I came up on a great deal, but now I have a dilemma!

Joe

This head gasket and most other copper head gaskets require either the block or heads to be O-ringed

Use this calculator

http://www.kb-silvolite.com/calc.php?action=comp

Paul

 

So I guess the only option is the .080 cometic? That sucks! I'm having a hard time trying to figure out my compression. How can I CC my own heads or do I need to take them to get CC'd?

 

The accurate method is pretty well described here:

http://www.circletrack.com/techarticles/ctrp_0611_cylinder_head_volumes/viewall.html

If it's not something you plan to do a lot of in the future, you can get by using an inexpensive setup like this and still get a pretty good measurement of volume, or make/buy what you need on your own:

http://www.steigerperformance.com/products/sp90005.html

You can use the same setup to measure the volume of the piston's valve reliefs too.

Devon

 

I have a couple thoughts;

I would have a concern as to how straight the bores are to the crank C/L, because the block is not decked square. If they used a machine that referenced from the deck, the bores could be crooked. If a main bar/saddle reference, it will be at least correct from end to end. Call the shop that did it and ask which type they use. Another way to tell is to mic the deck clearance on all 4 corners. You need to use the same piston and rod to know for sure, as there can be length variations. Even with that, you are at the mercy of the crank index..If you pull the crank out, you can measure it. Anyway, it's important, and has been covered on here in detail.

Anyway, as far as compression, you need the deck clearance to be no more than .055" period. Getting the compression where you want it is going to have to be done somewhere else. first off, what type of piston is it? If it is offered in a dish as well, the flattop can more than likely be machined to a dish as they would use the same forging. Just leave enough of the squish band on the OD of the piston to give piston to head quench. I have done "D" shaped dishes to achieve this.
Just mount and square it in a rotary table, cut your "D" shape and depth with a ball mill, change tool to an end mill and pull the center out. You can knock a point of compression out real easy. Not many pistons won't take a .075" cut though. Even at that, at a 3.5" dish would probably add over 10cc from the TDC volume. Check you numbers and see what you need, I'm just guessing. Oh, I just noticed in one of your posts that the piston sticks out of the deck .010", hooray! knock that off too while it's in the milling machine. I noticed its a Ross piston too. It's plenty thick. I would sonic test them to put a number on it so you could sleep.

Rebalance the pistons and crank and you're done. No crutches or compromises, no twin tanks, no race fuel that leaves corrosive lead exhaust residue all over the ass of your car, and no expensive fuel.

You have a VERY easy fix here. Just get those pistons and crank out and get to it.

 

Paul, thanks for the input. I did some rechecking, looks like when I was running the iron heads and 308S solid cam, I ran it straight up at 108, so the intake was closing at 57 ABDC compared to Joe's 288-98H at 51 ABDC which from a DCR point of view should have been favorable for me. On top of that my combustion chambers, valve faces, piston dishes and notches were deburred and polished to as close to a mirror finish I could manage including the quench area of the chamber above the pistons within the gasket diameter. In hot weather, even with fresh air induction routed from the high beam sockets, detonation was a problem at 32 total timing on 93 aki above 5000 rpm, with about 0.050" piston-to-head clearance with a composition gasket. The pistons were the inexpensive Sealed Power forgings that only have a narrow band around the dish that actually provides the true quench area, which I believe is a disadvantage compared to other designs discussed (D dish, spherical dish).

Having lost previous builds to detonation in the past while I was learning, I'm just hoping to keep everything within a safety margin for someone like Joe who maybe hasn't had to suffer the hard knocks (pardon the pun!). I kept my build happy by learning how to read the plugs in the end, and just getting a "feel" for what the weather was probably going to do to me.

Devon

 

Thanks Devon for the advice. I've added some more pictures after I talked to the machine shop who did the work. Its been over a year so he didn't have all the information but he told me the shortblock was blue printed and balanced. All the oiling mods were done and he said only top of the line parts were used. The pics I took show that each piston has its own part number engraved that are matched to each piston 71309 A3 -71309 H3. Also the numbers 1-8 on the bottom of each piston. There is also caps that have 19/32 over the cam. It looks to be balanced off the numbers that were engraved on the pistons and rods. With this new information I think I'm gonna keep the shortblock built the way it is and just put money toward the head gaskets. Take a look at the pics and let me know what you guys see.

 

The pickup passage is stock (for a 70 block). It should have been enlarged. I don't know what "all oil mods" mean. You have no paper work with the engine. What about bearing, thrust and rod side clearance o No: What kind if bearings? If they are hp race bearings they will chew up the crank. There are to many unknowns. Was it align honed? Was it washed out out after the TA cam bearing were put in? Why weren't the decks equalized? The guy said it was balanced. Is there any sings of extra holes in the crank throws or flexplate it came with? The engine needs to be taken down measured and inspected.
Ray

 

Ahhh, is it my eyesight, or does that connecting rod bolt say "CROWER"???
That sure as hell looks like a billet rod to me..if that's the case, you got the deal of the decade. Those things are $1200.00 alone.
Ross, indeed does scribe a number on each piston? It has nothing to do with balance. The A-H in the part number is just like 1-8, as in number of pistons made. If you order 10 they will go to "L"...

