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Re: Bigger pistons and cylinders

Posted: Sun Mar 08, 2020 6:39 pm
by wreck
It’s a sliding scale going larger , the 40s will be small and what size BAS header ?

Re: Bigger pistons and cylinders

Posted: Sun Mar 08, 2020 7:07 pm
by pnikas
wreck wrote: Sun Mar 08, 2020 6:39 pm It’s a sliding scale going larger , the 40s will be small and what size BAS header ?
It is bolting up on stock oval port heads, it has thin walls though , I will have to measure it.
Will the 40 drlas restrict it a lot?
At least they can be replaced after, do you agree with the displacement heads and cam in general terms ?

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 4:17 am
by wreck
yes a 2400cc with a 86C cam will be restricted with 40mm carbs and 42mm intake valves . this 98mm cylinder kit with a 71mm crank will give you a 2143cc engine that will work with the 86C and your heads as they are with better springs and the carbs will be a little small but still work . I'd recommend 10.0 to 1 comp . If you have good fuel then 10.5 to 1 .
It still won't have a lot of low end torque because of the cam .

http://vwparts.aircooled.net/Piston-Cyl ... t4b-je.htm

springs
https://www.thesamba.com/vw/classifieds ... id=2077442

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 5:12 am
by pnikas
wreck wrote: Mon Mar 09, 2020 4:17 am yes a 2400cc with a 86C cam will be restricted with 40mm carbs and 42mm intake valves . this 98mm cylinder kit with a 71mm crank will give you a 2143cc engine that will work with the 86C and your heads as they are with better springs and the carbs will be a little small but still work . I'd recommend 10.0 to 1 comp . If you have good fuel then 10.5 to 1 .
It still won't have a lot of low end torque because of the cam .

http://vwparts.aircooled.net/Piston-Cyl ... t4b-je.htm

springs
https://www.thesamba.com/vw/classifieds ... id=2077442
Would it be a good idea to add 44mm intake valves and 38mm exhaust valves ? If not mistaken vw had 38mm intakes , can they be installed as exhaust valves ?

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 5:15 am
by pnikas
wreck wrote: Mon Mar 09, 2020 4:17 am yes a 2400cc with a 86C cam will be restricted with 40mm carbs and 42mm intake valves . this 98mm cylinder kit with a 71mm crank will give you a 2143cc engine that will work with the 86C and your heads as they are with better springs and the carbs will be a little small but still work . I'd recommend 10.0 to 1 comp . If you have good fuel then 10.5 to 1 .
It still won't have a lot of low end torque because of the cam .

http://vwparts.aircooled.net/Piston-Cyl ... t4b-je.htm



springs
https://www.thesamba.com/vw/classifieds ... id=2077442
This combo you propose seems great . The only reason I am still thinking about a 2.4 is that I want to do the job once . The engine is in a convertible so torque is greatly appreciated . What 2.4 would you build around the parts I already have ? Bigger valves and carbs ? Both intake and exhaust valves ?

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 12:07 pm
by pnikas
wreck wrote: Mon Mar 09, 2020 4:17 am yes a 2400cc with a 86C cam will be restricted with 40mm carbs and 42mm intake valves . this 98mm cylinder kit with a 71mm crank will give you a 2143cc engine that will work with the 86C and your heads as they are with better springs and the carbs will be a little small but still work . I'd recommend 10.0 to 1 comp . If you have good fuel then 10.5 to 1 .
It still won't have a lot of low end torque because of the cam .

http://vwparts.aircooled.net/Piston-Cyl ... t4b-je.htm

springs
https://www.thesamba.com/vw/classifieds ... id=2077442
Also another question , should I expect 22mm pins or 24mm ones for the pistons ? 2l 914 engine mostly

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 2:25 pm
by wreck
stock 914/ type4 rods and stock length rods use 24mm pins , the cam is the wrong choice for what you want to achieve . It works from over 3000 to over 7000. If you go with 104mm bore , change valves /seats, get minor head port work for 46 /38 valves . 44 or 48mm carbs . better rod bolts or rods (if not already fitted). you will need a minimum of a 1 5/8 header . those are the components to match that cam and a 104mm bore .
What revs do you want the power to start ?

