1970 LT-1 piston

[GerryLP]

Hey folks,

You guys are the experts -is the LT-1 piston for a 70 corvette cast or forged? Also, does anyone have the part number for a 0.040" over size pistonfor the LT-1?

GerryLP:cool

 

[MidShark]

All LT-1 pistons from '70-'72 were forged. Can't help you with the .040 part #, though.

Rich

 

[GerryLP]

All LT-1 pistons from '70-'72 were forged. Can't help you with the .040 part #, though.

Rich

Thanks, Rich. I also wrote to GM, and they told me that it is no longer produced. I guess I will contact http://www.egge.com/ for a quote.

GerryLP:cool

 

[MidShark]

Gerry

I'm fairly certain you could buy a set of TRWs without much problem. That's what I used (at .030) on my LT-1 rebuild a few years ago.

Rich

 

[GerryLP]

Gerry

I'm fairly certain you could buy a set of TRWs without much problem. That's what I used (at .030) on my LT-1 rebuild a few years ago.

Rich

Thanks Rich! I'll try their parts search program. (http://www.21cgt.com/FMWebCatalog/default.htm)

GerryLP:cool

 

[Jack]

Not LT1 specific because I don't have LT1 experience ... I have both older & newest SpeedPro catalogs.

I understand this motor came w/ 64cc heads. Suggest SpeedPro (aka TRW) L2417F, L2327F, L2490F ... all are forged & flat w/ 2 reliefs except 2417 has a single trough ... any of them in +30 will make right at 10:1 cr w/64cc comb cham.

Unfortunately, my understanding the above 3 pistons NOT available in +40.

I believe SpeedPro L2252AF is still available in +40 ... it has .200" dome and would make about 11.9:1 cr in +40 w/64cc. IMHO, that's aholotta CR for street motor w/iron heads ... and today's crappy gas.

Do you need a whole set of 8? Will +30 work or do you need larger? Some Ross, JE, SRP, Mahle are available in +35 too.
JACK:gap

-edit-L2304F may be correct replacement for LT1. Understand still available in std, +30, +60 only ... BTW, SP says needs 96 octane. L2304F has .100" dome ... should make about 10.6:1 cr in +30 w/64cc. LiteWeight version LW2304F about 47g less; otherwise same.

 

[GerryLP]

Not LT1 specific because I don't have LT1 experience ... I have both older & newest SpeedPro catalogs.

I understand this motor came w/ 64cc heads. Suggest SpeedPro (aka TRW) L2417F, L2327F, L2490F ... all are forged & flat w/ 2 reliefs except 2417 has a single trough ... any of them in +30 will make right at 10:1 cr w/64cc comb cham.

Unfortunately, my understanding the above 3 pistons NOT available in +40.

I believe SpeedPro L2252AF is still available in +40 ... it has .200" dome and would make about 11.9:1 cr in +40 w/64cc. IMHO, that's aholotta CR for street motor w/iron heads ... and today's crappy gas.

Do you need a whole set of 8? Will +30 work or do you need larger? Some Ross, JE, SRP, Mahle are available in +35 too.
JACK:gap

-edit-L2304F may be correct replacement for LT1. Understand still available in std, +30, +60 only ... BTW, SP says needs 96 octane. L2304F has .100" dome ... should make about 10.6:1 cr in +30 w/64cc. LiteWeight version LW2304F about 47g less; otherwise same.

Hey Jack, thanks for the info. ..yeah.. I may have to bore the block to a 0.060" overbore to accomodate the pistons. I will be using aluminum heads, so this will help me on the CR, and besides, I drive mostly between 5,000' and 7,000', so it should be ok. Once I get down to sea-level for a cruise-fest or other, it should be able to handle the compression with premium or octane booster (I am aiming to 11:1 CR).

I have a 1968 3914678 block, and would hate to bore it that large, but it is a truck (suffix YC) block, so it should take the bore adjustment just fine. I also just won an e-bay 4-bolt main 010 509 020 block (that should be a cast# 3970010 high tin block if the seller is correct). Perhaps that block will only need a 0.030" boring.

What do you know about the LT-1 cam?

Here is something I found in one of GM's websites:

3972178 Mechanical Flat Tappet
This mechanical flat tappet is used on the 70-71 Corvette and Camaro LT-1. It is a good all around street mechanical cam (ID#3972182). The duration at lash point in degrees (intake/exhaust) is 300/312; duration at .050" tappet lift (intake/exhaust) is 242/254; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 435/455. Valve lash is 024/030 and lobe centerline is 116 degrees.

I think that Crane had some Blueprinting series cams available that matches the LT-1 cam. I have been craving for a solid cam, but if it is not available, then I'll use the XE274H that I have. Could the large difference in intake/exhaust lobe lift be entirely due to valve clearance?