I don't see that the bottoms OD the bores are chamfered. You may want to do this. It helps the oil film from getting scraped off the piston shirt at BDC. They will run cooler and scuff less with chamfers.

It is possible that they did not deck it because of the numbers. You may want to run them by someone on here and see what block you have.

Nice score!

 

I looked again. It says "Ross" on the piston. Get that thing apart, check/correct anything that may not be right, make sure it has P series bearings and rebalance after cutting the pistons. You will have one helluva engine.

If it needs a linehone, install a stud kit too.

 

Thank everyone; the parts alone (yep, those are billet rods) are worth the price!

Keep in mind the other advice you're getting from the other guys here though, the parts don't necessarily make a well built engine.

Without a build sheet from the builder, you don't know if the block is in good shape from a cylinder wall thickness standpoint unless sonic checking was done before boring was done. Even if that was done prior to the machine work, you don't have any info about the quality of that machine work yet.

This all adds up, even down to the type of piston rings installed and whether or not they were gapped correctly and whether or not the correct final bore finish agrees with the rings!

You're not done yet. I agree that it should all be checked out before you run it. "Checking it out" will cost more $$, but it's better than destroying great parts because of bad machine work.

Devon

 

Devon I was thanking you for that specific post. Ofcourse I am very grateful to all who have replied. It's amazing how helpful this board has been during the whole process of my car. I've owned chevy, gmc and olds before this n just like the cars you Buick guys are first class. You guys could have told me it was a great find now slap the rest together but u guys took the time to let me know the right way to go forward. Thanks again fellas!

 

So I called Ross Racing and they said they couldn't machine the pistons. So after doing all the calculations with the compression calculator it looks like I will have to mix 100 octane regardless of what head gasket I use (.040 12.1) and (.080 11.1). Should I just use the Orange crush copper .040 and use the money on TA high performance water pump because I will have to mix gas either way. Is the valve to piston clearance to short at .030 or will it be ok?

 

Joe

What was Ross Racing's reason for not being able to machine the pistons?

Paul

 

They said it would make them to thin. I asked if they could take even a little off and they said no. Like you said earlier Paul I'm just gonna add the high performance water pump and mix some 100 octane. There's a gas station close to my house that has the 100. Now I'm debating if I should buy a new cam like the TA 413, but I don't know how much of a difference it would be from my TA 288-98H. It seems like a lot of guys go with the 413 on the board, but the specs are pretty close.

 

Even though you will have piston head clearance, don't overlook your valve clearance with what you plan to do.

I ran a 413 cam, with 1.6 ratio rocker arms and the valve was close to the minimum clearance near edge of the dish and this was with stock dished pistons that were way down .090 in the hole. The cam was advanced 6*, head gasket 0.27".

I wasn't using the same heads as you though (not sure if the valve position is exactly the same across heads?).

 

Joe

The TA 413 actually makes the problem worse because it has 3 degrees less lobe separation than the TA 288-98.
The Dynamic Compression Ratio (DCR) is determined by when the intake valve closes on the seat.
The advertised duration or the .006" lobe lift value is generally used as to when the valve opens and closes on the seat.

With the cams installed straight up as previously discussed, the intake valve on the 288-98 will have its lobe center at 116 degrees ATDC.
Add 1/2 the advertised duration of 288 or 144 degrees, and the intake valve closes 116 + 144 or 260 ATDC which is 80 degrees ABDC.
Using the Cometic .051 head gasket at .050 crush thickness,
Plug 80 degrees into the calculator and the DCR is 8.2

The 413 has 286 advertised intake duration on a 113 lobe center.
Doing the calculation show an intake valve closing at 76 degrees ABDC

The DCR is now 8.5 or 0.3 points higher than the 288-98 which will increase the problem with detonation.

Besides, the 288-98 has 7.5 degrees less valve overlap than the 413 for a smoother idle and more manifold vacuum in case you are using power brakes.

Paul

 

Thanks Satch wasn't thinking about that and I have 1.65 rockers. Paul if I used my 288-98 cam n advanced it 4 would I still be ok. I sort of want to keep the tq n hp low in the rpm range up to about 5500. On the thread that jim weise had the engine it looks like he lost a lot of numbers by running it straight n I don't mind mixing a little 100 because we only got 91 octane out here in Cali so I will probably have to mix anyway.

 

Joe

If you want to keep the power band low, go ahead and try 4 degrees advanced.
As long as you can mix the octane high enough to prevent detonation, fine.
With 12:1 static compression ratio and 4 degrees cam advance you should have a torque monster and the converter stall speed can be fairly low.

Just be sure to check the intake valve to piston clearance using a light valve spring and dial indicator. Clearance should not be less than .100"

Also the combustion chambers need to be polished so there are no hot spots to cause pre-ignition.

For an extra margin of safety, you may also want to consider the Water/Alcohol injection for the times when your foot is in it at higher rpm.

Paul

 

When I talked to Ross they said the valve cut out were 6cc and when I checked the actual piston it was only .005 above the deck so it looks like the compression will be around 11.5. Keeping the quench around 45 will hopefully help with the detonation with the .050 gasket. What would the DCR be at 4 advanced? Where do you get the water/alcohol injection?

 

Joe

If the SCR is 11.5 then the DCR will be 8.3 with the intake lobe center at 112 degrees ATDC

Back on post #25 Steve suggested Snow Performance.

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