Question for Engine Gurus
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 2,675
Likes: 13
From: Sudbury MA
Question for Engine Gurus
I am having my 68 L79 327cid 350 hp engine rebuilt by a local machine shop that has been doing this work for 28 years and was recommended.
My question is, I supplied all the original parts from GM and they are twlling me it will only have 10.25 to 1 compression (instead of 11to1) and will take 60 days plus $3000 to do.
Why is it that GM was able to build this motor and achieve certain results and specifications and that cannot be duplicated by a machine shop using the same parts, many of whihc are brand new from GM.
I don;t know anything about engine building so would appreciate some insight from those of you who do.
Something stinks to me based upon just simple common sense.
Thank you,
My question is, I supplied all the original parts from GM and they are twlling me it will only have 10.25 to 1 compression (instead of 11to1) and will take 60 days plus $3000 to do.
Why is it that GM was able to build this motor and achieve certain results and specifications and that cannot be duplicated by a machine shop using the same parts, many of whihc are brand new from GM.
I don;t know anything about engine building so would appreciate some insight from those of you who do.
Something stinks to me based upon just simple common sense.
Thank you,
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: Question for Engine Gurus (ksbunting)
Don't know about the compression but 60 DAYS. Why. It sure does not take that long to machine and build a motor. Is the 3000 just for labor or is that parts and labor. If just labor I'd go elsewhere.
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
Re: Question for Engine Gurus (ksbunting)
Sixty days & $3K to rebuild a stock motor with OEM parts...that you're supplying???? :eek:
I did my '70 L46 350/350 with an established, high end, race shop that has TONS of business and it took 4 weeks and about $5000. That included all new parts and labor!!!! New aluminum TFS heads, new Comp Cams cam & valvetrain components, new forged OEM pistons, Air Gap intake, Demon carb....the works!!
The 10.25 versus 11 to 1 thing is baffling. If its built using OEM specs and parts it should match the original compression unless you're using larger chamber heads, different pistons or a thicker (much) head gasket.
Walk away!!!
I did my '70 L46 350/350 with an established, high end, race shop that has TONS of business and it took 4 weeks and about $5000. That included all new parts and labor!!!! New aluminum TFS heads, new Comp Cams cam & valvetrain components, new forged OEM pistons, Air Gap intake, Demon carb....the works!!
The 10.25 versus 11 to 1 thing is baffling. If its built using OEM specs and parts it should match the original compression unless you're using larger chamber heads, different pistons or a thicker (much) head gasket.
Walk away!!!
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: Question for Engine Gurus (ksbunting)
That does not sounds like a shop you'd want to go to.
60 days is insane. Also, if everything stays equal and only the bore is enlarged the compression should raise. If they deck the block, the compression raises also.
The only reason for a lower compression that I can think of right now is the use of cheap 4 dish cast pistons & thicker head gsaket.
Marck
[Modified by Twinnie, 7:33 PM 10/2/2002]
60 days is insane. Also, if everything stays equal and only the bore is enlarged the compression should raise. If they deck the block, the compression raises also.
The only reason for a lower compression that I can think of right now is the use of cheap 4 dish cast pistons & thicker head gsaket.
Marck
[Modified by Twinnie, 7:33 PM 10/2/2002]
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Question for Engine Gurus (ksbunting)
I believe the original head gaskets were a shim steel gasket that is seldom used today. When it is replaced by a modern composite gasket the compression will be lower. Also, I believe that Chevrolet gave the highest figure for compression ratio and may have erred on the high side. You are really better off with the lower ratio considering the Gas we have today..I know it may sound great to have an 11:1 engine but it is really a problem unless you have access to some 100 octane fuel. Enjoy..
Melting Slicks
Joined: Oct 2001
Posts: 2,064
Likes: 1,382
From: Halifax, Nova Scotia, Canada
Re: Question for Engine Gurus (ksbunting)
To Clarify: 327 Ci In
If you have dome pistons with 64CC stock '68 heads (1.94 or 2.02), steel head gaskets, then GM said that was 11:1...
Same engine with "flat top" pistons, then it was 10.25:1 compression.
Any other combination will result in a different compression ratio.
Barry
If you have dome pistons with 64CC stock '68 heads (1.94 or 2.02), steel head gaskets, then GM said that was 11:1...
Same engine with "flat top" pistons, then it was 10.25:1 compression.
Any other combination will result in a different compression ratio.
Barry
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Question for Engine Gurus (Barry's70LT1)
The sixty day part is fine, dosen't mean they are going to take sixty days to build an engine, means they are busy and busy usually ( not all the time ) means they are half decent engne building shop.
The $3000.00 baffles me if yu are supplying the parts, way out of line :eek:
The $3000.00 baffles me if yu are supplying the parts, way out of line :eek:
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Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
Re: Question for Engine Gurus (ksbunting)
DONT WALK AWAY RUN AWAY. Rebuilding an engine is not dificult provided you have the correct equipment and a reasonable amount of intelligence.
$3000 and you are supplying the parts?
:eek: I wonder what theyre smoking at that shop.
$3000 and you are supplying the parts?
:eek: I wonder what theyre smoking at that shop.
Burning Brakes
Joined: Jul 2001
Posts: 1,160
Likes: 0
From: Ajax Ontario
Re: Question for Engine Gurus (ksbunting)
My rebuild (same engine as you) was $2,200 CDN ( approx. $1,500 US)by Agostino Racing Engines (Forum sponsor and subject of a feature article in current Corvette Fever mag.). All parts needed for rebuild, including new hyper. pistons, boring the block etc. were included with the exception of the cam/lifters/timing chain that I had purchased. It also took about a month for the reason that Agostino is always very busy......
Your quote sounds very expensive for labour only and would recommend getting other quotes before deciding.
:cheers:
Your quote sounds very expensive for labour only and would recommend getting other quotes before deciding.
:cheers:
Team Owner
Joined: Dec 1999
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Re: Question for Engine Gurus (68shark)
What kind of gas are you planning on using with 11: 1?
By the way, my rebuilt is taking just under 30 days for about $4K and $950 of that is labor. Compression ratio is going to be about 9.7: 1. 330 hp, 380 ft-lb torque.
I pick it up next week. :)
[Modified by OHSIXX, 4:57 PM 10/3/2002]
[Modified by OHSIXX, 4:59 PM 10/3/2002]
By the way, my rebuilt is taking just under 30 days for about $4K and $950 of that is labor. Compression ratio is going to be about 9.7: 1. 330 hp, 380 ft-lb torque.
I pick it up next week. :)
[Modified by OHSIXX, 4:57 PM 10/3/2002]
[Modified by OHSIXX, 4:59 PM 10/3/2002]