GerryLP:cool

 

[Jack]

Gerry:
I don't know what valve to piston clearance is on LT1 ... but that's something that should be measured whenever building a hi-po motor. Flattops & small chamber aluminum heads will get you lotsa compression and leave plenty of room for valve to piston clearance (big cam). A set of L98 vette alum heads (58cc) and any of the +30 flattops listed above will net you between 10.7-10.8 cr ... that's w/ a stock uncut deck. No doubt Lt1 cam is a good one but others may be better ... suggest www.howardscams.com & www.camcraftcams.com . I use howard's direct lube solid flat lifters (has a tiny face-centered hole that lubes lobes) and camcraft solid flat cam in circle track car that has about same duration as LT1 but 485"/485" lift but at about 108 centerline. It dynos right at 370hp @ crank w/ flattops, unported IRON 70cc heads, TWO barrel carb on 110 octane. Keep in mind 2 barrels make lots more vacuum than 4 ... higher intake velocity ... this motor will NOT idle ... but it buzzes to 7200 lap after lap, night after night ... very quick & reliable.

Those relatively cheap L98 heads are also on zz4 motor and it has hypereutectic (cheaper than forged) FLATTOPS ... it comes with 208*/221* 474"/510" cam ... and can drop in hot cam kit that's 218*/228* 525"/525". So, the flattops listed above should work with L98 heads & alotta cam too & have valve to piston clearance. As you know those zz4 cams are hyd roller cams and will not fit your old block ... not without alotta machinework. But you can sure get a solid flat in about any profile you want that'll fit your old block.
JACK:gap

 

[GerryLP]

Gerry:
I don't know what valve to piston clearance is on LT1 ... but that's something that should be measured whenever building a hi-po motor. Flattops & small chamber aluminum heads will get you lotsa compression and leave plenty of room for valve to piston clearance (big cam). A set of L98 vette alum heads (58cc) and any of the +30 flattops listed above will net you between 10.7-10.8 cr ... that's w/ a stock uncut deck. No doubt Lt1 cam is a good one but others may be better ... suggest www.howardscams.com & www.camcraftcams.com . I use howard's direct lube solid flat lifters (has a tiny face-centered hole that lubes lobes) and camcraft solid flat cam in circle track car that has about same duration as LT1 but 485"/485" lift but at about 108 centerline. It dynos right at 370hp @ crank w/ flattops, unported IRON 70cc heads, TWO barrel carb on 110 octane. Keep in mind 2 barrels make lots more vacuum than 4 ... higher intake velocity ... this motor will NOT idle ... but it buzzes to 7200 lap after lap, night after night ... very quick & reliable.

Those relatively cheap L98 heads are also on zz4 motor and it has hypereutectic (cheaper than forged) FLATTOPS ... it comes with 208*/221* 474"/510" cam ... and can drop in hot cam kit that's 218*/228* 525"/525". So, the flattops listed above should work with L98 heads & alotta cam too & have valve to piston clearance. As you know those zz4 cams are hyd roller cams and will not fit your old block ... not without alotta machinework. But you can sure get a solid flat in about any profile you want that'll fit your old block.
JACK:gap

Jack,

As always, thanks for the great information. I will try to find a very similar cam to the LT-1 profile. I'll check out those web links you posted. Thanks!


GerryLP:cool

 

[Jack]

Gerry:
SpeedPro (aka TRW) also grinds a clone of GM 3972178 LT1 solid cam.

SP P/N CS1145R is cam only.

SP P/N KC1145R is cam with lifters.

SP stuff is made real well ... as good or better than OE ... $shop around.
JACK:gap

 

[GerryLP]

Gerry:
SpeedPro (aka TRW) also grinds a clone of GM 3972178 LT1 solid cam.

SP P/N CS1145R is cam only.

SP P/N KC1145R is cam with lifters.

SP stuff is made real well ... as good or better than OE ... $shop around.
JACK:gap

Jack,

That is great news. I think I'll order that one. I just decided last night to go with the solid cam. Thanks again!

GerryLP:cool

 

[Jack]

Melling LT-1 cam & lifter

Gerry:
SpeedPro (aka TRW) also grinds a clone of GM 3972178 LT1 solid cam.

SP P/N CS1145R is cam only.

SP P/N KC1145R is cam with lifters.

SP stuff is made real well ... as good or better than OE ... $shop around.
JACK:gap

Also, Melling makes it. In addition to all those oil pumps, Melling makes alotta cams too. Just as above, quality as good or better than OE.

Melling P/N CCR-15 is cam only.

JACK:gap