it's possible this is a 366 cube truck block and crank

 

Made a QUICK stop by the machine shop today after work. The pistons are TRW L2300 040 (odd, in a block I believed to be 060 overbored), which to my surprise do have a subtle dome... .140" tall with a volume of 16.8cc. The heads (closed chamber) have a nominal volume of 100.9cc, but have been planed to some degree (don't know how much exactly) prior to now and .005" off as a cleanup since disassembly. I have no directly measured volume yet. The pistons were sitting about .020 down in the bore before they were removed from the block, which has not been decked...date code on the block is for 1974, uncertain if it originally held a 454 crank or a 427, but definitely has a forged 427 crank in it now.

Sooo....still no final number on compression, but at least I have some less speculative data on the pistons, block, and crank. Once that has been determined I'll be back with an update.

 

Well this is good stuff. If the heads are still around 101cc then you have 10.05 compression or so.

JIM

 

I just figured this. Using hypothetical numbers.
Chambers are 100 CC
Pistons down in the hole .020
Piston dome is 16.8
Bore 4.290
Stroke 3.76
Gasket bore 4.380
Gasket thickness .021
Compression ratio is 10.567 to 1
If the heads are milled to 95 CC you are 11.111 to 1
If the heads are 100 CC and you use a .040 gasket your compression is 10.1 to 1
As you can see the heads need to be CCed and all measurements need to be exact to accurately figure compression

What rear end ratio and trans do you have?

Jim is right, The piston dome is a good thing. You can get to a decent compression number to make good power. With the oval port closed chamber heads I would seriously look at a roller cam. The extra lift vs duration will help fill the cylinders better. A little porting, bowl work and bumping the valve size up would help a lot too since you are rebuilding the heads anyway.

 

I've never measured the rear end ratio (although it's on blocks with the transmission out, now will be a good time) and can't find anything on the differential case that tells me. The gear ratios on the Tremec are 3.27 1st, 1.98 2nd, 1.34 3rd, 1.00 4th, and 0.68 5th. The combustion chambers will be cc'd, but the current estimate by the machinist based on approximate degree of observed planing of heads is 95cc.

 

you are going to use the closed chambered heads? Does the shop shop have a flow bench? Might be worthwhile to put the heads on the bench and check flow numbers before putting any money in them, then compare what's on the market today...

 

surfacing heads doesn't really change compression enough to worry about. I would still go with the before posted solid flat lifter 236/242 with 10.5 or less. 242/244 for over 10.5.

As to the rear end gear. That is really more of a concern if you have wimpy little 350 ci motors or 3 - 4 speed automatic trannies. When you have 500+ foot pounds of TQ. and a 5 speed traction is the problem

 

...now THAT'S the kind of problem I need

 

Not going to put too much work on the heads themselves, and not planning on upgrading at this time...although it's tempting to get carried away. Pretty soon I'd be doing this:

http://cgi.ebay.com/ebaymotors/462-B...Q5fAccessories

 

If you haven't made a decision on your cam yet...............it would be well worth your time to at least talk to Chris Straub at Straub Technologies. He helped me...................and continues to do so.

Here is a link to his website:

http://www.straubtechnologies.com/

 

I just dug out the paperwork on my rebuild to see what pistons we used- it wasn't listed there. However I know that the TRW L2300 at .060 over was written by me on a list of parts to purchase when I was planning my rebuild and I'm all but sure that's what's in the motor. We milled the pistons slightly, checking for chamber cc, until we got it down to 9.5 to 1 comp ratio to keep it safe for pump gas which was getting worse and worse at the time.

This was using the original closed chamber oval port heads upgraded with 2.19 and 1.88 valves. At the time I ran a slightly hot street Crower hydraulic lifter cam. I bring this up because your scenario is so similar except that your cam is unknown so far.

This is where it gets interesting. A few years, but not a lot of miles, later I wanted more cam and went with the flat tappet solid lifter cam I mentioned earlier in this thread. In the mock up to check for valve to piston clearance we found that we had to relieve the pistons, although I can't remember exactly how much. Point being, and I'm sure you and your builder plan to check for clearance, with my specific cam, pistons, and closed chamber heads there wasn't enough clearance. Any more cam would be even more of an issue. Given the similarities between our motors I thought this might be useful to you.

 

Definitely. The clearances will be checked before a cam is ordered. I'd like to keep the compression as high as practically possible for 93 octane pump gas plus lead additive, so there will be no milling of those tiny little domes. If I can get a suitable cam in there without getting valve reliefs cut I will, but it's an option on the table.

 

With the TKO 500 5 speed even with a 3.08, which you more than likely have, gearing should be no problem. The heads will be the weak point on ths build. I would try to keep the compression under 10.5 to 1 and go with a hydraulic roller cam since those heads without some port and bowl work will not pull much past 6000 RPM anyway. with some others that, since you have a rectangular port intake, need a valve job, need new springs and have to mill and setup the heads anyway you would be better off to sell the heads to a restoration project, take the head sale $ put the rebuild and spring $ with it and buy some new aftermarket aluminum heads with rectangular ports that match your intake with the correct springs, bump compression to 11 to 1 and go solid roller and be able to pull strong to 7000 RPM. Not much difference in total cost when it is all said and done and a much stronger build. Before you do anything it would be good to check piston to valve clearance as others have said they had clearance issues and you also had indications of clearance issues. The only aluminum heads with 100 CC chambers I know of are the edlebrocks and I think they have oval ports. The Victor JR's are rectangular port but are 106 CC.

 

Les, how did this run for you? Does it kind of have the race stucco idle?



# Duration @ .050 (Int/Exh): 243/251
# Gross Valve Lift (Int/Exh): .586/.600
# LSA/ICL: 110/104
# Valve Lash (Int/Exh): .026/.030
# RPM Range: 2500-6800

 

George,
It's not crazy but there's no doubt there's a healthy cam in there when you hear it idle- 850 RPMs is right about where it likes to be. It has good grunt, in fact it's very similar to the milder cam that preceded it. It pulls hard from midrange on- traction is an issue even with the Nittos and the shift into 2nd comes pretty quick. If I'm running through the gears I use 6500 RPMs as my shiftpoint but there's definitely more RPM in it- good thing because it's hard to time my shift right at 6500.

In summary it's just what I was looking for. I realize that it's too mild for some and too much for others but I'm very satisfied.

 

The poster wanted to stay with about 6000 is why I came in with 236 or 242 for intake. One other item in favor of the CC cams is the tighter lash. .016 instead of the Crower .026. Years ago when I ran larger like .024 lash cams I would end up with the tips damaged on my push rods. So I have become a tighter lash fan.


Les did you go for a Vette Cruise Sat? I put a bunch of miles on mine just goofing off

 

George, our group of 20 Vettes went well over 250 miles- over Ebbetts Pass, stopped in Topaz for a break, crossed over to Bridgeport for a late lunch, and then home via the Sonora Pass. The scenery was awesome and the driving, for some, was.....spirited! Just a few hours later both passes were closed due to snow!

 

An option..use L-88 pistons and fly cut the dome to reduce cr this will give you a wider choice of cams and not have to worry about valve to piston clearance or dropping points in cr...

I used these pistons with open chamber heads and the 288 roller....this worked very well for me..