock). cams need to be degreed. I do wish Jim would do a video as it took me quite a while to get mine degreed although after doing it I'm glad I did.

 

I agree with everything Jim has said, Take the time to learn how to degree a cam, and use TA's Rollmaster timing set. The timing set is a bit confusing at first, but I Took the time to learn it, and how to degree a cam, thats probably why my 350 GS with the TA 413 cam can idle in gear at 550 to 650 rpm, operates power brakes fine, and has a TON of low end, I have it degreed to within .5 degrees of where it says on the cam card. Degree your cam, its worth it and the car will definatley run better:grin:

 

I know how to degree a cam but the engine builder should have done this when he assembled the engine. Now with the radiator, shroud, water pump, PS , alt and A/C brackets in place it is a little more trouble