L-72, final assembly
 

L72 MN fa

Re: L-72, final assembly
 

Will your Daytona Douglass Yenko make the reunion?

Re: L-72, final assembly
 

I will make it. The car is 50/50. If it is not ready by then, I will just have to pal around with you and your white one all weekend [img]/ubbthreads/images/icons/smile.gif[/img]

Re: L-72, final assembly
 

Man, those pistons look sweet. I should have used them instead of TRW's! Will this motor be a true 11:1 with them???
Peter

Re: L-72, final assembly
 

That's what I was thinking, Pete [img]/ubbthreads/images/icons/frown.gif[/img] . I will NOT buy TRW's again.

Re: L-72, final assembly
 

Shor,
The pistons look very high in the non decked block. Did the machinist achieve this with the out of the box pistons or was the wrist pin location custom ordered?

Re: L-72, final assembly
 

FYI:

The TRW pistons in our last L-72 measured ~28cc, where as they are supposed to be 34cc. I sure wish I had gone with Ross or JE like I had originally planned...oh well, when I build the original L-72 to AMA specs it should be a REAL animal then. If my memory serves me correctly, Pete's pistons were on the "smallish" side as well...Pete?

Re: L-72, final assembly
 

That is a big difference, approx. 1/2 point of compression ratio right out the window.

What would you say that would equate to HP wise, about 10-15 at the rear wheels?

Re: L-72, final assembly
 

Hey guys. We went with the stock NHRA JE pistons 138814 .005 It was supposed to be 4 weeks for the custom order, but was really closer to 8 weeks. The journals on the crank were practically new std/std and we were able to track down a set of new gm 400 bearings.(and an original timing chain and ...ughh nylon gear) The machinist thought I was nuts, but I now have him on my "original" wavelength. He did insist on ARP fasteners though. Yea, it will be an 11:1 compression ratio, at least until I get tired of heading down to Sunoco at the Marina and paying 5.80 a gallon for the purple racing fuel. Nick did say that the advertised factory compression ratios of the day were actually the maximum and a "real" number was always slightly less, like a 10.7 or a 10.8 or 10.9, due to manufacturing tolerences and deviations. He said in my undecked block the top of the piston, the piston, not the dome, will be .030 below the deck at TDC. He said, after examining these JE pistons, that they had the true dome, faithfull in all respects to the original engineering spec. of the day; unlike some other "brands". This with the cleaning and balancing and polishing of the rods should put me at a true 10.7,10.8.( I think that is what he said...does it make sense?) If it becomes too much of a pain, I have a set of 71 ls6 heads waiting on the shelf. I'll keep you posted!

Re: L-72, final assembly
 

You are correct Rob. My 12:1 TRW's for the ZL-1 actually worked out to 10.8:1 [img]/ubbthreads/images/icons/frown.gif[/img] Live and learn!!!!) Part of the problem was my deck hieght. I did'nt want to deck a new block. Suppose to be 8 thou. out of the hole , and was 30 thou in the hole! Next time It will have a true 12:1 and then LOOK OUT!!!!
Peter

Re: L-72, final assembly
 

Hey;
Same story with my 'correct' TRW, 11:1, LT1 pistons [img]/ubbthreads/images/icons/mad.gif[/img]
Won't do that again, next time only JE's.

Re: L-72, final assembly
 

I know someone who would like to have those 990 heads [img]/ubbthreads/images/icons/smirk.gif[/img] I believe they were LS7 crate motor heads which were located in "The Postmans"1971 Corvette. The production 1971 LS6 Corvette heads were aluminum.

Re: L-72, final assembly
 

Shor, you'll still be darn lucky if your compression is close to 11:1. Has anything been done to your heads? My chambers were like 113+cc, where they are supposed to be 107(?)cc...that also makes a BIG difference in compression. Also, what head gasket will you be running? Stock they came with steel shims, which were in the .020" neighborhood, where most of your gaskets are in the .038"-.042" range. Again, this makes a difference. And, your engine builder is right about the deck height...but I'd bet my "left leg" that it's larger than that if it's truly a virgin block. Also, BE SURE and go with a GM cam! I also learned that the hard way, even after Pete told me over and over.

All of this little stuff adds up, and EATS power. Live and learn I guess. [img]/ubbthreads/images/icons/tongue.gif[/img]

Re: L-72, final assembly
 

Rob,
Doesn't Comp Cams make the blue printed cams and lifters for GM?

Re: L-72, final assembly
 

Thanks Rob. On my notes I have written 108cc and next to it is written 10.321 ??
The cc's must refer to my heads. The stock 840 heads, from what I understand, have been off the car since 71 and have been resting in various places over the years. Including the trunk for about 10 years. The 10.321 must be some sort of compression number. Since it has a third digit after the decimal it must have came from some sort of exact formula. I will know more tommorrow. We went with the Comp cam stock l72 valvetrain kit. Nick said that the Gm kit is made buy Comp anyway? The assembled engine is now in my garage waiting for it's trip to Latrobe. Stefano was right about the spare heads, they are the ls7 iron.

Re: L-72, final assembly
 

If the heads are virgin, I would seriously doubt they are 108cc...which I believe is what the AMA spec is on them. That's what you want them to be, but from the factory they left plenty of room.

As for who makes the GM cams, I was thinking it was Crane, but you 2 said Comp, so it very well could be. All I know is that our next one will come from the GMPP book. Pete, any idea who grinds GM's cams?

Re: L-72, final assembly
 

Oh, here is a really good online calculator: compression calculator

Re: L-72, final assembly
 

Rob you were right. It is Crane. I don't know why I was thinking comp. Fummy thing, stefano was thinking comp also. The part # on the box is 969961 if anyone needs one.

Re: L-72, final assembly
 

(fummy)
I must be getting tired

Re: L-72, final assembly
 

It's only 11pm, itz bin u long weak, Benjamin won't sleap,
gotta go towrork, cnt stop typing, the big brown dog jumped over the lazy fox
zzzzzzzzzzzzzzzzzzzzz [img]/ubbthreads/images/icons/smirk.gif[/img]

Re: L-72, final assembly
 

I wasn't certain that is why I was asking [img]/ubbthreads/images/icons/smile.gif[/img]