Thread: 70 Monte 454 Fuelie Bad Combo Questions:(

Tweet

So it goes in this week for boring.
I would like to keep the heads if possible, why are they too big?
Or is the cam too small? If I have to go to mechanical roller cam I can do that.
Breathers are stock PCV valve and a small air filter on the opposite valve cover.
Never any sign of blowby from the pcv or open breather on the opposite valve cover.
Car will be used very little with some 1/4 mile passes.

Thanks, John

what the cc runner of them rect port heads i built bbc with rect ports but were hi winders or bigger then 454s for the street low rpm big O ports work good . i think i said the cam was abit short for your CR you do not need to go solid roller HYD roller like you have is fine . just tell me what your trying to do

290cc intake runners
12363390 GM heads

http://sdparts.com/details/gm-perfor...parts/12363390

4000 lbs. car T400 trans, 3.30ish 12 bolt posi (I forgot exact ratio) 26.5 diam tire.
93 octane. I want the best I can get performance/drivability.
Was looking for 550/550 Tq Hp

Thanks, John

Originally Posted by ssvolvo

290cc intake runners
12363390 GM heads

http://sdparts.com/details/gm-perfor...parts/12363390

4000 lbs. car T400 trans, 3.30ish 12 bolt posi (I forgot exact ratio) 26.5 diam tire.
93 octane. I want the best I can get performance/drivability.
Was looking for 550/550 Tq Hp

Thanks, John

ok them heads are fine i used them there more of the roval ports if were not open up or over ported .what cr are you using for the new piston

That's my big question right now.
It has to run on pump gas.
I think the 2 variables now are piston design/compression and camshaft.
I feel everything else will fall into place.
36 lbs. per/hr. injectors are most likely on the edge and may need to be replaced with larger units.
I would like a piston that is designed for "semi-open" chamber as long as we are replacing them anyway.
TechInspector has a valid point with compression ratio.
I wish I knew more about big block does/dont's. That is why I am asking for your help.|
The other thing I just found out is that Edelbrock makes these heads for GM.

What would you do if this was your project?

Just tore the valves out and the seals are like new, pliable. Guide clearance appears very nice.
Oil rings all have .060" plus gap. Looks like this is the oiling problem, yes it burned 5 quarts in a few hundred miles. CATS covered this up, no blue smoke. Compression ring gaps all nice and tight. Looks like I screwed up checking the oil rings in my haste.

Witness mark from the roller rocker on the valve stem are small indicating correctly sized pushrods.

I am used to running almost 11 to 1 CR with LS engines on pump gas. Looks like a bit much for Big Block on the street.

John

bad hone job oil ring gap is ok if you can run on 92 pump ?or get it i been building bbc for 30 years

your dynamic cr with the right cam will be fine with the same piston you used the first time with Alum heads and get the deck set at 0 or down in the hole no more then 0.010 the cam i would use is a 238/246 @050 627/627 on a 112 with this cam your pistons and dynamic CR will be fine if you run a smaller cam you have to watch your dynamic CR with them pistons.i would have to run the numbers to check this but getting the block deck right helps alot. well thats not a big dome we used much bigger you can look at the SRP but 10.5 with good gas i done with that cam i listed many times .has for the heads yes gm and edlebrocks are about the same the last set i did get from Sgoggin Dickeys seim finsh

I will set the crank and one piston back in to get actual deck height.

Pat, Is this you? http://nssn.racingjunk.com/category/...-Cams-NEW.html

Thanks,
John

Originally Posted by ssvolvo

I will set the crank and one piston back in to get actual deck height.

Pat, Is this you? http://nssn.racingjunk.com/category/...-Cams-NEW.html

Thanks,
John

yep thats two cams left over from two builds

Gasket is at .040" removed from the engine.

Piston is .040" below deck at TDC.

So my squish was at .080". Not good.

Originally Posted by ssvolvo

Gasket is at .040" removed from the engine.

Piston is .040" below deck at TDC.

