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Cheap bottom end upgrades?
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Juho  



Joined: 03 Oct 2018
Posts: 66
Location: Finland

PostPosted: Wed Sep 25, 2019 8:00 am    Post subject: Cheap bottom end upgrades? Reply with quote

Well, i was just doing a final bits on my efi conversion and snapped a bolt in the cylinder head. The bolt is so hard that it cant be drilled or welded out so i need to take whole cylinder head off and get it machined. This got me thinking that i wont be probaly able to drive the car til next summer so might aswell take the whole engine out and paint the bay and do upgrades the engine. Is there "cheap" bottom end upgrades to make the car rev higher and make more power na.
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morghen  



Joined: 21 Jan 2005
Posts: 8089
Location: Romania

PostPosted: Wed Sep 25, 2019 8:27 pm    Post subject: Reply with quote

Lighten the crank, lighten the rods, lighten the flywheel, get the whole thing balanced properly.
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924RACR  



Joined: 29 Jul 2001
Posts: 8198
Location: Royal Oak, MI, USA

PostPosted: Wed Sep 25, 2019 11:10 pm    Post subject: Reply with quote

Yeah, and consider pistons; if they're in rough shape, consider a higher compression aftermarket replacement. Since you're going EFI etc, you can readily tune for the higher octane fuel that's readily available now.

I've sourced mine (for the 924 NA racecar) from EBS Racing in Reno NV, they sell JE Pistons - excellent quality, though not cheap.

A fair bit of dead weight can be taken off the rods without compromising strength - that's just time to grind away, no parts purchase.

Definitely ARP head studs, if you don't already have. Maybe Cometic HG, depending on how aggressive you want to get. I put off doing the head studs on the race motor, and it eventually bit me, now it has them.

I don't recall if you have a turbo or not? Another not-cheap item, consider if your turbo is fresh enough or needs a rebuild. If it needs it, there's never a easier time, and also well worth considering an upgraded modern billet wheel. Massive PITA to swap after the engine's back in...

A crank scraper is another relatively inexpensive power mod, worth having in a built motor. Will require fitting (with a grinder), but not too much trouble. I did have some fitment issues with the bolt head against the pan on the rear main bearing, but the grinder fixed that too:
http://www.crank-scrapers.com/

If you knife-edge the crank or such major machining, your scraper will be more custom-fit, that'll need to be taken into account when ordering.
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'79 924 #77 ITB racecar
'82 931 Plat. Silver
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1840
Location: Somerset, UK

PostPosted: Thu Sep 26, 2019 3:11 am    Post subject: Re: Cheap bottom end upgrades? Reply with quote

Juho wrote:
Is there "cheap" bottom end upgrades to make the car rev higher and make more power na.


Light. Strong. Cheap.

Pick two.....
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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safe  



Joined: 18 Mar 2017
Posts: 98
Location: Sweden

PostPosted: Thu Sep 26, 2019 3:48 am    Post subject: Re: Cheap bottom end upgrades? Reply with quote

Juho wrote:
Well, i was just doing a final bits on my efi conversion and snapped a bolt in the cylinder head. The bolt is so hard that it cant be drilled or welded out so i need to take whole cylinder head off and get it machined. This got me thinking that i wont be probaly able to drive the car til next summer so might aswell take the whole engine out and paint the bay and do upgrades the engine. Is there "cheap" bottom end upgrades to make the car rev higher and make more power na.


Best cheap mod ever for an NA, deck the block 1.5 mm for added compression.
Grind away the rough edges in the ports, especially around the valve seats.
Port match the intake and intake gasket to the head.
Balance the pistons and rods, crank is mostly fine as is.

All this is "free", just time and some labour in the machine shop.
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Juho  



Joined: 03 Oct 2018
Posts: 66
Location: Finland

PostPosted: Thu Sep 26, 2019 8:54 am    Post subject: Re: Cheap bottom end upgrades? Reply with quote

safe wrote:

Best cheap mod ever for an NA, deck the block 1.5 mm for added compression.
Grind away the rough edges in the ports, especially around the valve seats.
Port match the intake and intake gasket to the head.
Balance the pistons and rods, crank is mostly fine as is.

All this is "free", just time and some labour in the machine shop.