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 3:33 pm
by pnikas
wreck wrote: Mon Mar 09, 2020 2:25 pm stock 914/ type4 rods and stock length rods use 24mm pins , the cam is the wrong choice for what you want to achieve . It works from over 3000 to over 7000. If you go with 104mm bore , change valves /seats, get minor head port work for 46 /38 valves . 44 or 48mm carbs . better rod bolts or rods (if not already fitted). you will need a minimum of a 1 5/8 header . those are the components to match that cam and a 104mm bore .
What revs do you want the power to start ?
Around 2000rpm , I think that’s the best for a daily

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 3:36 pm
by pnikas
wreck wrote: Mon Mar 09, 2020 2:25 pm stock 914/ type4 rods and stock length rods use 24mm pins , the cam is the wrong choice for what you want to achieve . It works from over 3000 to over 7000. If you go with 104mm bore , change valves /seats, get minor head port work for 46 /38 valves . 44 or 48mm carbs . better rod bolts or rods (if not already fitted). you will need a minimum of a 1 5/8 header . those are the components to match that cam and a 104mm bore .
What revs do you want the power to start ?
The combo I have now will be better with 104 pistons or worse ?

Re: Bigger pistons and cylinders

Posted: Mon Mar 09, 2020 4:34 pm
by wreck
It will be better but a 96 mm bore , no machining , a better matched cam will give the same output for a lot less work

Re: Bigger pistons and cylinders

Posted: Tue Mar 10, 2020 3:53 pm
by pnikas
wreck wrote: Mon Mar 09, 2020 4:34 pm It will be better but a 96 mm bore , no machining , a better matched cam will give the same output for a lot less work
If I end up building a big engine with the associated parts, what should I choose between 1)AA 104mm pistons and cylinders 2)JE 105mm pistons with usa provides cylinders ?

Re: Bigger pistons and cylinders

Posted: Wed Mar 11, 2020 1:26 am
by wreck
check out "Get Back On Track" on FB and PM Jakob , he has a lot of big bore experience and will most likely have used both sets in engine builds .

Re: Bigger pistons and cylinders

Posted: Wed Mar 11, 2020 11:07 am
by cal 67
86C is a huge cam and needs stiff springs, like CB650s. Also, the larger the engine, the lower the RPM your peak power will be with the same heads. Just installing a 44 doesn't really help. It needs to flow well enough to support however many ccs at whatever rpm the cam is meant to peak at.

Sealing: six studs. There are other ways, but six studding is proven and reliable. It's not cheap. The heads need to be disassembled and welded to accept more studs. I recommend not going into the rocker box with the center bottom studs. Use those little rows of fins near the exhaust port. Fill them in, mill the seating surface flat, drill for a stud.

Re: Bigger pistons and cylinders

Posted: Wed Mar 11, 2020 11:59 am
by pnikas
cal 67 wrote: Wed Mar 11, 2020 11:07 am 86C is a huge cam and needs stiff springs, like CB650s. Also, the larger the engine, the lower the RPM your peak power will be with the same heads. Just installing a 44 doesn't really help. It needs to flow well enough to support however many ccs at whatever rpm the cam is meant to peak at.

Sealing: six studs. There are other ways, but six studding is proven and reliable. It's not cheap. The heads need to be disassembled and welded to accept more studs. I recommend not going into the rocker box with the center bottom studs. Use those little rows of fins near the exhaust port. Fill them in, mill the seating surface flat, drill for a stud.
what is your opinion on 105mm pistons and cylinders ? Je pistons with usa provided cylinders?

Re: Bigger pistons and cylinders

Posted: Sun Mar 22, 2020 12:55 pm
by cal 67
I’m personally having a hard time finding someone to bore/hone my barrels in a torque plate. Round in your hand means nothing. It needs to be round when torqued on the case. I need to keep pestering a friend till he gives me his honing contact. Anybody that’s honing by hand is giving you warped barrels. They need to stay in that fixture till they’re complete.