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Big Bore Do-over

Leon_pp said:
not long to find my picture on facebook, i ask for join the Historic Volvo society so i get you some more pictures of the head.
Head is mounted on 8 bolts B20 block with B21A flat pistons.
I am currently finishing wiring of the ITB on standalone Ecu. Need to find a good solution for throttle cable.
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Holy crap! That head is way shaved down, what are the CC's and projected static compression ratio??? Also, are the intake and exhaust valves sharing recesses? That's nuts. What kind of performance are you looking at? What will be the primary use of this car?
 
If you guys want to talk what it takes to build a fast pushrod motor, call Rob Gordon at Vol-Tech. He's been pretty open about sharing information, especially if you're not racing against him :)

He does most of his own engines, and they rip.
 
culberro said:
If you guys want to talk what it takes to build a fast pushrod motor, call Rob Gordon at Vol-Tech. He's been pretty open about sharing information, especially if you're not racing against him :)

He does most of his own engines, and they rip.
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Rob Gordon as in the original owner of IPD? I'm sure he does know a thing or two :nod:
 
That dude is super cool. Easy af to talk to.

I vote for cc the chambers after you take a deburr knife or file to the edges and give them a solid 2mm radius.

Then measure bore, deck height, and plug it in to a calculator. Figure out the scr, hg thickness, and aim for a scr that your cam likes, as close to .000” deck as the tallest piston, and rock on. If the scr is high due to piston height, break out the Dremel and have at it. Remove sharp edges, increase radius the the valve face, and dial it..
 
R32RennSport said:
Holy crap! That head is way shaved down, what are the CC's and projected static compression ratio??? Also, are the intake and exhaust valves sharing recesses? That's nuts. What kind of performance are you looking at? What will be the primary use of this car?
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The R-Sport head I found on eBay waaay backinttheday was shaved *way* down as well. To the point it's into that curved edge on the shelf over the pushrod galley. I took out metal in the chambers (unshrouding the valves, matching the sides to the B21-sized bores), and even then , to make it drivable on pump 93, I had to use small dished B21A pistons.
 
just a taste of what it takes for these heads to flow right (not done)
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2OdivQEh.jpg
 
Jack said:
just a taste of what it takes for these heads to flow right (not done)
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That's some pretty intense work. I don't think I have anyone local willing to do that kind of work for me. Most machine shops in my area don't care much for early European stuff, mostly cater to the V8 crowd.
 
Jack is spot on. Fill the floor with something and raise it 6-10mm, and get a much better SSR.
 
OK, so million dollar question, who should I send my head out to on the west coast to have it worked on by someone that A) has experience with these and B) could turn it around in reasonable amount of time?

Horsepower goal is ambiguous because I'm look for overall drivability with a focus more on torque then RPM. As stated previously the engine puts down 110/110 to the ground so you can guess crank numbers. I mean more the better but I don't have unlimited funds rather quite the opposite. I've read most of the B20 head threads that I could find, there is a ton of intricacies to these heads to produce serious power but could it be as simple as just figuring out CCs in the chambers and decking the head and/or block and calling it a day with a bump in compression without all the porting work? I know that sounds ignorant but I'm looking for good enough without looking for that extra few percent, this is after all just a street car.
 
Do the simple stuff (porting/smoothing) yourself, and then get a shop to deck the head.
Honestly, decking the head for higher CR is going to be 80% (pulled out of my bum) of what you're after.
 
R32RennSport said:
Thanks guys, I appreciate everyone for their input. Just want to move in the right direction without overthinking it.
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I am looking for some numbers on combustion chamber volume given how much is shaved off the head. Can you share the combustion chamber volume measurements when you take them?
 
spock345 said:
I am looking for some numbers on combustion chamber volume given how much is shaved off the head. Can you share the combustion chamber volume measurements when you take them?
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Sure thing. I'll definitely be taking a bunch more measurements the second time around and documenting as I go along.
 
forgot to add
the intake ports on these heads are pretty crappy. Adding tapered spacers helps. I wish heads were aluminum because then you can add and subtract as you wish

need more fiddling but you get the idea
7Ztw5Crh.jpg


1p66Fu4h.jpg
 
R32RennSport said:
Holy crap! That head is way shaved down, what are the CC's and projected static compression ratio??? Also, are the intake and exhaust valves sharing recesses? That's nuts. What kind of performance are you looking at? What will be the primary use of this car?
Click to expand...

I just had a set of Gary's gstellsr valves installed, 46/38's :omg: and they're sitting about 0.008-0.010" apart. Had to have then intake seats installed, then the exhaust seat cut to overlap the intake :rofl: Looks like it'll be money. I've still got to re-cc the chambers, clean up the seat>port blend, then decide how much I want to futz with the exhaust SSR. So far, its just bowl blended, and very lightly radiused, then smoothed to 180 grit roloc drums. There is some thought about doing what Jacks got there, but I had seen a couple that used a tongue off the header to take up some space in the floor... Not set on anything yet, gotta get the fun monies back up so I can tackle the butchered bottom end.

The hope at the moment is to have the exhaust flowing decent, and the intake at 42.5mm from the manifold to the valve. Surprising how much I was able to open up at the bowls.
 
cwdodson88 said:
I just had a set of Gary's gstellsr valves installed, 46/38's :omg: and they're sitting about 0.008-0.010" apart. Had to have then intake seats installed, then the exhaust seat cut to overlap the intake :rofl: Looks like it'll be money.
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Good luck with it and hope you get the extra flow you are looking for. However be aware that with simeased valve seats like this in B20 heads the head itself tends to crack between the seats in race engines.
 
vintagewrench said:
Good luck with it and hope you get the extra flow you are looking for. However be aware that with simeased valve seats like this in B20 heads the head itself tends to crack between the seats in race engines.
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Totally aware... Although I dont plan to beat on it too hard since I've been overpowering my trans since the last turbo/IC setup. I have started designing a billet head just in case. I've got 3 pieces of scrap to try. Couple cases of beer for the programmer, and a weekend in front of the 5 axis should do it.
 
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