Turbo head question...

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acarlson
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Location: Dahlonega, GA

Turbo head question...

Post by acarlson »

I am about to rebuild my Corsa engine. I have some invoices from a previous owner - he apparently did the same thing back in 2009.

So, according to the invoices, he installed .032 cylinder base gaskets plus .052 big bore head gaskets. Now he may have done this to reduce the compression ratio so he could run regular gas in the turbo engine. He may also have done this because he had the heads machined and he needed to push them out to compensate for the material loss during the machining process.He installed an OTTO cam at the same time so he may also have installed fatter gaskets to keep the pistons from running into the valves.

So, my question is - when I get the heads off, how can I tell if it's machining, the cam or just cheap gas ???

Alec
Alec Carlson
Dahlonega, GA
1965 Regal Red Corsa 4 Speed Turbo Convertible
Restoration "In Progress"...
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MyLonewolf25
Posts: 11
Joined: Tue Mar 14, 2017 11:56 am

Re: Turbo head question...

Post by MyLonewolf25 »

acarlson wrote:I am about to rebuild my Corsa engine. I have some invoices from a previous owner - he apparently did the same thing back in 2009.

So, according to the invoices, he installed .032 cylinder base gaskets plus .052 big bore head gaskets. Now he may have done this to reduce the compression ratio so he could run regular gas in the turbo engine. He may also have done this because he had the heads machined and he needed to push them out to compensate for the material loss during the machining process.He installed an OTTO cam at the same time so he may also have installed fatter gaskets to keep the pistons from running into the valves.

So, my question is - when I get the heads off, how can I tell if it's machining, the cam or just cheap gas ???

Alec
Cc the heads
Check lift
Etc


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Scott V
Posts: 707
Joined: Wed Jun 30, 2010 2:31 am

Re: Turbo head question...

Post by Scott V »

like the other post said.......cc the heads so you know what you got.

does the invoice say what otto cam is in the engine? it would have to be a real big cam to let the valves run into the piston.

he prob added all the gaskets cuz he didnt understand what he was doing.

i dont think the heads needed to be machined .040 to clean them up. if the heads were stock.....the extra .040 gasket thickness would make the engine around 7.5 compression. stock is 8. 7.5 c-r & regular gas wont work too good if your going to boost your engine.........your still going to ping.

-Scott V.
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MyLonewolf25
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Joined: Tue Mar 14, 2017 11:56 am

Re: Turbo head question...

Post by MyLonewolf25 »

Scott V wrote:like the other post said.......cc the heads so you know what you got.

does the invoice say what otto cam is in the engine? it would have to be a real big cam to let the valves run into the piston.

he prob added all the gaskets cuz he didnt understand what he was doing.

i dont think the heads needed to be machined .040 to clean them up. if the heads were stock.....the extra .040 gasket thickness would make the engine around 7.5 compression. stock is 8. 7.5 c-r & regular gas wont work too good if your going to boost your engine.........your still going to ping.

-Scott V.
Machining the head would increase compression ratios not lower but if he added extra gaskets to lower it and it needed that much machining the head was either badly warped or nicked


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Jerry Whitt
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Re: Turbo head question...

Post by Jerry Whitt »

The cylinder walls fit up inside the heads. Machining the heads on the flat surfaces would not increase compression ratio. If the cylinders sleeve edges were machined, now the compression ratio would increase.

The heads being machined upside where the cylinder barrels fit is quite unlikely. To check, measure the depth from the flat surface of the head to the top of the head, near the valves. I just measured a nice set of heads on my bench. With a straight edge across the flat part of the head, I measured to the flat part of the combustion chamber near the valves. It measured 11/16 ths. These heads are 140s, with a compression ration at 9:1. The turbo engine should have a ratio of about 8:1, therefore the difference would be MORE than 11/16ths
Jerry Whitt
ASE CERTIFIED MASTER TECHNICIAN
Retired
Hemet, Callifornia
65 Monza, purchased new
65 Corsa convertible
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acarlson
Posts: 454
Joined: Wed Nov 02, 2016 5:54 pm
Location: Dahlonega, GA

Re: Turbo head question...

Post by acarlson »

Scott V wrote: Tue Mar 21, 2017 4:03 pm he prob added all the gaskets cuz he didnt understand what he was doing.
Now that does make me worry ! :think:

Thanks everyone for the advice. I'll let you know what I find when I get to it...

Alec
Alec Carlson
Dahlonega, GA
1965 Regal Red Corsa 4 Speed Turbo Convertible
Restoration "In Progress"...
Scott V
Posts: 707
Joined: Wed Jun 30, 2010 2:31 am

Re: Turbo head question...

Post by Scott V »

MyLonewolf25 wrote: Tue Mar 21, 2017 4:13 pm
Scott V wrote:like the other post said.......cc the heads so you know what you got.

does the invoice say what otto cam is in the engine? it would have to be a real big cam to let the valves run into the piston.

he prob added all the gaskets cuz he didnt understand what he was doing.

i dont think the heads needed to be machined .040 to clean them up. if the heads were stock.....the extra .040 gasket thickness would make the engine around 7.5 compression. stock is 8. 7.5 c-r & regular gas wont work too good if your going to boost your engine.........your still going to ping.

-Scott V.
Machining the head would increase compression ratios not lower but if he added extra gaskets to lower it and it needed that much machining the head was either badly warped or nicked
confused...............were did i say machining the head would lower the c/r?

-Scott V.
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