So my squish was at .080". Not good.

well with that piston. if you use a srp they 9.780 for O deck you do not deck the block till you know your CH of the new pistons. i first use the BHJ tru deck the block . then O the boring bar to the new fresh cut deck. so i am true 90. if the guy is just decking your block it can be way off and along with bores then your pissing in the wind and if you go this far the engine should be honed with torque plates to .so a blue printed block most all blocks get this i do

I have appointment with engine guy Saturday AM.
This is a reputable place. He does engines for the Nascar Camping World series.
Thanks to your help (again) I can ask the right questions.

John

Edit 4-20-2011
Engine going back together. Will update this thread.

Engine is going back together.
Machinist's eyes got very wide when I picked the stuff up from his shop.

Said the bore was ****ed. Nuff said.

I also noticed a stain in the intake ports around the rocker stud hole---you need to put sealer on the intake rocker stud threads

looked again, saw that was fuel injector nozzles but fact remains to seal the rocker stud threads

Originally Posted by techinspector1

Pat McCarthy and Jerry Clayton, among others, have way more experience building big block Chevies than I do, but I enjoy sitting down and figuring out what's going on and how to fix it. In the end, every motor out there is just a big ole air pump that responds to pretty much the same parts and procedures as the next one.

First thing I see is that the squish isn't tightened up as much as it could be. Also, that big lump of dome on the piston is gettin' in the way of flame propogation. And the static compression ratio is too high for pump gas and the cam you're using.

The piston you have used has a compression height of 1.640". Add a 6.135" rod and a 2.000" stroke radius and you have a stack of 9.775" in a ~9.800" block deck height, leaving you with a 0.025" piston deck height. Add a nominal 0.040" head gasket to that and the squish measures 0.065". You can't use a thinner gasket because of the aluminum heads, so you have to do whatever else you can to fix the situation.

If we were to cut the block decks 0.010", registering off the centerline of the main bearing bore and use pistons with a taller compression height, like SRP forged #141635 that measure 1.645", you could improve the squish by 0.015" and arrive at a ~0.050" squish. The other plus side of using this piston is that the dome is 14 cc's instead of the 25.7 cc dome you have in the motor now, so flame propogation across the chamber should work a lot better.
Static compression ratio should end up at 9.72:1 and I'd bet that would work pretty well on pump gas with the Lunati cam you're using.

The SRP pistons are designed to work with the Edelbrock Recti-Oval heads you have. Here is a blurb about them....

"SRP big block Chevy small dome profile pistons are designed to fit Edelbrock 110cc and GM Signature series heads. They're 4032 low-expansion, high-silicon aluminum alloy that's heat-treated to SRP specifications. CNC-machined domes with radiused valve reliefs provide optimum flame travel. They include pin fitting, double Spiro locks, and wrist pin."
SRP, Racing Pistons, Chev BB Small Dome (Closed), 4.280 Bore-Competition Products

Here are the volumes I used in computing the SCR....
4.280" x 4.000" = 943 cc's
Chambers +/- 110 cc's
Pistons 14 cc's
Piston deck height (block deck height 9.790", piston deck height 0.010") 2.4 cc's
0.039"/0.040" composition gasket for aluminum heads 9.7 cc's.

Deduct the dome from the chamber. 110 less 14 = 96 cc's. This is what we use for chamber volume. Piston volume is now zero.

Figured thusly....
943 (cylinder) + 96 (chamber) + 0 (piston) + 2.4 (piston deck height) + 9.7 (head gasket) = 1051.1 cc's.

96 + 0 + 2.4 + 9.7 = 108.1

Divide 1051.1 by 108.1 and find 9.723:1 static compression ratio.

Oh, and by the way, your present static compression ratio is 10.55:1

Also, I ran into a blurb somewhere that said the valve guides are semi-finished as produced. Check with whomever finished the guides. That may be where the oiling is coming from. Just a thought. Also, when you pull the motor apart, look closely at the intake gaskets to see if they are pinched all the way around. If you were pulling crankcase air into the ports from the bottom side because of a mis-match at the sealing surfaces, the motor could have been going lean and you'd never be able to find it.

That's quite the calculation Tech.

I checked the dynamic and came up with 9.5.
Would this have more to do with pinging than the static of 10.55:1 ?

I'm curious about this as I'm planning a similar project (EFI) with 10.45:1 static and 8.5:1 dynamic using the same aluminum heads on a stroker.