Could decking my block make my engine into a interference engine? Does decking the block result in noticeable increase in power?
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safe  



Joined: 18 Mar 2017
Posts: 98
Location: Sweden

PostPosted: Thu Sep 26, 2019 7:20 pm    Post subject: Re: Cheap bottom end upgrades? Reply with quote

Juho wrote:
safe wrote:

Best cheap mod ever for an NA, deck the block 1.5 mm for added compression.
Grind away the rough edges in the ports, especially around the valve seats.
Port match the intake and intake gasket to the head.
Balance the pistons and rods, crank is mostly fine as is.

All this is "free", just time and some labour in the machine shop.


Could decking my block make my engine into a interference engine? Does decking the block result in noticeable increase in power?


Pretty sure it will still clear the valves if you cut it by 1.5mm. Not a big issue if it doesn't, most engines don't.
You will pick up 10+ hp to my best guess. If you clean up the ports, "low hanging fruit porting" so to speak you can be up to 140ish HP.
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Juho  



Joined: 03 Oct 2018
Posts: 66
Location: Finland

PostPosted: Thu Sep 26, 2019 10:16 pm    Post subject: Reply with quote

What about taking 2mm off the head? Is it possible to replace the headstuds whilst the engine is in the car? i read you can easily ruin the threads if you replace the headstuds whilst the engine is in the car.
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safe  



Joined: 18 Mar 2017
Posts: 98
Location: Sweden

PostPosted: Thu Sep 26, 2019 10:30 pm    Post subject: Reply with quote

Juho wrote:
What about taking 2mm off the head? Is it possible to replace the headstuds whilst the engine is in the car? i read you can easily ruin the threads if you replace the headstuds whilst the engine is in the car.


From what I heard 2 mm is also possible (I know 1.5 is good), but I would rather do 1.5 and a thinner head gasket if it was my engine.

Do you mean the bolts that hold the head to the block? Very replaceable without removing the head or engine, unless it is broken deep down.
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924RACR  



Joined: 29 Jul 2001
Posts: 8198
Location: Royal Oak, MI, USA

PostPosted: Thu Sep 26, 2019 10:40 pm    Post subject: Reply with quote

There are specs in the manual on how much is safe to remove from the head. No performance advantage, but sometimes a light skim is needed to clean up the surface for a good seal.

I'm trying to remember if the studs would clear the strut tower with the engine in the car. I suspect the head may not slide off them easily - as in, the studs would need to be unscrewed from the block with the head in place (using an allen wrench, they're machined on the top for this) and then the whole assembly of head with studs loose inside removed from the block.
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safe  



Joined: 18 Mar 2017
Posts: 98
Location: Sweden

PostPosted: Thu Sep 26, 2019 10:46 pm    Post subject: Reply with quote

Sorry, misread.
You can't take more than light skims from the head to make it flat. You must take the material from the block to increase compression.
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Juho  



Joined: 03 Oct 2018
Posts: 66
Location: Finland

PostPosted: Fri Sep 27, 2019 1:07 am    Post subject: Reply with quote

safe wrote:
Sorry, misread.
You can't take more than light skims from the head to make it flat. You must take the material from the block to increase compression.


if i can take the head off and replace the studs without removing the engine from the car im going to drive it for a month and then start building the engine. but if i have to pull the engine now, inorder to get the cylinder head off i might aswell start building the bottom end now
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safe  



Joined: 18 Mar 2017
Posts: 98
Location: Sweden

PostPosted: Fri Sep 27, 2019 1:43 am    Post subject: Reply with quote

Juho wrote:
safe wrote:
Sorry, misread.
You can't take more than light skims from the head to make it flat. You must take the material from the block to increase compression.


if i can take the head off and replace the studs without removing the engine from the car im going to drive it for a month and then start building the engine. but if i have to pull the engine now, inorder to get the cylinder head off i might aswell start building the bottom end now


No problem removing the head without removing the engine. Biggest issue might be to remove the exhaust manifold from either the head or the exhaust.
But if you are to replace the exhaust manifold studs and don't need to be careful its not that difficult either.
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1840
Location: Somerset, UK

PostPosted: Fri Sep 27, 2019 5:15 am    Post subject: Reply with quote

If you are intending to use head studs v bolts, you may need to land the head onto the block first then insert the studs. I say this from turbo experience where you have to bolt on the exhaust manifold before installing the head. No idea with the NA
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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Juho  



Joined: 03 Oct 2018
Posts: 66
Location: Finland

PostPosted: Fri Sep 27, 2019 5:34 am    Post subject: Reply with quote

https://racingfuel.es/head-stud-kit-porsche-924-20-all-models-arp-complete-head-studs-n1?lang=en

Has anyone ordered from this site?
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